MRF Bearing Feedback Actuator for Compact Steer-by-Wire Feel
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Solution Overview
Problem
Existing steer-by-wire steering systems face challenges in providing a realistic steering feel with a complex and bulky feedback actuator design, which hinders space efficiency and simplicity.
Innovation Solution
A feedback actuator utilizing an electric motor with a motor shaft rotating in magnetorheological fluid and a ring-shaped coil to generate passive force feedback, allowing for controlled damping and torque transmission, integrated within a compact rolling bearing housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a feedback actuator with spring elements is used to generate steering feel, then steering feel is provided, but the build volume and construction complexity increase
Solution Approach 1:
The patent replaces the mechanical spring element system with a magnetorheological fluid-based damping device. The MRF fluid's viscosity can be controlled magnetically to provide the required damping torque for steering feel, eliminating the need for complex mechanical spring elements and reducing construction complexity while maintaining the steering feel function
Solution Approach 2:
The patent changes the physical state parameter of the damping medium from solid spring elements to magnetorheological fluid. By controlling the magnetic field applied to the MRF fluid, the damping characteristics can be adjusted dynamically, providing the required steering feel with a simpler system that has fewer mechanical parts
2Ease of operation
If a feedback actuator with spring elements is used to generate steering feel, then steering feel is provided, but the build volume increases
Solution Approach 1:
The patent replaces the bulky mechanical spring element assembly with a compact magnetorheological fluid damping device. The MRF system achieves the same steering feel function in a more space-efficient manner, reducing the overall build volume of the feedback actuator
Solution Approach 2:
The patent integrates the damping device directly into the motor shaft assembly, combining the feedback actuator components into a more compact unified structure. This merging of components reduces the overall build volume while maintaining all necessary functions
3Power
If magnetorheological fluid is used in rolling bearings, then passive force feedback is achieved with reduced motor torque, but the system requires magnetic field control mechanisms
Solution Approach 1:
The magnetorheological fluid in the rolling bearings automatically provides passive force feedback based on the magnetic field applied to it. The MRF self-adjusts its viscosity characteristics in response to magnetic field changes, eliminating the need for additional active control mechanisms and reducing the motor torque requirements while maintaining a relatively simple system 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 improved steering feel with reduced motor torque and cost, while maintaining a space-saving and simple design, enabling continuous damping control and enhanced safety features like end position lock and curb protection.
Implementation Method 1
the rolling elements of the at least one rolling bearing are arranged in a magnetorheological fluid and wherein the feedback actuator further comprises means to pass a magnetic field through said magnetorheological fluid for stiffening said fluid and restricting movement of said rolling elements
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a steer-by-wire steering system (1) for a motorized vehicle comprising a feedback actuator (4) to simulate a steering feel to a steering device (5), wherein said feedback actuator (4) has an electric motor (11) with a motor shaft (12) connected to a driver input shaft (6) to be able to transmit a torque, wherein said motor shaft (12) is able to be rotated in at least one rolling bearing (20), characterized in that the rolling elements (23) of the at least one rolling bearing (202) are arranged in a magneto rheological fluid (27) and that the feedback actuator (4) further comprises means (24) to pass a magnetic field through said magnetorheological fluid (27) for stiffening said fluid and restricting movement of said rolling element (23).