Washing Machine Motor Harmonic Compensation
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Solution Overview
Problem
Washing machines experience motor noise due to cogging torque, which generates torque ripple and is amplified by resonance with surrounding structures, causing vibration and noise.
Innovation Solution
A washing machine with a motor and inverter circuit, controlled by a processor that compensates for m-th order harmonic components using a bandpass filter to offset these harmonics, reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor operates at high speed during spin-dry process, then water separation efficiency is improved, but motor noise and vibration are amplified due to resonance with surrounding structures
Solution Approach 1:
The control device applies preliminary anti-action by detecting resonance conditions and proactively generating compensating current commands to offset cogging torque harmonics before they cause excessive noise and vibration. The system predicts when resonance will occur based on motor speed and load conditions, and pre-applies corrective current adjustments to prevent the harmful effects rather than reacting after they occur.
Solution Approach 2:
The system changes electrical parameters (current command values) dynamically based on detected resonance conditions. By adjusting the q-axis current command to compensate for specific harmonic components (e.g., 6th, 12th, 18th harmonics) when resonance is detected, the system modifies the motor's electrical characteristics to reduce mechanical vibration and noise while maintaining the high-speed operation needed for effective water separation.
2Power
If the motor generates high torque for spin-drying, then water separation performance is improved, but torque ripple and vibration increase due to cogging torque harmonics
Solution Approach 1:
The control device implements feedback by continuously monitoring motor current, speed, and vibration levels during spin-dry operation. Based on this feedback, the control device dynamically adjusts the current command values to compensate for cogging torque harmonics. The system uses feedback from vibration sensors and current measurements to detect when torque ripple occurs and applies real-time corrections to maintain stable torque output while preserving high power for effective water separation.
3Productivity
If the motor operates continuously during wash and spin-dry processes, then washing productivity is improved, but heat accumulation and energy loss increase
Solution Approach 1:
The control device applies periodic action by implementing intermittent high-speed spin cycles alternating with lower-speed operations. During spin-dry, the motor operates at high speed for water separation, then reduces speed during transitions or when resonance conditions are detected. This periodic variation in operating speed maintains washing productivity while reducing continuous high-energy consumption and heat accumulation, improving overall energy efficiency.
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
The solution effectively reduces motor noise and its amplification by offsetting harmonic components, improving operational silence.
Implementation Method 1
filtering, by a bandpass filter, a preset m th order harmonic component of a speed error value
Implementation Method 2
Cogging torque generates torque ripple in the form of specific harmonic components, causing torque fluctuations in the motor
Implementation Method 3
Motors may generate cogging torque due to magnetic force interaction between a rotor and a stator
Implementation Method 4
The motor noise is transmitted to surrounding structures connected to the motor, and may be significantly amplified when the motor noise coincides with a natural resonant frequency of the surrounding structures
Data Source
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AI summary
A washing machine includes: a drum configured to be rotatable inside a tub; a motor including a stator and a rotor, and configured to rotate the drum; an inverter circuit connected to the motor; and at least one processor configured to compensate for a q-axis current command value of the motor based on an mth-order harmonic component (m is a natural number) and a position of the rotor, and control the inverter circuit to drive the motor based on the compensated q-axis current command value, the mth-order harmonic component being filtered by a bandpass filter from a speed error value of the rotor.