Adjustable threshold for forward collision warning system

• US 8,788,176 B1
• Filed: 06/19/2013
• Issued: 07/22/2014
• Est. Priority Date: 06/19/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Yopp, Wilford Trent
• Primary Examiner(s): Dager, Jonathan M
• Application Number:
  US13/921,498
• Time in Patent Office: 398 Days
• US Class Current: 701/96
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2520/30 Wheel torque
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2554/00 Input parameters relating to objects
• CPC Class Codes: B60W 2554/80 Spatial relation or speed relative to objects
• CPC Class Codes: B60W 2554/802 Longitudinal distance
• CPC Class Codes: B60W 2554/804 Relative longitudinal speed
• CPC Class Codes: B60W 2554/806 Relative heading
• CPC Class Codes: B60W 30/09 Taking automatic action to avoid collision, e.g. braking and steering
• CPC Class Codes: B60W 30/095 Predicting travel path or likelihood of collision
• CPC Class Codes: B60W 30/10 Path keeping cruise control for automatically following a preceding vehicle B60W30/165
• CPC Class Codes: B60W 30/162 Speed limiting therefor
• CPC Class Codes: B60W 50/14 Means for informing the driver, warning the driver or prompting a driver intervention
• CPC Class Codes: G08G 1/16 Anti-collision systems road vehicle drive control systems for predicting or avoiding probable or impending collision otherwise than by control of a particular sub-unit B60W30/08
• CPC Class Codes: G08G 1/166 for active traffic, e.g. moving vehicles, pedestrians, bikes

Abstract

A driver assistance system for a motor vehicle monitors approaching objects around the vehicle in order to take a driver assistance action in response to a predicted impact with an approaching object according to a time-to-impact threshold. the time-to-impact threshold includes a nominal or default value that is adjusted according to several different measures of vehicle and driving conditions. Respective offsets determined by a load monitor, a braking monitor, and a steering monitor are added to the threshold in response to measured vehicle performance parameters being different from expected values. The driver assistance action may be a perceptible warning for a forward collision warning system, a speed reduction in an adaptive cruise control system, or a braking action in a brake-steer system.

Claims

1. Apparatus for a vehicle comprising:

a driver assistance system monitoring approaching objects around the vehicle and configured to take a driver assistance action in response to a predicted impact with an approaching object according to a time-to-impact threshold;

a load monitor detecting whether a trailer is being towed by the vehicle and determining a first offset in response to a result of the detection, wherein the first offset is substantially equal to zero if no trailer is detected;

a braking monitor detecting a braking intensity and a resulting change related to vehicle speed, determining an expected change related to vehicle speed in response to the braking intensity, and selecting a second offset in response to a braking difference between the resulting speed change to the expected speed change, wherein the second offset is substantially equal to zero if the braking difference is below a braking threshold;

a steering monitor detecting a steering angle of the vehicle and a resulting change related to vehicle yaw, determining an expected change in vehicle yaw in response to the steering angle, and selecting a third offset in response to a steering difference between the resulting yaw change to the expected yaw change, wherein the third offset is substantially equal to zero if the steering difference is below a steering threshold;

an updater determining a magnitude of the time-to-impact threshold in response to the first, second, and third offsets.

2. The apparatus of claim 1 wherein the updater determines the magnitude of the time-to-impact threshold according to a sum of a nominal threshold value for the vehicle and the first, second, and third offsets.

3. The apparatus of claim 1 further comprising:

a traction monitor detecting a disparity between a driven-wheel speed and an undriven-wheel speed, determining a torque being applied to the driven-wheel, determining an expected disparity in response to the determined torque, and selecting a fourth offset in response to a difference between the detected disparity and the expected disparity, wherein the fourth offset is substantially equal to zero if the difference between the detected disparity and the expected disparity is below a threshold;

wherein the updater determines the magnitude of the time-to-impact threshold in response to the first, second, third, and fourth offsets.

