PATH PLANNING FOR TOW VEHICLE AND TRAILER

A method of planning a path for reversing a trailer along a defined path a includes defining a desired end point for a trailer path and determining a set of reversing trailer curvatures for moving the trailer between each of a plurality of possible waypoints along a possible trailer path. A steering angle is determined for each of the curvatures. The reversing trailer path to the end point is then created based on a set of waypoints selected based on the determined reversing trailer curvature at each of the plurality of possible waypoints that meets a defined path determination criteria.

The present disclosure relates to method and system for planning a path for a vehicle and trailer.

BACKGROUND

Autonomously operated or assisted vehicles may aid a vehicle operator and/or take over control of the vehicle. Autonomous and semi-autonomous operation is of use for vehicle maneuvers that are most challenging to a vehicle operator. For example, parallel parking and reversing of a vehicle with a trailer. Reversing of a vehicle trailer is a maneuver that most drivers do not perform often and therefore autonomous or semi-autonomous assist systems are of great value to vehicle consumers.

Path planning is accomplished in various ways based on sensor and generated local area maps. Path planning for a reversing trailer is challenging as such a maneuver is naturally unstable. Moreover, objects and practical angle limitations between a trailer and tow vehicle may further complicate creation of an efficient reversing trailer path. Automotive system and parts manufactures continually seek to improve vehicle operation, efficiencies and customer satisfaction.

The background description provided herein is for the purpose of generally presenting a context of this disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

SUMMARY

A method of planning a path for reversing a trailer along a defined path according to a disclosed exemplary embodiment includes, among other possible things, defining a desired end point for a trailer path, determining a set of reversing trailer curvatures for moving the trailer between each of a plurality of possible waypoints along a possible trailer path, determining a steering angle for a tow vehicle coupled to the trailer corresponding to each of the determined set of reversing trailer curvatures, and determining the trailer path to the end point based on a set of waypoints selected based on the determined reversing trailer curvature at each of the plurality of possible waypoints that meets a defined path determination criteria.

Another exemplary embodiment of the foregoing method further comprises determining a start pose of the trailer at the starting point within a predefined local reference frame.

Another exemplary embodiment of any of the foregoing methods further comprises defining a finish pose of the trailer at the end point within the local reference frame.

Another exemplary embodiment of any of the foregoing methods further comprises defining a distance between the possible way.

In another exemplary embodiment of any of the foregoing methods, the defined path determination criteria comprises a shortest distance.

In another exemplary embodiment of any of the foregoing methods, the defined path determination comprises a predefined range of steering angles and each of the waypoints selected correspond with a reversing trailer curvature attainable with a steering angle within the predefined range of steering angles.

In another exemplary embodiment of any of the foregoing methods, the predefined range of steering angles is less than a maximum range of a tow vehicle steering system.

In another exemplary embodiment of any of the foregoing methods, the tow vehicle includes a controller with a memory storing computer executable instructions executable by a controller and further comprising prompting the controller to determine the set of reversing trailer curvatures according to the stored computer executable instructions.

In another exemplary embodiment of any of the foregoing methods, the tow vehicle includes a controller with a memory storing computer executable instructions executable by a controller and further comprising prompting the controller to determine the steering angle corresponding to each of the determined set of reversing trailer curvatures according to the stored computer executable instructions.

An autonomous vehicle control system according to another exemplary embodiment includes, among other possible things, a controller with computer executable instructions configured to determine, when executed by at least one processor, a path for reversing a trailer from a starting point to a desired end point, wherein the determination of the reversing trailer path includes defining a desired end point for a trailer path, determining a set of reversing trailer curvatures for moving the trailer between each of a plurality of possible waypoints along a possible trailer path, determining a steering angle for a tow vehicle coupled to the trailer corresponding to each of the determined set of reversing trailer curvatures, and determining the trailer path to the end point based on a set of waypoints selected based on the determined reversing trailer curvature at each of the plurality of possible waypoints that meets a defined path determination criteria.

In another embodiment of the foregoing autonomous vehicle control system, the controller is further configured to determine a start pose of the trailer at the starting point within a predefined local reference frame and a desired finish pose of the trailer at the end point within the local reference frame.

In another embodiment of any of the foregoing autonomous vehicle control systems, the defined path determination comprises a predefined range of steering angles and the controller is further configured to select each of the waypoints that correspond with a reversing trailer curvature attainable with a steering angle within the predefined range of steering angles.

In another embodiment of any of the foregoing autonomous vehicle control systems, the predefined range of steering angles is less than a maximum range of a tow vehicle steering system.

Another embodiment of any of the foregoing autonomous vehicle control system further includes a sensor system disposed within the tow vehicle for providing information indicative of a pose of the trailer and to vehicle odometry.

