Steer-by-Wire Steering Friction Control and Rotation Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Steer-by-wire (SBW) systems lack sufficient feedback to drivers due to the absence of mechanical connections, resulting in low frictional forces that can cause vibrations and unstable steering, especially when tires reach their turning limits, leading to unintended wheel rotation during curbstone collisions.
Innovation Solution
A steering apparatus that combines a structure to change frictional force and limit steering wheel rotation, using a friction member with a ball screw mechanism and solenoids to adjust frictional force based on vehicle speed and steering angle, and stoppers to regulate wheel rotation, mimicking the feedback and stability of conventional systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the SBW system uses a motor to generate steering reaction force, then steering feedback is provided to the driver, but vibration is generated when the driver releases the steering wheel due to low frictional force
Solution Approach 1:
The patent changes the frictional force parameter by adjusting the contact pressure between the friction member and shaft through the ball screw mechanism. By varying the frictional force from low to high based on steering conditions, the system provides steering feedback while preventing vibration when the driver releases the steering wheel
Solution Approach 2:
The patent makes the frictional force dynamic rather than static by using the ball screw mechanism to adjust the contact pressure between the friction member and shaft. The frictional force is adjusted in real-time based on steering angle and vehicle speed, allowing the system to adapt to different driving conditions and eliminate vibration
2Device complexity
If the SBW system has low frictional force (0.5 Nm or less), then mechanical connection complexity is reduced, but the steering wheel may be operated with very little force at the neutral position, requiring additional friction for stabilization
Solution Approach 1:
The patent changes the frictional force parameter dynamically using the ball screw mechanism. At the neutral position, the frictional force is increased to provide stabilization and prevent the steering wheel from moving with minimal force, while at other positions, the frictional force is reduced to maintain ease of operation
3Adaptability or versatility
If the SBW system has no mechanical connection structure, then freedom of layout is increased and fuel economy is improved, but the steering wheel may continue to rotate even when a tire collides with a curbstone
Solution Approach 1:
The patent applies preliminary anti-action by using the stopper mechanism to prevent excessive steering wheel rotation before it can cause damage. When a tire collides with a curbstone, the stopper limits the steering wheel rotation, preventing the wheel from continuing to rotate indefinitely as would occur in a purely electronic system
4Loss of information
If the SBW system uses a motor to provide steering reaction force, then steering feedback is achieved, but the system frictional force must be precisely controlled to avoid vibration
Solution Approach 1:
The patent introduces a friction member as an intermediary between the steering wheel and the motor system. This friction member, controlled by the ball screw mechanism, provides a mechanical means to adjust system friction independently of the motor control, simplifying the overall control strategy by separating the feedback provision function from the vibration suppression function
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 adjustable frictional force for improved steering sense and stability, preventing unintended wheel rotation during tire collisions, thus enhancing safety and reducing vibrations by replicating the behavior of conventional steering systems.
Implementation Method 1
The tightening means may include a ball screw mechanism connected to opposite ends of the friction member, and the ball screw mechanism includes a screw configured to rotate, and a nut configured to move linearly in response to the rotation of the screw.
Implementation Method 2
The friction actuator may include a first solenoid including a movable iron core configured to move linearly when current is supplied to a coil of the first solenoid. A rack gear may be provided at the end of the movable iron core, and a pinion gear may be formed at the end of the screw, the rack gear and the pinion gear being engaged with each other such that the screw rotates in response to the linear movement of the movable iron core.
Data Source
AI summary
A steering apparatus of a steer-by-wire (SBW) system includes a structure for changing the frictional force of the system and a structure for limiting the rotation range of a steering wheel. The steering apparatus includes: a shaft rotatably interlocked with a steering wheel, a friction member surrounding the shaft and contacting the shaft, a frictional force provision device for narrowing and widening the friction member in the radial direction of the shaft to change the frictional force of the friction member that contacts the shaft, and a steering limitation device for regulating the rotation of the shaft using a stopper provided at the friction member during the rotation of the shaft to limit the steering of the steering wheel.