Rotor Position Detection Using Magnetic Saturation

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Solution Overview

Problem

Existing methods for detecting the initial rotor angular position in surface mounted permanent magnetic motors are ineffective, limiting the ability to implement sensorless control in dynamoelectric machines, which are desirable for reduced weight, cost, and improved reliability.

Innovation Solution

A method involving driving the dynamoelectric machine into partial magnetic saturation by supplying a voltage to its windings, measuring currents, filtering them, and using a phase locked loop to estimate the rotor angular position, facilitated by a power inverter and microcontroller with programmed algorithms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a shaft mechanical sensor is installed on the rotor to detect initial rotor angular position, then measurement precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improveinitial rotor angular position detectionVSAvoidsensor installation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical sensor system with an electrical measurement system. Instead of using a shaft mechanical sensor coupled to the rotor shaft, the invention uses voltage and current measurements from the motor windings combined with signal processing algorithms to detect rotor position electrically, thereby eliminating the need for mechanical sensors and their associated complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces signal processing algorithms as an intermediary between the electrical measurements and the rotor position determination. The algorithms process the measured voltage and current signals to extract rotor position information, serving as a mediator that translates electrical measurements into positional data without requiring direct mechanical sensing

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If back EMF method is used to detect rotor position, then measurement precision is improved at high velocity, but reliability deteriorates at low velocity and standstill

Engineering Contradiction:

Improve rotor position detection accuracyVSAvoidsensorless control reliability across all speeds

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the operating parameters for position detection based on motor speed. At low speeds and standstill, it uses carrier injection with spatial saliency detection, while at higher speeds it transitions to back EMF methods. This parameter adaptation ensures reliable operation across the entire speed range by selecting the appropriate detection method for each operating condition

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If carrier injection approach is used to detect initial rotor position, then measurement precision is improved through spatial saliency detection, but applicability deteriorates for surface mounted permanent magnetic motors

Engineering Contradiction:

Improveinitial rotor position detection accuracyVSAvoidcompatibility with different motor types

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies different detection methodologies tailored to specific motor construction types. For interior permanent magnet motors, it uses standard carrier injection exploiting spatial saliency. For surface mounted permanent magnet motors where saliency is minimal, it employs alternative methods such as analyzing the relationship between applied voltage and measured current, or using magnetic saturation effects, thereby adapting the detection approach to the local characteristics of each motor type

Inventive Principle:

Principle #3Local quality

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

Enables accurate detection of the initial rotor angular position and successful start-up of the dynamoelectric machine without mechanical sensors, enhancing reliability and reducing weight and cost.

Implementation Method 1

driving the dynamoelectric machine into partial magnetic saturation to determine the initial rotor angular position

Methodology Applied

Scientific EffectMagnetic saturation: Magnetic Saturation

Implementation Method 2

applying a phase locked loop to each current filtered to estimate the initial rotor angular position

Methodology Applied

Scientific EffectPhase locked loop:

Data Source

PatentUS9160264B2Initial rotor position detection and start-up system for a dynamoelectric machine

Publication Date: 2015.10.13 HAMILTON SUNDSTRAND CORP

AI summary

A method for detecting an initial rotor angular position and starting a dynamoelectric machine having a stator and a rotor includes the steps of driving the dynamoelectric machine into partial magnetic saturation to determine the initial rotor angular position of the dynamoelectric machine, and starting the dynamoelectric machine utilizing the initial rotor angular position previously determined.