TRAILER BACKUP ASSIST SYSTEM WITH PREDICTIVE HITCH ANGLE FUNCTIONALITY

• US 20190071088A1
• Filed: 09/01/2017
• Published: 03/07/2019
• Est. Priority Date: 09/01/2017
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Hu, Zheng, Lavoie, Erick Michael, Recker, Darrel Alan, Joyce, John P., Mattern, Donald Jacob, Hafner, Michael, Xu, Li, Tseng, Eric Hongtei, Pilutti, Thomas Edward
• Granted Patent: US 10,710,585 B2
• Time in Patent Office: Days
• CPC Class Codes: B60D 1/245 for facilitating push back or parking of trailers
• CPC Class Codes: B60D 1/62 involving supply lines, electric circuits, or the like
• CPC Class Codes: B60K 35/00 Instruments specially adapted for vehicles; Arrangement of instruments in or on vehicles
• CPC Class Codes: B60R 2300/307 virtually distinguishing relevant parts of a scene from the background of the scene
• CPC Class Codes: B60R 2300/80 characterised by the intended use of the viewing arrangement
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 10/20 including control of steering systems
• CPC Class Codes: B60W 2710/18 Braking system
• CPC Class Codes: B60W 2710/20 Steering systems
• CPC Class Codes: B60W 30/18036 Reversing
• CPC Class Codes: B62D 1/22 Alternative steering-control elements, e.g. for teaching purposes
• CPC Class Codes: B62D 13/06 for backing a normally drawn trailer
• CPC Class Codes: B62D 15/027 Parking aids, e.g. instruction means
• CPC Class Codes: G06T 11/60 Editing figures and text; Combining figures or text
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30264 Parking
• CPC Class Codes: G06T 7/13 Edge detection
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: G06T 7/80 : Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

A trailer backup assist system is provided herein. The system includes a calibration feature for calibrating an imaging device used for hitch angle detection. The system also employs multiple hitch angle detection methods, a number of which may run in parallel to increase the intervals at which a hitch angle can be measured. The system additionally includes a predictive feature in which a hitch angle can be predicted in instances where a trailer sensing device fails. The system is further configured to estimate a trailer length and generate steering commands that are invariant to the estimated trailer length under certain conditions.

Claims

1. A calibration method comprising the steps of:

using an imaging device to capture an image of a rear bumper; and

providing a controller configured to;

process the captured image;

identify a boundary separating the rear bumper from a ground;

compare the identified boundary to an ideal boundary; and

determine an offset between the identified boundary and the ideal boundary.

2. The calibration method of claim 1, wherein the ideal boundary comprises a continuous line.

3. The calibration method of claim 1, wherein the ideal boundary comprises a line having a break.

4. The calibration method of claim 1, wherein the ideal boundary is overlaid onto the captured image.

5. The calibration method of claim 1, wherein the offset is defined by a vector having a horizontal component, a vertical component, and a rotational component.

6. The calibration method of claim 4, wherein the controller determines the offset by iterating on candidates for each of the horizontal, vertical, and rotational components until the identified boundary overlaps with the ideal boundary.

7. The calibration method of claim 1, wherein the controller is further configured to generate a warning if the offset is unable to be determined.

8. A trailer backup assist system comprising:

a device configured to sense a trailer; and

a controller configured to determine a hitch angle between a vehicle and the trailer based on data provided by the device, wherein if the device fails, the controller predicts the hitch angle based on a last known hitch angle, a last known angular velocity of the trailer, and an execution cycle time.

9. The trailer backup assist system of claim 8, wherein the device comprises an imaging device and the controller is configured to predict the hitch angle if the imaging device becomes obstructed or otherwise fails.

10. The trailer backup assist system of claim 8, wherein the controller is further configured to predict the hitch angle up until an error band reaches a threshold.

11. The trailer backup assist system of claim 8, wherein the controller is further configured to determine an upper and lower error band of the predicted hitch angle, and enact a countermeasure if the upper error band reaches a maximum controllable hitch angle or the lower error band reaches a minimum controllable hitch angle, whichever comes first.

12. The trailer backup assist system of claim 11, wherein the upper and lower error bands are each determined based on a predicted hitch angle, an initial degree error at the moment the device fails, an accumulative vehicle travel distance, and a trailer length.

13. The trailer backup assist system of claim 11, wherein the countermeasure comprises at least one of steering the vehicle to keep from exceeding the maximum controllable hitch angle or the minimum controllable hitch angle and reducing a speed of the vehicle.

14. The trailer backup assist system of claim 8, wherein the last known angular velocity is based on an angular velocity that is adjusted by a percentage error.

15. A method of determining hitch angle between a vehicle and a trailer, comprising the steps of:

selecting at least one hitch angle detection method amongst a plurality of hitch angle detection methods;

using the selected at least one hitch angle detection method to determine a hitch angle between a vehicle and a trailer; and

transitioning to another hitch angle detection method in the event the selected at least one hitch angle detection method becomes unavailable.

16. The method of claim 15, wherein the plurality of hitch angle detections methods each employ imager-based hitch angle detection.

17. The method of claim 15, wherein the plurality of hitch angle detection methods are ranked based on a confidence score assigned to each hitch angle detection method, and wherein the at least one selected hitch angle detection comprises an available hitch angle detection method having the highest confidence score.

18. The method of claim 17, further comprising the step of limiting the speed of the vehicle based on the confidence score assigned to the at least one selected hitch angle detection method.

19. The method of claim 15, further comprising the step of predicting the hitch angle during the transitioning between the at least one selected hitch angle detection method and another hitch angle detection method or if each of the plurality of hitch angle detection methods become unavailable.

20. The method of claim 15, further comprising the step of using the determined hitch angle to control at least one of a hitch angle operating range, a speed limit of the vehicle, and the curvature of a backing path of the trailer.

21. A trailer backup assist system comprising:

a steering input device configured to provide a curvature command based on user input; and

a controller configured to estimate a trailer length based on a vehicle and trailer yaw rate and generate a steering command based on the estimated trailer length, the curvature command, a maximum steering angle, and a vehicle speed, wherein the generated steering command is invariant to the estimated trailer length under certain conditions.

22. The trailer backup assist system of claim 21, wherein the steering input device comprises a rotatable knob configured to allow a user to input a desired direction and curvature of a backing path of a trailer backed by a vehicle.

23. The trailer backup assist system of claim 21, wherein the controller comprises a curvature input scaling module configured to scale the curvature command by a maximum effective curvature to generate a curvature input based on the maximum steering angle and the estimated trailer length.

24. The trailer backup assist system of claim 22, wherein the controller further comprises a curvature mapping module configured to generate a reference hitch angle based on the curvature input and the estimated trailer length.

25. The trailer backup assist system of claim 24, wherein the controller further comprises a subtractor configured to subtract an estimated hitch angle from the reference hitch angle to generate a signal provided to a proportional-integral controller configured to generate a control variable, wherein the estimated hitch angle is based on the vehicle and trailer yaw rate.

26. The trailer backup assist system of claim 25, wherein the controller further comprises a hitch angle controller configured to generate the steering angle based on the control variable, the estimated trailer length, and the vehicle speed.

27. The trailer backup assist system of claim 25, wherein a proportional coefficient of the proportional-integral controller is based only on the estimated trailer length such that a transient response of the controller is invariant to the estimated trailer length.

28. The trailer backup assist system of claim 21, wherein the certain conditions comprise one of a zero curvature command, a maximum curvature command, and a minimum curvature command.