Lateral Movement Control Using Non-Linear Optimization
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Solution Overview
Problem
Existing methods for controlling vehicle lateral movement lack smoothness and accuracy, especially during mild lateral acceleration, and kinematic models are not accurate at higher speeds.
Innovation Solution
A method and apparatus that use quasi-steady state approximations and non-linear optimization to determine road wheel angle or steering torque commands, minimizing path tracking errors by calculating the center of vehicle rotation and applying these commands through an electronic power steering module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If kinematic models are used for vehicle lateral movement control, then the control system is simple to implement, but the accuracy deteriorates at higher speeds
Solution Approach 1:
The patent transitions from a kinematic model to a dynamic model that incorporates velocity-dependent parameters such as cornering stiffness, understeer gradient, and suspension compliance. This parameter change allows the model to accurately represent vehicle behavior across different speed ranges, particularly improving high-speed path tracking accuracy while maintaining computational tractability through quasi-steady state approximations.
2Ease of operation
If conventional control methods are used for lateral movement, then the control approach is straightforward, but the smoothness and accuracy during mild lateral acceleration deteriorate
Solution Approach 1:
The patent implements a feedback control mechanism using a cost function that minimizes path tracking errors. The controller continuously adjusts the steering torque command based on the difference between the desired path and actual vehicle position, incorporating weighted costs for radial distance error and heading error. This feedback approach ensures smooth and accurate path tracking during mild lateral acceleration maneuvers.
Solution Approach 2:
The patent employs a dynamic vehicle model that accounts for velocity-dependent behaviors including cornering stiffness variations, understeer gradient effects, and suspension compliance. This dynamic approach captures the complex vehicle responses during mild lateral acceleration, enabling smooth and accurate path tracking that adapts to changing operating conditions.
3Measurement precision
If a dynamic model with multiple parameters is used, then the path tracking accuracy improves, but the computational complexity increases
Solution Approach 1:
The patent performs preliminary calculations of the center of vehicle rotation using quasi-steady state approximations before executing the full optimization routine. By pre-computing key parameters such as the instantaneous center of rotation based on current vehicle state, the system reduces the computational burden of the subsequent non-linear optimization while maintaining accurate path tracking performance.
Data Source
AI summary
A method and apparatus that control lateral movement of a vehicle are provided. The method includes receiving vehicle information and path information of the vehicle, determining a center of vehicle rotation from the vehicle information, minimizing a path tracking error based on the path information of the vehicle, determining a road wheel angle command or a steering torque command using non-linear optimization based on the minimized path tracking error, and controlling an actuator according to the road wheel angle command or steering torque command.