Steering Control Device Torque Feedback Limit Angle Handling
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Solution Overview
Problem
Existing steer-by-wire systems face challenges in naturally presenting the steering angle end to drivers, as feedback control can cancel out the torque for presenting the steering angle end, leading to an unnatural steering experience.
Innovation Solution
A steering control device that includes a reaction force device, a turning device, and a torque sensor, with a steering wheel torque controller and an end controller, which calculates a basic reaction force torque command value and an end presentation command value to prevent the steering wheel from being rotated beyond a predetermined limit angle, thereby stopping the feedback control when the angle reaches the limit, ensuring a natural steering angle end is presented to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is applied to make the torque sensor detection value follow the target value, then the steering control precision is improved, but the steering angle end torque is canceled out leading to unnatural steering experience
Solution Approach 1:
The patent segments the control into two distinct parts: a steering wheel torque controller for feedback control and an end controller for limit angle management. The feedback control is applied only to the steering wheel torque, while the end controller separately manages the reaction force torque near limit angles, preventing cancellation of end presentation torque.
Solution Approach 2:
The patent applies different control qualities to different operating conditions. Normal steering operations use standard feedback control, while operations near limit angles use a specialized end control mode that prioritizes natural end presentation over precise torque following.
2Force
If the reaction force torque is increased to prevent steering beyond limit angle, then the steering angle end is presented to driver, but the feedback control cancels out the end presentation torque
Solution Approach 1:
The end controller detects when the reaction force device angle or turning device angle approaches the limit angle and preemptively adjusts the reaction force torque command value. This preliminary action prevents the feedback control from canceling out the end presentation torque by anticipating the limit condition before it occurs.
Solution Approach 2:
The end controller acts as an intermediary between the steering wheel torque controller and the reaction force device. It modifies the reaction force torque command value to ensure that end presentation torque is maintained while still allowing feedback control to operate on the steering wheel torque.
3Measurement precision
If feedback control operates continuously, then the torque following precision is maintained, but the steering wheel becomes hard to rotate when approaching limit angle
Solution Approach 1:
The patent dynamically adjusts the control strategy based on the current operating state. When approaching limit angles, the end controller modifies the reaction force torque to maintain natural steering feel. The system transitions between normal feedback control and end control modes dynamically, ensuring both precision and ease of operation throughout the full range of motion.
Data Source
AI summary
A steering control device for use in a steer-by-wire system is provided. The steering control device controls a reaction force device and a turning device of a steer-by-wire system. The steering control device includes a steering wheel torque controller that calculates a basic reaction force torque command value being a basic value of a reaction force torque command value so that a detection value of the torque sensor follows a target value. The steering control device further includes an end controller that stops a control of the steering wheel torque controller when: an absolute value of angle of the reaction force device or the turning device is equal to or greater than a limit angle value; and a physical quantity corresponding to an output torque of the turning device and the detection value of the torque sensor are values corresponding to approach to the limit angle value.