Sensorless Motor Startup Control to Prevent Drum Reverse Rotation
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Solution Overview
Problem
Laundry treatment machines without position sensors face challenges in accurately estimating the rotor position of the motor, leading to potential reverse rotation of the drum due to load, which affects the reliability of washing and spinning operations.
Innovation Solution
A motor driving apparatus that estimates the rotor position of the motor without a position sensing unit by using an inverter controller to generate a PWM-based switching control signal based on output current and voltage, allowing for accurate control of the motor in a sensorless mode, and supplies an alignment current during startup to prevent reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is used to sense rotor position, then motor control accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the position sensing function from a dedicated position sensor and implements it through software-based estimation using readily available current and voltage signals from the inverter controller, thereby eliminating the need for additional hardware sensors while maintaining control accuracy
Solution Approach 2:
The system uses its own operating signals (current and voltage) to estimate rotor position, making the system self-sufficient without requiring external sensing components. The inverter controller performs both motor control and position estimation functions using existing hardware
2Ease of manufacture
If sensorless mode is used to reduce cost, then manufacturing cost decreases, but rotor position estimation accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the estimated rotor position is continuously used to generate commutation signals, which in turn control motor operation. The system monitors current and voltage signals to continuously update position estimation, creating a closed-loop control system that maintains accuracy without physical sensors
Solution Approach 2:
The patent replaces the mechanical/electrical position sensor system with a computational estimation approach using software algorithms that process electrical signals (current and voltage) to derive rotor position information, substituting physical sensing with signal processing
3Device complexity
If no alignment current is supplied during startup, then device complexity is reduced, but reverse rotation phenomenon occurs
Solution Approach 1:
The patent applies preliminary action by supplying an alignment current during the startup phase to establish proper rotor positioning before normal operation begins. This preliminary current ensures the rotor is correctly aligned with the stator magnetic field, preventing reverse rotation that would occur without this initial positioning action
Solution Approach 2:
The alignment current is supplied periodically during specific phases of motor startup, creating distinct operational stages: alignment phase with alignment current, and normal operation phase without it. This periodic application of alignment current ensures reliable startup while maintaining simple control during normal operation
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 reliable operation of the laundry treatment machine by accurately controlling the motor in a sensorless mode, preventing reverse rotation of the drum and ensuring stable washing and spinning cycles.
Implementation Method 1
a method according to any one of claims 1 to 3, wherein the inverter controller generates a PWM-based switching control signal based on the output current and the output voltage
Implementation Method 2
a motor driving apparatus that estimates a rotor position of a motor without a position sensing unit
Data Source
Figure 1
Figure 2~3
Figure 4A
AI summary
A motor driving apparatus and a laundry treatment machine including the same are disclosed. The laundry treatment machine includes a drum, a motor to rotate the drum, and a driving unit to drive the motor, wherein the driving unit includes an inverter to convert direct current (DC) voltage into alternating current (AC) voltage and to output the AC voltage to the motor and an inverter controller to control the inverter to supply an alignment current to the motor so as to align the motor during a starting operation of the motor and to supply a torque current for rotating the motor to the motor together with the alignment current after the motor is aligned. Consequently, it is possible to prevent a reverse rotation phenomenon of the drum due to load.