Steering Control Device Torque Restriction for End Abutting Impact
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Solution Overview
Problem
Existing steering control systems, such as those described in JP 2015-20506 A, face issues where incorrect steering angle or rotation angle measurements due to sensor abnormalities can hinder steering operations by applying excessive steering reaction forces, leading to potential end abutting impacts.
Innovation Solution
A steering control device that calculates a torque command value with a restricting value based on the absolute value of the rotation angle and angular velocity, restricting the motor torque to prevent excessive steering angle and velocity when the rotation angle exceeds a threshold, thereby mitigating end abutting impacts and ensuring smooth steering operations even with incorrect sensor readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large correction value is used to prevent end abutting impact, then the steering reaction force is increased before rack end contact, but steering operation is hindered when sensor readings are incorrect
Solution Approach 1:
The restricting value is made dynamic by calculating it based on the absolute value of the rotation angle and angular velocity. As the absolute value of the rotation angle increases or the angular velocity increases, the restricting value decreases. This dynamic adjustment allows the system to apply stronger restrictions when approaching rack end vicinity or during high-speed steering, while maintaining normal operation during regular steering maneuvers.
Solution Approach 2:
The system changes the parameter of the restricting value based on the rotation angle and angular velocity. By using these two parameters to dynamically adjust the restricting value, the system can adaptively prevent end abutting impact under critical conditions while avoiding unnecessary hindrance to normal steering operations when sensor readings may be incorrect.
2Reliability
If the restricting value is set low to prevent end abutting impact, then steering safety is improved, but steering responsiveness is reduced during normal operation
Solution Approach 1:
The restricting value dynamically adjusts based on the absolute value of the rotation angle and angular velocity. During normal steering operations where these values are low, the restricting value remains high, maintaining good steering responsiveness. When approaching rack end vicinity (high rotation angle) or during high-speed steering (high angular velocity), the restricting value automatically decreases to prevent end abutting impact, thus ensuring steering safety.
Solution Approach 2:
The system changes the restricting value parameter based on real-time rotation angle and angular velocity measurements. This parameter change strategy allows the system to maintain high responsiveness during normal operation while automatically reducing the restricting value under critical conditions to prioritize steering safety.
3Strength
If the steering reaction force is increased to mitigate end abutting impact, then rack end protection is improved, but steering smoothness is reduced when sensor readings are incorrect
Solution Approach 1:
The steering reaction force is dynamically controlled through the angular velocity restriction component. During normal steady-state steering, the angular velocity is low, so the restricting value remains high and does not interfere with steering smoothness. When rapid steering movements occur (high angular velocity), the restricting value automatically decreases to limit the motor torque and prevent harsh steering reaction forces that would occur with incorrect sensor readings.
Solution Approach 2:
The system changes the restricting value parameter based on the angular velocity to adaptively control the steering reaction force. This parameter change ensures that rack end protection is activated only when necessary (during high-speed steering or when approaching rack end vicinity), while maintaining steering smoothness during normal operations with potentially incorrect sensor readings.
Data Source
AI summary
A steering control device includes a microcomputer. The microcomputer is configured to calculate a torque command value that is a target value of a motor torque, set a restricting value that is an upper limit of an absolute value of the torque command value, restrict the absolute value of the torque command value to be equal to or less than the restricting value, control driving of a motor such that the motor torque follows the restricted torque command value, calculate a steering angle restricting value that decreases based on an increase of an absolute value of a rotation angle, and an absolute value of an angular velocity, when the absolute value of the rotation angle of the rotary shaft exceeds a steering angle threshold, and set the restricting value to be a value equal to or less than the steering angle restricting value.