Motor Drive Device Temperature Estimation Filter
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Solution Overview
Problem
Conventional motor-coil temperature estimation methods fail to accurately estimate motor coil temperature due to heat transfer lag and variable heat resistance, leading to protection errors, especially when the motor is first activated or when attached to different devices.
Innovation Solution
A motor drive device that uses a filter with phase-lead and low-pass characteristics to correct temperature sensor output for ambient temperature estimation and calculates an increased temperature based on current, combining these to provide accurate motor coil temperature estimation and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is provided in the periphery of the motor to detect temperature, then the temperature can be measured, but heat transfer lag causes large estimation errors during the initial activation period
Solution Approach 1:
The patent applies preliminary action by calculating the temperature rise amount based on motor current before the temperature sensor reading becomes accurate. The control unit computes the squared motor current multiplied by a gain coefficient and integrates it over time to estimate temperature rise, providing early temperature protection during the heat transfer lag period before the peripheral temperature sensor reflects the actual coil temperature.
Solution Approach 2:
The patent uses the motor current as an intermediary to indirectly measure the temperature rise. Instead of waiting for the temperature sensor to detect the actual coil temperature through heat transfer, the system uses the motor current (which directly causes heating) as a proxy indicator, multiplying it by a gain to represent temperature rise amount, thereby bypassing the heat transfer lag issue.
2Device complexity
If a fixed gain value is used for calculating temperature rise from motor current, then the calculation is simple, but estimation errors increase when the motor is attached to different devices with varying heat resistance
Solution Approach 1:
The patent applies dynamics by making the gain coefficient adjustable rather than fixed. The control unit can change the gain coefficient based on operating conditions such as motor current magnitude, duty cycle, or attached device characteristics. This dynamic adjustment allows the system to adapt to different heat resistance conditions while maintaining estimation accuracy across various应用场景.
Solution Approach 2:
The patent changes the parameter of the gain coefficient based on operating conditions. By adjusting the gain value according to factors like motor current level, duty cycle, or detected temperature trends, the system optimizes the temperature rise calculation for different operating states and device configurations, improving accuracy without significantly increasing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces temperature estimation errors by accounting for heat transfer lag and varying heat resistance, ensuring accurate motor coil protection across different conditions.
Implementation Method 1
an ambient temperature detection unit that detects an ambient temperature of the motor coil
Implementation Method 2
a heat transfer lag correction unit that corrects a detected temperature by using a filter including both a phase-lead characteristic and a low-pass characteristic
Implementation Method 3
a motor-coil increased-temperature estimation unit that calculates a motor-coil increased-temperature estimation value on a basis of the current
Data Source
AI summary
A motor drive device in embodiments includes: a motor drive unit that generates a current for driving a motor on a basis of a position command and a position detection value of the motor; a motor-coil ambient-temperature estimation unit that calculates a motor-coil ambient-temperature estimation value by correcting an output value of a temperature sensor provided in a peripheral portion of a motor coil of the motor by using a filter including both a phase-lead characteristic and a low-pass characteristic; a motor-coil increased-temperature estimation unit that calculates a motor-coil increased-temperature estimation value on a basis of the current; and a motor-coil protection unit that limits the current on a basis of the motor-coil ambient-temperature estimation value and the motor-coil increased-temperature estimation value.