Washing Machine Spin Control to Avoid Tub Resonance
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Solution Overview
Problem
Washing apparatuses using uncontrolled motors face challenges in precisely controlling rotating speeds, leading to resonance phenomena during spin-drying, which cause vibrations and noise due to the coincidence of tub rotation frequency with motor rotation frequency.
Innovation Solution
A washing apparatus equipped with an AC motor, a clutch unit, and a controller that detects rotating speeds and performs intermittent spin-drying operations by alternating power supply to the AC motor, avoiding resonance areas by setting maximum and minimum speeds within the resonance range, and includes a pulley unit and speed detector for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an uncontrolled motor is used to reduce cost, then the price of the washing apparatus is reduced, but the rotating speed cannot be precisely controlled causing resonance phenomenon
Solution Approach 1:
A speed detector is introduced as an intermediary component between the uncontrolled motor and the control system. The speed detector detects the rotating speed of the motor or clutch unit and provides feedback to the controller, enabling precise speed control without replacing the inexpensive uncontrolled motor with an expensive controlled motor.
Solution Approach 2:
The control system implements feedback control by continuously monitoring the rotating speed through the speed detector and adjusting the power supply to the motor based on the detected speed. This feedback mechanism enables precise speed control while maintaining the use of cost-effective uncontrolled motors.
2Device complexity
If the rotating tub is controlled only through on-time and off-time of the motor, then the control system is simple, but it is difficult to avoid the resonance phenomenon
Solution Approach 1:
The control system uses feedback from the speed detector to determine when to supply and cut off power to the motor. By monitoring the actual rotating speed and comparing it with the resonance area, the controller can intelligently adjust the power supply timing to avoid resonance, moving beyond simple on-time/off-time control.
Solution Approach 2:
The control system dynamically changes the operating parameters (power supply timing) based on the detected rotating speed. By adjusting the power supply cut-off point based on speed feedback, the system avoids the resonance area while maintaining simple hardware 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
The solution effectively minimizes resonance-related vibrations and noise by controlling the AC motor's power supply based on detected rotating speeds, ensuring stable operation and reduced wear on the washing apparatus.
Implementation Method 1
an AC motor configured to generate a rotating force
Implementation Method 2
a speed detector configured to detect a rotating speed of at least one of the AC motor and the clutch unit
Implementation Method 3
a clutch unit configured to selectively transmit the rotating force to a rotating tub and a pulsator
Implementation Method 4
the laundry is spin-dried using a centrifugal force generated by rotation of the rotating tub
Data Source
AI summary
A washing apparatus including an AC motor configured to generate a rotating force, a clutch unit configured to selectively transmit the rotating force to a rotating tub and a pulsator, a speed detector configured to detect a rotating speed of at least one of the AC motor and the clutch unit, and a controller configured to repeat power supply and power cut-off to the AC motor according to the rotating speed. The washing apparatus can control the power supply and power cut-off to the AC motor based on the rotating speed.