U-Shape Single-Phase PM Motor Control Using Back-EMF Estimation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

U-shape single phase synchronous permanent magnetic motors (U-SPSPM) in home appliances like dishwashers and washing machines face challenges with sensorless control due to cogging torque and inability to estimate rotor position without sensors, leading to inefficient power regulation and maximum torque achievement.

Innovation Solution

A method and circuit for controlling U-SPSPM motors using feedback signals for voltage and current measurements, estimating back electromotive force (back-EMF) with a high-fidelity observer model, and triggering power supply based on these estimates to initiate start sequences and control motor commutation independently of AC power source frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If sensorless control is used in U-SPSPM motors, then costs and energy consumption are reduced, but rotor position estimation becomes inaccurate due to cogging torque and inability to detect position without sensors

Engineering Contradiction:

Improveenergy consumptionVSAvoid rotor position estimation accuracy

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical sensor-based position detection system with an electrical field-based back-EMF estimation system. By measuring voltage and current signals and calculating back-EMF through an observer model, the system obtains rotor position information without physical contact or additional mechanical components, thereby reducing energy consumption while maintaining measurement accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces back-EMF as an intermediary parameter to indirectly obtain rotor position information. Instead of directly measuring position, the system measures voltage and current, calculates back-EMF, and derives position from it. This intermediary approach overcomes the direct measurement limitations in sensorless control while maintaining accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If voltage signal only is used for sensorless control, then device complexity is reduced, but power regulation and torque achievement become suboptimal

Engineering Contradiction:

Improvecontrol circuit complexityVSAvoidoutput power and torque

Core Design Contradiction:

Device complexityVSPower

Solution Approach 1:

The patent implements a feedback control system that simultaneously measures both voltage and current signals. The current feedback enables the observer model to accurately calculate back-EMF and derive rotor position, which in turn optimizes the commutation timing and power regulation, achieving maximum torque and power output without increasing overall device complexity.

Inventive Principle:

Principle #23Feedback

3Device complexity

If commutation is synchronized with AC power source frequency, then device complexity is reduced, but fine-time-scale commutation control is lost

Engineering Contradiction:

Improvecontrol system complexityVSAvoidcommutation timing precision

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent transitions from a static commutation approach (fixed to AC power frequency) to a dynamic commutation strategy based on real-time back-EMF estimation. The commutation timing is continuously adjusted according to the estimated rotor position from back-EMF, enabling fine-time-scale control that adapts to actual motor operating conditions rather than being constrained by fixed frequency synchronization.

Inventive Principle:

Principle #15Dynamics

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 efficient sensorless control of U-SPSPM motors by providing high-fidelity back-EMF estimates, allowing for fine-time-scale commutation and improved motor performance without the need for physical position sensors, reducing costs and energy consumption.

Implementation Method 1

estimating back electromotive force (back-EMF) of the motor based on an observer model with inputs indicative of the measured feedback signals

Methodology Applied

Scientific EffectBack electromotive force (back-EMF): Electromagnetic Induction

Data Source

PatentUS10075110B2Method and circuit for controlling or starting a u-shape single phase synchronous permanent magnet motors

Publication Date: 2018.09.11 WHIRLPOOL CORP

AI summary

A method and circuit for controlling or starting a U-shape single phase synchronous permanent magnetic motor (U-SPSPM motor) having a rotor and a stator and coupled to a single phase alternating current (AC) power source through a switch, including estimating back electromotive force (back-EMF) of the motor based on an observer model with inputs indicative of the measured signals, and triggering the switch to supply power to the motor based on the estimates of the back-EMF.