In another embodiment of any of the foregoing autonomous vehicle control systems, the controller includes a memory device in communication with the processor, the memory device including the computer executable instructions.

A computer readable medium according to another exemplary embodiment includes, among other possible things, instructions executable by a controller configured to determine, when executed by at least one processor, a steering angle of a tow vehicle required to maneuver an attached trailer along a predefined path, wherein the instructions include, instructions prompting the controller to define a desired end point for a trailer path, instructions prompting the controller to determine a set of reversing trailer curvatures for moving the trailer between each of a plurality of possible waypoints along a possible trailer path, instructions prompting the controller to determine a steering angle for a tow vehicle coupled to the trailer corresponding to each of the determined set of reversing trailer curvatures, and instructions prompting the controller to determine the trailer path to the end point based on a set of waypoints selected based on the determined reversing trailer curvature at each of the plurality of possible waypoints that meets a defined path determination criteria.

Another embodiment of the foregoing computer readable medium further includes instructions prompting the controller to determine a start pose of the trailer at the starting point within a predefined local reference frame and a desired finish pose of the trailer at the end point within the local reference frame.

Another embodiment of any of the foregoing computer readable mediums further includes instructions prompting the controller to select each of the waypoints that correspond with a reversing trailer curvature attainable with a steering angle within the predefined range of steering angles.

DETAILED DESCRIPTION

Referring toFIG.1, a control system20for planning a reversing trailer path utilizes information regarding different trailer curvature paths corresponding to different tow vehicle steering angles. The example control system20is configured to determine a set of trailer curvatures56,58, and60at each waypoints along a potential reversing trailer path. A corresponding steering angle62,64and66is determined for each of the trailer curvatures56,58and60. The curvatures56,58and60along with the steering angles62,64and66are utilized by the control system20to create a reversing trailer path that meets predefined criteria. The predefined criteria can include a shortest distance, the fastest route and/or any other criteria for evaluating and selecting a desired reversing trailer path.

The tow vehicle22includes a steered wheel26that is spaced apart from a vehicle axle36. The tow vehicle22includes a steering control system54for moving the steered wheel. A wheel base30is the distance between the steering wheel26and the vehicle axle36and a hitch length32is a distance between the axle36and a coupling35. The trailer24includes a wheel base34from the coupling35to the trailer axle36.

An angle40between a center line of the tow vehicle22and the trailer24is created in response to a steering angle28. The steering angle28is provided by a steered wheel26of the two vehicle22. The angle40should be constrained within a limited range to provide practical maneuvering of the trailer24. As appreciated, a large angle40may result in an orientation between the tow vehicle22and the trailer22that does not provide for further movement nor is practical for maneuvering of reversing trailer24. For example, if the trailer24jackknifes relative to the tow vehicle, no further reversing is possible. The example control system20prevents the use of such impractical trailer reversing angles.

The control system20includes a controller42that includes a processor44and a memory device46that holds software instructions48. The memory device46may include a computer readable medium50that holds the software instructions48. The software instructions prompt the processor and controller to determine specific reversing trailer curvatures at each of a plurality of waypoints.

The example controller42may be a separate controller dedicated to the control system20are may be part of an overall vehicle controller. Accordingly, example controller42relates to a device and system for performing necessary computing and/or calculation operations of the control system20. The controller42may be specially constructed for operation of the control system20, or it may comprise at least a general-purpose computer selectively activated or reconfigured by software instructions48stored in the memory device46. The computing system can also consist of a network of (different) processors.

The memory device46provides for the storage of the software instructions48that prompt operation of the controller42. The software instructions48may be embodied in a computer program that uses data obtained from the sensor systems52and data stored in the memory device46that may be required for its execution.

The instructions48for configuring and operating the controller42, the control system20and the processor44are embodied in software instructions that may be stored on the computer readable medium50. The computer readable medium50may be embodied in structures such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, magnetic-optical disks, read-only memories (ROMs), random access memories (RAMS), EPROMs, EEPROMs, magnetic or optical cards, application specific integrated circuits (ASICs), or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. The disclosed computer readable medium may be a non-transitory medium such as those examples provided.

Moreover, the software instructions48may be saved in the memory device46. The disclosed memory device46, may can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). The software instructions48in the memory device46may include one or more separate programs, each of which includes an ordered listing of executable instructions for implementing logical functions. The disclosed controller42is configured to execute the software instructions48stored within the memory device46, to communicate data to and from the memory device48, and to generally control operations pursuant to the software. Software in memory, in whole or in part, is read by the processor44, perhaps buffered within the processor, and then executed.

At each of a plurality of waypoints along a trailer reversing path, a set the trailer reversing curvature at each waypoint, a steering angle corresponding with each of those waypoints is also determined. Utilizing the trailer curvature and the corresponding steering angle, a path between a starting point and desired end point is determined according to predetermined criteria.

