Washer Basket Acceleration Control for Unbalanced Spin Loads
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Solution Overview
Problem
Washing machines face high stresses and mechanical wear due to unbalanced loads during high-speed spin cycles, which can lead to excessive force on the basket, drive system, and suspension system, causing damage and inefficiency.
Innovation Solution
A washing machine system that includes a variable speed motor and an inverter controlled by a controller to accelerate the basket above its natural resonant frequency, with a method of initially spinning at a speed below the resonant frequency to reduce unbalance before increasing speed, ensuring the torque matches the drag torque, thereby minimizing mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the basket is accelerated to high rotational velocity for water extraction, then water extraction efficiency is improved, but mechanical stress and wear on the basket, drive system, and suspension system increase
Solution Approach 1:
The system performs preliminary action by detecting unbalance at low speeds before high-speed extraction begins, and by using the brake to deliberately create controlled unbalance effects that redistribute laundry. This preliminary detection and adjustment prevents severe mechanical stress when high-speed extraction later occurs, as the unbalance is already mitigated.
Solution Approach 2:
The system converts the harmful effect of unbalance into a beneficial measurement signal. By using the brake to create controlled unbalance effects and measuring the resulting motor load variations, the system transforms what would be a harmful mechanical stressor into a useful diagnostic tool for detecting and correcting unbalance conditions before high-speed operation.
2Measurement precision
If the motor load is used to detect unbalance at high speeds, then unbalance detection precision is improved, but measurement becomes impossible at low speeds due to brake drag interference
Solution Approach 1:
The system applies periodic action by cycling the brake on and off during low-speed operation. By alternately applying and releasing the brake, the system creates periodic variations in motor load that reveal unbalance conditions. This periodic modulation allows the measurement system to distinguish brake drag effects from unbalance effects, enabling detection at low speeds where continuous brake application would otherwise mask the signal.
Solution Approach 2:
The system performs preliminary unbalance detection and correction at low speeds using the periodic brake application method before proceeding to high-speed extraction. This preliminary measurement and correction phase establishes a balanced condition that eliminates the need for complex real-time unbalance compensation during high-speed operation.
3Reliability
If the basket speed is limited to prevent exceeding design limits, then reliability is improved, but water extraction productivity decreases
Solution Approach 1:
The system performs preliminary unbalance detection and correction at low speeds before acceleration to high speeds. By detecting and mitigating unbalance conditions in advance, the system ensures that when the basket accelerates to high rotational velocities, the unbalance forces are already reduced, allowing operation near design limits without exceeding them, thus maintaining both reliability and productivity.
Solution Approach 2:
The system uses feedback from motor load measurements to continuously monitor and assess unbalance conditions during acceleration. This feedback allows the control system to adjust operation dynamically, preventing conditions that would cause the basket to exceed design speed limits while maximizing extraction efficiency within safe operating parameters.
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 approach reduces mechanical wear, improves energy efficiency, and extends the lifespan of the washing machine by avoiding excessive unbalanced loads and optimizing spin cycle performance.
Implementation Method 1
Water is extracted from the laundry items by revolving the perforated laundry item containing the laundry items at a high rotational velocity. Centrifugal forces pull the majority of the water out of the laundry items and through the holes in the rotating basket.
Implementation Method 2
accelerating the basket to a rotational speed above a natural resonant frequency (NRF) of the basket assembly, holding the basket at the rotational speed above the NRF for a first time period
Data Source
AI summary
A washing machine includes a cabinet, a tub mounted within the cabinet, and a basket rotationally mounted within the tub for relative rotation therewith. A suspension assembly supports the tub within the cabinet. A variable speed motor is included for rotating the basket about a rotation axis, and an inverter is operatively coupled to the motor. A controller is operatively coupled to the inverter and the motor and is configured to control the motor based on a drag torque on the basket.