Motor Torque Estimation with Magnet Temperature Compensation
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Solution Overview
Problem
Existing motor temperature and torque estimation devices face reduced accuracy in torque control due to temperature variations of permanent magnets, especially during heavy loading or high rotational speeds, leading to degraded loss and temperature estimation.
Innovation Solution
A motor temperature and torque estimation device that includes a temperature sensor, loss estimation units for iron, mechanical, and copper losses, and multiple temperature estimation units to accurately calculate magnet temperature and magnetic flux, enhancing estimation accuracy through corrected magnetic flux and voltage equations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor and loss estimation model are used to estimate magnet temperature, then temperature estimation is enabled, but estimation accuracy degrades when energizing current is large or rotational speed is high
Solution Approach 1:
The patent divides the temperature estimation problem into two separate estimation paths: a first temperature estimation unit using thermal models and loss estimation, and a second temperature estimation unit using magnetic flux estimation. Each path is optimized for different operating conditions, and their results are combined through a selection unit that chooses the more reliable estimation based on current operating parameters.
Solution Approach 2:
The patent changes the estimation parameters dynamically based on operating conditions. The selection unit switches between different estimation methods depending on energizing current magnitude and rotational speed, using weighting factors or coefficients to change over between the two estimation means, thereby maintaining accuracy across the full operating range.
2Measurement precision
If magnetic flux is measured preliminarily for accurate torque control, then torque control accuracy is improved, but temperature variations of permanent magnets reduce the accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the estimated magnet temperature is used to correct the magnetic flux value. The magnetic flux estimation unit calculates flux based on voltage equations and current, then the temperature correction unit adjusts this flux value according to the estimated temperature, creating a closed-loop system that compensates for thermal effects on magnetic properties.
Solution Approach 2:
The patent performs preliminary temperature estimation and magnetic flux correction before torque control is executed. By estimating the magnet temperature and correcting the magnetic flux in advance, the system prepares accurate torque control parameters that account for thermal conditions, enabling precise torque control despite temperature variations.
3Device complexity
If a single temperature estimation method is used, then device complexity is reduced, but estimation accuracy is insufficient under varying operating conditions
Solution Approach 1:
The patent creates a universal temperature estimation system that can handle multiple operating conditions through a single integrated architecture. The selection unit serves as a multi-functional component that routes between different estimation methods based on operating parameters, making the system adaptable to various conditions without requiring separate dedicated systems for each scenario.
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 device improves the accuracy of loss and torque estimation, allowing for more precise motor control and higher torque output by accounting for magnet temperature and thermal demagnetization effects.
Implementation Method 1
a temperature sensor for detecting a temperature of an object to be measured
Implementation Method 2
an iron loss estimator for estimating an iron loss which is one of losses of the motor
Implementation Method 3
a copper loss estimator for estimating a copper loss which is one of losses of the motor
Implementation Method 4
a magnet's magnetic flux calculator for calculating magnet's magnetic flux of the motor on the basis of an energizing current of the motor, on that of an armature voltage thereof, on that of a coil resistance thereof and on that of inductance of the motor
Implementation Method 5
a torque estimation unit for estimating torque of the motor on the basis of magnet's magnetic flux, on that of the iron loss and on that of the mechanical loss
Data Source
AI summary
A motor temperature and torque estimation device comprises: a temperature sensor; a losses estimation circuitry to estimate an iron loss; a first temperature estimation circuitry to estimate a first magnet temperature from the estimated iron loss and a sensor's detected temperature; a second temperature estimation circuitry, to input into a magnet's magnetic flux calculator thereinside motor's modified inductance, to estimate a second magnet temperature from magnet's magnetic flux calculated through voltage equations; a magnet-temperature estimation circuitry to estimate a motor's magnet temperature from the first and second magnet temperatures; a magnet's magnetic estimation circuitry to estimate magnetic flux based on the calculated/modified one, the motor's estimated magnet temperature and temperature characteristics, and to output the estimated magnetic flux into the losses estimator; and a torque estimation circuitry to estimate torque based on the estimated magnetic flux and iron loss, wherein a motor's magnet temperature(s) and torque are estimated.