Motor Control Device for Sensorless Synchronous Motor Constant Identification
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Solution Overview
Problem
Existing motor constant identification methods for sensorless synchronous motors are prone to reduced precision due to errors between the voltage instruction output and the actual drive voltage applied to the motor.
Innovation Solution
A motor control device incorporating a PWM signal generator, current detector, and identifier that sets an offset voltage and superimposes an identification signal on the d-axis target voltage to detect the motor constant using a recursive least squares method, improving precision by subtracting the offset voltage and current from the detected values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage instruction is output from the current control means to identify the motor constant, then the motor constant identification process can be performed, but the identification precision is reduced due to error between the voltage instruction and actual drive voltage
Solution Approach 1:
The patent applies preliminary action by setting an offset voltage (DC component) before the identification process. This offset voltage is determined in advance to compensate for the voltage error, ensuring that when the AC identification signal is superimposed and processed, the resulting voltage and current values are already corrected for the systematic error, thereby improving identification precision without requiring real-time correction
Solution Approach 2:
The patent changes the voltage parameter by superimposing an AC identification signal on top of the DC offset voltage. This creates a composite voltage signal where the AC component enables identification while the DC component compensates for errors. The identifier then processes this composite signal to extract accurate motor constant information despite the presence of voltage instruction errors
Data Source
AI summary
To improve identification precision of a motor constant that controls a motor by vector control. A parameter identifier sets an offset voltage of a DC component as a first d-axis target voltage, and detects a d-axis current that flows accordingly as an offset current. The parameter identifier also sets a voltage obtained by superimposing an identification signal of a predetermined AC component on the first d-axis target voltage as a second d-axis target voltage, and detects the d-axis current that flow accordingly. The parameter identifier then identifies the motor constant using a voltage obtained by subtracting the first d-axis target voltage from the second d-axis target voltage and a current obtained by subtracting the offset current from the d-axis current as inputs.