Washing Machine Drum Unbalance Detection via Generator-Mode Power
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Solution Overview
Problem
Existing methods for determining the load and unbalance of a washing machine's laundry drum require resistance and regenerative braking, making them inefficient and time-consuming.
Innovation Solution
A method using a power inverter-controlled electric motor with a control unit to measure current and intermediate circuit voltage during generator operation, allowing for precise determination of load and unbalance by evaluating the energy supplied and moment of inertia of the drum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance braking and regenerative braking are used to determine load, then measurement precision is improved, but loss of time increases and productivity decreases
Solution Approach 1:
The invention extracts the load determination process from the complex multi-stage braking procedure and performs it during the normal generator operation phase. By measuring current and intermediate circuit voltage during the deceleration phase that naturally occurs after motor operation, the system obtains load information without requiring separate resistance braking and regenerative braking cycles, thus reducing time loss while maintaining measurement precision.
Solution Approach 2:
The generator operation serves dual purposes: it naturally decelerates the laundry drum while simultaneously providing the conditions needed for load determination. The same generator operation that would otherwise be a transitional phase is now utilized for measurement, eliminating the need for dedicated braking cycles and improving productivity without sacrificing measurement accuracy.
2Measurement precision
If multiple braking cycles are implemented for load determination, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The invention merges the load determination function with the existing generator operation control. Instead of implementing separate resistance braking and regenerative braking sequences, the system combines load measurement with the natural deceleration phase, using the same control unit and measurement infrastructure already present in the washing machine, thereby reducing device complexity while maintaining determination accuracy.
Solution Approach 2:
The generator operation inherently provides the conditions needed for load determination through its own electrical characteristics (current and voltage behavior during deceleration). The system uses these self-generated signals for measurement without requiring external braking mechanisms or additional control complexity, allowing the operation to serve its own measurement needs.
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 quick and precise determination of load and unbalance without the need for additional braking cycles, improving efficiency and accuracy in assessing drum conditions.
Implementation Method 1
the laundry drum is slowed down, i.e. a changeover from a motor operation into a generator operation of the electric motor takes place. When slowing down the laundry drum, in other words in generator operation, an electric current flowing over the at least one winding of the stator and/or an electric intermediate circuit voltage are measured
Data Source
AI summary
In a method for determining a load and/or an unbalance of a laundry drum of a washing machine driven by an electric motor having a stator with at least one winding coupled to a power inverter controlled by a control unit, the laundry drum is accelerated to a predetermined rotational speed and then slowed down. During the slow-down, the motor operates in generator mode and an electric current flowing through the at least one winding and/or an electric intermediate circuit voltage is measured. The time dependence of the electric power supplied by the electric motor in generator mode is evaluated during a revolution of the laundry drum. The unbalance and/or the load are determined from the measured current values and/or the intermediate circuit voltage and from the determined electric power. A corresponding circuit arrangement and a washing machine with this circuit arrangement are also disclosed.