Steering Reaction Force Control for SBW Vibration Restraint
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Solution Overview
Problem
In steer-by-wire systems, the lack of dynamic force transmission between the steering wheel and the turning wheel makes it difficult for drivers to experience a moderate steering feeling for road surface reaction forces, leading to potential steering wheel vibrations due to unstable control situations.
Innovation Solution
A steering control device that includes a processor to execute reaction force command variable calculation, control, and restriction processes, limiting the contribution of predetermined components to the steering wheel torque in unstable conditions, using torque detection and system stabilization methods to prevent excessive vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reaction force that is given to the steering wheel is set depending on a predetermined frequency component of electric current in a motor that turns the turning wheel, then it is possible to transmit the road surface reaction force to the steering wheel, but in a situation where a system including the SBW is unstable, there is a possibility that the control cannot be appropriately performed and the steering wheel vibrates beyond the influence of the road surface reaction force
Solution Approach 1:
The patent applies dynamics by making the contribution degree of the predetermined frequency component variable rather than fixed. The control device dynamically adjusts the contribution degree based on system stability conditions, switching between different contribution degrees (first contribution degree when stable, second contribution degree when unstable) to adapt to changing operating conditions and prevent excessive steering wheel vibration
Solution Approach 2:
The patent changes the parameter of contribution degree based on system stability. When the system is determined to be unstable, the contribution degree of the predetermined frequency component to the reaction force command variable is changed from a first contribution degree to a second contribution degree (where the second is smaller than the first), thereby adjusting the system response to maintain stability
2Object-affected harmful factors
If the degree of contribution of the predetermined component to the reaction force command variable is restricted to a smaller degree in an unstable situation, then it is possible to restrain the steering wheel from vibrating, but the road surface reaction force transmission may be reduced
Solution Approach 1:
The system dynamically adjusts the contribution degree based on real-time stability assessment. When the system is stable, a higher contribution degree (first contribution degree) is used to maintain good road surface reaction force transmission. When instability is detected, the contribution degree is reduced (second contribution degree) to prevent excessive vibration, thus optimizing the balance between information transmission and system stability
Solution Approach 2:
The control device uses feedback from system stability determination to adjust the contribution degree. The stability determination unit continuously monitors system conditions and provides feedback to the control unit, which then adjusts the contribution degree accordingly, creating a closed-loop control system that balances road surface information transmission with vibration suppression
Data Source
AI summary
A steering control device includes a processor. The processor is configured to execute a process in a state where dynamic force transmission between a steering wheel and a turning wheel is not performed. The process includes: a process of controlling a reaction force that is given to the steering wheel, by operating torque of the reaction force motor depending on the value of a reaction force command variable; a process of reflecting a predetermined component of a frequency signal that is given to the turning wheel in the value of the reaction force command variable; and a process of restricting the degree of contribution of the predetermined component to the value of the reaction force command variable, to a smaller degree, in a situation where a steering system including the steering wheel is unstable.