Smart blind spot sensor with object ranging

• US 5,517,196 A
• Filed: 06/28/1994
• Issued: 05/14/1996
• Est. Priority Date: 08/14/1992
• Status: Expired due to Term

• Current Assignee: Bendix Commercial Vehicle Systems LLC (Estate of Heinz Hermann Thiele)
• Original Assignee: Vorad Safety Systems, Inc.
• Inventors: Pakett, Allan G., Asbury, Jimmie R.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/267,424
• Time in Patent Office: 686 Days
• Field of Search: 342/70, 342/71, 342/72, 342/27, 342/28
• US Class Current: 342/70
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/52 Discriminating between fixed and moving objects or between objects moving at different speeds
• CPC Class Codes: G01S 13/582 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/9315 Monitoring blind spots
• CPC Class Codes: G01S 2013/932 using own vehicle data, e.g. ground speed, steering wheel direction
• CPC Class Codes: G01S 2013/9324 Alternative operation using ultrasonic waves
• CPC Class Codes: G01S 2013/93272 in the back of the vehicles
• CPC Class Codes: G01S 2013/93274 on the side of the vehicles

Abstract

A radar system for sensing the presence of obstacles in a vehicle'"'"'s "blind spots" and generating a signal to the vehicle operator indicative of the presence of such an obstacle. The system uses a common radar transceiver that transmits a multi-frequency radio signal directed at a blind spot of the vehicle. The signal is reflected off any obstacles that are present in that blind spot region. Doppler shifts in the received reflected multi-frequency signal generally indicates that an obstacle has moved into the blind spot. Doppler frequencies attributable to objects which are of no interest, such as stationary objects, are filtered out. The system has a signal processor which determines if a potentially hazardous object is within a pre-determined range from the vehicle. Only objects that are traveling at approximately the same speed and direction as the vehicle, and that are within a pre-determined range of the vehicle, are considered to be of interest, and will cause the blind spot sensor to generate an indication that an obstacle is present within the blind spot. The indication is preferably an unobtrusive illuminated indicator which is affixed to one of the vehicle'"'"'s mirrors. In addition to the illuminated indicator affixed to a mirror, an obtrusive audible indicator is provided in the preferred embodiment of the present invention which creates an audible tone, whistle, or buzz when an obstacle is present and the vehicle'"'"'s turn signal is active.

Claims

1. A blind spot sensor for detecting the presence and range of an object in at least one blind spot region of a vehicle controlled by and operator, including:

a. object detection means for detecting an object comprising at least one transmit means for transmitting a signal directed toward at least one blind spot region, and a receiving means for receiving reflections of the transmit signal;

b. signal processing means, coupled to the object detection means, for processing the received reflections to detect if an object is present in at least one blind spot region, and to detect if the object is within a pre-determined range, but at least a predetermined minimum distance from the vehicle;

c. processing means, coupled to the signal processing means, for determining if a detected object poses a hazard to the vehicle; and

d. indicator means, coupled to the processing means, for indicating to the vehicle operator at least the presence of a detected object which poses a hazard to the vehicle.

2. The blind spot sensor of claim 1, wherein the object detection means is a radar transceiver.

3. The blind spot sensor of claim 1, wherein received reflections from a detected obstacle must persist a selected duration of time to be determined to pose a threat to the vehicle.

4. The blind spot sensor of claim 3, wherein the selected duration of time varies with the speed of the vehicle.

5. The blind spot sensor of claim 1, wherein the indicator means generates a first indication to signify that the system is active.

6. The blind spot sensor of claim 1, wherein the indicator means generates a first indication to signify that a detected object is present in at least one blind spot region of the vehicle and is within the pre-determined, but at least a predetermined minimum distance from the vehicle.

7. The blind spot sensor of claim 1, wherein the vehicle includes a turn signal, further including sensor means for detecting activation of the turn signal, the sensor means being coupled to the processing means, and wherein the indicator means generates a first indication to signify that a hazardous object is present in at least one blind spot region of the vehicle and that the turn signal has been activated.

8. The blind spot sensor of claim 7, wherein the indicator means includes an audible alarm for generating the first indication.

