Motor Control Apparatus Offset Correction for Torque Ripple Suppression
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Solution Overview
Problem
A redundant-system motor control apparatus experiences torque ripple due to phase differences in current ripples generated during pulse shifts between systems, leading to motor torque fluctuations and impaired steering performance.
Innovation Solution
The motor control apparatus stores offset correction values for the maximum and minimum phases and uses these values to correct detected currents, thereby suppressing torque ripple by optimizing current detection patterns and PWM duty ratio signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse shift is conducted to prevent PWM pulse widths from resembling each other, then current detection accuracy is improved, but torque ripple occurs due to phase difference of current ripple between systems
Solution Approach 1:
The patent changes the parameter of PWM pulse width by introducing offset correction values for maximum and minimum phases. This modifies the pulse timing parameters to eliminate current ripple while maintaining accurate current detection, thereby resolving the torque ripple issue without sacrificing measurement precision
Solution Approach 2:
The patent implements feedback by detecting the actual current values and comparing them with expected values, then applying offset correction values to adjust the PWM pulse widths. This closed-loop approach ensures that current detection accuracy is maintained while eliminating the harmful torque ripple effect
2Object-generated harmful factors
If offset correction values are applied to maximum and minimum phases, then torque ripple is suppressed, but device complexity increases due to additional correction mechanisms
Solution Approach 1:
The patent applies offset correction values selectively only to the maximum and minimum phases rather than all three phases. This localized approach suppresses torque ripple by correcting only the critical phases where current ripple occurs, thereby reducing the overall control system complexity compared to a full-phase correction approach
Data Source
AI summary
A microcomputer stores an offset correction value for correcting an offset of a detected current along with a pulse shift for each of a detected current of a maximum phase to which power is supplied for the longest time among three phases and a detected current of a minimum phase to which power is supplied for the shortest time among the three phases, and corrects the detected current of each of the phases with use of the stored offset correction values for the detected current of the maximum phase and the detected current of the minimum phase.