Steering Reaction Force Control for Stable Steer-By-Wire Feedback
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Solution Overview
Problem
In steer-by-wire systems, the lack of dynamic power transmission between the steering wheel and turning wheel makes it difficult for drivers to feel a moderate steering sensation corresponding to road surface reaction forces, leading to potential instability and increased vibration.
Innovation Solution
A steering control device that includes a processor to set and control steering reaction forces using frequency components reflecting road surface information, adjusting variables to stabilize the system and assist the driver's steering operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the reaction force given to the steering wheel is set depending on a predetermined frequency component of motor current, then road surface information can be transmitted to the driver, but the steering system may become unstable and vibration increases
Solution Approach 1:
The patent applies dynamics by making the filter characteristics variable rather than fixed. The reflection specifying variable dynamically adjusts the frequency characteristics of the bandpass filter based on steering conditions, allowing the system to adapt between transmitting road surface information and maintaining stability. This is achieved by changing the center frequency and bandwidth of the filter according to steering angle and steering angle change amount.
Solution Approach 2:
The patent changes parameters by adjusting the reflection specifying variable that controls filter characteristics. When steering conditions indicate potential instability (large steering angle change amount), the system modifies the frequency parameters to reduce amplification of unstable components. This parameter adjustment allows the system to balance information transmission with stability maintenance.
2Force
If the gain of steering reaction force with respect to steering shaft operation is increased, then steering reaction force increases, but the steering system becomes more prone to instability
Solution Approach 1:
The system dynamically adjusts the gain of steering reaction force based on steering conditions. When the steering angle change amount is large (indicating potential instability), the system reduces the gain through filter parameter adjustment. When steering is stable, the system can maintain higher gain for better road surface information transmission. This dynamic gain control prevents instability while maintaining effective reaction force transmission.
Data Source
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AI summary
A steering control device (50) controls a steering system including a reaction force motor (22) that gives a steering reaction force to a steering shaft (14) and a turning motor (42) that turns a turning wheel (34) in a state where dynamic power transmission from the steering shaft (14) is blocked. The steering control device (50) includes a processor (52) that executes a reaction force setting process and a reaction force giving process. In the reaction force setting process, the processor (52) sets the steering reaction force using a predetermined-component reflecting process. In the reaction force giving process, the processor (52) operates the reaction force motor (22) such that the reaction force motor (22) gives the steering reaction force set by the reaction force setting process.