Steering Control Device Axial Force Allocation
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Solution Overview
Problem
The existing steer-by-wire steering control apparatuses face inaccuracies in steering reaction force control due to decreased accuracy of the control amount based on the steering wheel angle, leading to inappropriate steering reaction forces.
Innovation Solution
The solution involves allocating feedback and feedforward axial forces at a ratio based on their difference, with the final steering-rack axial force being set to drive the reaction force motor, ensuring a more appropriate steering reaction force by compensating for phase delays and road surface disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control amount of the reaction force motor is calculated by adding the control amount of the steering reaction force based on the yaw rate to the control amount of the steering reaction force based on the steering wheel angle, then the steering reaction force reflects the tire transverse force, but the steering reaction force becomes inappropriate when the accuracy of the control amount based on the steering wheel angle decreases
Solution Approach 1:
The patent introduces feedback control by calculating a feedback axial force based on the yaw rate and comparing it with the feedforward axial force based on the steering wheel angle. The allocation ratio is dynamically adjusted based on the axial force difference, allowing the system to rely more on feedback when feedforward accuracy deteriorates, thus maintaining reliable steering reaction force control
Solution Approach 2:
The patent dynamically adjusts the allocation ratio between feedforward and feedback axial forces based on the axial force difference. This dynamic adjustment allows the control system to adapt to varying conditions and maintain appropriate steering reaction force even when the accuracy of steering wheel angle-based control decreases
2Measurement precision
If feedback axial force and feedforward axial force are allocated based on axial force difference, then the steering reaction force accuracy is improved, but the control system complexity increases
Solution Approach 1:
The patent changes the parameter allocation ratio dynamically based on the axial force difference. By adjusting this single parameter based on a simple difference calculation, the system achieves improved accuracy without introducing complex control mechanisms, maintaining relative system simplicity while enhancing performance
Data Source
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AI summary
A control computing unit (11) allocates a feedback axial force (TFB) and a feedforward axial force (TFF) at an allocation ratio based on an axial force difference which is a difference between the feedback axial force (TFB) and the feedforward axial force (TFF) to set a final axial force as a steering-rack axial force. The control computing unit (11) drives a reaction force motor (9A) on the basis of the set final axial force.