Washer Drum Speed Control to Avoid Resonance Vibration
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Solution Overview
Problem
Drum-type washing machines experience vibration and noise issues due to imbalanced loads during rotation, particularly at resonance frequencies, despite the use of counterweights, as these counterweights can lag behind the drum speed and either correct or exacerbate the imbalance.
Innovation Solution
A washing machine system with a cylindrical basket and a balance ring containing counterweight balls that move to compensate for imbalanced masses, controlled by a motor and a controller that adjusts rotational speeds to prevent prolonged operation at resonance frequencies, ensuring the basket rotates with non-zero acceleration between minimum and maximum resonance speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If counterweight balls are used to compensate for imbalanced mass, then load imbalance is reduced, but vibration and noise increase at resonance frequencies due to counterweight lag
Solution Approach 1:
The controller implements periodic acceleration and deceleration cycles through the resonance frequency range, preventing the drum from dwelling at constant speeds where counterweight balls lag and cause vibration. The speed profile continuously varies rather than maintaining steady state, ensuring counterweights remain effective without causing resonance amplification.
Solution Approach 2:
The system transitions from static constant-speed operation to dynamic variable-speed operation. The controller actively adjusts the drive motor speed in real-time, creating non-zero acceleration conditions that prevent counterweight lag and maintain effective load balancing while avoiding resonance problems.
2Productivity
If the drum rotates at constant speed for extended periods, then washing efficiency is improved, but vibration and noise increase due to prolonged operation at resonance frequencies
Solution Approach 1:
The controller implements periodic speed variations that pass through the resonance frequency range without dwelling. This creates effective washing action through controlled acceleration and deceleration cycles while preventing the drum from operating at constant resonant speeds that cause excessive vibration and noise.
Solution Approach 2:
The system rapidly accelerates through the problematic resonance frequency range rather than dwelling at constant speeds within it. This 'skipping' approach minimizes the time spent in the vibration-prone speed range while still achieving necessary washing functions at higher speeds.
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
This solution effectively mitigates vibration and noise by preventing prolonged operation at resonance frequencies, maintaining the counterweight balls in an out-of-phase position to avoid amplifying imbalanced load effects, thus reducing machine vibration and noise.
Implementation Method 1
counter-weights to offset the imbalanced wash load. One type of counter-weight system includes spheres that can run in a track around the periphery of the rotating drum. As the drum rotates, the counter-weighting balls move to the opposite side of the drum than the imbalanced wash load
Implementation Method 2
at some spin speeds, spherical balls used as counterweights can remain in a state of transition as they lag behind the drum spin speed. As this lag occurs, the transitioning counterweights sometimes correct the imbalanced load, but can also add to the imbalanced load while in transition. This effect is particularly prevalent close to resonance frequencies of the combined rotating mass of the drum and the wash material
Data Source
AI summary
A washing machine system comprising an outer tub with a basket rotatably supported within the outer tub. The basket receives launderable items and wash water. The washing machine includes a drive motor that rotates the basket during the wash operation, and a balance ring associated with the basket containing counterweights that move within the balance ring to compensate for an imbalanced mass in the basket. The washing machine includes a controller communicating with the motor. The controller sends signals to the motor to rotate the basket at selective rotational speeds, and receives electronic signals indicating the power used to rotate the basket at selective speeds. The controller compensates for the imbalanced mass by preventing the drive motor from rotating the basket at a substantially constant speed between a predetermined minimum resonance speed and a predetermined maximum resonance speed for more than a predetermined maximum dwell time during the wash operation.