4. The apparatus of claim 1 wherein the driver assistance system includes a forward-collision warning system, and wherein the driver assistance action is comprised of a perceptible warning signal to alert the driver of the predicted impact.

5. The apparatus of claim 1 wherein the driver assistance system includes an adaptive cruise control system, and wherein the driver assistance action is comprised of reducing a commanded speed of the adaptive cruise control system to avoid the predicted impact.

6. The apparatus of claim 1 wherein the driver assistance system includes a brake-steer system, and wherein the driver assistance action is comprised of applying a braking force to avoid the predicted impact.

7. The apparatus of claim 1 wherein the load monitor identifies a trailer class of a detected trailer, and wherein the load monitor includes a trailer table relating the trailer class to a respective value for the first offset.

8. The apparatus of claim 1 wherein the braking monitor includes a first table relating the braking intensity to a respective value for the expected speed change and a second table relating the braking difference to a respective value for the second offset.

9. The apparatus of claim 1 wherein the steering monitor includes a first table relating the steering angle to a respective value for the expected yaw change and a second table relating the steering difference to a respective value for the third offset.

10. A method of adjusting a driver assistance system that monitors approaching objects around a vehicle and is configured to take a driver assistance action in response to a predicted impact with an approaching object according to a time-to-impact threshold, the method comprising the steps of;

detecting whether a trailer is being towed by the vehicle;

determining a first offset in response to a result of the detection, wherein the first offset is substantially equal to zero if no trailer is detected;

detecting a braking intensity and a resulting change related to vehicle speed;

determining an expected change related to vehicle speed in response to the braking intensity;

selecting a second offset in response to a braking difference between the resulting speed change to the expected speed change, wherein the second offset is substantially equal to zero if the braking difference is below a braking threshold;

detecting a steering angle of the vehicle and a resulting change related to vehicle yaw;

determining an expected change in vehicle yaw in response to the steering angle;

selecting a third offset in response to a steering difference between the resulting yaw change to the expected yaw change, wherein the third offset is substantially equal to zero if the steering difference is below a steering threshold;

determining a magnitude of the time-to-impact threshold in response to the first, second, and third offsets.

11. The method of claim 10 wherein the step of determining a magnitude of the time-to-impact threshold includes forming a sum of a nominal threshold value for the vehicle and the first, second, and third offsets.

12. The method of claim 10 further comprising the steps of:

detecting a disparity between a driven-wheel speed and an undriven-wheel speed;

determining a torque being applied to the driven-wheel;

determining an expected disparity in response to the determined torque; and

selecting a fourth offset in response to a difference between the detected disparity and the expected disparity, wherein the fourth offset is substantially equal to zero if the difference between the detected disparity and the expected disparity is below a threshold;

wherein the step of determining a magnitude of the time-to-impact threshold includes forming a sum of a nominal threshold value for the vehicle and the first, second, third, and fourth offsets.

13. The method of claim 10 wherein the driver assistance system includes a forward-collision warning system, the method further comprising the step of:

generating a perceptible warning signal to alert the driver of the predicted impact.

14. The method of claim 10 wherein the driver assistance system includes an adaptive cruise control system, the method further comprising the step of:

reducing a commanded speed of the adaptive cruise control system to avoid the predicted impact.

15. The method of claim 10 wherein the driver assistance system includes a brake-steer system, the method further comprising the step of:

applying a braking force to avoid the predicted impact.

16. The method of claim 10 further comprising the step of:

identifying a trailer class of a detected trailer;

wherein the first offset is determined from a trailer table relating the trailer class to a respective value for the first offset.

17. The method of claim 10 wherein the second offset is determined from a first table relating the braking intensity to a respective value for the expected speed change and a second table relating the braking difference to a respective value for the second offset.

18. The method of claim 10 wherein the third offset is determined from a first table relating the steering angle to a respective value for the expected yaw change and a second table relating the steering difference to a respective value for the third offset.