9. The blind spot sensor of claim 1, wherein the indicator means includes a first visual indicator to signify that the system is active, and a second visual indicator to signify that a hazardous object is present in the blind spot region of the vehicle and is within the pre-determined range, but at least a predetermined minimum distance from the vehicle.

10. The blind spot sensor of claim 9, wherein the vehicle includes at least one automotive mirror, and the first and second visual indicators are mounted on or in close proximity to at least one such automotive mirror.

11. The blind spot sensor of claim 9, wherein the vehicle includes a turn signal, further including sensor means for detecting activation of the turn signal, the sensor means being coupled to the processing means, wherein the indicator means includes an audible indicator to signify that a hazardous object is present in at least one blind spot region of the vehicle, that the object is within the pre-determined range of the vehicle, and that the turn signal has been activated.

12. The blind spot sensor of claim 2, wherein the radar transceiver is a pulse Doppler radar transceiver.

13. The blind spot sensor of claim 2, wherein the radar transceiver is mounted on the right side of the vehicle.

14. The blind spot sensor of claim 2, wherein the radar transceiver is mounted on the rear of the vehicle.

15. A blind spot sensing system for detecting the presence and range of an object in a blind spot region of an operator-controlled vehicle, including:

a) microwave transceiver means, mounted on the vehicle, for transmitting a multi-frequency transmit signal, receiving reflections of the transmit signal, and comparing the frequencies of the transmit signal to the frequencies of the received reflections to produce a multi-frequency difference signal;

b) signal processing means, coupled to the microwave transceiver means, for amplifying and filtering the multi-frequency difference signal, wherein the signal processing means time demultiplexes the amplified difference signal to produce a plurality of difference signals, and wherein the signal processing means includes a comparison means for calculating the phase difference between the plurality of difference signals, and wherein the signal processing means determines whether an object is within a pre-determined range of but a minimum distance from, the vehicle based upon the calculated phase difference;

c) processing means, coupled to the signal processing means, for determining if the vehicle'"'"'s operator should be warned of the presence of the object; and

d) indicator means, coupled to the processing means, for indicating to the operator the presence of the object.

16. A blind spot sensor for determining if an object is present in at least one blind spot region of a vehicle controlled by an operator and within a range which poses a threat to the vehicle, including:

a) a transceiver means for transmitting a multi-frequency transmit signal directed toward at least one blind spot region, and for receiving reflections of the multi-frequency transmit signal;

b) signal processing means, coupled to the transceiver means, for processing the received reflections to detect if an object is present in at least one blind spot region, and to determine if the object is within a pre-determined range from the vehicle, wherein the signal processing means includes;

i) a preamplifier, coupled to the transceiver means, for amplifying the received reflections,

ii) a demodulator, coupled to the preamplifier, for time demultiplexing the amplified received reflections into a plurality of receive channel signals,

iii) a sampling circuit, coupled to the demodulator, for converting the receive channel signals into smooth receive channel signals,

iv) a first processing means, coupled to the sampling circuit, for comparing the phase differential between the smooth receive channel signals, and for calculating the range of a detected object based upon the comparison, wherein the first processing means generates an output signal indicative of whether the object is within a predetermined range of but a minimum distance from, the vehicle;

c) second processing means, coupled to the signal processing means, for determining if a detected object poses a hazard to the vehicle; and

d) indicator means, coupled to the second processing means, for indicating to the vehicle operator at least the presence of a detected object which poses a hazard to the vehicle.

17. The blind spot sensor of claim 16, wherein the first processing means compares the phase differential between the smooth receive channel signals by performing an exclusive-or operation on the plurality of smooth receive channel signals to produce an exclusive-or output signal, and by measuring the duty cycle of the exclusive-or output signal.

18. The blind spot sensor of claim 17, wherein the first processing means determines the range that an object is from the vehicle by averaging the calculated phase differential over a pre-determined number of phase difference measurements.

