Vehicular anticipatory sensor system
1. A vehicle including a system to prevent collisions between the vehicle and different objects in a path of the vehicle, comprising:
- a laser radar system arranged on the vehicle and configured to direct laser beams outward from the vehicle, said laser radar system receiving, in a first operating stage, laser beams that have been reflected from objects in the paths of the outward directed laser beams, said laser radar system being configured to generate the laser beams in an eye-safe portion of the electromagnetic spectrum at a wavelength above 1.4 microns and comprising a high-powered laser radar;
a processor coupled to said laser radar system and configured to receive signals derived from the laser beams received in the first operating stage and process the signals to determine a distance between said laser radar system and each of the objects from which the received laser beams have been reflected in the first operating stage;
an imaging receiver for receiving laser beams that have been reflected from any of the objects in the paths of the laser beams directed outward from said laser radar system and creating images from the received laser beams,said processor being further configured to determine a plurality of range gates to apply at different times, in a second operating stage, to said imaging receiver such that when each of the range gates is applied to said imaging receiver, an image is created from only laser beams received from objects in that range gate,each of the range gates being determined for a respective one of the objects from which the laser beams received in the first operating stage have been reflected based on the determined distance between said laser radar system and the respective one of the objects from which the laser beams received in the first operating stage have been reflected such that said imaging receiver is thus configured to receive reflections of laser beams directed outward from said laser radar system in the second operating stage only from the respective one of the objects from which the laser beams received in the first operating stage have been reflected and any other objects in the same range gate;
anda reactive system coupled to said processor, said processor being configured to control said reactive system to selectively indicate the presence of any of the objects from which the received laser beams have been reflected.
System and method for preventing collisions between a vehicle and objects in a path of the vehicle includes a laser system arranged to direct at least one laser beam outward therefrom and which is in an eye-safe portion of the electromagnetic spectrum, an imaging receiver for receiving at least one laser beam reflected from objects in the path of the laser beam, a processor coupled to the receiver and arranged to receive signals derived from the received laser beam and process the signals to determine a distance between the laser system and the objects from which the laser beam has been reflected, and one or more reactive systems coupled to the processor. The processor controls the reactive system to indicate the presence of objects at specific distances from the vehicle. This indication may be used to take preventive action to avoid the collision, either manually or automatically.
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- 1. A vehicle including a system to prevent collisions between the vehicle and different objects in a path of the vehicle, comprising:
a laser radar system arranged on the vehicle and configured to direct laser beams outward from the vehicle, said laser radar system receiving, in a first operating stage, laser beams that have been reflected from objects in the paths of the outward directed laser beams, said laser radar system being configured to generate the laser beams in an eye-safe portion of the electromagnetic spectrum at a wavelength above 1.4 microns and comprising a high-powered laser radar; a processor coupled to said laser radar system and configured to receive signals derived from the laser beams received in the first operating stage and process the signals to determine a distance between said laser radar system and each of the objects from which the received laser beams have been reflected in the first operating stage; an imaging receiver for receiving laser beams that have been reflected from any of the objects in the paths of the laser beams directed outward from said laser radar system and creating images from the received laser beams, said processor being further configured to determine a plurality of range gates to apply at different times, in a second operating stage, to said imaging receiver such that when each of the range gates is applied to said imaging receiver, an image is created from only laser beams received from objects in that range gate, each of the range gates being determined for a respective one of the objects from which the laser beams received in the first operating stage have been reflected based on the determined distance between said laser radar system and the respective one of the objects from which the laser beams received in the first operating stage have been reflected such that said imaging receiver is thus configured to receive reflections of laser beams directed outward from said laser radar system in the second operating stage only from the respective one of the objects from which the laser beams received in the first operating stage have been reflected and any other objects in the same range gate; and a reactive system coupled to said processor, said processor being configured to control said reactive system to selectively indicate the presence of any of the objects from which the received laser beams have been reflected.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 21, 22, 23)
- 10. A method for preventing collisions between a vehicle and different objects in a path of the vehicle, comprising:
in a first operating stage, directing laser beams outward from a laser radar system on the vehicle, the laser radar system being configured to generate the laser beams in an eye-safe portion of the electromagnetic spectrum at a wavelength above 1.4 microns and comprising a high-powered laser radar; receiving, at a laser beam receiving system, laser beams that have been reflected from objects in the paths of the outward directed laser beams; receiving, at a processor, signals derived from the received laser beams; processing, at the processor, the received signals to determine a distance between the laser radar system and each of the objects from which the received laser beams have been reflected; determining, using the processor or a different processor, a plurality of range gates to apply at different times to the laser beam receiving system such that when each of the range gates is applied to the laser beam receiving system, an image is created from only laser beams received from objects in that range gate; in a second operating stage, directing laser beams outward from the laser radar system; receiving, at the laser beam receiving system, laser beams that have been reflected from objects in the paths of the outward directed laser beams; applying the range gates at different times to the laser beam receiving system to thereby create an image from only laser beams received from objects in the applied one of the range gates, each of the range gates being applied for a respective one of the objects from which the laser beams received in the first stage have been reflected based on the determined distance between the laser radar system and the respective one of the objects from which the laser beams received in the first operating stage have been reflected such that the laser beam receiving system is thus configured to receive reflections of laser beams directed outward from the laser radar system in the second operating stage only from the respective one of the objects from which the laser beams received in the first operating stage have been reflected and any other objects in the same range gate; creating, when each of the range gates is applied to the laser beam receiving system, an image from only laser beams received from objects in the applied one of the range gates and then controlling a reactive system on the vehicle to indicate the presence of any of the objects.
- View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 24, 25, 26)
This application is a divisional of U.S. patent application Ser. No. 11/923,929 filed Oct. 25, 2007, which is:
1. a CIP of U.S. patent application Ser. No. 10/413,426 filed Apr. 14, 2003, now U.S. Pat. No. 7,415,126, which is a CIP of U.S. patent application Ser. No. 10/151,615 filed May 20, 2002, now U.S. Pat. No. 6,820,897; and
2. a CIP of U.S. patent application Ser. No. 10/895,121 filed Jul. 21, 2004, now U.S. Pat. No. 7,407,029, which is a continuation of U.S. patent application Ser. No. 10/733,957 filed Dec. 11, 2003, now U.S. Pat. No. 7,243,945, which is:
- A. a CIP of U.S. patent application Ser. No. 10/151,615 filed May 20, 2002, now U.S. Pat. No. 6,820,897;
- B. a CIP of U.S. patent application Ser. No. 10/365,129 filed Feb. 12, 2003, now U.S. Pat. No. 7,134,687; and
3. a CIP of U.S. patent application Ser. No. 10/940,881 filed Sep. 13, 2004, now U.S. Pat. No. 7,663,502, which is:
- A. a CIP of U.S. patent application Ser. No. 10/151,615 filed May 20, 2002, now U.S. Pat. No. 6,820,897;
- B. a CIP of U.S. patent application Ser. No. 10/365,129 filed Feb. 12, 2003, now U.S. Pat. No. 7,134,687; and
- C. a CIP of U.S. patent application Ser. No. 10/931,288 filed Aug. 31, 2004, now U.S. Pat. No. 7,164,117.
All of the applications mentioned herein are incorporated by reference.
The present invention relates generally to an anticipatory sensing system and method for vehicles and more particularly to a system and method for detecting objects in a path of a vehicle to enable action to be taken to prevent an accident between the vehicle and the detected objects.
A detailed discussion of background information is set forth in the parent applications, all of which are incorporated by reference herein.
All of the patents, patent applications, technical papers and other references mentioned below and in the parent applications are incorporated by reference herein in their entirety. No admission is made that any or all of these references are prior art and indeed, it is contemplated that they may not be available as prior art when interpreting 35 U.S.C. §102 in consideration of the claims of the present application.
Definitions of terms used in the specification and claims are also found in the parent applications.
A vehicle, such as an airplane, in accordance with the invention included a system to prevent collisions between the vehicle and objects in a path of the vehicle. This collision preventing system includes a laser system arranged to direct at least one laser beam outward therefrom and which is in an eye-safe portion of the electromagnetic spectrum, an imaging receiver for receiving at least one laser beam reflected from objects in the path of the at least one laser beam, a processor coupled to the receiver and arranged to receive signals derived from the received at least one laser beam and process the signals to determine a distance between the laser system and the objects from which the at least one laser beam has been reflected, and one or more reactive systems coupled to the processor. The processor controls the reactive system to indicate the presence of objects at specific distances from the vehicle. This indication may be used to take preventive action to avoid the collision, either manually or automatically.
The laser system may project a bright spotlight in the eye-safe portion of the electromagnetic spectrum in a direction in which the vehicle is heading or in a direction forward of a front of the vehicle. The processor may include a pattern recognition algorithm arranged to process the signals to determine whether any objects are in the vehicle'"'"'s path and optionally an identification of the objects determined to be in the vehicle'"'"'s path. The pattern recognition algorithm may include or consist of a trained neural network, a combination neural network, an optical correlation system or a sensor fusion algorithm.
The reactive system may be a heads-up display which is controlled by the processor to project an image into a field of view of an occupant of the vehicle, the image being derived from the object. The processor may be arranged to select a form of the image, i.e., an icon, to project into the field of the view of the occupant based on the received signals. When a system for determining a location of the occupant'"'"'s head and/or eyes is provided, the heads-up display may be controlled by the processor to project the image into the field of view of the occupant based on the determined location of his or her head or eyes.
Another reactive system is an alarm system which provides a visual and/or audible warning to an occupant of the vehicle when an object is determined to be within a threshold distance from the vehicle.
The receiver may be arranged to apply range gating to obtain reflections from objects within a predetermined range from the vehicle. This would be useful during poor visibility.
A method for preventing collisions between a vehicle and objects in a path of the vehicle in accordance with the invention includes directing at least one laser beam outward from the vehicle and which is in an eye-safe portion of the electromagnetic spectrum, receiving at least one laser beam reflected from objects in the path of the at least one laser beam, processing the received at least one laser beam on the vehicle to determine a distance between the vehicle and objects from which the at least one laser beam has been reflected, and controlling at least one reactive system on the vehicle to indicate the presence of objects at specific distances from the vehicle. The same variations described above may be applied in this method as well.
For example, processing the received at least one laser beam may entail deriving signals from the received at least one laser beam and processing the signals in a pattern recognition algorithm which is programmed to determine whether any objects are in the vehicle'"'"'s path and optionally an identification of the objects. When the reactive system is a heads-up display, controlling the heads-up display may entail projecting an image into a field of view of an occupant of the vehicle derived from the object, which may be obtained by first identifying the object and then selecting a form of the image, i.e., an icon, to project into the field of the view of the occupant based on an identification of the object.
Further, there are disclosed several processors or controllers, that perform various control operations. The specific form of processor is not important to the invention. In its preferred form, the computing and analysis operations are divided into several cooperating computers or microprocessors. However, with appropriate programming well known to those of ordinary skill in the art, the inventions can be implemented using a single, high power computer. Thus, it is not applicant'"'"'s intention to limit his invention to any particular form or location of processor or computer. For example, it is contemplated that in some cases, the processor may reside on a network connected to the vehicle such as one connected to the Internet.
Further examples exist throughout the disclosure, and it is not applicant'"'"'s intention to exclude from the scope of his inventions the use of structures, materials, or acts that are not expressly identified in the specification, but nonetheless are capable of performing a claimed function.
The above and other objects and advantages of the present invention are achieved by preferred embodiments that are summarized and described below.
The various hardware and software elements used to carry out the invention described herein are illustrated in the form of system diagrams, block diagrams, flow charts, and depictions of neural network algorithms and structures. Preferred embodiments are illustrated in the following figures:
1. Vehicle Collision Warning and Control
Neural networks have been mentioned above and since they can play an important role in various aspects of the invention, a brief discussion is now presented here.
In this embodiment, 141 data points are appropriately interconnected at 25 connecting points of layer 1, and each data point is mutually correlated through the neural network training and weight determination process. In some implementations, each of the connecting points of the layer 1 has an appropriate threshold value, and if the sum of measured data exceeds the threshold value, each of the connecting points will output a signal to the connecting points of layer 2. In other cases, an output value or signal will always be outputted to layer 2 without thresholding.
The connecting points of the layer 2 comprises 20 points, and the 25 connecting points of the layer 1 are appropriately interconnected as the connecting points of the layer 2. Similarly, each data value is mutually correlated through the training process and weight determination as described above and in neural network texts. Each of the 20 connecting points of the layer 2 can also have an appropriate threshold value, if thresholding is used, and if the sum of measured data exceeds the threshold value, each of the connecting points will output a signal to the connecting points of layer 3.
The connecting points of the layer 3 comprises 3 points in this example, and the connecting points of the layer 2 are interconnected at the connecting points of the layer 3 so that each data is mutually correlated as described above.
The value of each connecting point is determined by multiplying weight coefficients and summing up the results in sequence, and the aforementioned training process is to determine a weight coefficient Wj so that the value (ai) is a previously determined output.
ai=ΣWj·Xj (j=1 to N)+W0
wherein Wj is the weight coefficient,
- Xj is the data
- N is the number of samples and
- W0 is bias weight associated with each node.
Based on this result of the training, the neural network circuit 63 generates the weights and the bias weights for the coefficients of the correlation function or the algorithm.
At the time the neural network circuit 63 has learned from a suitable number of patterns of the training data, the result of the training is tested by the test data. In the case where the rate of correct answers of the object identification unit based on this test data is unsatisfactory, the neural network circuit 63 is further trained and the test is repeated. Typically, about 200,000 feature patterns are used to train the neural network 63 and determine all of the weights. A similar number is then used for the validation of the developed network. In this simple example chosen, only three outputs are illustrated. These can represent another vehicle, a truck and a pole or tree. This might be suitable for an early blind spot detector design. The number of outputs depends on the number of classes of objects that are desired. However, too many outputs can result in an overly complex neural network and then other techniques such as modular neural networks can be used to simplify the process. When a human looks at a tree, for example, he or she might think “what kind of tree is that?” but not “what kind of tiger is that”. The human mind operates with modular or combination neural networks where the object to be identified is first determined to belong to a general class and then to a subclass etc. Object recognition neural networks can frequently make use of this principle with a significant simplification resulting.
In the above example, the image was first subjected to a feature extraction process and the feature data was input to the neural network. In other cases, especially as processing power continues to advance, the entire image is input to the neural network for processing. This generally requires a larger neural network. Alternate approaches use data representing the difference between two frames and the input data to the neural network. This is especially useful when a moving object of interest is in an image containing stationary scenery that is of no interest. This technique can be used even when everything is moving by using the relative speed as a filter to remove unwanted pixel data. Any variations are possible and will now be obvious to those skilled in the art. Alternately, this image can be filtered based on range, which will also significantly reduce the number of pixels to be analyzed.
In another implementation, the scenes are differenced based on illumination. If infrared illumination is used, for example, the illumination can be turned on and off and images taken and then differenced. If the illumination is known only to illuminate an object of interest then such an object can be extracted from the background by this technique. A particularly useful method is to turn the illumination on and off for alternate scan lines in the image. Adjacent scan lines can then be differenced and the resulting image sent to the neural network system for identification.
The neural network can be implemented as an algorithm on a general-purpose microprocessor or on a dedicated parallel processing DSP, neural network ASIC or other dedicated parallel or serial processor. The processing speed is generally considerably faster when parallel processors are used and this can also permit the input of the entire image for analysis rather than using feature data. A combination of feature and pixel data can also be used.
