Steer-by-Wire Axial Force Control for Understeer Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing steer-by-wire systems fail to provide appropriate steering feeling to drivers when a vehicle is in a critical state such as understeer or oversteer, as they do not consider these conditions in their control algorithms.
Innovation Solution
A steer-by-wire system that calculates multiple axial forces based on different parameters to generate a steering reaction force corresponding to the vehicle state, reducing the force during understeer and increasing it during oversteer, allowing for accurate detection and response to these conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the steering reaction force is controlled based on basic axial force only, then the control system is simple, but the steering feeling is inappropriate during understeer or oversteer conditions
Solution Approach 1:
The control system dynamically adjusts the steering reaction force based on real-time vehicle state (understeer/oversteer detection). The steering reaction force is modified by adding a correctional axial force that varies with vehicle stability, enabling the system to adapt to different driving conditions and provide appropriate steering feedback during critical states
Solution Approach 2:
The system changes the parameters of axial force calculation by introducing additional factors (vehicle stability, understeer/oversteer degree) to the basic axial force calculation. This transforms the single-parameter control into a multi-parameter control system that accounts for vehicle dynamics states
2Reliability
If multiple axial forces are calculated with different parameters, then the steering feeling accuracy is improved, but the device complexity increases
Solution Approach 1:
The axial force is segmented into multiple components: basic axial force (from steering angle) and correctional axial force (from vehicle stability analysis). This segmentation allows the system to handle different aspects of steering control separately while maintaining overall system manageability and clarity
3Reliability
If the steering reaction force is reduced during understeer, then the steering force reducing feeling is reproduced, but the control algorithm becomes more complex
Solution Approach 1:
The system uses feedback from vehicle state sensors (yaw rate, lateral acceleration) to detect understeer/oversteer conditions and adjusts the steering reaction force accordingly. This closed-loop feedback mechanism enables accurate reproduction of steering feelings while maintaining systematic control
Data Source
AI summary
A steer-by-wire system includes a turning device that turns a vehicle wheel; and a steering reaction force control unit that controls a steering reaction force applied to a steering wheel. The steering reaction force control unit is configured to calculate a plurality of kinds of axial forces, calculate a final axial force based on the axial forces, and generate the steering reaction force corresponding to the final axial force. The axial forces include a basic axial force, and an under axial force that becomes smaller than the basic axial force during understeer. The steering reaction force control unit is configured to calculate a degree of understeer reflecting a difference between the basic axial force and the under axial force during the understeer and to reduce the final axial force during the understeer to a value smaller than the basic axial force by an amount corresponding to the degree of understeer.