Motor Angle Correction Using Three-Phase Short-Circuit Peaks
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Solution Overview
Problem
The accuracy of rotation angle calculation in three-phase AC motors is compromised due to detection errors in phase current measurements, which can lead to decreased power efficiency and acceleration failures.
Innovation Solution
A motor control device that corrects the rotation angle by comparing the peak-current-time rotation angle with a reference rotation angle during a three-phase short circuit, using the difference to adjust the detection value and improve calculation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase current detection is used for motor control, then motor control function is achieved, but detection errors (offset error or gain error) reduce the accuracy of phase error correction value
Solution Approach 1:
The patent extracts and eliminates the harmful influence of current sensor detection errors from the phase error correction calculation. By using a correction method that does not depend on current detection values during the correction process, the system separates the angle correction function from the current detection function, thereby achieving accurate angle correction independent of current sensor accuracy.
Solution Approach 2:
The patent introduces an intermediary approach where the phase error correction is performed through voltage commands and motor parameters rather than directly through current detection values. This intermediary method allows the system to calculate phase error without being affected by current sensor offset or gain errors, improving the accuracy of rotation angle calculation.
2Ease of operation
If magnetic pole position sensor attachment position is displaced, then sensor installation flexibility is improved, but error in rotation angle measurement is generated
Solution Approach 1:
The patent performs preliminary angle correction by calculating the phase error correction value in advance during a three-phase short circuit state before normal motor operation. This preliminary action allows the system to pre-compensate for attachment position displacement errors, ensuring accurate rotation angle measurement from the start of motor operation without requiring precise sensor installation.
Solution Approach 2:
The patent implements a feedback mechanism where the phase error correction value is calculated based on the actual motor response during three-phase short circuit and used to correct subsequent rotation angle measurements. This feedback approach automatically compensates for attachment position displacement, maintaining measurement accuracy regardless of sensor installation variations.
Data Source
AI summary
A motor control device controls a motor, which is driven by three-phase alternating currents and to which a magnetic pole position sensor measuring a magnetic pole position of a rotor is attached, using a detection value of a rotation angle of the motor based on a measurement result of the magnetic pole position by the magnetic pole position sensor, compares a peak-current-time rotation angle representing the detection value of the rotation angle at a peak of a current value of a target phase and a reference rotation angle representing the rotation angle at a peak of a predetermined current waveform of the target phase using any one phase of the three-phase alternating currents during a three-phase short circuit of the motor as the target phase, and corrects the detection value of the rotation angle based on a result of the comparison.