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 and minimizing steering performance degradation, particularly during high-speed maneuvers where micro line-taking steering patterns are involved, as existing methods can inadvertently block the operator's intention and increase the steering wheel's inertia feeling.
Innovation Solution
An electric power steering apparatus that extracts torque ripple vibration components based on motor angular velocity and angular acceleration, using a vibration extracting filter and compensation values calculated from these components to adjust the current command value, thereby suppressing torque ripples while preserving essential steering feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If vibration suppression compensation is applied to suppress torque ripple, then torque ripple is reduced, but steering performance degrades and steering wheel inertia feeling increases
Solution Approach 1:
The patent applies different vibration suppression strategies to different frequency ranges. High-frequency vibration components are suppressed using vibration suppression compensation, while low-frequency components are preserved to maintain steering feel. This local differentiation of suppression intensity resolves the contradiction by targeting harmful vibrations without destroying useful steering feedback.
Solution Approach 2:
The patent dynamically adjusts the vibration suppression compensation value based on real-time motor angular velocity and steering state. The compensation strength varies with operating conditions, being stronger when torque ripple is prominent and weaker when steering precision is critical. This dynamic adaptation allows the system to suppress vibrations without permanently degrading steering performance.
2Object-generated harmful factors
If vibration suppression compensation is applied during high-speed maneuvers, then torque ripple is suppressed, but operator's intended steering feedback is blocked
Solution Approach 1:
The patent differentiates between high-frequency vibration components (to be suppressed) and low-frequency steering components (to be preserved). By applying vibration suppression only to specific frequency bands, the system eliminates torque ripple while maintaining the operator's steering feedback information, preventing information loss during high-speed maneuvers.
Solution Approach 2:
The patent extracts vibration components before they can interfere with steering feedback. By preliminarily identifying and separating vibration signals from steering signals through spectral analysis, the system prepares compensation values that target vibrations without affecting the integrity of steering feedback information.
3Object-generated harmful factors
If broad-spectrum vibration extraction is used, then torque ripple is suppressed, but steering accuracy decreases due to over-compensation
Solution Approach 1:
The patent applies narrow-band frequency filtering to extract only the specific frequency components corresponding to torque ripple, rather than using broad-spectrum extraction. This localized approach ensures that compensation is applied only to harmful vibrations, preserving steering accuracy by avoiding over-compensation of useful steering signals.
Data Source
AI summary
An electric power steering apparatus includes: a current command value determining section that determines a current command value based on steering torque and vehicle speed; a vibration extracting filter that extracts a first vibration component having a predetermined amplitude and first predetermined frequency range depending on motor angular velocity; a vibration extracting section that extracts a second vibration component having a second predetermined frequency range depending on motor angular acceleration; a first compensation value calculating section that calculates a first vibration suppression compensation value based on the first vibration component extracted by the vibration extracting filter; and a second compensation value calculating section that calculates a second vibration suppression compensation value based on the second vibration component; and suppresses vibrations of the motor by feeding back the first vibration suppression compensation value and the second vibration suppression compensation value calculated to the current command value.