TRAJECTORY PLANNER FOR A TRAILER BACKUP ASSIST SYSTEM

• US 20140249691A1
• Filed: 04/21/2014
• Published: 09/04/2014
• Est. Priority Date: 04/19/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Pilutti, Thomas Edward, Hafner, Michael
• Granted Patent: US 9,708,000 B2
• Time in Patent Office: Days
• US Class Current: 701/1
• CPC Class Codes: B62D 13/06 for backing a normally drawn trailer
• CPC Class Codes: B62D 15/0275 by overlaying a vehicle path based on present steering angle over an image without processing that image
• CPC Class Codes: B62D 15/0285 Parking performed automatically

Abstract

In one embodiment of the disclosed subject matter, a trailer backup assist system includes a state estimator that determines a current position of a trailer relative to a waypoint position. In addition, the trailer backup assist system includes a trajectory planner that generates first and second circular trajectories tangent to one another spanning between the current and waypoint positions. The trailer backup assist system also includes a controller that reverses the trailer to the waypoint position along the first and second circular trajectories, which are dynamically regenerated as the trailer reverses along the first circular trajectory.

Claims

1. A method for reversing a trailer, comprising:

identifying a waypoint position;

determining a current position of the trailer relative to the waypoint position;

generating first and second circular trajectories tangent to one another connecting between the current and waypoint positions;

guiding the trailer on the first circular trajectory while regenerating the first and second circular trajectories; and

guiding the trailer on the second circular trajectory to the waypoint position.

2. The method of claim 1, wherein the current and waypoint positions each include a coordinate location and an angular orientation of the trailer.

3. The method of claim 2, wherein the angular orientation of the trailer at the current and waypoint positions is substantially tangent to the respective first and second circular trajectories.

4. The method of claim 2, wherein the current position of the trailer is determined based on a hitch angle sensed between the trailer and a vehicle and a localized coordinate system generated proximate the waypoint position.

5. The method of claim 1, further comprising:

switching from guiding the trailer along the first circular trajectory to guiding the trailer along the second circular trajectory when the trailer reaches a tangent position between the first and second circular trajectories.

6. The method of claim 1, wherein generating the first and second circular trajectories includes reducing a path distance of the first and second circular trajectories by generating a plurality of potential pairs of tangent circular trajectories between the current and waypoint positions and determining arc lengths between the current and waypoint positions along the plurality of potential pairs of tangent circular trajectories.

7. The method of claim 1, further comprising:

guiding the trailer substantially straight to the waypoint position if the trailer becomes generally collinear with the waypoint position.

8. The method of claim 1, wherein guiding the trailer includes generating a steering angle command for a vehicle as a function of a hitch angle between the trailer and the vehicle, a steering angle of the vehicle, and a curvature of the respective first or second circular trajectory.

9. The method of claim 8, wherein feedback linearization is provided for generating the steering angle command and avoiding the hitch angle exceeding a jackknife threshold angle.

10. A trailer backup assist system comprising:

a state estimator determining a current position of a trailer relative to a waypoint position;

a trajectory planner generating first and second circular trajectories tangent to one another spanning between the current and waypoint positions; and

a controller reversing the trailer to the waypoint position along the first and second circular trajectories, which are dynamically regenerated as the trailer reverses along the first circular trajectory.

11. The trailer backup assist system of claim 10, wherein the current and waypoint positions each include a coordinate location and an angular orientation, such that the first and second circular trajectories are tangent to the angular orientation of the current and waypoint positions.

12. The trailer backup assist system of claim 10, wherein the trajectory planner includes a first operating mode continuously generating the first and second circular trajectories as the trailer reverses along the first circular trajectory and a second operating mode generating the second circular trajectory as the trailer reverses along the second circular trajectory.

13. The trailer backup assist system of claim 12, wherein the trajectory planner switches from the first operating mode to the second operating mode when the trailer reaches a tangent position tangent to both the first and second circular trajectories.

14. The trailer backup assist system of claim 12, wherein the second operating mode generates the second circular trajectory irrespective of the angular orientation of the waypoint position.

15. The trailer backup assist system of claim 10, further comprising:

a hitch sensor sensing a hitch angle between the trailer and a vehicle, wherein the controller generates a steering angle command for the vehicle as a function of the hitch angle, a steering angle of the vehicle, and a curvature of the respective first or second circular trajectory.

16. The trailer backup assist system of claim 10, wherein the state estimator determines the current position of the trailer based on a hitch angle sensed between the trailer and a vehicle and a localized coordinate system generated proximate the waypoint position.

17. The trailer backup assist system of claim 10, wherein the state estimator includes a positioning device on a vehicle and the current position of the trailer is determined based on a hitch angle sensed between the vehicle and the trailer.

18. A trajectory planner for reversing a trailer with a trailer backup assist system, comprising:

a first operating mode dynamically generating first and second circular trajectories tangent to one another connecting between a current position of the trailer and a waypoint position as the trailer reverses along the first circular trajectory; and

a second operating mode dynamically generating the second circular trajectory to the waypoint position as the trailer reverses along the second circular trajectory.

19. The trajectory planner of claim 18, wherein the second operating mode generates the second circular trajectory based on a location of the waypoint position irrespective of an angular orientation of the waypoint position.

20. The trajectory planner of claim 18, further comprising:

a projection mode guiding the trailer substantially straight to the waypoint position if the trailer becomes generally collinear with the waypoint position.