Neural networks have certain known potential problem areas that various researchers have attempted to eliminate. For example, if data representing an object that is totally different from those objects present in the training data is input to the neural network, an unexpected result can occur which, in some cases, can cause a system failure. To solve this and other neural network problems, researchers have resorted to adding in some other computational intelligence principles such as fuzzy logic resulting in a neural-fuzzy system, for example. As the Road to Zero Fatalities® (RtZF®) system evolves, such refinements will be implemented to improve the accuracy of the system. Thus, although pure neural networks are currently being applied to the problem, hybrid neural networks such as modular, combination, ensemble and fuzzy neural networks will undoubtedly evolve.
A typical neural network processing element known to those skilled in the art is shown in
Neural networks used in the accident avoidance system of this invention are trained to recognize roadway hazards including automobiles, trucks, animals and pedestrians. Training involves providing known inputs to the network resulting in desired output responses. The weights are automatically adjusted based on error signal measurements until the desired outputs are generated. Various learning algorithms may be applied with the back propagation algorithm with the Delta Bar rule as a particularly successful method.
2. Accurate Navigation
2.2 DGPS, WAAS, LAAS and Pseudolites
Additional details relating to
It is important to note that future GPS and Galileo satellite systems plan for the transmission of multiple frequencies for civilian use. Like a lens, the ionosphere diffracts different frequencies by different amounts and thus the time of arrival of a particular frequency will depend on the value of that frequency. This fact can be used to determine the amount that each frequency is diffracted and thus the delay or error introduced by the ionosphere. Thus with more than one frequency being emitted by a particular satellite, the equivalent of the DGPS corrections can be determined be each receiver and there is no longer a need for DGPS, WADGPS, WAAS, LAAS and similar systems.
The WAAS system is another example of WADGPS for use with airplanes. The U.S. Government estimates that the accuracy of the WAAS system is about 1 meter in three dimensions. Since the largest error is in the vertical direction, the horizontal error is much less.
3. Maps and Mapping
All information regarding the road, both temporary and permanent, should be part of the map database, including speed limits, presence of guard rails, width of each lane, width of the highway, width of the shoulder, character of the land beyond the roadway, existence of poles or trees and other roadside objects, exactly where the precise position location apparatus is located, etc. The speed limit associated with particular locations on the maps should be coded in such a way that the speed limit can depend upon the time of day and/or the weather conditions. In other words, the speed limit is a variable that will change from time to time depending on conditions. It is contemplated that there will be a display for various map information which will always be in view for the passenger and for the driver at least when the vehicle is operating under automatic control. Additional user information can thus also be displayed such as traffic conditions, weather conditions, advertisements, locations of restaurants and gas stations, etc.
A map showing the location of road and lane boundaries can be easily generated using a specially equipped survey vehicle that has the most accurate position measurement system available. In some cases, it might be necessary to set up one or more temporary local DGPS base stations in order to permit the survey vehicle to know its position within a few centimeters. The vehicle would drive down the roadway while operators, using specially designed equipment, sight the road edges and lanes. This would probably best be done with laser pointers and cameras. Transducers associated with the pointing apparatus record the angle of the apparatus and then by triangulation determine the distance of the road edge or lane marking from the survey vehicle. Since the vehicle'"'"'s position would be accurately known, the boundaries and lane markings can be accurately determined. It is anticipated that the mapping activity would take place continuously such that all roads in a particular state would be periodically remapped in order to record any changes which were missed by other monitoring systems and to improve the reliability of the maps by minimizing the chance for human error. Any roadway changes that were discovered would trigger an investigation as to why they were not recorded earlier thus adding feedback to the mapping part of the process.
The above-described method depends on human skill and attention and thus is likely to result in many errors. A preferred approach is to carefully photograph the edge of the road and use the laser pointers to determine the location of the road lines relative to the pointers and to determine the slope of the roadway through triangulation. In this case, several laser pointers would be used emanating from above, below and/or to the sides of the camera. The reduction of the data is then done later using equipment that can automatically pick out the lane markings and the reflected spots from the laser pointers. One aid to the mapping process is to place chemicals in the line paint that could be identified by the computer software when the camera output is digitized. This may require the illumination of the area being photographed by an infrared or ultraviolet light, for example.
In some cases where the roadway is straight, the survey vehicle could travel at moderate speed while obtaining the boundary and lane location information. In other cases, where the road in turning rapidly, more readings would be required per mile and the survey vehicle would need to travel more slowly. In any case, the required road information can be acquired semi-automatically with the survey vehicle traveling at a moderate speed. Thus, the mapping of a particular road would not require significant time or resources. It is contemplated that a few such survey vehicles could map all of the interstate highways in the U.S. in less than one year. Eventually, it is contemplated that between 50 and 100 such vehicles using photogramity techniques would continuously map and remap the Unites States.
The mapping effort could be supplemented and cross-checked though the use of accurate detailed digital photogrammetic systems which, for example, can determine the road altitude with an accuracy to <50 cm. Efforts are underway to map the earth with 1-meter accuracy. The generated maps could be used to check the accuracy and for missing infrastructure or other roadside installations of the road-determined maps.
A preferred approach is to accomplish the majority of the mapping function utilizing a vehicle equipped with a selection of several cameras, accurate RTK DGPS and appropriate illumination including one or more laser pointers or equivalent. The resulting pictures would initially be converted to maps manually but eventually, most of the process could be automated. Such map creation can be economically accomplished by the Karpensky Institute in Kyiv, Ukraine. This institute, in combination with the inventors herein, have further designed a vehicle capable of collecting the required photographic data.
Another improvement that can be added to the system based on the maps is to use a heads-up display for in-vehicle signage. As the vehicle travels down the road, the contents of roadside signs can be displayed on a heads up display, providing such a display is available in the vehicle, or on a specially installed LCD display. This is based on the inclusion in the map database of the contents of all highway signs. A further improvement would be to include signs having varying messages which would require that the message be transmitted by the sign to the vehicle and received and processed for in-vehicle display. This could be done either directly, by satellite, the Internet, cell phone etc.
As the roadway is being mapped, the availability of GPS satellite view and the presence of multipath reflections from fixed structures can also be determined. This information can then be used to determine the advisability of locating a local precise location system (PPS), or other infrastructure, at a particular spot on the roadway. Cars can also be used as probes for this process and for continuous improvement to check the validity of the maps and report any errors.
Multipath is the situation where more than one signal from a satellite comes to a receiver with one of the signals resulting from a reflection off of a building or the ground, for example. Since multipath is a function of geometry, the system can be designed to eliminate its effects based on highway surveying and appropriate antenna design. Multipath from other vehicles can also be eliminated since the location of the other vehicles will be known.
An important part of some embodiments of the invention is the digital map that contains relevant information relating to the road on which the vehicle is traveling. The digital map usually includes the location of the edge of the road, the edge of the shoulder, the elevation and surface shape of the road, the character of the land beyond the road, trees, poles, guard rails, signs, lane markers, speed limits, etc. as discussed elsewhere herein. Additionally, it can contain the signature as discussed above. This data or information is acquired in a unique manner for use in the invention and the method for acquiring the information and its conversion to a map database that can be accessed by the vehicle system is part of this invention. The acquisition of the data for the maps will now be discussed. It must be appreciated though that the method for acquiring the data and forming the digital map can also be used in other inventions.
Local area differential GPS can be utilized to obtain maps with an accuracy of about 2.0 cm (one sigma). Temporary local differential stations are available from such companies as Trimble Navigation. These local differential GPS stations can be placed at an appropriate spacing for the road to be mapped, typically every 30 kilometers. Once a local differential GPS station is placed, it requires some time period such as an hour or more for the station to determine its precise location. Therefore, sufficient stations are required to cover the area that is to be mapped within, for example, four hours. This may require as many as 10 or more such differential stations for efficient mapping.
With reference to
A processor including a printed circuit board 224 is coupled to the GPS receivers 226, the IMUs 206, the video cameras 208, the linear cameras 210 and the scanning laser radars 212 (see
An alternate preferred approach uses a series of 4-6 cameras looking forward, backward, and one, two or more on each side. In this configuration, the linear cameras and scanning laser radars can be omitted and all relevant information would come from the IMU and GPS with differential corrections. The scene may be illuminated with general illumination which can be in the IR part of the spectrum. In some cases, laser pointers or another form of structured light is also used primarily to permit later analysis of various elevation changes, especially at the side of the roadway. The resulting data is analyzed using photogramity techniques to obtain a fully digital map.
The map database can be of any desired structure or architecture. Preferred examples of the database structure are of the type discussed in U.S. Pat. No. 6,144,338 (Davies) and U.S. Pat. No. 6,247,019 (Davies).
The data acquisition modules 202 are essentially identical and each can mount to the vehicle roof on an extension assembly 214 which extends forward of the front bumper. Extension assembly 214 can include a mounting bracket 216 from the roof of the vehicle 200 forward to each data acquisition module 210, a mounting bracket 218 extending from the front bumper upward to each data acquisition module 202 and a cross mounting bracket 220 extending between the data acquisition modules 202 for support. Since all of the data acquisition equipment is co-located, its precise location is accurately determined by the IMU, the mounting location on the vehicle and the differential GPS system.
The forward-looking video cameras 208 can provide views of the road as shown in
The video camera system can be used by itself with appropriate software as is currently being done by Lamda Tech International Inc. of Waukesha, Wis., to obtain the location of salient features of a road. However, such a method to obtain accurate maps is highly labor intensive and therefore expensive. The cameras and associated equipment in the present invention are therefore primarily used to supplement the linear camera and laser radar data acquisition systems to be described now. This however is one approach with a preferred alternate approach using four, six or more cameras as described above.
In this approach, the mapping vehicle data acquisition modules will typically contain both a linear camera and a scanning laser radar, however, for some applications one or the other may be omitted.
The linear camera 210 is a device that typically contains a linear CCD, CMOS or other light sensitive array of, for example, four thousand pixels. An appropriate lens provides a field of view to this camera that typically extends from approximately the center of the vehicle out to the horizon. This camera records a one-dimensional picture covering the entire road starting with approximately the center of the lane and extending out to the horizon. This linear array camera 210 therefore covers slightly more than 90 degrees. Typically, this camera operates using natural illumination and produces effectively a continuous picture of the road since it obtains a linear picture, or column of pixels, for typically every one-inch of motion of the vehicle. Thus, a complete two-dimensional panoramic view of the road traveled by the mapping vehicle is obtained. Since there are two such linear camera units, a 180 degree view is obtained. This camera will typically record in full color thus permitting the map database team to have a complete view of the road looking perpendicular from the vehicle. The view is recorded in a substantially vertical plane. This camera will not be able to read text on traffic signs, thus the need for the forward-looking cameras 208. Automated software can be used with the images obtained from these cameras 208, 210 to locate the edge of the road, lane markers, the character of land around and including the road and all areas that an errant vehicle may encounter. The full color view allows the characterization of the land to be accomplished automatically with minimal human involvement.
The scanning laser radar 212 is typically designed to cover a 90 degree or less scan thus permitting a rotating mirror to acquire at least four such scans per revolution. The scanning laser radar 212 can be coordinated or synchronized with the linear camera 210 so that each covers the same field of view with the exception that the camera 210 typically will cover more than 90 degrees. Scanning laser radar 212 can be designed to cover more or less than 90 degrees as desired for a particular installation. The scanning laser radar 212 can operate in any appropriate frequency from above ultraviolet to the terahertz. Typically, it will operate in the eye-safe portion of the infrared spectrum for safety reasons, that is, at wavelengths above 1.4 microns. The scanning laser radar 212 can operate either as a pulse-modulated or a tone-modulated laser as is known in the art. If operating in the tone-modulated regime, the laser light will be typically modulated with three or more frequencies in order to eliminate distance ambiguities. Noise or code modulated radar can also be used.
For each scan, the laser radar 212 provides the distance from the scanner to the ground for up to several thousand points in a vertical plane extending from approximately the center of the lane out to near the horizon. This device therefore provides precise distances and elevations to all parts of the road and its environment. The precise location of signs that were observed with the forward-looking cameras 204, for example, can now be easily and automatically retrieved. The scanning laser radar therefore provides the highest level of mapping automation.
Scanning laser radars have been used extensively for mapping purposes from airplanes and in particular from helicopters where they have been used to map portions of railway lines in the US. Use of the scanning laser radar system for mapping roadways where the radar is mounted onto a vehicle that is driving the road is believed to be novel to the current assignee.
Ideally, all of the above-described systems are present on the mapping vehicle. Although there is considerable redundancy between the linear camera and the scanning laser radar, the laser radar operates at one optical frequency and therefore does not permit the automatic characterization of the roadway and its environment.
As with the forward-looking cameras, it is frequently desirable to use filters and polarizing lenses for both the scanning laser radar and the linear camera. In particular, reflections from the sun can degrade the laser radar system unless appropriate filters are used to block all frequencies except frequency chosen for the laser radar.
Laser radars are frequently also referred to as ladars and lidars. All such devices that permit ranging to be accomplished from a scanning system, including radar, are considered equivalent for the purposes of this invention.
4. Precise Positioning
Another important aid as part of some of the inventions disclosed herein is to provide markers along the side(s) of roadways which can be either visual, passive or active transponders, reflectors, or a variety of other technologies including objects that are indigenous to or near the roadway, which have the property that as a vehicle passes the marker it can determine the identity of the marker and from a database it can determine the exact location of the marker. The term “marker” is meant in the most general sense. The signature determined by a continuous scan of the environment, for example, would be a marker if it is relatively invariant over time such as, for example, buildings in a city. Basically, there is a lot of invariant information in the environment surrounding a vehicle as it travels down a road toward its destination. From time to time, a view of this invariant landscape or information may be obstructed but it is unlikely that all of it will be during the travel of a mile, for example. Thus, a vehicle should be able to match the signature sensed with the expected one in the map database and thereby obtain a precise location fix. This signature can be obtained through the use of radar or laser radar technologies as reported elsewhere herein. If laser radar is used, then an IR frequency can be chosen in the eyesafe part of the spectrum. This will permit higher transmitted power to be used which, especially when used with range gating, will permit the penetration of a substantial distance through fog, rain or snow. See in particular Section 5 below and for example, Wang Yanli, Chen Zhe, “Scene matching navigation based on multisensor image fusion” SPIE Vol. 5286 p. 788-793, 2003 and more recently “Backing up GNSS with laser radar & INS, RAIM in the city, antenna phase wind-up”, Inside GNDD July/August 2007.
For the case of specific markers placed on the infrastructure, if three or more of such markers are placed along a side of the roadway, a passing vehicle can determine its exact location by triangulation. Note that even with two such markers using radar with distance measuring capability, the precise position of a vehicle can be determined as discussed below in reference to the Precise Positioning System. In fact, if the vehicle is only able to observe a single radar or lidar reflector and take many readings as the reflector is passed, it can determine quite accurately its position based on the minimum distance reading that is obtained during the vehicle'"'"'s motion past the reflector. Although it may be impractical to initially place such markers along all roadways, it would be reasonable to place them in particularly congested areas or places where it is known that a view of one or more of the GPS satellites is blocked. A variation of this concept will be discussed below.
