Torque Correction Mechanism for Synchronous Motor Control

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Solution Overview

Problem

Existing motor control systems for synchronous motors struggle to maintain a fixed torque constant due to individual differences in motor production and electronic component variations, leading to torque variations that affect precision control.

Innovation Solution

A motor control device with a torque correction mechanism that uses a correction torque coefficient to adjust the torque command, calculated as the ratio of unloaded speeds or voltages between a reference motor and mass-produced motors, ensuring a consistent torque constant across different motors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed torque constant is used in speed control, then the control system is simple, but torque variations occur due to individual differences in motor production and electronic component variations

Engineering Contradiction:
Improvecontrol system complexityVSAvoidtorque constant consistency
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The patent changes the torque constant parameter from a fixed value to a variable that is automatically adjusted based on detected torque information. The control unit detects actual torque output and modifies the torque constant parameter dynamically, allowing each motor to operate with its optimal torque constant despite individual manufacturing variations, thereby resolving the contradiction between system simplicity and torque consistency.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If the torque constant is corrected for each individual motor, then torque control precision is improved, but the device complexity increases

Engineering Contradiction:
Improvetorque control precisionVSAvoidcontrol system complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The control system performs self-adjustment by automatically detecting the actual torque output and autonomously modifying its own torque constant parameter without requiring external calibration equipment or manual intervention. This self-service mechanism enables precise torque control for each individual motor while keeping the system relatively simple, as the motor itself provides the information needed for correction.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent implements a feedback loop where the control unit continuously detects actual torque output and uses this information to adjust the torque constant parameter. This closed-loop feedback mechanism ensures that torque control precision is maintained by constantly adapting to individual motor characteristics, while the feedback process is integrated into the existing control architecture to minimize added complexity.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP3157162B1Motor control device, and method for correcting torque constant in such motor control device
Publication Date: 2020.07.15 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD
  • EP3157162B1 patent drawingFigure 1
  • EP3157162B1 patent drawingFigure 2
  • EP3157162B1 patent drawingFigure 3

AI summary

A motor control device at least includes a speed control part for controlling a motor rotation speed. The motor control device includes a torque correction means for suppressing variation in torque constant due to individual differences of motors. In addition, the motor control device corrects the torque constant by using a correction torque coefficient calculated based on an unloaded speed when a fixed voltage is applied. Alternatively, the torque constant is corrected using the correction torque coefficient calculated based on the motor applied voltage when the motor speed is fixed.