Low Speed Lateral Vehicle Control via Steering Torque Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Autonomous driving systems face challenges in maintaining accurate lateral control at low vehicle speeds, as existing systems require more torque to steer and often encounter singularities near zero speed, leading to inefficiencies in path tracking.
Innovation Solution
A method for low-speed lateral vehicle control using vehicle front steering, which involves receiving sensor data, determining optimal steering control signals through one-dimensional nonlinear optimization to minimize path tracking errors, and providing these signals to a steering controller, while defining a cost function that accounts for radial and heading errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lateral control systems are used at low speeds, then the vehicle can maintain basic steering functionality, but the system requires excessive torque and encounters singularities near zero speed
Solution Approach 1:
The patent transforms the control parameters from road wheel angle to steering torque as the primary control variable. By formulating the cost function in terms of steering torque and using the relationship between torque and road wheel angle through the vehicle model, the system avoids singularities and excessive torque requirements that occur with direct road wheel angle control at low speeds
Solution Approach 2:
The patent replaces direct mechanical road wheel angle control with a model-based control approach that uses steering torque as the control input. The vehicle dynamics model is used to transform torque commands into effective path tracking, eliminating the need for high torque outputs and avoiding singularities near zero speed
2Reliability
If conventional lateral control systems are used at low speeds, then basic steering is maintained, but path tracking accuracy deteriorates due to singularities and torque limitations
Solution Approach 1:
The patent implements a feedback mechanism where the actual vehicle path is continuously compared with the desired path, and the path tracking error is used to adjust the steering torque commands. The cost function incorporates both radial and heading errors with feedback gains that are optimized to minimize tracking accuracy loss while avoiding singularities
Solution Approach 2:
The patent uses dynamic vehicle modeling to account for the changing dynamics at low speeds. The vehicle model captures the nonlinear relationship between steering torque and road wheel angle, allowing the control system to adapt to varying vehicle conditions and maintain path tracking accuracy without encountering singularities
3Ease of operation
If road wheel angle control is used, then steering response is direct, but the system becomes complex and requires singularity handling
Solution Approach 1:
The patent extracts the complexity of singularity handling and coordinate transformations by working directly in the steering torque domain. By formulating the entire control problem in terms of steering torque rather than road wheel angle, the system eliminates the need for complex singularity detection and handling mechanisms while maintaining steering responsiveness
Data Source
AI summary
A method for providing low speed lateral steering control for a vehicle is disclosed. The method includes receiving sensor data corresponding to a road wheel angle, determining a planned vehicle path of travel, defining a road wheel angle search range based on a maximum road wheel angle rate, determining a steering control goal using the road wheel angle that tracks and measures a difference between a current vehicle path and the planned vehicle path, determining an optimal steering control signal using the road wheel angle and the steering control goal and providing the control signal to a steering controller.