Although initially, it is preferred to use the GPS navigational satellites as the base technology, the invention is not limited thereby and contemplates using all methods by which the location of the vehicle can be accurately determined relative to the earth surface. The location of the roadway boundaries and the location of other vehicles relative to the earth surface are also to be determined and all relevant information used in a control system to substantially reduce and eventually eliminate vehicle accidents. Only time and continued system development will determine the mix of technologies that provide the most cost effective solution. All forms of information and methods of communication to and between vehicles are contemplated including direct communication with stationary and moving satellites, communication with fixed earth-based stations using infrared, optical, terahertz, radar, radio and other segments of the electromagnetic spectrum, direct or indirect communication with the internet and inter-vehicle communication. Some additional examples follow:
A pseudo-GPS can be delivered from cell phone stations, in place of or in addition to satellites. In fact, the precise location of a cell phone tower need not initially be known. If it monitors the GPS satellites over a sufficiently long time period, the location can be determined as the calculated location statistically converges to the exact location. Thus, every cell phone tower could become an accurate DGPS base station for very little cost. DGPS corrections can be communicated to a vehicle via FM radio via a sub-carrier frequency for example. An infrared or radar transmitter along the highway can transmit road boundary location information. A CD-ROM or, DVD or other portable mass storage can be used at the beginning of a controlled highway to provide road boundary information to the vehicle. Finally, it is contemplated that eventually a satellite will broadcast periodically, perhaps every five minutes, a table of dates covering the entire CONUS that provides the latest update date of each map segment. If a particular vehicle does not have the latest information for a particular region where it is operating, it will be able to use its cell phone or other communication system to retrieve such road maps perhaps through the Internet or from an adjacent vehicle. Emergency information would also be handled in a similar manner so that if a tree fell across the highway, for example, all nearby vehicles would be notified.
To implement map updating, a signal may be directed by the infrared or radar transmitter to the area covered by a segment of the map relating to the latest update information for that segment in a form receivable by a transmitter on vehicles passing through the area. A processor on the vehicle receives the signals, analyzes it and determines whether its map includes the latest updated map information for the segment in which the vehicle is presently located. If not, an update for the vehicle'"'"'s map information is downloaded via the transmitter. This embodiment is particularly advantageous when the transmitter is arranged before a section of road and thus provides vehicles entering the road and in range of the transmitter with the map data they will subsequently need.
The transmitter which transmits information to the vehicle, weather map information or other information, may be movable and thus would be particularly useful for roads undergoing construction, subject to closure or blockage in view of construction or other factors, or for which map data is not yet available. In this case, the movable, temporary transmitter would be able to provide map data for the affected section of road to vehicles in range of the transmitter. As the transmitter is moved along the roadway, the information transmitted can be changed.
One of the possible problems with the RtZF® system described herein is operation in areas of large cities such as lower Manhattan. In such locations, unless there are a plurality of local pseudolites or precise position location system installations or the environment signature system is invoked such as with adaptive associative memories as described above, the signals from the GPS satellites can be significantly blocked. Also, there is frequently a severe multipath problem in cities. A solution is to use the LORAN system as a backup for such locations. The accuracy of LORAN can be comparable to DGPS. Use of multiple roadway-located Precise Positioning Systems would be a better solution or a complementary solution. Additionally, some location improvement can result from application of the SnapTrack system as described in U.S. Pat. No. 5,874,914 and other patents to Krasner of SnapTrack.
The use of geo-synchronous satellites as a substitute for earth bound base stations in a DGPS system, with carrier phase enhancements for sub-meter accuracies, is also a likely improvement to the RtZF® system that can have a significant effect in urban areas.
Another enhancement that would be possible with dedicated satellites and/or earth bound pseudolites results from the greater control over the information transmitted than is available from the present GPS system. Recognizing that this system could save in excess of 40,000 lives per year in the U.S. alone, the cost of deploying such special purpose stations can easily be justified. For example, say there exists a modulated wave that is 10000 kilometers long, another one which is 1000 km long etc. down to 1 cm. It would then be easy to determine the absolute distance from one point to the other. The integer ambiguity of RTK DGPS would be eliminated. Other types of modulation are of course possible to achieve the desired result of simply eliminating the carrier integer uncertainty that is discussed in many U.S. patents and other literature. This is not meant to be a recommendation but to illustrate that once the decision has been made to provide information to every vehicle that will permit it to always know its location within 10 cm, many technologies will be there to make it happen. The cost savings resulting from eliminating fatalities and serious injuries will easily cover the cost of such technologies many times over. The provision of additional frequencies can also enhance the system and render differential corrections unnecessary. Each frequency from a satellite is diffracted differently by the ionosphere. The properties of the ionosphere can thus be determined if multiple frequencies are transmitted. This will partially be achieved with the launch of the European Galileo GPS satellite system as well as others by Japan, Russia and China in combination with the U.S. GPS system.
It is expected, especially initially, that there will be many holes in the DGPS or GPS and their various implementations that will leave the vehicle without an accurate means of determining its location. The inertial navigation system described above will help in filling these holes but its accuracy is limited to a time period significantly less than about an hour and a distance of less than about 50 miles before it needs correcting. That may not be sufficient to cover the period between DGPS availability. It is therefore contemplated that the RtZF® system will also make use of low cost systems located along the roadways that permit a vehicle to accurately determine its location.
Such a position-determination assistance system would include a plurality of transmitters placed on or alongside a road, with signals from the transmitters being directed to an area in the path of a traveling vehicle to enable the vehicle to determine its position using the transmitted signals and information about the position of the transmitters. Positional information about the transmitters either being previously provided to the vehicle'"'"'s processor, e.g., from a map database, or along with the transmission. The transmitters may be a group of a linked Micropower Impulse Radar (MIR), IR or RF transmitters which direct signals to a common area through which vehicles pass. Alternatively, the transmitters may be a group of a plurality of RFID devices, in which case, one or more interrogators are arranged on the vehicle to cause the RFID devices to direct signals in response to an interrogation signal from the interrogator.
One example of such a system would be to use a group of three Micropower Impulse Radar (MIR) units such as developed by Lawrence Livermore Laboratory.
A MIR operates on very low power and periodically transmits a very short spread spectrum radar pulse. The estimated cost of a MIR is less than $10 even in small quantities. If three such MIR transmitters, 151, 152 and 153, as shown in
Several such readings and position determinations can be made with one approach to the MIR installation, the vehicle need not wait until they all arrive simultaneously. Also the system can be designed so that the signals never arrive at the same time and still provide the same accuracy as long as there is a sufficiently accurate clock on board the vehicle. One way at looking at
The power requirements for the MIR transmitters are sufficiently low that a simple photoelectric cell array can provide sufficient power for most if not all CONUS locations. With this exact location information, the vehicle can become its own DGPS station and can determine the corrections necessary for the GPS. It can also determine the integer ambiguity problem and thereby know the exact number of wave lengths between the vehicle and the satellites or between the vehicle and the MIR or similar station. These calculations can be done on vehicle if there is a connection to a network, for example. This would be particularly efficient as the network, once it had made the calculations for one vehicle, would have a good idea of the result for another nearby vehicle and for other vehicles passing the same spot at a different time. This network can be an ad-hoc or mesh network or the internet using WiMAX, for example. Alternately, the information can be broadcast from the vehicle.
MIR is one of several technologies that can be used to provide precise location determination. Others include the use of an RFID tag that is designed in cooperation with its interrogator to provide a distance to the tag measurement. Such as RFID can be either an active device with an internal battery or solar charger or a passive device obtaining its power from an RF interrogation signal to charge a capacitor or a SAW-based tag operating without power. An alternate and preferred system uses radar or other reflectors where the time of flight can be measured, as disclosed elsewhere herein.
Once a vehicle passes a Precise Positioning Station (PPS) such as the MIR triad described above, the vehicle can communicate this information to surrounding vehicles. If the separation distance between two communicating vehicles can also be determined by the time-of-flight or equivalent method, then the vehicle that has just passed the triad can, in effect, become a satellite equivalent or moving pseudolite. That is, the vehicle sends (such as by reflection so as not to introduce a time delay) its GPS data from the satellite and the receiving vehicle then gets the same message from two sources and the time difference is the time of flight. Finally, if many vehicles are communicating their positions to many other vehicles along with an accuracy of position assessment, each vehicle can use this information along with the calculated separation distances to improve the accuracy of its position determination. In this manner, as the number of such vehicles increases, the accuracy of the entire system increases until an extremely accurate positioning system for all vehicles results. Such a system, since it combines many sources of position information, is tolerant of the failure of any one or even several such sources. Thus, the RtZF® system becomes analogous to the Internet in that it cannot be shut down and the goal of perfection is approached. Some of the problems associated with this concept will be discussed below.
Precise Positioning was described above and relates to methods of locating a vehicle independently of GPS within sub meter accuracy. This can be done using an MIR triads; barcodes painted on the roadway; radar, laser radar or terahertz radar and infrastructure mounted reflectors; RFID markers; or through the use of matching a signature obtained from the environment with a stored signature using, for example, Adaptive Associative Memories (AAM) based on Cellular Neural Networks (CNN), for example.
AAM is a type of neural network that is distinguished in that it can do precise identification from poor and sparse data in contrast to ordinary back propagation neural networks discussed elsewhere herein that generalize and always give an approximate answer. Applications for AAM include: (1) Occupant recognition (face, iris, voice print, fingerprints etc.), and (2) Vehicle location recognition for the RtZF® Precise Positioning System, which is the focus here. In contrast to other PPS systems described above, AAM permits the precise location of a vehicle on a roadway within centimeters without the use of additions to the infrastructure. A radar, laser scanner, or terahertz radar continuously is projected from the vehicle toward the environment, such as the roadway to the side of the vehicle, and from the returned reflected waves it obtains a signature of the passing environment and compares it with a recorded signature using ASM. This signature, for example, can be the distance from the vehicle to the infrastructure which has been normalized for the purpose of signature matching with some method such as the average or some other datum. Thus, it is the relative distance signature that can be compared with a stored signature thus removing the position of the vehicle on the roadway as a variable. When a match is found the distance to a precise object can be determined placing the vehicle precisely on the road in both the longitudinal and lateral dimensions. As discussed above, this can make the vehicle a DGPS station for correction of the GPS errors but it also can be used as the primary location system without GPS.
Other methods can be used to precisely locate a vehicle using the infrastructure and only one preferred method has been described herein. For example, the vertical motion signature of the vehicle can in some cases be used. This could involve determining this signature from the natural road or a pattern of disturbances similar to a rubble strip can be placed in the roadway and sensed by an accelerometer, microphone or other sensor. Even the signature of the magnetic or reflective properties of the roadway or the environment at the side of road can be candidates with the appropriate sensors. Basically, any system that provides a signature indication location that is derived from the infrastructure with appropriate sensors would qualify.
Another method, for example, is to match camera images where again an AAM can be used. Since the vehicle knows approximately where it is, the recorded signature used in the AAM will change as the vehicle moves and thus only a small amount of data need be used at a particular time. The AAM system is fast and relatively simple. Typically twenty data points will be used to determine the match, for example. What follows is a general description of AAM
Associative (context-addressable) memory is frequently dedicated to data search and/or restoration from available fragments. Associative retrieval requires minimal information on sought objects, so such a machine might be used for most complicated tasks of data identification for partially destroyed or corrupted images. It can be applied to authenticity attribution, document falsification detection, message fragment identification in the Internet etc. as well as signature matching with the environment for PPS.
Neural associative memory works due to multi-stability of strong feedback systems. Common models like Hopfield networks and bi-directional associative memory provide memorization by means of computation network weights. It does not corrupt previously stored images. Unfortunately, these networks cannot be widely used because of their low capacity and inefficient physical memory usage. A number M of vectors memorized does not exceed 14% of the number of neurons in the network N. Since a network contains N2 connections, it needs storage of at least 25M2 real weight values. Implementation of this technique can be aided through consultation of International Scientific Research in Kyiv, Ukraine. Cellular architecture can exhaustively solve the problem of physical memory usage. Cellular memories have band-like synaptic matrix. The volume (number of elements) grows linearly with respect to neuron number. This is why cellular neural networks (CNNs) can be useful for very large data processing problems. Pioneering models of associative memories via CNNs were proposed in some earlier works. However, more detailed studies showed some fundamental limitations. Indeed, it has now been shown that the number of images stored is restricted by a cell size. Hence, it does not depend on the number of neurons. A more efficient way of redundancy reduction has also been found due to connection selection after training. This results in the use of only a small part of physical memory without corruption of memorized data. The network after weight selection looks like the cellular one; so by combining cellular training algorithms and weight selection, a novel network paradigm has resulted. It is an adaptive neural paradigm with great memorizing capacity.
At present, some breakthrough associative memories have been implemented in a software package available from the current assignee. The results can be applied for processing of large databases, real-time information retrieval, PPS etc. Other applications for this technology include face, iris, fingerprint, voiceprint, character, signature, etc. recognition.
Vehicle 18 contains two receivers 160,161 for the micropower impulse radar (MIR) implementation of the invention. MIR or ultrawideband (UWB) transmitter devices are placed at locations 151, 152 and 153 respectively. They are linked together with a control wire, not shown, or by a wireless connection such that each device transmits a short radar or RF pulse at a precise timing relative to the others. These pulses can be sent simultaneously or at a precise known delay. Vehicle 18 knows from its map database the existence and location of the three MIR transmitters. The transmitters 151,152 and 153 can either transmit a coded pulse or non-coded pulse. In the case of the coded pulse, the vehicle PPS system will be able to verify that the three transmitters 151, 152, 153 are in fact the ones that appear on the map database. Since the vehicle will know reasonably accurately its location and it is unlikely that other PPS transmitters will be nearby or within range, the coded pulse may not be necessary. Two receivers 160 and 161 are illustrated on vehicle 18. For the MIR implementation, only a single receiver is necessary since the position of the vehicle will be uniquely determined by the time of arrival of the three MIR pulses. A second receiver can be used for redundancy and also to permit the vehicle to determine the angular position of the MIR transmitters as a further check on the system accuracy. This can be done since the relative time of arrival of a pulse from one of the transmitters 151, 152, 153 can be used to determine the distance to each transmitter and by geometry its angular position relative to the vehicle 18. If the pulses are coded, then the direction to the MIR transmitters 151, 152, 153 will also be determinable.
The micropower impulse radar units require battery power or another power mechanism to operate. Since they may be joined together with a wire in order to positively control the timing of the three pulses, a single battery can be used to power all three units. This battery can also be coupled with a solar panel to permit maintenance free operation of the system. Since the MIR transmitters use very small amounts of power, they can operate for many years on a single battery.
Although the MIR systems are relatively inexpensive, on the order of ten dollars each, the installation cost of the system will be significantly higher than the RFID and radar reflector solutions discussed next. The MIR system is also significantly more complex than the RFID system; however, its accuracy can be checked by each vehicle that uses the system. Tying the MIR system to a GPS receiver and using the accurate clock on the GPS satellites as the trigger for the sending of the radar pulses can add additional advantages and complexity. This will permit vehicles passing by to additionally accurately set their clocks to be in synchronization with the GPS clocks. Since the MIR system will know its precise location, all errors in the GPS signals can be automatically corrected and in that case, the MIR system becomes a differential GPS base station. For most implementations, this added complexity is not necessary since the vehicle themselves will be receiving GPS signals and they will also know precisely their location from the triad of MIR transmitters 151, 152, 153.
A considerably simpler alternate approach to the MIR system described above utilizes reflective RFID tags. These tags, when interrogated by an interrogator type of receiver 160, 161, reflect or retransmit after a known delay a modified RF signal with the modification being the identification of the tag. Such tags are described in many patents and books on RFID technology and can be produced for substantially less than one dollar each. The implementation of the RFID system would involve the accurate placement of these tags on known objects on or in connection with infrastructure. These objects could be spots on the highway, posts, signs, sides of buildings, poles, in highway reflectors or structures that are dedicated specifically for this purpose. In fact, any structure that is rigid and unlikely to change position can be used for mounting RFID tags. In downtown Manhattan, building sides, street lights, stoplights, or other existing structures are ideal locations for such tags. A vehicle 18 approaching a triad of such RFID tags represented by 151, 152, 153 would transmit an interrogation pulse from interrogator 160 and/or 161. The pulse would reflect off of, or be retransmitted by, each tag within range and the signal would be received by the same interrogator(s) 160, 161 or other devices on the vehicle. Once again, a single interrogator is sufficient. It is important to note that the range to RFID tags is severely limited unless a source of power is provided. It is very difficult to provide enough power from RF radiation from the interrogator for distances much greater than a few feet. For longer distances, a power source should be provided which can be a battery, connection to a power line, solar power, energy harvested from the environment via vibration, for example, unless the RFID is based on SAW technology. For SAW technology, reading ranges may be somewhat extended. Greater distances can be achieved using reflectors or reflecting antennas.
