Salient Motor Current Correction for Robust Torque Ripple Control
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Solution Overview
Problem
Existing torque ripple suppression methods for electric motors are ineffective when there are errors in the acquisition values of electrical characteristics, such as armature inductance and magnetic flux, leading to incomplete suppression of torque ripples.
Innovation Solution
An electric motor control device that calculates d-axis and q-axis current correction instructions to reduce the sensitivity of torque ripples to errors in electrical characteristics, using a sensitivity setting-value to adjust the magnitudes of these instructions and achieve effective suppression even with errors in motor parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional torque ripple suppression methods using median values of electrical parameters are used, then the control is simplified, but torque ripple suppression effectiveness deteriorates when acquisition values have errors
Solution Approach 1:
The patent changes the control parameters from using only median values to using both median values and pulsation terms. The current correction instruction is calculated as: id correction = - (ΔΦd0 * iq0 + ΔL0 * iq0^2) and iq correction = - (ΔΦd0 * id0 + ΔL0 * (id0^2 - iq0^2))/2, where ΔΦd0 and ΔL0 are the pulsation terms. This parameter change enables effective torque ripple suppression even when acquisition values have errors.
2Ease of manufacture
If torque ripple suppression is performed using only median values of electrical parameters, then the calculation is simplified, but suppression effectiveness is reduced when parameter acquisition values deviate from true values
Solution Approach 1:
The patent performs preliminary action by calculating and storing the pulsation terms (ΔΦd0 and ΔL0) in advance. These pulsation terms represent the deviation between acquisition values and true values of electrical parameters. By pre-calculating these correction factors, the system can compensate for parameter errors during operation without adding complex real-time calculations, thus maintaining calculation simplicity while improving suppression precision.
3Measurement precision
If electrical characteristics are acquired with higher accuracy preliminarily, then torque ripple suppression control can be achieved, but the system remains sensitive to errors in acquisition values
Solution Approach 1:
The patent implements feedback by calculating the pulsation terms (ΔΦd0 and ΔL0) that represent the error between acquisition values and true values of electrical parameters. These pulsation terms are fed back into the current correction instruction calculation to compensate for parameter errors. The feedback mechanism continuously adjusts the control based on the detected parameter deviations, making the system robust against acquisition errors while maintaining measurement precision.
Data Source
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AI summary
An electric motor control device is provided which can suppress a torque ripple even when electrical characteristics on an electric motor have errors or variations. The electric motor control device comprises: a fundamental electric-current instruction generator (1) for outputting a d-axis fundamental electric-current instruction and a q-axis fundamental electric-current instruction for thereby outputting fundamental torque from an electric motor (7) having saliency; a position dependency component generator (101) for outputting a position dependency component(s) of the electric motor (7) in accordance with a rotational position of the electric motor (7); an electric current correction instruction calculator (103) for calculating a d-axis current correction instruction and a q-axis current correction instruction from the d-axis fundamental electric-current instruction and the q-axis fundamental electric-current instruction, and from the position dependency component(s); an electric current correction instruction superposition unit (2) for generating a d-axis electric current instruction and a q-axis electric current instruction by performing superposition of the d-axis current correction instruction and the q-axis current correction instruction on the d-axis fundamental electric-current instruction and the q-axis fundamental electric-current instruction, respectively; and an electric current controller (3) for controlling an electric current to flow through the electric motor (7) by way of an inverter (6), based on the d-axis electric current instruction and the q-axis electric current instruction.