Sensorless Motor Control via Resistance-Based Temperature Compensation

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Solution Overview

Problem

Conventional sensorless control methods for motors face performance degradation due to temperature-induced changes in motor resistance and magnetic flux, leading to errors in estimating rotor speed and position, especially in applications with varying loads and temperatures, and often require additional temperature sensors, increasing costs and complexity.

Innovation Solution

A sensorless control apparatus and method that compensates for temperature-induced changes in motor resistance and magnetic flux by estimating these parameters based on measured resistance values and temperature characteristics, without the need for additional temperature sensors, using a position estimator to generate estimated speed and position of the rotor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If additional temperature sensors are installed at the motor to directly measure temperature, then the accuracy of temperature measurement and parameter compensation is improved, but the production cost and device complexity increase

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidcontrol apparatus structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The motor's own resistance serves as a temperature sensor. The resistance value changes with temperature, and this inherent property is utilized to estimate temperature without adding external sensing components. The control apparatus uses the measured resistance value to estimate motor temperature and compensate parameters accordingly.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent replaces the mechanical/physical temperature sensor system with an electrical measurement system. Instead of using a separate temperature sensor to detect thermal conditions, the system uses electrical resistance measurements (which naturally vary with temperature) to infer temperature and drive the compensation process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If temperature of the motor is estimated through the temperature of an inverter module, then the device complexity is reduced, but the accuracy in estimating the temperature of the motor and compensating parameters is low

Engineering Contradiction:

Improvecontrol apparatus structureVSAvoidtemperature estimation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

3Device complexity

If parameters such as resistance and magnetic flux are not compensated for temperature changes, then the device complexity remains low, but the error between actual motor and model increases, degrading sensorless control performance

Engineering Contradiction:

Improvecontrol apparatus structureVSAvoidsensorless control performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent makes the control parameters dynamic rather than static. The resistance and magnetic flux values are adjusted in real-time based on the estimated temperature derived from resistance measurements. This dynamic adaptation allows the control model to track actual motor conditions across varying temperatures, maintaining high sensorless control performance.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter values (resistance and magnetic flux) based on temperature conditions. By using the measured resistance to estimate temperature and then adjusting the control parameters accordingly, the system adapts to temperature variations and maintains accurate sensorless control performance across different operating conditions.

Inventive Principle:

Principle #35Parameter changes

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

This approach enables stable and accurate sensorless control of motors across varying temperatures, reducing the risk of motor and inverter damage from excess current, while eliminating the need for additional temperature sensors, thus simplifying the control apparatus and lowering production costs.

Implementation Method 1

measuring resistance values at a plurality of temperatures in advance... the change of the resistance value according to the temperature of the motor may correspond to a temperature coefficient of the resistance

Methodology Applied

Scientific EffectTemperature coefficient of resistance: Electrical Resistance

Implementation Method 2

estimate change of the magnetic flux value of the permanent magnet based on the estimated the temperature by temperature characteristics of a residual magnetic flux density of the permanent magnet of the motor... the change of the magnetic flux value of the permanent magnet based on the estimated temperature may correspond to a temperature coefficient of the residual magnetic flux density

Methodology Applied

Scientific EffectTemperature coefficient of residual magnetic flux density: Magnetic Field

Data Source

PatentUS8981694B2Sensorless control apparatuses of motors and control methods thereof

Publication Date: 2015.03.17 SAMSUNG ELECTRONICS CO LTD

AI summary

A sensorless control apparatus of a motor may include: a position estimator configured to compensate for a resistance and a magnetic flux of a permanent magnet of the motor according to a temperature of the motor, and/or configured to generate an estimated speed of a rotor of the motor based on the compensated resistance and the compensated magnetic flux of the permanent magnet; and/or a speed controller configured to generate a command current based on a command speed of the rotor and the estimated speed of the rotor.