Electronic circuitry, not shown, associated with the interrogator 160 and/or 161 would determine the precise distance from the vehicle to the RFID tag 151, 152, 153 based on the round trip time of flight and any retransmission delay in the RFID. This will provide the precise distance to the three RFID tags 151, 152, 153. Once again, a second interrogator 161 can also be used, in which case, it could be a receiver only and would provide redundancy information to the main interrogator 160 and also provide a second measure of the distance to each RFID tag. Based on the displacement of the two receivers 160, 161, the angular location of each RFID tag relative into the vehicle can be determined providing further redundant information as to the position of the vehicle relative to the tags.
Radar corner or dihedral reflectors can be placed on poles or other convenient places such that a radar or laser beam pointed upwards at an angle, such as 30 to 45 degrees from the vehicle, will cause the beam to illuminate the reflector and thereby cause a reflection to return to the vehicle. Through well-known methods, the distance to the reflector can be accurately measured with pulse radar, modulated radar and phase measurements or noise radar and correlations measurements. In such a manner, the host vehicle can determine its position relative to one or more such reflectors and if the location of the reflector(s) is known and recorded on the map database, the vehicle can determine its position to within about 2 centimeters. The more reflectors that are illuminated, the better the accuracy of vehicle location determination. The reflectors can be simple corner or dihedral reflectors or a group of reflectors can be provided giving a return code to the host vehicle. A code should not be necessary as the vehicle should know the approximate location of the reflector from map data. A description of dihedral reflectors is set forth in U.S. Pat. No. 7,089,099, incorporated by reference herein. Briefly, a dihedral reflector rotates a polarized beam on reflection by some angle such as 90 degrees. This makes it easier to locate the reflector from other objects that might also reflect the radar or optical beam, or other electromagnetic transmission.
Using the PPS system, a vehicle can precisely determine its location within about two centimeters relative to the MIR, RFID tags or radar and reflectors and since the precise location of these devices has previously been recorded on the map database, the vehicle will be able to determine its precise location on the surface of the earth. With this information, the vehicle will thereafter be able to use the carrier wave phase to maintain its precise knowledge of its location, as discussed above, until the locks on the satellites are lost. This prediction of phase relies on the vehicle system being able to predict the phase of the signal from a given satellite that is reaching a fixed location such as the location that the vehicle was in when it was able to determine its position precisely. This requires an accurate knowledge on the satellite orbits and an accurate clock. Given this information, the vehicle system should be able to determine the phase of a satellite signal at the fixed location and at its new location and, by comparing the phase from such a calculation from each satellite, it should be able to precisely determine its position relative to the fixed location. Errors due to changes in the ionosphere and the vehicle clock accuracy will gradually degrade the accuracy of these calculations. The vehicle 18 can broadcast this information to vehicle 26, for example, permitting a vehicle that has not passed through the PPS triad to also greatly improve the accuracy with which it knows its position. Each vehicle that has recently passed through a PPS triad now becomes a differential GPS station for as long as the satellite locks are maintained assuming a perfect clock on-board the vehicle and a stable ionosphere. Therefore, through inter-vehicle communications, all vehicles in the vicinity can also significantly improve their knowledge of their position accuracy resulting in a system which is extremely redundant and therefore highly reliable and consistent with the “Road to Zero Fatalities”™ process. Once this system is operational, it is expected that the U.S. government and other governments will launch additional GPS type satellites, each with more civilian readable frequencies, or other similar satellite systems, further strengthening the system and adding further redundancy eventually resulting in a highly interconnected system that approaches 100% reliability and, like the Internet, cannot be shut down.
As the system evolves, the problems associated with urban canyons, tunnels, and other obstructions to satellite view will be solved by the placement of large numbers of PPS stations, or other devices providing similar location information.
Another PPS system uses reflected energy from the environment to create a signature that can be matched with a recorded signature using a technology such as adaptive associative memories (AAM), or equivalent including correlation. Since the AAM was discussed above, the correlation system will be discussed here. As the mapping vehicle traverses the roadway, it can record the distance to various roadside objects as a continuous signal having peaks and valleys. In fact, several such signatures can economically be recorded such that regardless of where on the roadway a subsequent vehicle appears, it will record a similar signature. The signature can be enhanced if dual frequency terahertz is used since the reflectance from an object can vary significantly from one terahertz frequency to another depending on the composition of the object. Thus, for one frequency, a metal and a wood object may both be highly reflective while at another frequency, there can be a significant difference. Significantly more information is available when more than one frequency is used. Another preferred approach is to use eye-safe IR.
Using the correlation system, a vehicle will continuously be comparing its received signature at a particular location to the previously recorded signature and shifting the two relative to each other until the best match occurs. Since this will be done continuously and since we will know the velocity of the vehicle, it should never deviate significantly from the recorded position and thus the vehicle will always have a non-GPS method of determining its exact location. There are certain areas where the signature matching may be problematic such as going by a wheat field or the ocean. Fortunately, such wide open spaces are precisely where the GPS satellite system should work best and similarly, the places where the signature method works best is where the GPS has problems. Thus, the systems are complementary. In most places, both systems will work well providing a high degree of redundancy.
Many mathematical methods exist for determining the best shift of the two signatures (the previously recorded one and a new one) and therefore the various correlation methods will not be presented here.
Although the system has been illustrated for use with automobiles, the same system would apply for all vehicles including trucks, trains an even airplanes taxiing on runways. It also would be useful for use with cellular phones and other devices carried by humans. The combination of the PPS system and cellular phones permits the precise location of a cellular phone to be determined within centimeters by an emergency operator receiving a 911 call, for example. Such RFID tags can be inexpensively placed both inside and outside of buildings, for example.
The range of RFID tags is somewhat limited to a few meters for current technology. If there are obstructions preventing a clear view of the RFID tag by the interrogator, the distance becomes less. For some applications where it is desirable to use larger distances, battery power can be provided to the RFID tags. In this case, the interrogator would send a pulse to the tag that would turn on the tag and at a precise, subsequent time, the tag would transmit an identification message. In some cases, the interrogator itself can provide the power to drive the RFID circuitry, in which case the tag would again operate in the transponder mode as opposed to the reflective mode.
The RFID tags discussed herein can be either the electronic circuit or SAW designs.
From the above discussion, those skilled in the art will understand that other devices can be interrogated by a vehicle traveling down the road. Such devices might include various radar types or designs of reflectors, mirrors, other forms of transponders, or other forms of energy reflectors. All such devices are contemplated by this invention and the invention is not limited to be specific examples described. In particular, although various frequencies including radar, terahertz and infrared have been discussed, this invention is not limited to those portions of the electromagnetic spectrum. In particular the X-ray band of frequencies may have some particular advantages for some external and interior imaging applications.
Any communication device can be coupled with an interrogator that utilizes the MIR, radar or RFID PPS system described above. Many devices are now being developed that make use of the Bluetooth communication specification. All such Bluetooth-enabled devices can additionally be outfitted with a PPS or GPS system permitting the location of the Bluetooth device to be positively determined. This enabling technology will permit a base station to communicate with a Bluetooth-enabled or similar device whose location is unknown and have the device transmit back its location. As long as the Bluetooth-enabled device is within the range of the base station or internet, its location can be precisely determined. Thus, the location of mobile equipment in a factory, packages within the airplane cargo section, laptop computers, cell phones, PDAs, and eventually even personal glasses or car keys or any device upon which a Bluetooth-enabled or similar device can be attached can be determined. Actually, this invention is not limited to Bluetooth devices but encompasses any device that can communicate with any other devices. An example of such a Bluetooth device is the Wibree device that sends out a periodic signal that can be received by a receiver that has an internet connection. A ubiquitous internet such as WiMAX, for example, can be such a device. A set of car keys, a pair of glasses in a case, a wallet, a cell phone which has been turned off or whose battery has run down can be equipped with a Wibree type device and its position recorded on the internet, providing the device is in range of a receiver, so that when the owner is searching for the item, he or she need only log onto the internet to find its location. A similar system can be used for any asset regardless how large or small it is and the Wibree device can be independent of external power and yet exist for years on a single battery charge due to its low duty cycle.
Once the location of an object can be determined, many other services can be provided. These include finding the device, or the ability to provide information to that device or to the person accompanying that device such as the location of the nearest bathroom, restaurant, or the ability to provide guided tours or other directions to people traveling to other cities, for example.
A particularly important enhancement to the above-described system uses precise positioning technology independent of GPS. The precise positioning system, also known as the calibration system, generally permits a vehicle to precisely locate itself independently of the IMU or DGPS systems.
One example of this technology involves the use of a radar or lidar and reflector system wherein radar or lidar transceivers are placed on the vehicle that send radar or lidar waves to reflectors that are mounted at the side of road. The location of reflectors either is already precisely known or is determined by the mapping system during data acquisition process. The radar or lidar transceivers transmit a pulse, code or frequency or noise modulated radar or lidar signal to the road-mounted reflectors, typically corner or dihedral reflectors, which reflect a signal back to the radar or lidar transceiver. This permits the radar or lidar system to determine the precise distance from the transceiver to the reflector by either time-of-flight or phase methods. Note that although “radar” will be used below in the illustrations, terahertz or lidar can also be used and thus the word “radar” will be used to cover appropriate parts of the electromagnetic spectrum.
In one possible implementation, each vehicle is equipped with two radar devices operating in the 24-77 GHz portion of the spectrum. Each radar unit will be positioned on the vehicle and can be aimed outward, slightly forward and up toward the sides of the roadway. Poles would be positioned along the roadway at appropriate intervals and would have multiple corner cube or dihedral radar reflectors mounted thereon to thereto, possibly in a vertical alignment. The lowest reflector on the pole can be positioned so that the vehicle radar will illuminate the reflector when the vehicle is in the lane closest to the pole. The highest reflector on the pole can be positioned so that the vehicle radar will illuminate the reflector when the vehicle is in the lane most remote from the pole. The frequency of the positioning of the poles will be determined by such considerations as the availability of light poles or other structures currently in place, the probability of losing access to GPS satellites, the density of vehicle traffic, the accuracy of the IMU and other similar considerations. Initially, rough calculations have found that a spacing of about ¼ mile would likely be acceptable.
If the precise location of the reflectors has been previously determined and is provided on a road map database, then the vehicle can use this information to determine its precise location on the road. In a more typical case, the radar reflectors are installed and the mapping vehicle knows its location precisely from the differential GPS signals and the IMU, which for the mapping vehicle is typically of considerably higher accuracy than will be present in the vehicles that will later use the system. As a result, the mapping vehicle can also map a tunnel, for example, and establish the locations of radar reflectors that will later be used by non-mapping vehicles to determine their precise location when the GPS and differential GPS signals are not available. Similarly, such radar reflectors can be located for an appropriate distance outside of the tunnel to permit an accurate location determination to be made by a vehicle until it acquires the GPS and differential GPS signals. Such a system can also be used in urban canyons and at all locations where the GPS signals can be blocked or are otherwise not available. Since the cost of radar reflectors is very low, it is expected that eventually they will be widely distributed on roads in the U.S.
Use of radar and reflectors for precise positioning is only one of many systems being considered for this purpose. Others include markings on roadway, RFID tags, laser systems, laser radar and reflectors, magnetic tags embedded in the roadway, magnetic tape, etc. The radar and reflector technology has advantages over some systems in that it is not seriously degraded by bad weather conditions, is not affected if covered with snow, does not pose a serious maintenance problem, and other cost and durability features. Any movement in the positioning of the reflectors can be diagnosed from vehicle PPS-mounted systems.
The radar transceivers used are typically mounted on either side of vehicle and pointed upward at between 30 and 60 degrees. They are typically aimed so that they project across the top of the vehicle so that several feet of vertical height can be achieved prior to passing over adjacent lanes where the signal could be blocked by a truck, for example. Other mounting and aiming systems can be used.
The radar reflectors are typically mounted onto a pole, building, overpass, or other convenient structure. They can provide a return code by the placement of several such reflectors such that the reflected pulse contains information that identifies this reflector as a particular reflector on the map database. This can be accomplished in numerous ways including the use of a collection of radar reflectors in a spaced-apart geometric configuration on a radius from the vehicle. The presence or absence of a reflector can provide a returned binary code, for example.
Operation of the system is as follows. A vehicle traveling down a roadway in the vicinity of the reflector poles would transmit radar or lidar pulses at a frequency of perhaps once per microsecond. These radar pulses would be encoded, perhaps with noise or code modulation, so that each vehicle knows exactly what radar or lidar returns are from its transmissions. As the vehicle approaches a reflector pole, it will begin to receive reflections based on the speed of the vehicle. By observing a series of reflections, the vehicle software can select either the maximum amplitude reflection or the average or some other scheme to determine the proper reflection to consider. The radar pulse will also be modulated to permit a distance to the reflector calculation to be made based on the phase of the returned signal or through correlation. Thus, as a vehicle travels down the road and passes a pair of reflector poles on either side of the roadway, for example, it will be able to determine its longitudinal position on the roadway based on the pointing angle of the radar devices and the selected maximum return as described above. It will also be able to determine its lateral position on the roadway based on the measured distance from the radar to the reflector.
Each reflector pole can have multiple reflectors determined by intersections of the radar or lidar beam from the vehicle traveling in the closest and furthest lanes. The spacing of reflectors on the pole would be determined by the pixel diameter of the radar or lidar beam. For example, a typical situation may require reflectors beginning at 4 m from the ground and ending at 12 m with a reflector every one-meter. For the initial demonstrations, it is expected that existing structures will be used. The corner cube or dihedral radar reflectors are very inexpensive so therefore the infrastructure investment will be small as long as existing structures can be used. In the downtown areas of cities, buildings etc. can also be used as reflector locations.
To summarize this aspect of the invention, an inexpensive infrastructure installation concept is provided which will permit a vehicle to send a radar or lidar pulse and receive a reflection wherein the reflection is identifiable as the reflection from the vehicle'"'"'s own radar or lidar and contains information to permit an accurate distance measurement. The vehicle can thus locate itself accurately longitudinally and laterally along the road. A variation of the PPS system using a signature from a continuously reflected laser or radar has been discussed above and will not be repeated here.
Instead of data about each transmitter being generated at 240, general data for transmission could also be generated such as road condition information or traffic information.
A vehicle 246 includes an antenna 248 coupled to a control module, control unit, processor or computer 250. The antenna, which can be an imager, 248 receives transmissions (waves or wireless signals) including transmissions 252 when in range of the transmitters. The processor 250 analyzes the transmissions 252. Such analysis may include a determination as to whether any transmissions are from transmitters within a pre-determined area relative to the vehicle, whether any transmissions are from transmitters situated within a pre-determined distance from the vehicle, whether any transmissions are from transmitters traveling in a direction toward the vehicle'"'"'s current position, whether any transmissions are from transmitters traveling in a direction toward the vehicle'"'"'s projected position based on its current position and velocity, the angle between the transmitter and the vehicle, and any combinations of such determinations. In general, the initial analysis may be any position-based filtering, location-based filtering, and/or motion-based filtering. Other analyses could be whether any transmissions are from particular transmitters which might be dedicated to the transmission of road conditions data, traffic data, map data and the like. Once the processor 250 ascertains a particular transmission from a transmitter of interest (for operation of the vehicle, or for any other pre-determined purpose), it extracts the information coded in the transmission, but preferably does not extract information coded in transmission from transmitters which are not of interest, e.g., those from transmitters situated at a location outside of the pre-determined area. It knows the code because the code is provided by the transmission, i.e., the initial part of the transmission 252a contains data on the location of the transmitter and the code is based on the location of the transmitter. As such, once the initial part of the transmission 252a is received and the location of the transmitter extracted, the code for the remainder of the transmission 252b can be obtained.
