Steering Reaction Force Control to Prevent Steer-By-Wire Hunting
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Solution Overview
Problem
In steer-by-wire systems, the lack of mechanical connection between the steering wheel and the steering mechanism results in reduced frictional torque, making it difficult for drivers to maintain the steering wheel in a turned position, leading to unstable fluctuations and degraded steering sensations.
Innovation Solution
A control system that determines the amount and direction of steering reaction force torque based on vehicle speed and steering operation information, using a combination of basic, hysteresis, and damping torques to stabilize the steering wheel position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the steering wheel is not mechanically connected to the steering mechanism in a steer-by-wire system, then the frictional resistance is reduced and the steering mechanism can be controlled more precisely, but the driver cannot retain steering to hold the steering wheel in the turned state and unstable fluctuations occur leading to hunting
Solution Approach 1:
The patent replaces the mechanical friction connection between the steering wheel and steering mechanism with an electronic control system that uses a reaction force actuator to generate artificial friction torque. This substitution eliminates the need for mechanical friction while maintaining steering stability through electronic torque control based on operation angle and operation history.
Solution Approach 2:
The patent dynamically adjusts the reaction force torque parameters based on the operation angle and operation history of the steering wheel. By changing the torque magnitude and direction according to these parameters, the system simulates friction to prevent hunting while maintaining stability during steering retention.
2Stability of the object's composition
If the feedback gain of the steering reaction force is made smaller when the steering wheel is turned back, then the hunting is suppressed, but the steering reaction force may not be sufficient to provide adequate steering feedback to the driver
Solution Approach 1:
The patent implements dynamic adjustment of the reaction force torque based on the operation angle and operation history. The torque magnitude and direction are continuously adapted according to the current steering state and past operations, allowing the system to provide sufficient feedback force while suppressing hunting through directional torque control rather than uniform gain reduction.
Solution Approach 2:
The patent uses feedback from the operation angle sensor and operation history to continuously adjust the reaction force torque. This closed-loop control ensures that the steering reaction force is optimized in real-time to maintain stability while providing adequate feedback to the driver based on actual steering conditions.
3Stability of the object's composition
If artificial friction torque is added to the steering wheel to prevent hunting, then the steering stability is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent makes the reaction force actuator serve multiple functions: it provides steering reaction force feedback to the driver and simultaneously generates artificial friction torque to prevent hunting. This multi-functionality eliminates the need for separate friction control mechanisms, reducing overall device complexity while maintaining steering stability.
Solution Approach 2:
The patent combines the friction control function with the existing reaction force actuator system. By merging the artificial friction generation into the same actuator that provides steering feedback, the system avoids adding separate control mechanisms and reduces overall complexity while achieving hunting prevention.
Data Source
AI summary
A steering reaction force control device, a steering reaction force control method, and a steering reaction force control system according to the present invention determine an amount of torque of a steering reaction force imparted by the reaction force actuator and a direction of torque for returning the steering operation input member to a neutral position from a physical quantity related to a vehicle speed of the vehicle and a physical quantity related to the operation information of the steering operation input member, and output a control signal based on the amount of torque and the direction of torque to the reaction force actuator. As a result, it is possible to prevent the hunting of the operating position of the steering operation input member when the steering operation input member is retained in a given steering position.