Referring toFIG.2, with continued reference toFIG.1, a flow diagram68schematically illustrates the process steps that the control system20proceeds through to determine the desired path. The process utilizes a trailer start pose and heading indicated at70. The trailer start pose and heading is determined by vehicle sensors52that are disposed within the tow vehicle22. The vehicle sensors52can include cameras, radar systems, inertial measurement units, and lidar systems as well as any other vehicle sensor system that provides information indicative of vehicle odometry. Information indicative of the trailer start pose and heading70are provided to a path planning module75.

A desired trailer end pose heading schematically indicated at72is determined and provided to the path planning module75. Both the trailer start pose and heading and trailer end pose and heading are indicated with reference to a local reference map schematically indicated at74. The local reference map74is provided to the path planning module75. The trailer start pose and heading70, trailer end pose and heading72, along with the local reference map74are inputs for the path planning module75.

The path planning module75determines specific reversing trailer curvatures indicated at80along with a tow vehicle steering angle82at each of a plurality of path waypoints78. At each path waypoint78, a set of reversing trailer curvatures is determined. The reverse trailer curvatures include the plurality of trailer curvatures56,58,60. It should be appreciated, that only a few trailer curvatures are shown by way of example. Additional curvatures may be determined within the scope and contemplation of this disclosure.

Each of these curvatures56,58and60are provided in response to a specific tow vehicle steering angle. Accordingly, the path planning module75determines a steering angle62,64and68for each of the curvatures56,58and60. The determination of the steering angles in the module75is schematically indicated at82.

In one example embodiment, the steering angle for each trailer curvature is provided by Equation 1.

Rcis the desired trailer curvature;δ is the vehicle steered wheel angle (bounded between the maximum turning angle, ±δmax);γ is the hitch angle;LTis the trailer wheelbase;LWBis the vehicle wheelbase; andLHis the length of the hitch (from vehicle axle to hitch point).

The steering angle28that provides the different radii of curvature is constrained within a predefined range. The predefined range of tow vehicle steering angles is less than the maximum range of steering angles that is possible by the tow vehicle22. As appreciated, some possible steering angles may result in a reversing trailer curvature that is not practical nor desired for use in a trailer reversing pay. For example, any steering angle28that results in a jack-knife of the trailer24is not practical and not utilized. Accordingly, only those curvatures56,58and60that correspond with steering angles28within the predefined range are considered. The steering angle range is less than maximum angles and may vary depending on a location along one of the proposed way points.

Path planning proceeds from one way point to another way point along a proposed path. The module75selects a plurality of way points as indicated at78at which the curvature and steering angle are determined. Accordingly, in this example, the vehicle path planning module75determines a plurality of reverse trailer curvatures28at each selected waypoint. Corresponding tow vehicle steering angles are also determined.

Once the path creation module75has determined a corresponding tow vehicle steering angle28for the set of trailer curvatures56,58and60at each waypoint, one of the waypoints is selected depending on predetermined criteria. As appreciated, one criteria is to provide the shortest most efficient route for reversing the trailer between a starting point and an end point. The process of determining a trailer curvature80and corresponding tow vehicle steering angles82proceeds for each way point from a starting point to a desired end point.

Referring toFIG.3, with continued reference toFIGS.1and2, the tow vehicle22and the trailer24are schematically shown within a local reference map74. The tow vehicle22and trailer24pose is schematically shown at a start point80. A proposed path76is schematically shown and includes the plurality of waypoints78. At each waypoint78, a set of trailer curvatures56,58and60as shown inFIG.1is determined. The corresponding steering angles62,64and66as shown inFIG.1are also determined. From this information, the path76from one waypoint78to another waypoint is determined. The system20proceeds for each waypoint78along the path76until a desired path between the starting point80and an end point84at an end pose and heading70and a desired end position72is obtained.

Referring toFIG.4, the trailer24and tow vehicle22is shown at the end point84with the end trailer pose and heading74. The path76to the end point84has been determined by selecting waypoints78that corresponds with a trailer curvature and steering angle that meet predefined criteria to form the path76.

It should be appreciated that a plurality of path planning algorithms and features may be included and operated in concert with the disclosed example method. In one example, a variation of a hybrid A* path planning algorithm is utilized. Operation of the hybrid A* path planning algorithm according to an example disclosed embodiments occurs as commonly known with the addition of the evaluation of trailer curvatures and respective steering angles at each waypoint.

Accordingly, rather than a fixed set of steering wheel inputs, the example proposed method utilizes a series of reversing trailer curvature functions to determine corresponding steering angles. A steering angle is calculated for each of the plurality of curvatures at each waypoint78. Incorporation of the example trailer curvature features and constrained steering angles provides for the creation of a path that includes practical and achievable trailer reversing maneuvers.