Electric Power Steering Torque Ripple Suppression
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Solution Overview
Problem
Conventional electric power steering systems face challenges in efficiently suppressing torque ripple while minimizing steering performance degradation, such as increased viscous feeling, especially during micro line-taking steering patterns and when road surface information is present, due to inadequate vibration component extraction and compensation.
Innovation Solution
An electric power steering apparatus that extracts torque ripple vibration components with arbitrary amplitude and frequency ranges based on electric power steering state parameters, using a vibration extraction filter with an inverse characteristic filter and amplitude window judging section to determine a vibration suppression compensation value, which is then fed back to the control system to adjust the current command value, thereby separating and suppressing unwanted vibrations while maintaining essential steering feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If vibration suppression compensation is applied to suppress torque ripple, then torque ripple vibration is reduced, but steering performance degrades (increased viscous feeling)
Solution Approach 1:
The patent applies different compensation strategies to different vibration components based on their characteristics. The vibration extraction filter selectively identifies torque ripple vibrations within specific frequency and amplitude ranges, applying suppression only to those components while preserving other vibration components that contribute to steering feedback and road surface information transmission.
Solution Approach 2:
The patent dynamically adjusts the vibration suppression compensation value based on operating conditions such as vehicle speed and steering state. By changing the compensation parameters according to the electric power steering state parameter, the system optimizes the balance between torque ripple suppression and steering performance across different operating scenarios.
2Object-affected harmful factors
If vibration extraction filter suppresses all vibration components, then torque ripple is reduced, but road surface information transmission to driver is blocked
Solution Approach 1:
The patent segments vibration components into different categories based on their frequency and amplitude characteristics. The vibration extraction filter distinguishes between harmful torque ripple vibrations (which are suppressed) and useful vibration components containing road surface information (which are preserved). This segmentation allows selective suppression without blocking important feedback information to the driver.
3Measurement precision
If conventional feedback control adjusts motor voltage to reduce current deviation, then current control accuracy is improved, but torque ripple vibrations occur
Solution Approach 1:
The patent introduces a vibration suppression compensation feedback mechanism that operates in parallel with the conventional current feedback control. The vibration extraction filter continuously monitors motor current and angular speed to identify torque ripple components, and the compensation value is fed back to adjust the current command value, creating a closed-loop control system that actively suppresses torque ripple while maintaining current control accuracy.
Solution Approach 2:
The vibration extraction filter and compensation value determining section act as intermediary components between the conventional feedback control and the motor drive system. These intermediaries process the motor current and angular speed signals to extract vibration components and generate compensation signals, which are then combined with the original control signals to produce the final current command, thereby eliminating torque ripple without disrupting the existing feedback control structure.
Data Source
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AI summary
An object of the present invention is to provide an electric power steering apparatus that is capable of efficiently suppressing vibrations and simultaneously minimizing steering performance degradation such as an increase in a steering wheel's viscous feeling by extracting a vibration component having an arbitrary amplitude and an arbitrary frequency range depending on an electric power steering state parameter and feeding back a vibration suppression compensation value determined depending on the extracted vibration component to a current command value. [Means for solving the problem] An electric power steering apparatus that provides a steering system of a vehicle with an assist force generated by a motor, comprising: a current command value determining section that determines a current command value based on a steering torque and a velocity; a vibration extraction filter that extracts a vibration component having a predetermined amplitude and a predetermined frequency range depending on an electric power steering state parameter; and a compensation value determining section that determines a vibration suppression compensation value based on the vibration component extracted by the vibration extraction filter, wherein vibrations of the motor are suppressed by feeding back the determined vibration suppression compensation value to the current command value.