Steer-by-Wire Reaction Torque Compensation for Natural Road Feel
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Solution Overview
Problem
In steer-by-wire (SBW) systems, drivers lack a natural road feel due to the absence of mechanical connection, leading to an artificial steering experience, and autonomous vehicles face control stability issues when transitioning from autonomous driving to driver control.
Innovation Solution
An SBW system that includes a reaction motor, steering motor, motor location detector, location controller, steering controller, and reaction controller, which generates and compensates reaction torque based on vehicle speed and steering angle, using a variable filter unit to adjust cutoff frequencies and determine steering modes to provide a natural steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If mechanical connection devices are removed in SBW system, then weight is reduced and damage risk is minimized, but driver loses natural road feel and steering becomes artificial
Solution Approach 1:
The patent introduces reaction torque as an intermediary force that mediates between the driver's steering input and the road conditions. The reaction torque generator creates artificial feedback forces on the steering wheel based on vehicle speed, steering angle, and road surface information, simulating the natural road feel that would otherwise be transmitted through mechanical connection
Solution Approach 2:
The patent replaces the mechanical connection system with an electrical control system that generates reaction torque. Instead of physically connecting the steering wheel to the wheels through mechanical linkages, the system uses sensors, controllers, and actuators to create artificial mechanical feedback through torque generation, substituting mechanical transmission with electro-mechanical control
2Reliability
If reaction torque is suddenly generated when transitioning from autonomous to manual control, then driver awareness is improved, but control stability deteriorates and driver experiences sense of difference
Solution Approach 1:
The patent implements dynamic adjustment of reaction torque based on the autonomous driving mode status. The reaction torque generator dynamically modifies the torque characteristics according to vehicle speed, steering angle, and crucially, the autonomous driving mode signal. During mode transitions, the system dynamically adjusts the torque buildup rate and magnitude to ensure smooth handover while maintaining driver awareness
Solution Approach 2:
The patent applies preliminary action by gradually increasing reaction torque before full manual control engagement during mode transitions. The system prepares the steering feel in advance by progressively building up reaction torque based on the transition timeline, preventing sudden jumps in torque that would cause driver discomfort or loss of control stability
3Manufacturing precision
If location control error is not compensated, then system complexity is reduced, but steering precision deteriorates and road feel becomes unnatural
Solution Approach 1:
The patent implements feedback control by continuously monitoring the location control error (difference between target and actual steering motor positions) and using this error signal to adjust the reaction torque. The reaction torque generator receives the location control error as input and generates compensatory torque to eliminate the error, creating a closed-loop control system that improves steering precision
Solution Approach 2:
The patent merges the location control function with the reaction torque generation function. Instead of implementing separate control loops for position accuracy and force feedback, the system combines both functions into a unified control architecture where the reaction torque generator simultaneously handles precision control and natural feel generation, reducing overall system complexity
Data Source
AI summary
The present invention relates to a steer-by-wire system for a vehicle, and the system may include a reaction motor generating reaction torque based on the turning of a steering wheel, a steering motor implementing a steering manipulation, a motor location detector measuring a current steering angle by detecting a rotation location of the steering motor, a location controller calculating a target steering angle by applying the amount of a location control error to a vehicle speed, command steering angle and current steering angle, a steering controller driving the steering motor based on the target steering angle, and a reaction controller generating the reaction torque according to a driver's steering state based on the vehicle speed and a steering angular velocity, compensating for the reaction torque based on the amount of the location control error, and driving the reaction motor based on the final reaction torque.