19. A blind spot sensor for determining if an object is present in at least one blind spot region of a vehicle controlled by an operator and is within a range which poses a threat to the vehicle, including:

a) a transceiver means for transmitting a multi-frequency transmit signal directed toward at least one blind spot region, and receiving reflections of the multi-frequency transmit signal;

b) a mixing means, coupled to the transceiver means, for comparing the frequencies of the transmit signal with the frequencies of the received reflections, and for generating a multi-frequency Doppler receive signal indicative of the comparison;

c) signal processing means, coupled to the mixing means, for processing the Doppler receive signal to determine if an object is present in at least one blind spot region, and to determine if the object is within a pre-determined range from the vehicle, wherein the signal processing means includes;

i) a preamplifier, coupled to the mixing means, for amplifying the multi-frequency Doppler receive signal,

ii) a sampling circuit, coupled to the preamplifier, for time demultiplexing the multi-frequency Doppler receive signal into a plurality of receive channel signals, wherein the sampling circuit produces a different receive channel signal for each frequency of the transmit signal,

iii) a plurality of low-pass filters coupled to the sampling circuit, wherein the filters produce a filtered channel signal for each receive channel signal,

iv) an analog to digital converter, coupled to the plurality of low-pass filters, which convert the filtered channel signals to digital receive channel signals, and

v) a digital signal processor, coupled to the analog to digital converter, for comparing the phase difference between the digital receive channel signals, and for calculating the range of a detected object based upon the phase comparison, wherein the digital signal processor generates an output signal indicative of the range that the object is from the vehicle;

d) processing means, coupled to the digital signal processor, for determining if a detected object poses a hazard to the vehicle; and

e) indicator means, coupled to the processing means, for indicating to the vehicle operator at least the presence of a detected object which poses a hazard to the vehicle.

20. The blind spot sensor of claim 19, wherein the digital signal processor compares the phase difference between the digital receive channel signals by performing a fast Fourier transform operation on the digital receive channel signals to produce transformed channel signals, and by applying the following formula:

space="preserve" listing-type="equation">ARCTAN[{(B×

C)-(A×

C)}/{(A×

C)+(B×

D)}]=φ

(difference in phase),

where

A=the value of the real portion of the transformed channel 1 signal,

B=the value of the imaginary portion of the transformed channel 1 signal,

C=the real portion of the transformed channel 2 signal, and

D=the value of the imaginary portion of the transformed channel 2 signal.

21. A blind spot sensor for determining if an object is present in at least one blind spot region of a vehicle controlled by an operator and within a range which poses a threat to the vehicle, including:

a) a transceiver which transmits a signal directed toward at least one blind spot region, and which receives reflections of the transmit signal;

b) a signal processor, coupled to the transceiver, wherein the signal processor processes the received reflections to detect if an object is present in at least one blind spot region, and wherein the signal processor determines if the object is within a pre-determined range from the vehicle, and wherein the signal processor includes;

i) a preamplifier, coupled to the transceiver, wherein the preamplifier amplifies the received reflections,

ii) a demodulator, coupled to the preamplifier, wherein the demodulator time demultiplexes the amplified received reflections into a plurality of receive channel signals,

iii) a sampling circuit, coupled to the demodulator, which converts the receive channel signals into smooth receive channel signals,

iv) a first processor, coupled to the sampling circuit, wherein the first processor compares the phase differential between the smooth receive channel signals, and wherein the first processor calculates the range of a detected object based upon the comparison, and wherein the first processor generates an output signal indicative of whether the object is within a predetermined range of the vehicle;

c) a second processor, coupled to the signal processor, wherein the second processor determines if a detected object poses a hazard to the vehicle; and

d) an indicator, coupled to the second processor, wherein the indicator generates an indication to the vehicle operator of at least the presence of a detected object which poses a hazard to the vehicle.

