Motor Control Device Torque Vibration Reduction
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Solution Overview
Problem
Existing electric machine control methods experience vibrations in output torque due to excessive modulation rates caused by noise and space harmonics, leading to inefficient voltage control.
Innovation Solution
An electric machine control method and device that calculates a compensation gain to linearize the relationship between voltage command values and output voltage, with a limitation on the compensation gain to prevent excessive values, ensuring stable output voltage control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the compensation gain is calculated based on the modulation rate to linearize the voltage relationship, then the voltage control accuracy is improved, but the modulation rate may increase excessively due to noise and space harmonics, causing vibrations in output torque
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the compensation gain based on the modulation rate. When the modulation rate exceeds a predetermined threshold, the compensation gain is reduced or clamped to prevent excessive correction that would cause torque vibrations. This resolves the contradiction by adapting the compensation level to the actual modulation conditions, maintaining voltage control accuracy while preventing harmful vibrations.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the modulation rate and using it to adjust the compensation gain. The system calculates the modulation rate from the voltage command value and power supply voltage, then feeds this information back to determine an appropriate compensation gain that prevents torque vibrations while maintaining voltage linearity. This closed-loop approach resolves the contradiction by responding to actual system conditions.
2Adaptability or versatility
If the compensation gain is increased to maintain voltage linearity under overmodulation conditions, then the voltage control range is extended, but the output current and torque vibrations are exacerbated
Solution Approach 1:
The patent applies dynamics by making the compensation gain variable rather than fixed. The compensation gain is dynamically adjusted based on the modulation rate, allowing the system to extend voltage control range under overmodulation while preventing torque vibrations. The gain is increased when needed for control range but constrained when modulation rate indicates potential instability, resolving the contradiction between adaptability and stability.
3Use of energy by moving object
If the modulation rate is allowed to increase beyond 1 for overmodulation operation, then the power utilization efficiency is improved, but the relationship between voltage command value and output voltage becomes nonlinear, causing control inaccuracies
Solution Approach 1:
The patent applies parameter changes by introducing a compensation gain that varies with the modulation rate. When the modulation rate exceeds 1 (overmodulation), the compensation gain is adjusted to restore linearity between the voltage command value and the fundamental wave component of the output voltage. This allows the system to operate in overmodulation for better power utilization while maintaining voltage control precision through dynamic parameter adjustment.
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
An electric machine control method includes: calculating a voltage command value based on a torque command value to an electric machine; calculating a modulation rate based on a power-supply voltage and the voltage command value; calculating a compensation gain in accordance with the modulation rate, the compensation gain being used to linearize a relationship between a magnitude of the voltage command value and a magnitude of a fundamental wave component of an output voltage to the electric machine; calculating a compensated voltage command value based on the voltage command value and the compensation gain; controlling the output voltage to the electric machine based on the compensated voltage command value; and limiting the compensation gain to be equal to or less than a predetermined upper limit.