In this manner, the extraction of information from radio frequency wave transmission may be limited based on a threshold determination (a filter of sorts) as to whether the transmission is of potential interest, e.g., to the operation of the vehicle based on its position, location and/or motion. To enable this threshold determination from the analysis of the waves or filtering of information, the initial part of the transmission 252a can be provided with positional or location information about the transmitter and information necessitated by the information transferring arrangement (communication protocol data) and the remainder of the transmission 252b provided with additional information of potential interest for operation of the vehicle. The information contained in initial part of each transmission (or set of waves) is extracted to determine whether the information in the final part of the transmission is of interest. If not, the information in the final part of the transmission is not extracted. This reduces processing time and avoids the unnecessary extraction of mostly if not totally irrelevant information. An information filter is therefore provided.
Generating the transmission based on a code derived from the position of the transmitter, and thus the vehicle or infrastructure in which or to which it is fixed, provides significant advantages as discussed above. The code required for spread spectrum, UWB or other communication systems is thus determined according to the position of the transmitter, and can be accomplished in several different ways, some of which are disclosed elsewhere herein. However, use of coded transmissions is not required in all embodiments of the information transferring method and arrangement.
An additional way for vehicle-mounted transmitters is to supply position information to a vehicle at an entrance to a highway or other entry and exit-limited roadway, in a wireless manner as described herein, and deriving the position information about the vehicle based on the initially provided information when the vehicle enters the highway and information about the speed of the vehicle or the distance the vehicle travels. The latter quantities are determined by systems on the vehicle itself. Thus, it becomes possible to extrapolate the current position of the vehicle based on the initially provided position information and the speed and/or traveling distance of the vehicle, using common physics equations relating to motion of an object as known to those skilled in the art. Even if the current position of the vehicle is not precise due to, for example, variations in the highway, the system is still operational and effective since all vehicles on the same highway are determining their position relative to the entrance. This embodiment may be considered a simpler system than described above wherein the position of the vehicle is determined using, for example, GPS-based systems. Basically, all vehicles on the same highway receive only a single wireless transmission when they enter the highway and update their position based on the distance traveled and/or speed of travel.
Further, the antenna 248 serves as a transmitter for transmitting signals generated by the processor 250. The processor 248 is constructed or programmed to generate transmissions or noise signals based on its location, determined by a position determining device 254 in any known manner including those disclosed herein, and encode information about the vehicle in the signals. The information may be an identification marker, the type of vehicle, its direction, its velocity or speed, its proposed course, its occupancy, etc. The processor 248 can encode the information in the signals in a variety of methods as disclosed above in the same manner that the data about the transmitter is encoded. Thus, the processor 248 not only interprets the signals and extracts information, it also is designed to generate appropriate noise or otherwise coded signals which are then sent from the antenna 248.
Consider the case where the automobile becomes a pseudolite or a DGPS equivalent station since it has just determined its precise location from the PPS. Thus the vehicle can broadcast just like a pseudolite. As the vehicle leaves the PPS station, its knowledge of its absolute position will degrade with time depending on the accuracy of its clock and inertial guidance system and perhaps its view of the satellites or other pseudolites. In some cases, it might even be possible to eliminate the need for satellites if sufficient PPS positions exist.
Another point is that the more vehicles that are in the vicinity of a PPS, the higher the likelihood that one of the vehicles will know precisely where it is by being at or close to the PPS and thus the more accurately every vehicle in the vicinity would know its own location. Thus, the more vehicles on the road, the accuracy with which every vehicle knows its location increases. When only a single vehicle is on the road, then it really doesn'"'"'t need to know its position nearly as accurately at least with regard to other vehicles. It may still need to know its accuracy to a comparable extent with regard to the road edges.
5. Radar and Laser Radar Detection and Identification of Objects External to the Vehicle
5.1 Sensing of Non-RtZF® Equipped Objects
Vehicles with the RtZF® system in accordance with the invention ideally should also be able to detect those vehicles that do not have the system as well as pedestrians, animals, bicyclists, and other hazards that may cross the path of the equipped vehicle.
Systems based on radar have suffered from the problem of being able to sufficiently resolve the images which are returned to be able to identify the other vehicles, bridges, etc. except when they are close to the host vehicle. One method used for adaptive cruise control systems is to ignore everything that is not moving. This, of course, leads to accidents if this were used with the instant invention. The problem stems from the resolution achievable with radar unless the antenna is made very large or the object is close. Since this is impractical for use with automobiles, only minimal collision avoidance can be obtained using radar.
Optical systems can provide the proper resolution but may require illumination with a bright light or laser. If the laser is in the optical range, there is a danger of causing eye damage to pedestrians or vehicle operators. At a minimum, it will be distracting and annoying to other vehicle operators. A laser operating in the infrared part of the electromagnetic spectrum avoids the eye danger problem, provided the frequency is sufficiently far from the visible, and, since it will not be seen, it will not be annoying. If the IR light is sufficiently intense to provide effective illumination for the host vehicle, it might be a source of blinding light for the system of another vehicle. Therefore a method of synchronization may be required. This could take the form of an Ethernet protocol, for example, where when one vehicle detects a transmission from another then it backs off and transmits at a random time later. The receiving electronics would then only be active when the return signal is expected. Transmission can also be synchronized based on the GPS time and a scheme whereby two nearby vehicles would transmit at different times. Since the transmission duration can be very short, since the intensity of the IR can be high if it is in the eye-safe range, many adjacent vehicles can transmit each fraction of a second without interfering with each other,
Another problem arises when multiple vehicles are present that transmit infrared at the same time if there is a desire to obtain distance information from the scene. In this case, each vehicle needs to be able to recognize its transmission and not be fooled by transmissions from another vehicle. This can be accomplished, as discussed above, through the modulation scheme. Several such schemes would suffice with a pseudo-noise or code modulation as a preferred method for the present invention. This can also be accomplished if each vehicle accurately knows its position and controls its time of transmission according to an algorithm that time multiplexes transmissions based on the geographical location of the vehicle. Thus, if multiple vehicles are sensed in a given geographical area, they each can control their transmissions based on a common algorithm that uses the GPS coordinates of the vehicle to set the time slot for transmission so as to minimize interference between transmissions from different vehicles. Other multiplexing methods can also be used such as FDMA, CDMA or TDMA, any of which can be based on the geographical location of the vehicles.
Infrared and terahertz also have sufficient resolution so that pattern recognition technologies can be employed to recognize various objects, such as vehicles, in the reflected image as discussed above. infrared has another advantage from the object recognition perspective. All objects radiate and reflect infrared. The hot engine or tires of a moving vehicle in particular are recognizable signals. Thus, if the area around a vehicle is observed with both passive and active infrared, more information can be obtained than from radar, for example. Infrared is less attenuated by fog than optical frequencies, although it is not as good as radar. Infrared is also attenuated by snow but at the proper frequencies it has about five times the range of human sight. Terahertz under some situations has an effective range of as much as several hundred times that of human sight. Note, as with radar, Infrared and terahertz can be modulated with noise, pseudonoise, or other distinctive signal to permit the separation of various reflected signals from different transmitting vehicles.
An example of such an instrument is made by Sumitomo Electric and is sufficient for the purpose here. The Sumitomo product has been demonstrated to detect leaves of a tree at a distance of about 300 meters. The product operates at a 1.5 micron wavelength.
This brings up a philosophical discussion about the trade-offs between radar with greater range and infrared laser radar, or lidar, with more limited range but greater resolution. At what point should driving during bad weather conditions be prohibited? If the goal of Zero Fatalities™ is to be realized, then people should not be permitted to operate their vehicles during dangerous weather conditions. This may require closing roads and highways prior to the start of such conditions. Under such a policy, a system which accurately returns images of obstacles on the roadway that are two to five times the visual distance should be adequate. In such a case, radar would not be necessary.
5.2 Laser and Terahertz Radar Scanning System
Note, when the term scanner is used herein, it is not meant to imply that the beam is so narrow as to require a back and forth motion (a scan) in order to completely illuminate an object of interest. To the contrary, inventions herein are not limited to a particular beam diameter other than that required for eye safety. Also a scanner may be limited to an angular motion that just covers a vehicle located 100 meters, for example, from the transmitting vehicle, which may involve no angular motion of the scanner at all, or to an angular motion that covers 90 or more degrees of the space surrounding the transmitting vehicle. Through the use of high-powered lasers and appropriate optics, an eye safe laser beam can be created that is 5 cm in diameter, for example, with a divergence angle less than one degree. Such an infrared spotlight requires very little angular motion to illuminate a vehicle at 100 meters, for example.
Generally herein, when laser radar, or lidar, is used it will also mean a system based on terahertz where appropriate. The laser radar or lidar scanner will return information as to distance to an object in the scanned field, e.g., laser beam reflections will be indicative of presence of object in path of laser beam 104 and from these reflections, information such as the distance between the vehicle and the object can be obtained. This will cover all objects that are on or adjacent to the highway. The laser pulse can be a pixel that is two centimeters or 1 meter in diameter at 50 meters, for example and that pixel diameter can be controlled by the appropriate optical system that can include adaptive optics and liquid lenses (such as described in “Liquid lens promises cheap gadget optics”, NewScientist.com news service, Mar. 8, 2004).
The scanner should scan the entire road at such a speed that motion of the car can be considered insignificant. Alternately, a separate aiming system that operates at a much lower speed, but at a speed to permit compensation for the car angle changes, may be provided. Such an aiming system is also necessary due to the fact that the road curves up and down. Therefore two scanning methods, one a slow, but for large angle motion and the other fast but for small angles may be required. The large angular system requires a motor drive while the small angular system can be accomplished through the use of an acoustic wave system, such as Lithium Niobate (LiNbO3), which is used to drive a crystal which has a large refractive index such as Tellurium dioxide. Other acoustic optical systems can also be used as scanners.
For these systems, frequently some means is needed to stabilize the image and to isolate it from vehicle vibrations. Several such stabilization systems have been used in the past and would be applicable here including a gyroscopic system that basically isolates the imaging system from such vibrations and keeps it properly pointed, a piezoelectric system that performs similarly, or the process can be accomplished in software where the image is collected regardless of the vibration but where the image covers a wider field of view then is necessary and software is used to select the region of interest.
Alternately, two systems can be used, a radar system for interrogating large areas and a laser radar for imaging smaller areas. Either or both systems can be range gated and noise or pseudonoise modulated.
The laser radar scanner can be set up in conjunction with a range gate 106 so that once it finds an object, the range can be narrowed so that only that object and other objects at the same range, 65 to 75 feet for example, are allowed to pass to the receiver. In this way, an image of a vehicle can be separated from the rest of the scene for identification by pattern recognition software 108. Once the image of the particular object has been captured, the range gate is broadened, to about 20 to 500 feet for example, and the process repeated for another object. In this manner, all objects in the field of interest to the vehicle can be separated and individually imaged and identified. Alternately, a scheme based on velocity can be used to separate a part of one object from the background or from other objects. The field of interest, of course, is the field where all objects with which the vehicle can potentially collide reside. Particular known and mapped features on the highway can be used as aids to the scanning system so that the pitch and perhaps roll angles of the vehicle can be taken into account.
Once the identity of the object is known, the potential for a collision between the vehicle and that object and/or consequences of a potential collision with that object are assessed, e.g., by a control module, control unit or processor 112. If collision is deemed likely, countermeasures are effected 114, e.g., activation of a driver alert system and/or activation of a vehicle control system to alter the travel of the vehicle (as discussed elsewhere herein).
Range gates can be achieved as high speed shutters by a number of devices such as liquid crystals, garnet films, Kerr and Pockel cells or as preferred herein as described in patents and patent applications of 3DV Systems Ltd., Yokneam, Israel including U.S. Pat. No. 6,327,073, U.S. Pat. No. 6,483,094, US2002/0185590, WO98/39790, WO97/01111, WO97/01112 and WO97/01113.
Prior to the time that all vehicles are equipped with the RtZF® system described above, roadways will consist of a mix of vehicles. In this period, it will not be possible to totally eliminate accidents. It will be possible to minimize the probability of having an accident however, if a laser radar system similar to that described in U.S. Pat. No. 5,529,138 (Shaw) with some significant modifications is used, or those described more recently in various patents and patent applications of Ford Global Technologies such as U.S. Pat. Nos. 6,690,017 and 6,730,913, and U.S. Pat. Appl. Publ. Nos. 2003/0034462, 2003/0155513 and 2003/0036881. It is correctly perceived by Shaw that the dimensions of a radar beam are too large to permit distinguishing various objects which may be on the roadway in the path of the instant vehicle. Laser radar provides the necessary resolution that is not provided by radar. Laser radar as used in the present invention however would acquire significantly more data than anticipated by Shaw. Sufficient data in fact would be attained to permit the acquisition of a three-dimensional image of all objects in the field of view. The X and Y dimensions of such objects would, of course, be determined knowing the angular orientation of the laser radar beam. The longitudinal or Z dimension can be obtained by such methods as time-of-flight of the laser beam to a particular point on the object and reflected back to the detector, by phase methods or by range gating. All such methods are described elsewhere herein and in patents listed above.
At least two methods are available for resolving the longitudinal dimension for each of the pixels in the image. In one method, a laser radar pulse having a pulse width of one to ten nanoseconds, for example, can be transmitted toward the area of interest and as soon as the reflection is received and the time-of-flight determined, a new pulse would be sent at a slightly different angular orientation. The laser, therefore, would be acting as a scanner covering the field of interest. A single detector could then be used, if the pixel is sufficiently small, since it would know which pixel was being illuminated. The distance to the reflection point could be determined by time-of-flight thus giving the longitudinal distance to all points in view on the object.
Alternately, the entire area of interest can be illuminated and an image focused on a CCD or CMOS array. By checking the time-of-flight to each pixel, one at a time, the distance to that point on the vehicle would be determined. A variation of this would be to use a garnet crystal as a pixel shutter and only a single detector. In this case, the garnet crystal would permit the illumination to pass through one pixel at a time through to a detector. A preferred method, however, for this invention is to use range gating as described elsewhere herein.
Other methods of associating a distance to a particular reflection point, of course, can now be performed by those skilled in the art including variations of the above ideas using a pixel mixing device (such as described in Schwarte, R. “A New Powerful Sensory Tool in Automotive Safety Systems Based on PMD-Technology”, S-TEC GmbH Proceedings of the AMAA 2000) or variations in pixel illumination and shutter open time to determine distance through comparison of range gated received reflected light. In the laser scanning cases, the total power required from the laser is significantly less than in the area illumination design. However, the ability to correctly change the direction of the laser beam in a sufficiently short period of time complicates the scanning design. The system can work approximately as follows: The entire area in front of the instant vehicle, perhaps as much as a full 180 degree arc in the horizontal plane can be scanned for objects using either radar or laser radar. Once one or more objects had been located, the scanning range can be severely limited to basically cover that particular object and some surrounding space using laser radar. Based on the range to that object, a range gate can be used to eliminate all background and perhaps interference from other objects. In this manner, a very clear picture or image of the object of interest can be obtained as well as its location and, through the use of a neural network, combination neural network or optical correlation or other pattern recognition system, the identity of the object can be ascertained as to whether it is a sign, a truck, an animal, a person, an automobile or other object. The identification of the object will permit an estimate to be made of the object'"'"'s mass and thus the severity of any potential collision.
