Sensorless Motor Drive for Rapid Rotor Alignment in Laundry Machines

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Solution Overview

Problem

Laundry treatment machines without position sensors face challenges in accurately estimating the rotor position of motors, leading to inefficiencies and potential damage during washing cycles, particularly at low-speed operations.

Innovation Solution

A sensorless motor driving system that estimates the rotor position using output current and voltage detection, generating PWM-based switching control signals to control the inverter and supply AC voltage to the motor, with additional voltage vector fixing methods during starting operations to enhance alignment and reduce noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a position sensor is used to sense rotor position, then rotor position detection accuracy is improved, but manufacturing cost increases

Engineering Contradiction:

Improverotor position detection accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical position sensor system with an electrical estimation system. The rotor position is determined by estimating back electromotive force (EMF) from voltage and current measurements, eliminating the need for physical sensors while maintaining adequate position detection capability for motor control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces back EMF estimation as an intermediary method to indirectly determine rotor position. Instead of directly measuring position with a sensor, the system uses voltage and current measurements combined with back EMF calculation to infer rotor position, serving as a mediator between electrical measurements and position information

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If sensorless control is used to reduce manufacturing cost, then manufacturing cost is reduced, but rotor position estimation accuracy deteriorates

Engineering Contradiction:

Improvemanufacturing costVSAvoidrotor position estimation accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent implements feedback control using estimated rotor position information. The back EMF estimation provides continuous position feedback to the control system, enabling closed-loop control that compensates for estimation errors and maintains accurate motor control without position sensors

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the control parameters by using estimated back EMF values instead of direct position sensor readings. By processing voltage and current measurements through back EMF calculation, the system transforms electrical measurements into position information that can be used for control decisions

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If back electromotive force is not compensated during starting operation, then device complexity is reduced, but rotor alignment accuracy deteriorates

Engineering Contradiction:

Improvecontrol complexityVSAvoid rotor alignment accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary compensation for back EMF during the starting operation phase. Before the motor reaches normal operating speed, the control system pre-compensates for back EMF effects to ensure accurate rotor alignment is achieved from the beginning, preventing alignment errors that would be difficult to correct later

Inventive Principle:

Principle #10Preliminary action

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 and efficient motor control without position sensors, improving rotor alignment and reducing noise during starting operations, while maintaining efficient operation at high speeds.

Implementation Method 1

generating PWM-based switching control signals to control the inverter

Methodology Applied

Scientific EffectPWM (Pulse Width Modulation):

Implementation Method 2

an inverter to convert direct current (DC) voltage into alternating current (AC) voltage and to output the AC voltage to the motor

Methodology Applied

Scientific EffectInversion (DC to AC conversion):

Implementation Method 3

current corresponding to a direction opposite to back electromotive force generated from the motor

Methodology Applied

Scientific EffectBack electromotive force (back EMF): Electromagnetic Induction

Data Source

PatentUS9708744B2Motor driving apparatus and laundry treatment machine including the same

Publication Date: 2017.07.18 LG ELECTRONICS INC

AI summary

The laundry treatment machine includes an inverter to convert direct current (DC) voltage into alternating current (AC) voltage and to output the AC voltage to a motor. The laundry treatment machine includes an inverter controller to control the inverter to supply current corresponding to a direction opposite to back electromotive force generated from the motor to the motor so as to align the motor during a starting operation of the motor. It is feasible to rapidly align a rotor of the motor during the starting operation of the motor.