Synchronous Motor Control Device Speed Reference Calculation
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Solution Overview
Problem
Current motor control devices for synchronous motors with saliency face challenges in accurately generating q-axis and d-axis current commands, leading to torque control errors due to circular reference calculations and division-based processing, which slows down the processing speed and accuracy.
Innovation Solution
A motor control device that calculates a speed reference value based on a torque command, determines the magnitude relation between input speed and speed reference values, and generates q-axis and d-axis current commands using equations that avoid division and circular references, allowing for high-speed and accurate torque control by selectively using equations that account for magnet torque and reluctance torque based on the speed command.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional current vector control is used for synchronous motors with saliency, then torque control is attempted, but processing speed decreases due to circular reference calculations and division operations
Solution Approach 1:
The patent transforms the control approach by changing the parameter representation from direct current command calculations (which require division and circular references) to speed reference value calculations. By introducing speed reference values that are calculated using only multiplication and addition operations, the system achieves high-speed processing while maintaining accurate torque control for synchronous motors with saliency.
2Measurement precision
If conventional current command generation is used, then torque control is attempted, but accuracy decreases due to circular reference issues
Solution Approach 1:
The patent improves torque control accuracy by changing the calculation parameters from direct current commands (prone to circular reference errors) to speed reference values. The speed reference values are computed using straightforward arithmetic operations that eliminate circular dependencies, thereby achieving both high accuracy and computational simplicity simultaneously.
3Productivity
If division-based equations are used for current command generation, then torque control is attempted, but processing speed slows down
Solution Approach 1:
The patent resolves this contradiction by fundamentally changing the mathematical parameters used in control calculations. Instead of using division-based current command equations, the system employs speed reference value calculations that rely solely on multiplication and addition. This parameter transformation maintains torque control precision while dramatically improving command generation speed.
4Productivity
If simple current command calculation is used, then processing speed increases, but torque control accuracy decreases due to inability to handle saliency effects
Solution Approach 1:
The patent achieves both high processing speed and accurate torque control by transforming the control parameters to speed reference values. These speed reference values inherently account for saliency effects through their calculation methodology, eliminating the need for complex division-based equations while maintaining both speed and accuracy requirements.
Data Source
AI summary
A motor control device includes: a calculating unit for calculating a speed reference value that decreases as a torque command increases; a determining unit for determining a magnitude relationship between a speed command and a speed reference value calculated for a torque command by the calculating unit; a q-axis-current commanding unit for generating a q-axis current command on the basis of a torque command and an inverse number of a torque constant of the synchronous motor when a speed command is smaller than a speed reference value, and generating the q-axis current command on the basis of a function of which independent variable is a speed command, the torque command, the inverse number of the torque constant, and when a speed command is equal to or larger than a speed reference value; and a d-axis-current commanding unit generating a d-axis current command, on the basis of a q-axis current command.