Once a pending collision is identified, this information can be made available to the driver and if the driver ceases to heed the warning, control of the vehicle could be taken from him or her by the system. The actual usurpation of vehicle control, however, is unlikely initially since there are many situations on the highway where the potential for a collision cannot be accurately ascertained. Consequently, this system can be thought of as an interim solution until all vehicles have the RtZF® system described above.
To use the laser radar in a scanning mode requires some mechanism for changing the direction of the emitted pulses of light. One acoustic-optic method of using an ultrasonic wave to change the diffraction angle of a Tellurium dioxide crystal is disclosed elsewhere herein. This can also be done in a variety of other ways such as through the use of a spinning multifaceted mirror, such as is common with laser scanners and printers. This mirror would control the horizontal scanning, for example, with the vertical scanning controlled though a stepping motor or the angles of the different facets of the mirror can be different to slightly alter the direction of the scan, or by other methods known in the art. Alternately, one or more piezoelectric materials can be used to cause the laser radar transmitter to rotate about a pivot point. A rotating laser system, such as described in Shaw is the least desirable of the available methods due to the difficulty in obtaining a good electrical connection between the laser and the vehicle while the laser is spinning at a very high angular velocity. Another promising technology is to use MEMS mirrors to deflect the laser beam in one or two dimensions. A newer product is the Digital Light Processor (DLP) from Texas Instruments which contains up to several million MEMS mirrors which can be rotated through an angle of up to 12 degrees. Although intended for displays, this device can be used to control the direction(s) of beams from a laser illuminator. The plus or minus 12 degree limitation can be expanded through optics but in itself, it is probably sufficient. See US published patent application No. 20050278098 for more details.
Although the system described above is intended for collision avoidance or at least the notification of a potential collision, when the roadway is populated by vehicles having the RtZF® system and vehicles which do not, its use is still desirable after all vehicles are properly equipped. It can be used to search for animals or other objects which may be on or crossing the highway, a box dropping off of a truck for example, a person crossing the road who is not paying attention to traffic. Motorcycles, bicycles, and other non-RtZF® equipped vehicles can also be monitored.
One significant problem with all previous collision avoidance systems which use radar or laser radar systems to predict impacts with vehicles, is the inability to know whether the vehicle that is being interrogated is located on the highway or is off the road. In at least one system of the present invention, the location of the road at any distance ahead of the vehicle would be known precisely from the sub-meter accuracy maps, so that the scanning system can ignore, for example, all vehicles on lanes where there is a physical barrier separating the lanes from the lane on which the subject vehicle is traveling. This, of course, is a common situation on super highways. Similarly, a parked vehicle on the side of the road would not be confused with a stopped vehicle that is in the lane of travel of the subject vehicle when the road is curving. This permits the subject invention to be used for automatic cruise control. In contrast with radar systems, it does not require that vehicles in the path of the subject vehicle be moving, so that high speed impacts into stalled traffic can be avoided.
If a system with a broader beam to illuminate a larger area on the road in front of the subject vehicle is used, with the subsequent focusing of this image onto a CCD or CMOS array, this has an advantage of permitting a comparison of the passive infrared signal and the reflection of the laser radar active infrared. Metal objects, for example appear cold to passive infrared. This permits another parameter to be used to differentiate metallic objects from non-metallic objects such as foliage or animals such as deer. The breadth of the beam can be controlled and thereby a particular object can be accurately illuminated. With this system, the speed with which the beam steering is accomplished can be much slower. Both systems can be combined into the maximum amount of information to be available to the system.
Through the use of range gating, objects can be relatively isolated from the environment surrounding it other than for the section of highway which is at the same distance. For many cases, a properly trained neural network or other pattern recognition system can use this data and identify the objects. An alternate approach is to use the Fourier transform of the scene as input to the neural network or other pattern recognition system. The advantages of this latter approach are that the particular location of the vehicle in the image is not critical for identification. Note that the Fourier transform can be accomplished optically and optically compared with stored transforms using a garnet crystal or garnet films, for example, as disclosed in U.S. Pat. No. 5,473,466.
At such time, when the system can take control of the vehicle, it will be possible to have much higher speed travel. In such cases all vehicles on the controlled roadway will need to have the RtZF® or similar system as described above. Fourier transforms of the objects of interest can be done optically though the use of a diffraction system. The Fourier transform of the scene can then be compared with the library of the Fourier transforms of all potential objects and, through a system used in military target recognition, multiple objects can be recognized and the system then focused onto one object at a time to determine the degree of threat that it poses.
Of particular importance is the use of a high powered eye-safe laser radar such as a 30 to 100 watt laser diode in an expanded beam form to penetrate fog, rain and snow through the use of range gating. If a several centimeter diameter beam is projected from the vehicle in the form of pulses of from 1 to 10 nanoseconds long, for example, and the reflected radiation is blocked except that from the region of interest, an image can still be captured even though it cannot be seen by the human eye. This technique significantly expands the interrogation range of the system and, when coupled with the other imaging advantages of laser radar, offers a competitive system to radar and may in fact render the automotive use or radar unnecessary. One method is to use the techniques described in the patents to 3DV listed above. In one case, for example, if the vehicle wishes to interrogate an area 250 feet ahead, a 10 nanosecond square wave signal can be used to control the shutter which is used both for transmission and reception and where the off period can be 480 nanoseconds. This can be repeated until sufficient energy has been accumulated to provide for a good image. In this connection, a high dynamic range camera may be used such as that manufactured by IMS chips of Stuttgart, Germany as mentioned above. Such a camera is now available with a dynamic range of 160 db. According to IMS, the imager can be doped to significantly increase its sensitivity to IR,
These advantages are also enhanced when the laser radar system described herein is used along with the other features of the RtZF® system such as accurate maps and accurate location determination. The forward-looking laser radar system can thus concentrate its attention to the known position of the roadway ahead rather than on areas where there can be no hazardous obstacles or threatening vehicles.
5.3 Blind Spot Detection
The RtZF® system of this invention also can eliminate the need for blind spot detectors such as discussed in U.S. Pat. No. 5,530,447. Alternately, if a subset of the complete RtZF® system is implemented, as is expected in the initial period, the RtZF® system can be made compatible with the blind spot detector described in the '"'"'447 patent.
One preferred implementation for blind spot monitoring as well as for monitoring other areas near the vehicle is the use of range-gated laser radar using a high power laser diode and appropriate optics to expand the laser beam to the point where the transmitted infrared energy per square millimeter is below eye safety limits. Such a system is described above
5.4 Anticipatory Sensing—Smart Airbags, Evolution of the System
A key to anticipating accidents is to be able to recognize and categorize objects that are about to impact a vehicle as well as their relative velocity. As set forth herein and in the current assignee'"'"'s patents and patent applications, this can best be done using a pattern recognition system such as a neural network, combination neural network, optical correlation system, sensor fusion and related technologies. The data for such a neural network can be derived from a camera image but such an image can be overwhelmed by reflected light from the sun. In fact, lighting variations in general plague camera-based images resulting in false classifications or even no classification. Additionally, camera-based systems are defeated by poor visibility conditions and, additionally, have interference problems when multiple vehicles have the same system which may require a synchronization taking time away from the critical anticipatory sensing function.
To solve these problems, imaging systems based on millimeter wave radar, laser radar (lidar) and more recently terahertz radar can be used. All three systems generally work for anticipatory sensors since the objects are near the vehicle where even infrared scanning laser radar in a non-range gated mode has sufficient range in fog. Millimeter wave radar is expensive and to obtain precise images a narrow beam is required resulting in large scanning antennas. Laser radar systems are less expensive and since the beams are formed using optic technology they are smaller and easier to manipulate.
When computational power is limited, it is desirable to determine the minimum number of pixels that are required to identify an approaching object with sufficient accuracy to make the decision to take evasive action or to deploy a passive restraint such as an airbag. In one military study for anti-tank missiles, it was found that a total of 25 pixels are all that is required to identify a tank on a battlefield. For optical occupant detection within a vehicle, thousands of pixels are typically used. Experiments indicate that by limiting the number of horizontal scans to three to five, with on the order of 100 to 300 pixels per scan that sufficient information is available to find an object near to the vehicle and in most cases to identify the object. Once the object has been located then the scan can be confined to the position of the object and the number of pixels available for analysis substantially increases. There are obviously many algorithms that can be developed and applied to this problem and it is therefore left to those skilled in the art. At least one invention is based on the fact that a reasonable number of pixels can be obtained from the reflections of electromagnetic energy from an object to render each of the proposed systems practical for locating, identifying and determining the relative velocity of an object in the vicinity of a vehicle that poses a threat to impact the vehicle so that evasive action can be taken or a passive restraint deployed. See the discussion in section 5.5 below for a preferred implementation.
The RtZF® system is also capable of enhancing other vehicle safety systems. In particular, by knowing the location and velocity of other vehicles, for those cases where an accident cannot be avoided, the RtZF® system will in general be able to anticipate a crash and assessment the crash severity using, for example, neural network technology. Even with a limited implementation of the RtZF® system, a significant improvement in smart airbag technology results when used in conjunction with a collision avoidance system such as described in Shaw (U.S. Pat. Nos. 5,314,037 and 5,529,138) and a neural network anticipatory sensing algorithm such as disclosed in U.S. Pat. No. 6,343,810. A further enhancement would be to code a vehicle-to-vehicle communication signal from RtZF® system-equipped vehicles with information that includes the size and approximate weight of the vehicle. Then, if an accident is inevitable, the severity can also be accurately anticipated and the smart airbag tailored to the pending event. Information on the type, size and mass of a vehicle can also be implemented as an RFID tag and made part of the license plate. The type can indicate a vehicle having privileges such as an ambulance, fire truck or police vehicle.
Recent developments by Mobileye (www.mobileye.com) describe a method for obtaining the distance to an object and thus the relative velocity. Although this technique has many limitations, it may be useful in some implementations of one or more of the current inventions.
A further recent development is reported in U.S. patent application publication No. 20030154010, as well as other patents and patent publications assigned to Ford Global Technologies including U.S. Pat. Nos. 6,452,535, 6,480,144, 6,498,972, 6,650,983, 6,568,754, 6,628,227, 6,650,984, 6,728,617, 6,757,611, 6,775,605, 6,801,843, 6,819,991, 20030060980, 20030060956, 20030100982, 20030154011, 20040019420, 20040093141, 20040107033, 20040111200, and 20040117091. In the disclosures herein, emphasis has been placed on identifying a potentially threatening object and once identified, the properties of the object such as its size and mass can be determined. An inferior system can be developed as described in U.S. patent application publication No. 20030154010 where only the size is determined. In inventions described herein, the size is inherently determined during the process of imaging the object and identifying it. Also, the Ford patent publications mention the combined use of a radar or a lidar and a camera system. Combined use of radar and a camera is anticipated herein and disclosed in the current assignee'"'"'s patents.
Another recent development by the U.S. Air Force uses a high powered infrared laser operating at wavelengths greater than 1.5 microns and a focal plane array as is reported in “Three-Dimensional Imaging” in AFRL Technology Horizons, April 2004. Such a system is probably too expensive at this time for automotive applications. This development illustrates the fact that it is not necessary to limit the lidar to the near infrared part of the spectrum and in fact, the further that the wavelength is away from the visible spectrum, the higher the power permitted to be transmitted. Also, nothing prevents the use of multiple frequencies as another method of providing isolation from transmissions from vehicles in the vicinity. As mentioned above for timing transmissions, the GPS system can also be used to control the frequency of transmission thus using frequency as a method to prevent interference. The use of polarizing filters to transmit polarized infrared is another method to provide isolation between different vehicles with the same or similar systems. The polarization angle can be a function of the GPS location of the vehicle.
It is an express intention of some of the inventions herein to provide a system that can be used both in daytime and at night. Other systems are intended solely for night vision such as those disclosed in U.S. Pat. No. 6,730,913, U.S. Pat. No. 6,690,017 and U.S. Pat. No. 6,725,139. Note that the use of the direction of travel as a method of determining when to transmit infrared radiation, as disclosed in these and other Ford Global patents and patent applications, can be useful but it fails to solve the problem of the transmissions from two vehicles traveling in the same vicinity and direction from receiving reflections from each others'"'"' transmissions. If the directional approach is used, then some other method is required such as coding the pulses, for example.
U.S. Pat. No. 6,730,913 and U.S. Pat. No. 6,774,367 are representative of a series of patents awarded to Ford Global Technologies as discussed above. These patents describe range gating as disclosed in the current assignee'"'"'s earlier patents. An intent is to supplement the headlights with a night vision system for illuminating objects on the roadway in the path of the vehicle but are not seen by the driver and displaying these objects in a heads-up display. No attempt is made to locate the eyes of the driver and therefore the display cannot place the objects where they would normally be located in the driver'"'"'s field of view as disclosed in the current assignee'"'"'s patents. Experiments have shown that without this feature, a night vision system is of little value and may even distract the driver to where his or her ability to operate the motor vehicle is degraded. Other differences in the '"'"'913 and '"'"'367 patent systems include an attempt to compensate for falloff in illumination due to distance, neglecting a similar and potentially more serious falloff due to scattering due to fog etc. In at least one of the inventions disclosed herein, no attempt is made to achieve this compensation in a systematic manner but rather the exposure is adjusted so that a sufficiently bright image is achieved to permit object identification regardless of the cause of the attenuation. Furthermore, in at least one embodiment, a high dynamic range camera is used which automatically compensates for much of the attenuation and thus permits the minimum exposure requirements for achieving an adequate image. In at least one of the inventions disclosed herein, the system is used both at night and in the daytime for locating and identifying objects and, in some cases, initiating an alarm or even taking control of the vehicle to avoid accidents. None of these objects are disclosed in the '"'"'913 or '"'"'367 patents and related patents. Additionally, US20030155513, also part of this series of Ford Global patents and applications, describes increasing the illumination intensity based on distance to the desired field of view. In at least one of the inventions disclosed herein, the illumination intensity is limited by eye safety considerations rather than distance to the object of interest. If sufficient illumination is not available on one pulse, additional pulses are provided until sufficient illumination to achieve an adequate exposure is achieved.
If the laser beam diverges, then the amount of radiation per square centimeter illuminating a surface will be a function of the distance of that surface from the transmitter. If that distance can be measured, then the transmitted power can be increased while keeping the radiation per square centimeter below the eye safe limits. Using this technique, the amount of radiated power can be greatly increased thus enhancing the range of the system in daylight and in bad weather. A lower power pulse would precede a high power pulse transmitted in a given direction and the distance measured to a reflective object would be measured and the transmitted power adjusted appropriately. If a human begins to intersect the path of transmission, the distance to the human would be measured before he or she could put his or her eye into the transmission path and the power can be reduced to remain within the safety standards.
It is also important to point out that the inventions disclosed herein that use lidar (laser radar or ladar) can be used in a scanning mode when the area to be covered is larger than the beam diameter or in a pointing mode when the beam diameter is sufficient to illuminate the target of interest, or a combination thereof.
It can be seen from the above discussion that the RtZF® system will evolve to solve many safety, vehicle control and ITS problems. Even such technologies as steering and drive-by-wire will be enhanced by the RtZF® system in accordance with invention since it will automatically adjust for failures in these systems and prevent accidents.
