Steer-by-Wire Reaction Force Control for Stable Road 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 steering wheel 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, even without direct power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the reaction force setting uses a predetermined frequency component to transmit road surface information, then the driver can feel road surface reaction forces, but the steering system becomes unstable and steering wheel vibration increases
Solution Approach 1:
The patent applies dynamics by making the filter factor variable rather than fixed. The control device dynamically adjusts the filter factor based on vehicle speed and steering angle, allowing the system to adapt its frequency response characteristics to different operating conditions. This enables stable transmission of road surface information across varying driving scenarios without causing steering wheel vibration.
Solution Approach 2:
The patent changes the parameter of the filter factor from a constant value to a variable that depends on vehicle speed and steering angle. By modifying this parameter dynamically, the system optimizes the frequency component extraction to maintain stability while preserving road surface information transmission effectiveness.
2Force
If the steering reaction force gain is increased to improve steering feeling, then the driver can better perceive road surface forces, but the steering system becomes more prone to instability
Solution Approach 1:
The patent implements dynamic adjustment of the reaction force characteristics through variable filter factors. Instead of applying a fixed gain, the system adapts the frequency response dynamically based on operating conditions, allowing adequate reaction force transmission while maintaining stability margins.
Solution Approach 2:
The system uses feedback from vehicle speed and steering angle sensors to continuously adjust the filter factor. This closed-loop control ensures that the steering reaction force remains within stable ranges while still providing adequate road surface information to the driver.
Data Source
AI summary
A steering control device controls a steering system including a reaction force motor that gives a steering reaction force to a steering shaft and a turning motor that turns a turning wheel in a state where dynamic power transmission from the steering shaft is blocked. The steering control device includes a processor that executes a reaction force setting process and a reaction force giving process. In the reaction force setting process, the processor sets the steering reaction force using a predetermined-component reflecting process. In the reaction force giving process, the processor operates the reaction force motor such that the reaction force motor gives the steering reaction force set by the reaction force setting process.