Steer-by-Wire Steering Shaft Friction Torque and Rotation Limiter
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Solution Overview
Problem
Conventional steer-by-wire steering devices lack the sensation of weight transmission to the driver due to the absence of mechanical linkage, resulting in poor steering feel and stability, especially when a wheel is stuck, as they cannot convey friction torque or restrict rotation effectively.
Innovation Solution
A steering device for steer-by-wire incorporating a first gear on the steering shaft, a second gear, a disk, and a rotation limiter with a fixed frame and actuator to apply friction torque and restrict rotation when the wheel is stuck, enhancing the driver's steering feel and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical linkage between steering shaft and wheels is eliminated to achieve steer-by-wire, then driver safety is improved and energy consumption is reduced, but the sensation of weight and steering feel are lost
Solution Approach 1:
The patent introduces a reaction force motor as an intermediary device between the steering shaft and the driver. This motor generates reaction torque that mimics the sensation of wheel weight and friction, allowing the driver to perceive steering feedback without direct mechanical linkage. The reaction force motor acts as a mediator that transmits tactile information from the wheel to the driver through the steering shaft.
Solution Approach 2:
The patent replaces the traditional mechanical linkage system with an electromechanical system. Instead of direct mechanical connection between steering shaft and wheels, the system uses electric motors and sensors to generate and detect forces. The reaction force motor substitutes for the mechanical connection, providing the necessary tactile feedback through electromagnetic force generation.
2Weight of moving object
If mechanical linkage is eliminated to reduce parts and weight, then vehicle weight is reduced and assembly complexity is decreased, but the ability to restrict rotation when wheel is stuck is lost
Solution Approach 1:
The patent implements a feedback control system using rotation angle sensors and reaction torque sensors. These sensors continuously monitor the steering shaft rotation and wheel position, providing feedback to the control unit. When the wheel is detected to be stuck, the control unit activates the reaction force motor to generate opposing torque, preventing further rotation of the steering shaft and ensuring driver safety.
Solution Approach 2:
The patent dynamically changes the operational parameters of the reaction force motor based on real-time sensor data. The control unit adjusts the motor torque, rotation angle limits, and friction characteristics according to the detected wheel status. When the wheel is stuck, the system changes the motor's torque output to match the stuck condition, providing appropriate rotation restriction.
3Productivity
If steer-by-wire system is implemented to save mechanical parts, then assembly time is reduced and energy consumption is lowered, but friction torque application is insufficient for realistic steering feel
Solution Approach 1:
The patent employs dynamic adjustment of friction characteristics through the reaction force motor. Instead of fixed mechanical friction, the system dynamically varies the reaction torque based on real-time conditions such as wheel speed, steering angle, and detected road conditions. This dynamic behavior replicates the complex friction characteristics of mechanical steering systems, providing realistic steering feel while maintaining the steer-by-wire architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides the sensation of weight to the driver's steering wheel manipulation by applying friction torque and restricting rotation when necessary, thereby improving steering feel and stability, even when a wheel is stuck.
Implementation Method 1
applying friction torque when the steering shaft rotates
Implementation Method 2
a first gear engaged with a gear part provided on an outer circumferential surface of a steering shaft, a second gear having an inner circumferential surface engaged with the first gear
Implementation Method 3
restrict rotation of the steering shaft in a situation where a wheel is no more rotated, e.g., by being stuck to a curb
Data Source
AI summary
According to the present embodiments, torque caused by friction when a steering shaft rotates is applied so as to provide weight to the operation of a steering wheel by a driver, and the steering shaft is restricted from rotating in certain situations in which wheels can no longer rotate, such as when the wheels are caught on a curb, thereby enabling the steerability and steering stability of the driver to be improved.