In the case where the vehicle is an airplane, the new ADS-B technology will permit all equipped planes to be aware of other similarly equipped planes and other ground-based vehicles through vehicle-to-vehicle communication. However, many commercial and especially general aviation planes and airport-based ground vehicles will not be equipped with the system and thus the ADS-B collision avoidance systems will not be available to prevent collisions, particularly on the ground at airports. In addition, there have been incidents in recent years when a plane is traveling on the wrong runway or on a taxiway that has objects in the plane'"'"'s path that the plane is unable to see or sense the error or objects. Therefore, a scanning system as disclosed herein is appropriate to solve these problems. Although several such systems can be used based on radar, laser radar etc., one preferred system using laser radar in the eye-safe part of the electromagnetic spectrum will be discussed here as a non-limiting preferred example.
For this implementation, the vehicle can project a bright spotlight in the eye-safe infrared part of the spectrum to illuminate its path. By using infrared, the light emitted by the plane will not distract pilots of other planes, yet it will brightly illuminate the path of the plane. Of course, visible light or even radar can also be used and this invention is not limited to use of the IR portion of the spectrum.
The reflected part of the illumination can be captured by an imager and analyzed using a pattern recognition system such as neural networks or optical correlation (see U.S. Pat. No. 5,473,466) to determine whether any objects exist in the plane'"'"'s path. If an object is discovered, it can be projected onto a heads-up display approximately in the location where the pilot would see it if he was able to do so. This might require the monitoring of the location of the head or eyes of the pilot which would require additional equipment. In any case, the displayed object can be emphasized to get the attention of the pilot, or other occupant of the vehicle, and a reactive system activated. For example, an alarm can be sounded and/or a warning displayed. When the visibility is poor, range gating can be used to reduce the effect of the poor visibility. In this case, only data about objects within a predetermined range from the vehicle would be obtained.
5.5 A Preferred Implementation
In some embodiments, it may be important to assure that the lens through which the laser radar radiation passes is clean. As a minimum, a diagnostic system is required to inform the RtZF® or other system that the lens are soiled and therefore the laser radar system cannot be relied upon. Additionally, in some applications, means are provided to clean one or more of the lens or to remove the soiled surface. In the latter case, a roll of thin film can be provided which, upon the detection of a spoiled lens, rolls up a portion of the film and thereby provides a new clean surface. When the roll is used up it can be replaced. Other systems provide one or more cleaning methods such as a small wiper or the laser radar unit can move the lens into a cleaning station. Many other methods are of course possible and the invention here is basically concerned with ascertaining that the lens is clean and if not informing the system of this fact and, in some cases, cleaning or removing the soiled surface. The lens can also be coated with a coating that resists soiling as disclosed in U.S. Pat. No. 7,136,494, U.S. Pat. No. 6,991,339 and U.S. Pat. No. 6,193,378.
Note that although laser radar and radar have been discussed separately, in some implementations, it is desirable to use both a radar system and a laser radar system. Such a case can be where the laser radar system is not capable to achieve sufficient range in adverse weather whereas the radar has the requisite range but insufficient resolution. The radar unit can provide a warning that a potentially dangerous situation exists and thus the vehicle speed should be reduced until the laser radar device and obtain an image with sufficient resolution to permit an assessment of the extent of the danger and determine whether appropriate actions should be undertaken.
6. The RtZF® System
6.1 Road Departure
The system shown in
Map database 48 works in conjunction with a navigation system 46 to provide a warning to the driver when he or she is about to run off the road, cross a center (yellow) line, run a stop sign, or run a red stoplight. The map database 48 contains a map of the roadway to an accuracy of 2 cm (1 σ), i.e., data on the edges of the lanes of the roadway and the edges of the roadway, and the location of all stop signs and stoplights and other traffic control devices such as other types of road signs. Another sensor, not shown, provides input to the vehicle indicating that an approaching stoplight is red, yellow or green. Navigation system 46 is coupled to the GPS and DGPS processing system 42. For this simple system, the driver is warned if any of the above events is detected by a driver warning system 45 coupled to the navigation system 46. The driver warning system 45 can be an alarm, light, buzzer or other audible noise, or, preferably, a simulated rumble strip for yellow line and “running off of road” situations and a combined light and alarm for the stop sign and stoplight infractions.
One implementation of the system 50 is as a system for determining accurate position of an object, whether a vehicle or another object the position of which is desired, such as a cell phone or emergency locator device. This positioning system would therefore include a GPS positioning system arranged to communicate with one or more satellites 2 to obtain GPS signals therefrom, and which may be incorporated into the GPS and DGPS processing system 42 in the integral, combined unit 40. A correction unit may also be included in the unit 40, e.g., in the GPS and DGPS processing system 42 which receives and/or derives positional corrections for positional data derived from the GPS signals to thereby improve accuracy of the position of the object provided by the GPS positioning system, for example, using signals from one or more of the DGPS satellites 30. A notification system, such as driver warning system 45, is coupled to the correction unit and is designed to notify a person concerned with the position of the object about the current position of the object. Navigation system 46 is coupled to the correction unit for receiving and acting upon the accurate positional information of the object provided by the correction unit, and as shown, is integrated into the common system 50. The optional map database 48 is coupled to the navigation system 46 which may then receive information about a travel lane the vehicle is traveling on and guide an operator of the vehicle based on the accurate positional information and travel lane information. In this case, the warning system would notify an operator of the vehicle of the position of the vehicle to prevent accidents involving the vehicle. In one embodiment, a display displays the position of the vehicle on a map along with the position of other vehicles to the driver or other personnel interested in the traffic on roads.
The correction unit 42 may be designed to communicate with satellites to receive positional corrections therefrom and/or with ground base stations to receive positional corrections therefrom. As discussed below with reference to
6.2 Accident Avoidance
As illustrated in
Infrastructure communication system 58 permits bi-directional communication between the host vehicle and the infrastructure and includes such information transfer as updates to the digital maps, weather information, road condition information, hazard information, congestion information, temporary signs and warnings, and any other information which can improve the safety of the vehicle highway system.
Cameras 60 are used generally for interrogating environment nearby the host vehicle for such functions as blind spot monitoring, backup warnings, anticipatory crash sensing, visibility determination, lane following, and any other visual information which is desirable for improving the safety of the vehicle highway system. Generally, the cameras will be sensitive to infrared and/or visible light, however, in some cases a passive infrared camera will the used to detect the presence of animate bodies such as deer or people on the roadway in front of the vehicle. Frequently, infrared or visible illumination will be provided by the host vehicle. In the preferred system, high brightness eye-safe IR will be used.
Radar 62 is primarily used to scan an environment close to and further from the vehicle than the range of the cameras and to provide an initial warning of potential obstacles in the path of the vehicle. The radar 62 can also be used when conditions of a reduced visibility are present to provide advance warning to the vehicle of obstacles hidden by rain, fog, snow etc. Pulsed, continuous wave, noise or micropower impulse radar systems can be used as appropriate. Also, Doppler radar principles can be used to determine the object to host vehicle relative velocity.
Laser or terahertz radar 64 is primarily used to illuminate potential hazardous objects in the path of the vehicle. Since the vehicle will be operating on accurate mapped roads, the precise location of objects discovered by the radar or camera systems can be determined using range gating and scanning laser radar as described above or by phase techniques.
The driver warning system 66 provides visual and/or audible warning messages to the driver or others that a hazard exists. In addition to activating a warning system within the vehicle, this system can activate sound and/or light systems to warn other people, animals, or vehicles of a pending hazardous condition. In such cases, the warning system could activate the vehicle headlights, tail lights, horn and/or the vehicle-to-vehicle, Internet or infrastructure communication system to inform other vehicles, a traffic control station or other base station. This system will be important during the early stages of implementation of RtZF®, however as more and more vehicles are equipped with the system, there will be less need to warn the driver or others of potential problems.
Map database subsystem 68, which could reside on an external memory module, will contain all of the map information such as road edges up to 2 cm accuracy, the locations of stop signs, stoplights, lane markers etc. as described above. The fundamental map data can be organized on read-only magnetic or optical memory with a read/write associated memory for storing map update information. Alternatively, the map information can be stored on rewritable media that can be updated with information from the infrastructure communication subsystem 58. This updating can take place while the vehicle is being operated or, alternatively, while the vehicle is parked in a garage or on the street.
Three servos are provided for controlling the vehicle during the later stages of implementation of the RtZF® product and include a brake servo 70, a steering servo 72, and a throttle servo 74. The vehicle can be controlled using deterministic, fuzzy logic, neural network or, preferably, neural-fuzzy algorithms.
As a check on the inertial system, a velocity sensor 76 based on a wheel speed sensor, or ground speed monitoring system using lasers, radar or ultrasonics, for example, can be provided for the system. A radar velocity meter is a device which transmits a noise modulated radar pulse toward the ground at an angle to the vertical and measures the Doppler velocity of the returned signal to provide an accurate measure of the vehicle velocity relative to the ground. Another radar device can be designed which measures the displacement of the vehicle. Other modulation techniques and other radar systems can be used to achieve similar results. Other systems are preferably used for this purpose such as the GPS/DGPS or precise position systems.
The inertial navigation system (INS), sometimes called the inertial reference unit or IRU, comprises one or more accelerometers 78 and one or more gyroscopes 80. Usually, three accelerometers would be required to provide the vehicle acceleration in the latitude, longitude and vertical directions and three gyroscopes would be required to provide the angular rate about the pitch, yaw and roll axes. In general, a gyroscope would measure the angular rate or angular velocity. Angular acceleration may be obtained by differentiating the angular rate.
A gyroscope 80, as used herein in the IRU, includes all kinds of gyroscopes such as MEMS-based gyroscopes, fiber optic gyroscopes (FOG) and accelerometer-based gyroscopes.
Accelerometer-based gyroscopes encompass a situation where two accelerometers are placed apart and the difference in the acceleration is used to determine angular acceleration and a situation where an accelerometer is placed on a vibrating structure and the Coriolis effect is used to obtain the angular velocity.
The possibility of an accelerometer-based gyroscope 80 in the IRU is made possible by construction of a suitable gyroscope by Interstate Electronics Corporation (IEC). IEC manufactures IMUs in volume based on μSCIRAS (micro-machined Silicon Coriolis Inertial Rate and Acceleration Sensor) accelerometers. Detailed information about this device can be found at the IEC website at iechome.com.
There are two ways to measure angular velocity (acceleration) using accelerometers. The first way involves installing the accelerometers at a distance from one another and calculating the angular velocity by the difference of readings of the accelerometers using dependencies between the centrifugal and tangential accelerations and the angular velocity/acceleration. This way requires significant accuracy of the accelerometers.
The second way is based on the measurement of the Coriolis acceleration that arises when the mass of the sensing element moves at a relative linear speed and the whole device performs a transportation rotation about the perpendicular axis. This principle is a basis of all mechanical gyroscopes, including micromachined ones. The difference of this device is that the micromachined devices aggregate the linear oscillation excitation system and the Coriolis acceleration measurement system, while two separate devices are used in the proposed second method. The source of linear oscillations is the mechanical vibration suspension, and the Coriolis acceleration sensors are the micromachined accelerometers. On one hand, the presence of two separate devices makes the instrument bigger, but on the other hand, it enables the use of more accurate sensors to measure the Coriolis acceleration. In particular, compensating accelerometer systems could be used which are more accurate by an order of magnitude than open structures commonly used in micromachined gyroscopes.
Significant issues involved in the construction of an accelerometer-based gyroscope are providing a high sensitivity of the device, a system for measuring the suspension vibration, separating the signals of angular speed and linear acceleration; filtering noise in the output signals of the device at the suspension frequency, providing a correlation between errors in the channels of angular speed and linear acceleration, considering the effect of nonlinearity of the accelerometers and the suspension on the error of the output signals.
A typical MEMS-based gyroscope uses a quartz tuning fork. The vibration of the tuning fork, along with applied angular rotation (yaw rate of the car), creates Coriolis acceleration on the tuning fork. An accelerometer or strain gage attached to the tuning fork measures the minute Coriolis force. Signal output is proportional to the size of the tuning fork. To generate enough output signal, the tuning fork must vibrate forcefully. Often, this can be accomplished with a high Q structure. Manufacturers often place the tuning fork in a vacuum to minimize mechanical damping by air around the tuning fork. High Q structures can be fairly fragile.
The gyroscope often experiences shock and vibration because it must be rigidly connected to the car to accurately measure yaw rate, for example. This mechanical noise can introduce signals to the Coriolis pick-off accelerometer that is several orders of magnitude higher than the tuning-fork-generated Coriolis signal. Separating the signal from the noise is not easy. Often, the shock or vibration saturates the circuitry and makes the gyroscope output unreliable for a short time.
Conventional MEMS-based gyroscopes are usually bulky (100 cm3 or more is not uncommon). This is partly the result of the addition of mechanical antivibration mounts, which are incorporated to minimize sensitivity to external vibration.
New MEMS-based gyroscopes avoid these shortcomings, though. For example, Analog Devices'"'"' iMEMS gyro is expected to be 7 by 7 by 3 mm (0.15 cm3). Rather than quartz, it uses a resonating polysilicon beam structure, which creates the velocity element that produces the Coriolis force when angular rate is presented to it. At the outer edges of the polysilicon beam, orthogonal to the resonating motion, a capacitive accelerometer measures the Coriolis force. The gyroscope has two sets of beams in antiphase that are placed next to each other, and their outputs are read differentially, attenuating external vibration sensitivity.
An accelerometer 78, as used herein in the IRU, includes conventional piezoelectric-based accelerometers, MEMS-based accelerometers (such as made by Analog Devices) and the type as described in U.S. Pat. No. 6,182,509.
Display subsystem 82 includes an appropriate display driver and either a heads-up or other display system for providing system information to the vehicle operator. Display subsystem 82 may include multiple displays for a single occupant or for multiple occupants, e.g., directed toward multiple seating positions in the vehicle. One type of display may be a display made from organic light emitting diodes (OLEDs). Such a display can be sandwiched between the layers of glass that make up the windshield and does not require a projection system.
The information being displayed on the display can be in the form of non-critical information such as the location of the vehicle on a map, as selected by the vehicle operator and/or it can include warning or other emergency messages provided by the vehicle subsystems or from communication with other vehicles or the infrastructure. An emergency message that the road has been washed out ahead, for example, would be an example of such a message.
Generally, the display will make use of icons when the position of the host vehicle relative to obstacles or other vehicles is displayed. Occasionally, as the image can be displayed especially when the object cannot be identified. Icons can be selected which are representative of the transmitters from which wireless signals are received.
A general memory unit 84 which can comprise read-only memory or random access memory or any combination thereof, is shown. This memory module, which can be either located at one place or distributed throughout the system, supplies the information storage capability for the system.
For advanced RtZF® systems containing the precise positioning capability, subsystem 86 provides the capability of sending and receiving information to infrastructure-based precise positioning tags or devices which may be based on noise or micropower impulse radar technology, IR lasers, radar or IR reflector (e.g. corner cube or dihedral) or RFIR technology or equivalent. Once again the PPS system can also be based on a signature analysis using the adaptive associative memory technology or equivalent.
In some locations where weather conditions can deteriorate and degrade road surface conditions, various infrastructure-based sensors can be placed either in or adjacent to the road surface. Subsystem 88 is designed to interrogate and obtained information from such road-based systems. An example of such a system would be an RFID tag containing a temperature sensor. This device may be battery-powered or, preferably, would receive its power from energy harvesting (e.g., solar energy, vibratory energy), the vehicle-mounted interrogator, or other host vehicle-mounted source, as the vehicle passes nearby the device. In this manner, the vehicle can obtain the temperature of the road surface and receive advanced warning when the temperature is approaching conditions which could cause icing of the roadway, for example. An RFID based on a surface acoustic wave (SAW) device is one preferred example of such a sensor, see U.S. Pat. No. 6,662,642. An infrared sensor on the vehicle can also be used to determine the road temperature and the existence of ice or snow.
