Electric Power Steering Phase Compensation Frequency Shifting
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Solution Overview
Problem
Electric power steering apparatuses experience fine vibrations and abnormal noise due to increased gain in a particular frequency band, which affects the steering sensation and commercial value.
Innovation Solution
The electric power steering apparatus employs a phase compensator that performs frequency shifting of poles and zero points to change the compensation frequency band, rather than increasing gain, to minimize vibrations and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gain is increased in a particular frequency band to reduce steering delay, then steering response is improved, but fine vibrations and abnormal noise occur in the steering mechanism
Solution Approach 1:
The patent changes the phase compensation characteristics by adjusting the gain and phase shift amounts at different frequency bands. Specifically, it reduces the gain in the 100-300Hz frequency band where vibrations occur, while maintaining or improving steering response in other frequency ranges. This parameter adjustment resolves the contradiction by optimizing the frequency-dependent compensation characteristics rather than applying uniform gain increase.
Solution Approach 2:
The patent implements dynamic phase compensation that adapts to different steering conditions and frequency components. The phase compensator dynamically adjusts compensation parameters based on the detected steering torque signal's frequency content, allowing the system to provide appropriate compensation for each frequency band rather than using a fixed gain approach. This dynamic adaptation prevents vibrations while maintaining responsive steering.
2Ease of operation
If phase compensation is performed to improve steering sensation, then steering feel is enhanced, but steering delay remains at certain frequency ranges
Solution Approach 1:
The patent applies different phase shift amounts and gain values for different frequency bands to optimize both steering sensation and response time. By analyzing the frequency characteristics of the steering torque signal, the system applies appropriate phase compensation parameters that enhance steering feel without introducing excessive delay in critical frequency ranges.
3Speed
If gain characteristic curve is changed to increase gain, then steering response improves, but the steering system becomes susceptible to noise in 100-300Hz band
Solution Approach 1:
The patent applies local quality by treating different frequency bands differently in the phase compensation process. Instead of applying uniform gain increase across all frequencies, the system selectively adjusts gain and phase parameters for specific frequency ranges. The 100-300Hz band receives reduced gain to prevent noise and vibrations, while other frequency bands receive appropriate compensation to maintain steering response performance.
Data Source
AI summary
Provided is an electric power steering device in which the operation feeling is improved without a decrease in commercial value. A phase compensation unit performs a frequency shift on a compensation frequency band compensated by the phase compensation unit. The phase compensation unit performs phase-shift in the compensation frequency band through a frequency shift process, instead of an increase in compensation gain. Therefore, it is possible to minimize occurrences of minute vibrations and abnormal noise in the steering system including the motor that accompany an increase in gain, and to improve the operation feeling and commercial value.