Variable Band Stop Filter for MDPS Vibration Control
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Solution Overview
Problem
Conventional motor-driven power steering (MDPS) systems experience vibrations and noise due to wheel imbalance, mechanical part distortions, and natural vibrations, which affect steering feel and stability.
Innovation Solution
A steering feel control apparatus and method that utilizes a variable band stop filter to detect and reduce vibrations in the MDPS system by adjusting its bandwidth and depth based on steering angular velocity, effectively filtering out noise components from the motor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional MDPS system operates without vibration filtering, then the system provides full motor current for steering assistance, but vibration and noise from wheel imbalance and mechanical distortions are transmitted to the steering wheel
Solution Approach 1:
The patent extracts and removes the harmful vibration component from the motor current signal using a band stop filter. The filter identifies and eliminates specific frequency ranges corresponding to wheel imbalance and mechanical distortion vibrations, while preserving the useful steering assistance current. This extraction approach reduces vibration transmission to the steering wheel without requiring complex mechanical modifications to the entire MDPS system.
Solution Approach 2:
The band stop filter acts as an intermediary component between the motor current generator and the motor. It processes the motor current signal to remove harmful vibrations before the current reaches the motor, thereby preventing vibration transmission to the steering wheel. This intermediary filtering approach allows the system to maintain full steering assistance capability while eliminating harmful vibrations through a relatively simple electronic component.
2Adaptability or versatility
If a fixed band stop filter is used to remove vibration, then specific vibration frequencies are filtered, but the filter cannot adapt to varying steering conditions and velocities
Solution Approach 1:
The patent implements a dynamic band stop filter whose parameters (center frequency and bandwidth) are adjusted in real-time based on the steering angular velocity. As the steering wheel rotates at different speeds, the filter automatically adapts its characteristics to maintain optimal vibration suppression. This dynamic adaptation allows the system to handle varying steering conditions effectively without requiring multiple fixed filters or complex mechanical adjustments.
Solution Approach 2:
The filter's key parameters (center frequency and bandwidth) are changed dynamically according to the steering angular velocity. When the steering velocity changes, the control unit recalculates and adjusts the filter parameters to match the current operating conditions. This parameter change approach enables the filter to maintain effectiveness across different steering scenarios while keeping the overall system structure relatively simple.
3Object-affected harmful factors
If the bandwidth of the band stop filter is wide to cover all vibration frequencies, then more vibrations are removed, but useful low-frequency steering signals are also attenuated
Solution Approach 1:
The patent applies local quality filtering by using a band stop filter with a narrow, targeted bandwidth that specifically addresses the frequency ranges where vibration occurs (typically higher frequencies associated with wheel imbalance and mechanical distortion). The filter's bandwidth is carefully selected to be wide enough to capture vibration frequencies but narrow enough to preserve useful low-frequency steering signals. This localized filtering approach ensures that only harmful vibrations are removed while maintaining the integrity of the steering control signals.
Data Source
AI summary
A steering feel control apparatus of a motor driven power steering (MDPS) system may include: a filter configured to filter a motor current inputted to a motor, in order to remove a vibration component which generates vibration on a steering wheel; and a controller configured to control the filter to remove the vibration component of the motor current when the MDPS is driven.