Power Steering Filter Control for High-Torque Vibration Suppression
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Solution Overview
Problem
The existing control devices for power steering systems experience vibration due to hunting of the control amount when excessively high steering torque is applied, causing the torque sensor signal to saturate and rendering the compensation for the delay system ineffective.
Innovation Solution
A control device for a power steering system that includes a low-pass filter unit with a cutoff frequency adjustment unit, which sets the cutoff frequency to a first value when the steering torque is below a predetermined threshold and to a lower second value when the steering torque exceeds this threshold, thereby attenuating high-frequency components and preventing signal saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a fixed cutoff frequency is used in the low-pass filter, then the system response is fast under normal conditions, but vibration occurs when steering torque exceeds the threshold causing signal saturation
Solution Approach 1:
The patent applies dynamics by making the cutoff frequency adjustable rather than fixed. The control device dynamically changes the cutoff frequency based on the steering torque signal magnitude: using a first cutoff frequency when torque is below the threshold and a second cutoff frequency when torque exceeds the threshold. This dynamic adjustment allows the system to adapt its response characteristics to different operating conditions, preventing vibration during high-torque scenarios while maintaining fast response during normal operation.
Solution Approach 2:
The patent implements parameter changes by modifying the cutoff frequency parameter of the low-pass filter based on the steering torque signal. When the steering torque signal exceeds a predetermined threshold, the system changes the cutoff frequency from a first value to a second value, thereby altering the filter's frequency response characteristics. This parameter change prevents signal saturation and the subsequent hunting phenomenon, resolving the contradiction between fast response and stability.
2Stability of the object's composition
If the cutoff frequency is set low to prevent vibration, then control stability is improved, but the system response becomes slow under normal operating conditions
Solution Approach 1:
The system dynamically adjusts the cutoff frequency based on real-time steering torque conditions. During normal operation when torque is below the threshold, the first cutoff frequency is used, providing fast system response. When torque exceeds the threshold and vibration risk arises, the system switches to the second cutoff frequency to ensure stability. This dynamic switching resolves the contradiction by providing different frequency settings for different operational states.
Solution Approach 2:
The patent changes the cutoff frequency parameter conditionally based on the steering torque signal magnitude. By setting the cutoff frequency to a first value under normal conditions and switching to a second value when torque exceeds the threshold, the system optimizes both response speed and stability for different operating scenarios, eliminating the need to compromise one for the other.
Data Source
AI summary
A control device for a power steering device includes a low-pass filter unit including a cutoff frequency adjustment unit configured to adjust a cutoff frequency for partially attenuating a component of an input signal, set the cutoff frequency to a first cutoff frequency when a steering torque signal is lower than a first predetermined torque value, and to set the cutoff frequency to a second cutoff frequency lower than the first cutoff frequency when the steering torque signal is equal to or higher than the first predetermined torque value.