Washing machine and method for operating a washing machine
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Solution Overview
Problem
Existing washing machines face challenges in accurately and cost-effectively determining the load quantity in the drum, particularly at subcritical speeds, leading to noise and stress on laundry, and limitations in imbalance detection and moisture estimation.
Innovation Solution
A method involving periodic variation of drum speed at a predetermined frequency to determine load quantity by analyzing torque fluctuations, allowing for subcritical mass moment of inertia calculation without the need for spin run-up, using signal amplitude analysis and spectral methods like FFT or Goertzel algorithm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the known inertia method is used to determine load size, then the load quantity can be determined, but the drum must be accelerated to supercritical spin speeds which increases noise emissions and causes stress on laundry
Solution Approach 1:
The patent changes the operating parameter from supercritical spin speeds to subcritical drum speeds for inertia-based load determination. By performing the measurement at lower speeds (below the critical threshold), the method achieves accurate load size determination without the harmful noise emissions and laundry stress associated with high-speed spin cycles.
Solution Approach 2:
The patent performs load determination as a preliminary action before the main wash program starts. By determining the load size at subcritical speeds before washing begins, the system obtains necessary measurement data without subjecting laundry to the harmful effects of high-speed spin cycles that would otherwise be required for accurate inertia-based measurement.
2Measurement precision
If the known inertia method is used to determine load size, then the load quantity can be determined, but the spin cycle takes time and results in increased noise emissions
Solution Approach 1:
The patent changes the speed parameter from supercritical to subcritical ranges, enabling load determination to be performed during or before the wash program without requiring a separate high-speed spin cycle. This eliminates the time loss associated with accelerating to and from supercritical speeds while maintaining measurement accuracy.
3Measurement precision
If a load sensor is integrated into the washing machine to determine load size, then the load quantity can be measured, but additional components and special dampers are required which increases cost
Solution Approach 1:
The patent replaces the mechanical load sensor system with an inertia-based measurement method using the existing drum and motor. Instead of adding physical sensors and dampers to directly measure load weight, the system uses torque measurements and drum acceleration characteristics at subcritical speeds to determine load size, leveraging existing mechanical components for measurement purposes.
Solution Approach 2:
The patent enables the washing machine's existing motor and drum to serve dual purposes: both for performing the wash function and for determining load size through inertia-based measurement. The motor's torque characteristics during subcritical acceleration naturally provide the measurement data needed, eliminating the need for separate measurement hardware.
4Measurement precision
If the known inertia method is used to determine load size, then the load quantity can be determined, but the determination can only be performed at supercritical speeds which limits availability during wash cycle for other processes
Solution Approach 1:
The patent changes the operational speed parameter from supercritical to subcritical range, enabling load determination to occur at the same speeds used for wash cycle operations. This allows simultaneous or sequential use of load size information for both the wash program control and subcritical imbalance detection without requiring separate high-speed measurement phases.
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 precise, low-noise, and cost-effective load determination, improving imbalance detection and residual moisture estimation, while reducing noise and stress on laundry.
Implementation Method 1
determination of torques of the motor driving the drum during the periodic variation of the drum speed
Implementation Method 2
determination of a signal amplitude of the torques determined over the predetermined period at at least one predetermined frequency component
Data Source
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AI summary
The invention relates to a method for operating a washing machine comprising a tub for holding washing liquid, a drum rotatably mounted in the tub for holding laundry, a motor for driving the drum, and a control device for controlling the motor. The method includes determining the drum load by the following steps: periodically varying the drum speed at a predetermined frequency; determining the torques of the motor driving the drum during the periodic variation of the drum speed over a predetermined period; determining the signal amplitude of the torques determined over the predetermined period at at least one predetermined frequency component; and determining the drum load using the determined signal amplitude. The invention further relates to a corresponding washing machine.