22. A blind spot sensor for determining if an object is present in at least one blind spot region of a vehicle controlled by an operator and is within a range which poses a threat to the vehicle, including:

a) a transceiver which transmits a signal directed toward at least one blind spot region, and receives reflections of the transmitted signal;

b) a mixer, coupled to the transceiver, wherein the mixer compares the frequencies of the transmitted signal with the frequencies of the received reflections, and wherein the mixer generates a multi-frequency Doppler receive signal indicative of the comparison;

c) a signal processor, coupled to the mixer, wherein the signal processor processes the Doppler receive signal to determine if an object is present in at least one blind spot region, and wherein the signal processor processes the Doppler receive signal to determine if the object is within a pre-determined range from the vehicle, and wherein the signal processor includes;

i) a preamplifier, coupled to the mixer, wherein the preamplifier amplifies the multi-frequency Doppler receive signal,

ii) a sampling circuit, coupled to the preamplifier, wherein the sampling circuit time demultiplexes the multi-frequency Doppler receive signal into a plurality of receive channel signals, and wherein the sampling circuit produces a different receive channel signal for each frequency of the transmitted signal,

iii) a plurality of low-pass filters coupled to the sampling circuit, wherein the filters produce a filtered channel signal for each receive channel signal,

iv) an analog to digital converter, coupled to the plurality of low-pass filters, wherein the analog to digital converter converts the filtered channel signals to digital receive channel signals, and

v) a digital signal processor, coupled to the analog to digital converter, wherein the digital signal processor compares the phase difference between the digital receive channel signals, and wherein the digital signal processor calculates the range of a detected object based upon the phase comparison, and wherein the digital signal processor generates an output signal indicative of the range that the object is from the vehicle;

d) a processor, coupled to the digital signal processor, for determining if a detected object poses a hazard to the vehicle; and

e) an indicator, coupled to the processor, wherein the indicator generates an indication to the vehicle operator of at least the presence of a detected object which poses a hazard to the vehicle.

23. A method of concurrently determining if an object is present in at least one blind spot region of a vehicle controlled by an operator and determining whether an object is within a range which poses a threat to the vehicle, including:

a) transceiving a signal by transmitting a signal directed toward at least one blind spot region, and receiving reflections of the transmitted signal;

b) processing the received reflections to detect if an object is present in at least one blind spot region, and to determine if the object is within a pre-determined range from the vehicle, wherein the processing step includes the following steps;

i) amplifying the received reflections,

ii) time demultiplexing the amplified received reflections into a plurality of receive channel signals,

iii) convening the receive channel signals into smooth receive channel signals,

iv) comparing the phase differential between the smooth receive channel signals, and calculating the range of a detected object based upon the comparison, and

v) generates an output signal indicative of whether the object is within a predetermined range of but a minimum distance from, the vehicle;

c) determining if a detected object poses a hazard to the vehicle; and

d) indicating to the vehicle operator at least the presence of a detected object which poses a hazard to the vehicle.

24. A system for detecting the presence of targets moving at slow speeds relative to the vehicle upon which the system is mounted and adjacent to, and on at least one side of, the vehicle upon which the system is mounted, including:

a. a transceiver for emitting signals along side a vehicle upon which the system is mounted and for receiving reflections of the emitted signals;

b. a Doppler circuit, coupled to the transceiver, for generating a Doppler signal having a frequency equal to the difference between the emitted signal and the received reflections;

c. a signal processing section including;

an amplifier, coupled to the Doppler circuit;

ii. square wave generator coupled to the sample and hold circuit for generating a square wave output having a frequency equal to the signal output from the sample and hold circuit;

iii. signal processing means, coupled to the square wave generator, for processing the output from the square wave generator to detect if an object is present in at least one blind spot region, and to detect if the object is at least a first predetermined distance away, but not more than a second predetermined distance;

iv. a persistence period circuit, coupled to the amplifier, for generating an output equivalent to the output of the amplifier when an object is present for a predefined minimum persistence period;

d. an indicator circuit, coupled to the persistence period circuit, for receiving the output of the persistence circuit and indicating to an operator of the vehicle on which the system is mounted, the presence of an object which is detected for a period which is longer than the persistence period, and that the object is within the range defined by the first and second predetermined distances.

