Trailer Backup Trajectory Planner Using Dynamic Circular Paths
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Solution Overview
Problem
Reversing a vehicle while towing a trailer is challenging, especially for unskilled drivers, due to the need for opposite steering inputs and amplified errors leading to jackknife conditions, and existing systems assume a zero curvature path, limiting their usefulness in real-world scenarios.
Innovation Solution
A trailer backup assist system that includes a state estimator and a trajectory planner to identify a waypoint position, generate circular trajectories, and dynamically regenerate them as the trailer reverses, allowing the system to guide the trailer along these trajectories and prevent jackknife conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a zero curvature path is assumed for trailer backup, then the control system is simplified, but the system becomes useless for real-world curved path scenarios
Solution Approach 1:
The system dynamically adjusts the curvature of the trailer path based on real-time conditions and driver input. The trajectory planner generates curved paths when needed rather than assuming a fixed zero curvature path, allowing the system to adapt between straight and curved trajectories as operating conditions change
Solution Approach 2:
The system changes the curvature parameter of the trailer path from zero (straight) to non-zero (curved) based on detected conditions such as obstacles, narrow spaces, or driver intent. This parameter change enables the system to handle diverse path requirements while maintaining a unified control architecture
2Reliability
If small steering errors occur while backing a trailer, then the trailer follows the desired path, but errors are amplified causing the trailer to depart from the desired path
Solution Approach 1:
The system continuously monitors the actual trailer position and compares it with the desired trajectory. When deviations are detected, the feedback mechanism adjusts the steering commands to correct the path, compensating for amplified errors in real-time and maintaining reliable path following
Solution Approach 2:
The trajectory planner pre-calculates the desired curved path before execution, anticipating the correct steering inputs needed to follow the path. This preliminary planning prevents error accumulation by providing a reference trajectory that accounts for the trailer's kinematics and potential error amplification
3Speed
If maximum steering input is applied to reverse a trailer, then the trailer reverses faster, but a jackknife condition occurs
Solution Approach 1:
The system dynamically adjusts the steering input magnitude based on the current hitch angle and trailer position. Rather than applying maximum steering input constantly, the controller modulates the steering angle in real-time, increasing steering when safe and reducing it when approaching jackknife conditions, enabling both speed and safety
Solution Approach 2:
The system detects conditions that precede jackknife (such as increasing hitch angle beyond a threshold) and applies counter-steering actions before the jackknife condition fully develops. This preliminary anti-action prevents the harmful condition while maintaining progress in the reversal maneuver
Data Source
AI summary
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.