U-Shaped Single-Phase PM Motor Sensorless Control via Back-EMF Observer
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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 inefficiencies in power regulation without rotor position information, and traditional sensor-based methods incur additional costs and energy consumption.
Innovation Solution
A method and circuit for controlling U-SPSPM motors using feedback signals from voltage, current, and zero-crossing measurements to estimate back electromotive force (back-EMF) and rotor position, allowing for sensorless operation without physical position sensors, with a microcontroller and triac configuration to supply power based on these estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor (Hall sensor, encoder) is used to obtain rotor position information, then the motor can be controlled with high precision and optimal power regulation, but the system incurs additional costs for sensor and wiring, requires more space for sensor and circuitry, and consumes more energy
Solution Approach 1:
The patent extracts the rotor position information from the back-EMF signal itself, removing the need for external sensors. The back-EMF observer extracts position and speed information directly from the motor's electrical characteristics, eliminating Hall sensors, encoders, and associated wiring while maintaining high measurement precision.
Solution Approach 2:
The patent introduces a back-EMF observer as an intermediary computational model that mediates between the motor's electrical signals and the control system. This observer processes voltage and current measurements to infer rotor position and speed, serving as a virtual sensor that replaces physical position sensing devices.
2Device complexity
If only voltage signal is used to estimate rotor position, then the system structure is simplified, but rotor position information can only be obtained when current equals zero, limiting maximum output power and torque
Solution Approach 1:
The patent merges voltage signal measurement with current signal measurement in the back-EMF observer. By combining both electrical signals, the system continuously estimates back-EMF and derives rotor position information at all operating conditions, not just when current is zero. This enables full-range power and torque output while maintaining simplified sensorless architecture.
Solution Approach 2:
The patent implements a dynamic back-EMF observer that continuously adapts to changing operating conditions. The observer model dynamically processes both voltage and current signals to track rotor position and speed in real-time, enabling the motor to operate at maximum power and torque across the entire speed range rather than being limited to specific operating points.
3Device complexity
If sensorless control is implemented without back-EMF estimation, then the system is simpler and cheaper, but optimal power regulation and efficient operation cannot be achieved
Solution Approach 1:
The patent implements a feedback mechanism through the back-EMF observer that continuously monitors motor operation and adjusts control parameters accordingly. By estimating back-EMF from voltage and current measurements, the system provides real-time feedback on rotor position and speed, enabling optimal commutation timing and current control to maximize efficiency and minimize energy losses without adding physical sensors.
Solution Approach 2:
The motor system performs self-diagnosis and self-regulation through the back-EMF observer, which uses the motor's own electrical signals (voltage and current) to determine its operational state. This self-service approach enables the motor to regulate its own power consumption and operating efficiency without external sensing, achieving optimal performance while maintaining simple sensorless architecture.
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 and cost-effective sensorless control of U-SPSPM motors by providing high-fidelity back-EMF estimation and rotor position determination, independent of AC power frequency, leading to improved power regulation and reduced energy consumption.
Implementation Method 1
estimating the back electromotive force (back-EMF) of the motor based on an observer model with inputs indicative of the measured feedback signals
Data Source
AI summary
A method for controlling a U-shape single phase synchronous permanent magnetic motor having a rotor and a stator and coupled to a single phase alternating current (AC) power source through a switch includes estimating back-electromotive force and the position of the rotor based on a voltage feedback signal, a current feedback signal, and a phase feedback signal indicative of a zero-crossing of the single phase AC power source. Once the speed and position of the rotor are determined, a controller can trigger a switch to supply power to the motor.