Radar system and method of operating same

• US 6,104,336 A
• Filed: 09/27/1999
• Issued: 08/15/2000
• Est. Priority Date: 11/12/1996
• Status: Expired due to Term

• Current Assignee: Valeo Radar Systems, Inc. (Valeo SE)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Potts, Steven L., Curran, Anthony, Crain, Arthur
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US09/406,302
• Time in Patent Office: 323 Days
• Field of Search: 342/70, 342/71, 342/72, 342/79, 342/107, 340/903, 340/904, 340/436, 702/143, 706/24
• 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 13/345 using triangular modulation
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/48 using multiple beams at emission or reception
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/932 using own vehicle data, e.g. ground speed, steering wheel direction
• CPC Class Codes: G01S 2013/9321 Velocity regulation, e.g. cruise control
• CPC Class Codes: G01S 2013/9325 for inter-vehicle distance regulation, e.g. navigating in platoons
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/356 involving particularities of FFT processing

Abstract

A method of operating a radar system, including the steps of digitally sampling a received signal at a predetermined sampling rate, to periodically provide a set of selected samples, the set of selected samples including positive going ramp samples, negative going ramp samples and CW burst samples and performing a first fast Fourier transform (FFT) on the positive going ramp samples, performing a second fast Fourier transform on the negative going ramp samples and performing a third fast Fourier transform on the CW burst samples is described. Utilizing the subsequent radar operations the method further includes the steps of tracking each resulting signal from the first fast Fourier transform performing steps, tracking each resulting signal from the second fast Fourier transform performing steps and tracking each resulting signal from the third fast Fourier transform performing steps and associating any resulting signals from the tracking steps to periodically provide output signals indicative of other vehicles.

Claims

1. A vehicle radar sensor to track targets proximate a vehicle traveling along a roadway, the radar sensor comprising:

(a) a controller for initializing the sensor and for placing the sensor in one of a standby mode or an active mode;

(b) an active mode processor, coupled to said controller, said active mode processor for placing the sensor in one of an acquisition mode or a follow mode;

(c) a field of view tracker, coupled to receive signals from said active mode processor, said field of view tracker for locating and tracking all targets in a predetermined field of view of the sensor;

(d) a reduced view tracker, coupled to receive signals from and transmit signals to said active mode processor, said reduced view tracker for tracking a follow target and all targets within a specified range around the follow target and for determining when a second vehicle can interfere with the track of the followed target; and

(e) a lane estimator coupled to said field of view tracker and said reduced view tracker, said lane estimator for receiving data from both the field of view tracker and the platform vehicle and for processing the data to provide an indication of when the roadway ahead of the vehicle is not straight, such that all the tracked targets can be expected to wander from the line directly in front of the sensor vehicle and wherein said lane estimator provides an output signal to said field of view tracker and said reduced view tracker to allow said field of view tracker and said reduced view tracker to determine the location of the targets.

2. The system of claim 1, wherein said field of view tracker comprises:

(a) a field of view file propagation processor coupled to receive information from said active mode processor;

(b) a field of view file association processor coupled to receive information from said field of view file propagation processor;

(c) a field of view file update processor coupled to receive information from said a field of view file association processor; and

(d) a field of view executive processor coupled to receive information from said field of view file update processor and to receive information from and provide information to said lane estimator.

3. The system of claim 2, wherein said reduced view tracker comprises:

(a) a reduced view file propagation processor coupled to receive information from said active mode processor;

(b) a reduced view file association processor coupled to receive information from said field of view file propagation processor;

(c) a reduced view file update processor coupled to receive information from said a field of view file association processor; and

(d) a reduced view executive processor coupled to receive information from said field of view file update processor and to receive information from and provide information to said lane estimator.

4. The system of claim 1 further comprising an interface unit coupled to said controller, said field-of-view tracker, said lane estimator and said reduced view tracker and adapted to couple to said vehicle and wherein said reduced view tracker provides information to said interface unit to control at least one of a brake system, and accelerator system and an alarm system of the vehicle.

5. The system of claim 1 wherein said lane estimator receives sensor speed and yaw rate data from the vehicle and the field of view tracker and predicts the direction of the road ahead and wherein said lane estimator further comprises:

a turn radius estimator;

a roadway boundary estimator; and

a target path estimator wherein said a roadway boundary estimator and said target path estimator receives inputs from the sensor; and

means for determining whether a given target is stationary or moving wherein if decision is made that a target is stationary, the data is fed to said roadway boundary estimator as information about the edge of the road and wherein if decision is made that a target is moving, the data is fed to said target path estimator as information about the direction in which the targets are moving going; and

a lane estimator for receiving signals from said turn radius estimator, said roadway boundary estimator and said target path estimator to generate a path prediction.

