Motor Driven Power Steering Vibration Reduction via Current Feedback
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Solution Overview
Problem
Motor-driven power steering systems experience vibrations due to wheel imbalance, eccentricity, or mechanical part distortions, leading to steering wheel shimmy and natural vibrations, which existing technologies fail to adequately address.
Innovation Solution
A vibration reduction apparatus and method that detects natural vibration frequencies in motor currents, adjusts damping values based on vehicle speed, and inversely compensates MDPS outputs to reduce vibrations, using a damping compensation unit, natural vibration frequency detection unit, phase control unit, and decoupling unit to filter and limit outputs effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the MDPS applies returning torque based on steering angle to assist returning operation, then the returning performance is improved, but steering wheel shimmy and natural vibration occur due to wheel imbalance, eccentricity, or mechanical part distortion
Solution Approach 1:
The patent detects the harmful vibration frequency from motor current and uses feedback control to generate a counteracting torque that cancels the vibration. The harmful vibration energy is converted into useful feedback information for active vibration cancellation, improving steering stability while maintaining returning performance.
Solution Approach 2:
The system continuously monitors motor current to detect vibration frequency, processes this information through a feedback controller, and adjusts the motor torque in real-time to cancel detected vibrations. This closed-loop feedback mechanism enables dynamic vibration suppression without compromising the returning operation assistance.
2Productivity
If the MDPS provides assist torque for steering assistance, then steering performance is improved, but vibration from wheel imbalance and mechanical distortion cannot be detected or reduced
Solution Approach 1:
The patent replaces traditional mechanical vibration sensors with electrical current analysis. By monitoring motor current signatures, the system detects vibration frequency electronically, avoiding the complexity and precision limitations of mechanical sensors while maintaining high detection accuracy for vibration cancellation.
3Object-generated harmful factors
If damping is increased to reduce vibration, then steering wheel shimmy is reduced, but steering responsiveness and returning performance deteriorate
Solution Approach 1:
The system dynamically adjusts damping characteristics by varying motor torque based on detected vibration frequency and magnitude. Instead of fixed high damping, the controller applies targeted counter-torque only when vibration is detected, maintaining low damping for normal steering responsiveness while providing vibration suppression when needed.
Solution Approach 2:
The patent changes the control parameter from fixed damping coefficient to variable torque command based on vibration detection. The feedback controller modulates motor torque in real-time, adjusting the effective damping characteristic dynamically to suppress vibration without compromising overall steering responsiveness and returning performance.
Data Source
AI summary
A damping reduction apparatus for a motor driven power steering (MDPS) may include: a natural vibration frequency detection unit configured to detect a natural vibration frequency from a motor current by variably controlling a bandwidth according to a steering condition; a damping compensation unit configured to additionally compensate for a damping value outputted from a damping unit according to a vehicle speed; and a compensation output unit configured to inversely compensate for an output of the MDPS according to the natural vibration frequency outputted from the natural vibration frequency output unit, and add the compensation to an output of the damping compensation unit.