Washing Drum Load and Unbalance Detection via Generator Braking
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Solution Overview
Problem
Existing methods for determining the load and imbalance of a washing machine's laundry drum are not precise and quick, requiring resistance and regenerative braking to measure load, which is inefficient.
Innovation Solution
A method using a permanent-magnet synchronous motor with an inverter-controlled stator winding, where the drum is accelerated and then braked to transition into generator mode, measuring current and intermediate circuit voltage to determine load and imbalance, leveraging the relationship between moment of inertia and load for precise calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance braking and regenerative braking are used to determine load, then load determination can be performed, but the process becomes complex and time-consuming
Solution Approach 1:
The patent extracts only the essential measurement moment from the complex braking process - specifically measuring current and intermediate circuit voltage at the peak value during regenerative braking. This eliminates the need for complex resistance braking while maintaining load determination capability, reducing process complexity while preserving measurement accuracy.
Solution Approach 2:
The control unit is pre-programmed with threshold values for load determination. During regenerative braking, the system performs preliminary measurements of current and voltage, compares them against stored thresholds, and determines load status without requiring complex real-time calculations or additional braking maneuvers.
2Measurement precision
If both resistance braking and regenerative braking are required, then load determination is possible, but the time required increases
Solution Approach 1:
The patent extracts only the critical measurement data needed from the regenerative braking process - current and intermediate circuit voltage at peak value. By eliminating resistance braking entirely and using only regenerative braking with threshold comparison, the system achieves load determination in a single braking event, significantly reducing the time required.
Solution Approach 2:
The system changes the measurement parameters from requiring multiple braking phases to measuring only current and voltage during a single regenerative braking event. The control unit compares these parameters against pre-stored threshold values, enabling rapid load determination without time-consuming complex braking sequences.
3Measurement precision
If current and intermediate circuit voltage are measured in generator mode, then load and imbalance can be determined precisely, but the system complexity increases
Solution Approach 1:
The inverter components that are already present for motor operation are made multi-functional by using them for measurement purposes during regenerative braking. The same current sensors and voltage measurement circuits used for motor control now also determine load and imbalance status, eliminating the need for separate measurement systems and reducing overall device complexity.
Solution Approach 2:
The system uses its own operational parameters (current and intermediate circuit voltage during regenerative braking) to determine load and imbalance status. The control unit leverages existing measurements and compares them against stored thresholds, allowing the system to self-diagnose without requiring external measurement devices or complex additional instrumentation.
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 and rapid determination of load and imbalance by utilizing the motor's efficiency and compact design, providing accurate results through energy calculation and power profile analysis.
Implementation Method 1
there is a transition from motor operation to generator operation of the electric motor. When the laundry drum is braked, that is to say in generator mode, an electrical current flowing through the at least one winding of the stator and / or an electrical intermediate circuit voltage is measured
Data Source
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Figure 2
AI summary
The invention relates to a method for obtaining information about the load and/or about the unbalance of a laundry drum of a washing machine, wherein the laundry drum is driven by an electric motor (9), the stator of which comprises at least one winding (W, V, U) that is coupled to a power inverter (8) controlled by a control unit (7). The laundry drum is accelerated to a predetermined rotational speed and is then slowed down. During the slowing down of the laundry drum, an electric current (lw, Iv, Iu) flowing over the at least one winding (W, V, U) of the stator and/or an electric intermediate circuit voltage are measured. Furthermore, the curve of the electric power supplied by the electric motor during generator operation is evaluated for the duration of a revolution of the laundry drum. The unbalance and/or the load is concluded depending on the measured values for the current (lw, Iv, Iu) and/or for the intermediate circuit voltage and depending on the evaluated power. The invention further relates to a corresponding circuit arrangement (1) and to a washing machine having a circuit arrangement (1).