6. The system of claim 4 further comprising:

(a) means, coupled to said field of view tracker for comparing track data for each target tracked by said field of view tracker and for identifying a target as a primary target based upon the results of the comparison; and

(b) means, coupled to said field of view tracker for receiving selected primary target information and for setting an indicator on the track of the primary target which determines which track generates the reduced view tracker and for directing all data to said field of view tracker but only that of the primary target and any other targets within a specified distance (range and angle) of the primary target to the reduced view tracker.

7. A method of selecting a primary target in a sensor disposed in a sensor vehicle traveling in a lane of a roadway, the method comprising the steps of:

(a) initially selecting a primary target by selecting a vehicle located in the same traveling lane as the sensor vehicle;

(b) using sequential lobing information to estimate a location of the primary target;

(c) generating track information in a target tracker, the track information including frequency locations of the primary target;

(d) using the track information obtained in step (c), to select a next primary target; and

(e) after selecting the next primary target, activating a reduced view tracker focused about the next primary target'"'"'s frequency locations.

8. The method of claim 7 further comprising the step of:

generating a target detection list; and

editing the target detection list to reduce processing required to provide information relevant to objectives of the target tracker by reducing the amount of processing performed on predetermined target frequencies.

9. The method of claim 8 wherein the target detection list corresponds to a constant false alarm rate (CFAR) detection list and the step of editing the editing the target detection list includes the steps of:

identifying stationary clutter targets in the CFAR detection list; and

deleting stationary clutter targets from the CFAR detection list.

10. The method of claim 9 wherein the step of identifying stationary clutter stationary clutter includes the step of identifying targets having substantially the same measured velocity as the sensor vehicle.

11. The method of claim 9 wherein the step of identifying stationary clutter includes the steps of:

identifying an object having an associated frequency detected in the up ramp which can also be detected in the down ramp at a frequency f_down which can be computed as f_down =-f_up +f_Doppler, in which f_Doppler represents the calculated Doppler frequency from a reported vehicle speed; and

tagging the object as stationary clutter.

12. A method for tracking targets proximate a vehicle traveling along a roadway, the method comprising the steps of:

tracking a plurality of targets along a roadway;

selecting a primary target and possible interfering targets;

tracking the primary target and the possible interfering targets and predicting a future location of the primary target and the possible interfering targets; and

activating a reduced view tracker focused about the primary target'"'"'s next frequency location.

13. The method of claim 12 wherein the tracking a plurality of targets step comprises the steps of:

sampling received signals at a predetermined sampling rate for periodically providing a set of selected samples, the set of selected samples comprising positive going ramp samples, negative going ramp samples and CW burst samples;

performing a first fast Fourier transform on the positive going ramp samples, performing a second fast Fourier transform on the negative going ramp samples and performing a third fast Fourier transform on the CW burst samples;

tracking one or more signals provided by the fast Fourier transform means wherein each of the one or more signals provided from the fast Fourier transform means represents a corresponding target and providing range, range rate, and acceleration of each corresponding target; and

associating the signals provided from the tracking step to periodically provide output signals corresponding to track states of the corresponding targets.

14. The method of claim 12 wherein the tracking and predicting a future location of the primary target and the possible interfering targets comprises the steps of:

determining a first frequency, frequency rate and frequency acceleration of a target during a first instance of time;

predicting frequency, frequency rate and frequency acceleration of said target during a second instance of time;

determining a second frequency, frequency rate and frequency acceleration of a target during a second instance of time; and

matching the estimated frequency, frequency rate and frequency acceleration of said target during a second instance of time with the second frequency, frequency rate and frequency acceleration of a target during a second instance of time to provide a track state.

15. The method as recited in claim 14 wherein the matching step comprises the steps of:

defining a frequency search window of a region a target frequency under track will most likely be found;

defining an order in which target frequencies under track will attempt to match with determined frequencies;

matching the predicted frequency with a determined frequency when the predicted frequency and the determined frequency are within the frequency search window.

16. The method as recited in claim 15 wherein the defining an order step comprises the steps of:

providing a track state file for each one of the track states of each of the corresponding targets; and

dating each track state at a time of creation and starting with the oldest track file.

17. The method as recited in claim 12 wherein the tracking and predicting a future location of the primary target and the possible interfering targets step comprises the steps of:

associating a predicted track state of the primary target with a measured track state of the primary target; and

associating a predicted track state of possible interfering targets with a measured track state of possible interfering targets starting with the closest target.

18. The method as recited in claim 12 further comprising the step of:

predicting a location of the roadway ahead.

19. The method as recited in claim 18 wherein the predicting step comprises the steps of:

obtaining sensor speed and yaw rate;

determining whether a target is a stationary target or a moving target;

predicting, from information on the stationary targets and the sensor speed and yaw rate, the location of the roadway ahead.

20. The method as recited in claim 19 further comprising the steps of:

redirecting a search for the primary target towards an expected location of the roadway.

21. The method as recited in claim 20 further comprising the steps of:

widening to no more than two lane widths the search for the primary target if the primary target is not found.