In order to completely eliminate automobile accidents, a diagnostic system is required on the vehicle that will provide advanced warning of any potential vehicle component failures. Such a system is described in U.S. Pat. No. 5,809,437.
For some implementations of the RtZF® system, stoplights will be fitted with transmitters which will broadcast a signal indicative of the status of the stoplight, e.g., when the light is red. Such a system could make use of the vehicle noise communication system as described above. This signal can be then received by the communication system of a vehicle that is approaching the stoplight provided that vehicle has the proper sensor or communication system as shown as 92. Alternatively, a camera can be aimed in the direction of stoplights and, since the existence of the stoplight will be known by the system, as it will have been recorded on the map, the vehicle will know when to look for a stoplight and determine the color of the light.
An alternative idea is for the vehicle to broadcast a signal to a receiver on or otherwise associated with the stoplight if, via a camera or other means, it determines that the light is red. If there are no vehicles coming from the other direction, the stoplight can be controlled to change from red to green thereby permitting the vehicle to proceed without stopping. Similarly, if the stoplight has a camera, it can look in all directions and control the light color depending on the number of vehicles approaching from each direction. A system of phasing vehicles can also be devised whereby the speed of approaching vehicles is controlled so that they interleave through the intersection and the stoplight may not be necessary.
Although atomic clocks are probably too expensive to the deployed on automobiles, nevertheless there has been significant advances recently in the accuracy of clocks to the extent that it is now feasible to place a reasonably accurate clock as a subsystem 94 to this system. Since the clock can be recalibrated from each DGPS transmission, the clock drift can be accurately measured and used to predict the precise time even though the clock by itself may be incapable of doing so. To the extent that the vehicle contains an accurate time source, the satellites in view requirement can temporarily drop from 4 to 3. An accurate clock also facilitates the carrier phase DGPS implementations of the system as discussed above. Additionally, as long as a vehicle knows approximately where it is on the roadway, it will know its altitude from the map and thus one less satellite is necessary.
Power is supplied to the system as shown by power subsystem 96. Certain operator controls are also permitted as illustrated in subsystem 98.
The control processor or central processor and circuit board subsystem 100 to which all of the above components 52-98 are coupled, performs such functions as GPS ranging, DGPS corrections, image analysis, radar analysis, laser radar scanning control and analysis of received information, warning message generation, map communication, vehicle control, inertial navigation system calibrations and control, display control, precise positioning calculations, road condition predictions, and all other functions needed for the system to operate according to design.
A display could be provided for generating and displaying warning messages which is visible to the driver and/or passengers of the vehicle. The warning could also be in the form of an audible tone, a simulated rumble strip and light and other similar ways to attract the attention of the driver and/or passengers. Although vibration systems have been proposed by others, the inventors have found that a pure noise rumble strip is preferred and is simpler and less costly to implement,
Vehicle control also encompasses control over the vehicle to prevent accidents. By considering information from the map database 48, from the navigation system 46, and the position of the vehicle obtained via GPS, DGPS and PPS systems, a determination can be made whether the vehicle is about to run off the road, cross a yellow line and run a stop sign, as well as the existence or foreseen occurrence of other potential crash situations. The color of an approaching stoplight can also be factored in the vehicle control as can information from the vehicle-to-vehicle, vehicle-to-infrastructure and around vehicle radar, visual or IR monitoring systems.
Processor 100A is coupled to the inertial reference unit and also is capable of performing the functions of vehicle control, such as via control of the brake system 70A, steering system 72A and throttle system 74A, crash sensing, rollover sensing, cassis control sensing, navigation functions and accident prevention as discussed herein.
Preferably, a Kalman filter is used to optimize the data from the inertial reference unit as well as other input sources of data, signals or information. Also, a neural network, fuzzy logic or neural-fuzzy system could be used to reduce the data obtained from the various sensors to a manageable and optimal set. The actual manner in which a Kalman filter can be constructed and used in the invention would be left to one skilled in the art. Note that in the system of the inventions disclosed herein, the extensive calibration process carried on by other suppliers of inertial sensors is not required since the system periodically corrects the errors in the sensors and revises the calibration equation. This in some cases can reduce the manufacturing cost on the IMU by a factor of ten.
Further, the information from the accelerometers 78A and gyroscopes 80A in conjunction with the time base or reference is transmittable via the communication system 56A,58A to other vehicles, possibly for the purpose of enabling other vehicles to avoid accidents with the host vehicle, and/or to infrastructure.
One particularly useful function would be for the processor to send data from, or data derived from, the accelerometers and gyroscopes relating to a crash, i.e., indicative of the severity of the accident with the potential for injury to occupants, to a monitoring location for the dispatch of emergency response personnel, i.e., an EMS facility or fire station. Other telematics functions could also be provided.
6.3 Exterior Surveillance System
As discussed above, the cameras 60 can use naturally occurring visible or infrared radiation (particularly eye-safe IR), or other parts of the electromagnetic spectrum including terahertz and x-rays, or they may be supplemented with sources of visible or infrared illumination from the host vehicle. Note that there generally is little naturally occurring terahertz radiation other than the amount that occurs in black body radiation from all sources. The cameras 60 used are preferably high dynamic range cameras that have a dynamic range exceeding 60 db and preferably exceeding 100 db. Such commercially available cameras include those manufactured by the Photobit Corporation in California and the IMS Chips Company in Stuttgart Germany. Alternately, various other means exist for increasing the effective dynamic range through shutter control or illumination control using a Kerr or Pokel cell, modulated illumination, external pixel integration etc.
These cameras are based on CMOS technology and can have the important property that pixels are independently addressable. Thus, the control processor may decide which pixels are to be read at a particular time. This permits the system to concentrate on certain objects of interest and thereby make more effective use of the available bandwidth.
Video processor printed circuit boards or feature extractor 61 can be located adjacent and coupled to the cameras 60 so as to reduce the information transferred to the control processor. The video processor boards or feature extractor 61 can also perform the function of feature extraction so that all values of all pixels do not need to be sent to the neural network for identification processing. The feature extraction includes such tasks as determining the edges of objects in the scene and, in particular, comparing and subtracting one scene from another to eliminate unimportant background images and to concentrate on those objects which had been illuminated with infrared or terahertz radiation, for example, from the host vehicle. By these and other techniques, the amount of information to be transferred to the neural network is substantially reduced.
The neural network 63 receives the feature data extracted from the camera images by the video processor feature extractor 61 and uses this data to determine the identification of the object in the image. The neural network 63 has been previously trained on a library of images that can involve as many as one million such images. Fortunately, the images seen from one vehicle are substantially the same as those seen from another vehicle and thus the neural network 63 in general does not need to be trained for each type of host vehicle.
As the number of image types increases, modular or combination neural networks can be used to simplify the system.
Although the neural network 63 has in particular been described, other pattern recognition techniques are also applicable. One such technique uses the Fourier transform of the image and utilizes either optical correlation techniques or a neural network trained on the Fourier transforms of the images rather than on the image itself. In one case, the optical correlation is accomplished purely optically wherein the Fourier transform of the image is accomplished using diffraction techniques and projected onto a display, such as a garnet crystal display, while a library of the object Fourier transforms is also displayed on the display. By comparing the total light passing through the display, an optical correlation can be obtained very rapidly. Although such a technique has been applied to scene scanning by military helicopters, it has previously not been used in automotive, plane or other vehicle applications.
The laser radar system 64 is typically used in conjunction with a scanner 65. The scanner 65 typically includes two oscillating mirrors, or a MEMS mirror capable of oscillating in two dimensions, which cause the laser light to scan the two dimensional angular field. Alternately, the scanner can be a solid-state device utilizing a crystal having a high index of refraction which is driven by an ultrasonic vibrator as discussed above or rotating mirrors. The ultrasonic vibrator establishes elastic waves in the crystal which diffracts and changes the direction of the laser light. Another method is to use the DLP technology from Texas Instruments. This technology allows more than 1 million MEMS mirrors to control the direction of the laser light.
The laser beam can be frequency, amplitude, time, code or noise modulated so that the distance to the object reflecting the light can be determined. The laser light strikes an object and is reflected back where it can be guided onto an imager, such as a pin diode, or other high speed photo detector, which will be considered part of the laser radar system 64 as shown in
The output from the imager of the laser radar system 64 may be provided to a trained pattern recognition system in a processor in which neural network 63 also resides. The trained pattern recognition system may be one or more of the following: a trained neural network, a combination neural network, an optical correlation system and a sensor fusion algorithm. It may be programmed to identify the object or objects from which the laser beams are being reflected. This identification then being used to control a reactive system, i.e., a warning device, or a heads-up display which projects an icon, from a plurality of such icons and which is selected based on the identification of the object, into the field of view of an occupant of the vehicle.
Alternatively, the time-of-flight of a short burst of laser light can be measured providing a direct reading of the distance to the object that reflected the light. By either technique, a three-dimensional map can be made of the surface of the reflecting object. Objects within a certain range of the host vehicle can be easily separated out using the range information. This can be done electronically using a technique called range gating, or it can be accomplished mathematically based on the range data. By this technique, an image of an object can be easily separated from other objects based on distance from the host vehicle.
In some embodiments, since the vehicle knows its position accurately and in particular it knows the lane on which it is driving, a determination can be made of the location of any reflective object and in particular whether or not the reflective object is on the same lane as the host vehicle. This fact can be determined since the host vehicle has a map and the reflective object can be virtually placed on that map to determine its location on the roadway, for example.
The laser radar system will generally operate in the near-infrared part of the electromagnetic spectrum and preferably in the eye-safe part. The laser beam will be of relatively high intensity compared to the surrounding radiation and thus even in conditions of fog, snow, and heavy rain, the penetration of the laser beam and its reflection will permit somewhat greater distance observations than the human driver can perceive. Under the RtZF® plan, it is recommended that the speed of the host vehicle be limited such that vehicle can come to a complete stop in one half or less of the visibility distance. This will permit the laser radar system to observe and identify threatening objects that are beyond the visibility distance, apply the brakes to the vehicle if necessary causing the vehicle to stop prior to an impact, providing an added degree of safety to the host vehicle.
Radar system 62 is mainly provided to supplement laser radar system. It is particularly useful for low visibility situations where the penetration of the laser radar system is limited. The radar system, which is most probably a noise or pseudonoise modulated continuous wave radar, can also be used to provide a crude map of objects surrounding the vehicle. The most common use for automotive radar systems is for adaptive cruise control systems where the radar monitors the distance and, in some cases, the velocity of the vehicle immediately in front of the host vehicle. The radar system 62 is controlled by the control processor 100.
Display system 82 was discussed previously and can be either a heads up or other appropriate display.
Control processor 100 can be attached to a vehicle special or general purpose bus 110 for transferring other information to and from the control processor to other vehicle subsystems.
In interrogating other vehicles on the roadway, a positive identification of the vehicle and thus its expected properties such as its size and mass can sometimes be accomplished by laser vibrometry. By this method, a reflected electromagnetic wave can be modulated based on the vibration that the vehicle is undergoing. Since this vibration is caused at least partially by the engine, and each class of engine has a different vibration signature, this information can be used to identify the engine type and thus the vehicle. This technique is similar to one used to identify enemy military vehicles by the U.S. military. It is also used to identify ships at sea using hydrophones. In the present case, a laser beam is directed at the vehicle of interest and the returned reflected beam is analyzed such as with a Fourier transform to determine the frequency makeup of the beam. This can then be related to a vehicle to identify its type either through the use of a look-up table or neural network or other appropriate method. This information can then be used as information in connection with an anticipatory sensor as it would permit a more accurate estimation of the mass of a potentially impacting vehicle.
Once the vehicle knows where it is located, this information can be displayed on a heads-up display and if an occupant sensor has determined the location of the eyes of the driver, the road edges, for example, and other pertinent information from the map database can be displayed exactly where they would be seen by the driver. For the case of driving in dense fog or on a snow covered road, the driver will be able to see the road edges perhaps exactly or even better than the real view, in some cases. Additionally, other information gleaned by the exterior monitoring system can show the operator the presence of other vehicles and whether they represent a threat to the host vehicle (see for example “Seeing the road ahead”, GPS World Nov. 1, 2003, which describes a system incorporating many of the current assignee'"'"'s ideas described herein).
The foregoing collision avoidance system may be utilized for airplanes whereby one airplane has the laser scanning system 64 and another does not. This would be appropriate for small airplanes which do not have intra-airplane communications devices which automatically communicate position between airplanes for the purpose of collision avoidance. The invention could therefore eliminate the possibility of accidents caused by a larger planes colliding with smaller airplanes on the ground at airports.
A five minute loss of satellite lock is unlikely except in tunnels or in locations where buildings or geological features interfere with the signals. In the building case, the problem can be eliminated through the placement of PPS stations, or through environmental signature analysis, and the same would be true for the geological obstruction case except in remote areas where ultra precise positioning accuracy is probably not required. In the case of tunnels, for example, the cost of adding PPS stations is insignificant compared with the cost of building and maintaining the tunnel.
6.5 Vehicle Control
6.6 Intersection Collision Avoidance
Using the teachings of this invention, vehicle 18 will know of the existence of the stop sign and if the operator attempts to proceed without stopping, the system will sound a warning and if that warning is not heeded, the system will automatically bring the vehicle 18 to a stop, preventing it from intruding into the intersection.
Another common accident is where vehicle 18 does in fact stop but then proceeds forward without noticing vehicle 25 thereby causing an accident. Since in the fully deployed RtZF® system, vehicle 18 will know through the vehicle-to-vehicle communication the existence and location of vehicle 25 and can calculate its velocity, the system can once again take control of vehicle 18 if a warning is not heeded and prevent vehicle 18 from proceeding into the intersection and thereby prevent the accident.
In the event that the vehicle 25 is not equipped with the RtZF® system, vehicle 18 will still sense the presence of vehicle 25 through the laser radar, radar and camera systems. Once again, when the position and velocity of vehicle 25 is sensed, appropriate action can be taken by the system in vehicle 18 to eliminate the accident.
In another scenario where vehicle 18 properly stops at the stop sign, but vehicle 26 proceeds without observing the presence of the stopped vehicle 18, the laser radar, radar and camera systems will all operate to warn the driver of vehicle 26 and if that warning is not heeded, the system in vehicle 26 will automatically stop the vehicle 26 prior to its impacting vehicle 18. Thus, in the scenarios described above the “Road to Zero Fatalities”® system and method of this invention will prevent common intersection accidents from occurring.
The systems described above can be augmented by infrastructure-based sensing and warning systems. Camera, laser or terahertz radar or radar subsystems such as placed on the vehicle can also be placed at intersections to warn the oncoming traffic if a collision is likely to occur. Additionally, simple sensors that sense the signals emitted by oncoming vehicles, including radar, thermal radiation, etc., can be used to operate warning systems that notify oncoming traffic of potentially dangerous situations. Thus, many of the teachings of this invention can be applied to infrastructure-based installations in addition to the vehicle-resident systems.
While the invention has been illustrated and described in detail in the drawings and the foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.
This application is one in a series of applications covering safety and other systems for vehicles and other uses. The disclosure herein goes beyond that needed to support the claims of the particular invention that is claimed herein. This is not to be construed that the inventors are thereby releasing the unclaimed disclosure and subject matter into the public domain. Rather, it is intended that patent applications have been or will be filed to cover all of the subject matter disclosed above.