25. A system for detecting the presence of targets moving at slow speeds relative to the vehicle upon which the system is mounted and adjacent to, and on at least one side of, the vehicle upon which the system is mounted, including:

a. a transceiver for emitting signals along side a vehicle upon which the system is mounted and for receiving reflections of the emitted signals;

b. a Doppler circuit, coupled to the transceiver, for generating a Doppler signal having a frequency equal to the difference between the emitted signal and the received reflections;

c. a signal processing section including;

an amplifier, coupled to the Doppler circuit, for amplifying the Doppler signal;

ii. a ranging circuit for determining the range of objects from which the emitted signal has reflected and indicating which signals are associated with objects that are at a distance that is greater than a first predetermined distance and less than a second predetermined distance, the second predetermined distance being greater than the first predetermined distance;

iii. a sample and hold circuit, coupled to the amplifier, for sampling the output of the amplifier during periods concurrent with the emission of the emitted signals and generating a signal having a voltage level that is proportional to the phase difference between the emitted signal and received reflections;

iv. square wave generator coupled to the sample and hold circuit, for generating a square wave output having a frequency equal to the sampled signal;

v. malfunction detector circuit, coupled to the output of the square wave generator and the output of the sample and hold circuit, for sensing the level of the direct current offset of the signal generated by the sample and hold circuit, to determine when the system is operating within specified limits, and indicating a malfunction in the detection system when the system is not operating within the specified limits;

d. an indicator circuit, coupled to the square wave generator, for receiving the output of the square wave generator and indicating to an operator of the vehicle on which the system is mounted, the presence of an object which is detected to be within the range determined by the first and second predetermined distances.

26. The system of claim 25, wherein the malfunction detector circuit is coupled to the indicator circuit for indicating to an operator of the vehicle on which the system is mounted when the system is operating within specified limits.

27. The system of claim 25, wherein:

a. the indicator circuit is coupled to at least one automotive turn signal;

b. the indication of the presence of an object is by means of a visual indicator; and

c. an audible alarm to the operator, in addition to the visual indication, is presented to the operator when an object is detected on the side of the vehicle to which the turn signal signals a turn.

28. The system of claim 25, wherein the low pass filter has a 3 decibel cutoff at approximately 100 Hertz.

29. A system for detecting the presence of objects moving at relatively slow speeds adjacent to, and on at least one side of, a vehicle upon which the system is mounted, including:

a. a transceiver for emitting signals along side a vehicle upon which the system is mounted and for receiving reflections of the emitted signals;

b. a Doppler circuit, coupled to the transceiver, for generating a Doppler signal having a frequency equal to the difference between the transmitted signal and the received signal;

c. signal processing section for;

i. sampling the Doppler signal during periods concurrent with the emission of the emitted signals and generating a voltage level proportional to the phase difference between the emitted and received signals;

ii. determining the range of objects which have reflected the emitted signals;

iii. disregarding targets that are determined to be less than a minimum distance away from the system;

iv. removing high frequency components and signals which represent objects moving rapidly relative to the vehicle upon which the system is mounted from the sampled Doppler signal;

v. sensing the level of the direct current offset of the signal sampled Doppler signal to determine when the system is operating within specified limits;

d. an indicator circuit, coupled to the signal processor, for indicating to the operator that an object is detected which is more than minimum distance away from the system, and which is moving relatively slowly.

30. A system for detecting the presence of targets moving at slow speeds relative to the vehicle upon which the system is mounted and adjacent to, and on at least one side of, the vehicle upon which the system is mounted, including:

a. a transceiver for emitting signals along side a vehicle upon which the system is mounted and for receiving reflections of the emitted signals;

b. a Doppler circuit, coupled to the transceiver, for generating a Doppler signal having a frequency equal to the difference between the emitted signal and the received reflections;

c. a signal processing section including;

i. an amplifier, coupled to the Doppler circuit;

ii. a low pass filter, coupled to the output of the amplifier, for filtering high frequency components and signals which represent objects moving rapidly relative to the vehicle upon which the system is mounted from the signal output by the amplifier;

iii. signal processor, coupled to the low pass filter, for processing the output from the low pass filter to detect if an object is present in at least one blind spot region, and to detect if the object is within a pre-determined range from the vehicle, but at least a predetermined minimum distance away;

d. an indicator circuit, coupled to the signal processor, for receiving the output of the signal processor and indicating to an operator of the vehicle on which the system is mounted, the presence of an object which has a relatively slow speed, as determined by the low pass filter, and which is at least a minimum distance as determined by the signal processor.