Trailer Backup Assist Calibration via Hitch Angle Offset
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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 steering errors, and the risk of jackknife conditions, which existing trailer backup assist systems often address with complex and costly solutions that assume a straight path and require complex human-machine interfaces.
Innovation Solution
A method and system for calibrating a backup assist system that includes sensing yaw and hitch angles, determining angle rates, and calculating offsets to allow drivers to specify desired trailer path curvatures using a user-friendly interface, such as a steering knob or touch screen, while controlling the vehicle to prevent jackknife conditions through electric power-assisted steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex human-machine interface devices are used to specify path, obstacles and goal, then the trailer backup assist system can achieve accurate path following, but the system complexity and cost increase significantly
Solution Approach 1:
The patent extracts and removes the complex path planning and obstacle detection functions from the system. Instead of requiring the system to know the desired path, obstacles, and goal points, the invention only requires detection of the current hitch angle and basic vehicle state parameters. This extraction of unnecessary complex functions directly reduces system complexity while maintaining adequate backup assist functionality through simpler angle-based control.
Solution Approach 2:
The system uses the vehicle's existing sensors and control systems to provide the backup assist functionality without requiring additional complex external devices. By leveraging already-available vehicle data (hitch angle sensors, steering angle sensors, vehicle speed) and existing control mechanisms (electric power steering), the system achieves path following capability through self-service rather than external complex instrumentation.
2Measurement precision
If high precision GPS and inertial navigation are used to determine desired path and stopping point, then the system can achieve accurate positioning and path following, but the system cost and complexity increase
Solution Approach 1:
The patent removes the requirement for high-precision GPS and inertial navigation systems entirely. Instead of using these complex external positioning systems, the invention relies on relative position detection through hitch angle measurement and basic vehicle kinematics. This extraction eliminates the need for expensive navigation hardware while maintaining sufficient accuracy for trailer backup operations through angle-based geometric calculation.
3Device complexity
If the system assumes zero curvature path for backup, then the control algorithm is simplified, but the system usefulness is significantly limited as most real-world cases involve curved paths
Solution Approach 1:
The patent implements dynamic path curvature capability without increasing control algorithm complexity by using real-time hitch angle feedback. The system dynamically adapts to curved paths by continuously monitoring the hitch angle and adjusting steering commands accordingly, rather than requiring pre-planned static paths. This dynamic approach allows the same simple angle-based controller to handle both straight and curved backup scenarios effectively.
4Reliability
If maximum steering input is applied continuously to reduce hitch angle, then the jackknife condition can be prevented, but the vehicle must be pulled forward when jackknife angle is achieved causing inconvenience and potential damage
Solution Approach 1:
The patent uses continuous hitch angle feedback to modulate steering input magnitude. Instead of applying maximum steering input unconditionally, the system monitors the hitch angle in real-time and adjusts steering commands proportionally to the detected angle and its rate of change. This feedback-based proportional control prevents jackknife conditions by applying just enough steering effort to reduce the hitch angle smoothly, avoiding the need for aggressive maximum steering inputs that cause oscillations and require corrective forward pulling.
Data Source
AI summary
A system and a method are provided for calibrating a backup assist system for a trailer attached to a vehicle. The method includes driving the vehicle forward substantially straight above a threshold speed, sensing a yaw rate of the vehicle, and sensing a measured hitch angle of the trailer. A yaw sensor continuously senses the yaw rate of the vehicle and a hitch sensor continuously measures the hitch angle for determining an angle rate based on the measured hitch angle. Further, a controller determines an offset between the measured hitch angle and an actual hitch angle when the yaw rate and angle rate are substantially zero or otherwise the same.