Washing Machine Drum Occupancy Detection Using Back-EMF
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Solution Overview
Problem
Washing machines pose a risk of drowning accidents if children or pets are inadvertently left inside, as users may not check for their presence before operating the machine, especially during the filling of water during washing and rinsing processes.
Innovation Solution
A method and system for a washing machine that detects the back electromotive force of the washing motor, analyzes its periodicity, and controls the output of an alarm sound or automatically opens the door to prevent accidents by determining if a child or pet is present based on the periodicity of the back electromotive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the washing machine operates normally without detection systems, then the device complexity is low and ease of operation is maintained, but safety reliability deteriorates due to drowning risk
Solution Approach 1:
The patent replaces complex mechanical detection systems with an electrical sensing approach. The weight sensor detects changes in weight caused by a child or pet entering the drum, and the back electromotive force sensor monitors motor characteristics to infer drum rotation and object presence. This electrical sensing substitution maintains safety while reducing mechanical complexity.
Solution Approach 2:
The system continuously monitors back electromotive force from the washing motor and uses this feedback to determine drum rotation status and detect objects. The weight sensor provides continuous feedback on drum load changes. This feedback mechanism enables real-time safety monitoring without requiring complex active scanning systems.
2Reliability
If the door is automatically opened when an object is detected, then safety is improved by preventing drowning accidents, but the ease of operation deteriorates due to unexpected door opening
Solution Approach 1:
The system applies preliminary anti-action by issuing an alarm sound before automatically opening the door. The alarm warns the user of the detected object, giving them a chance to intervene. Only if the alarm is not acknowledged does the system proceed to open the door, thus balancing safety with user convenience and avoiding unexpected operations.
Solution Approach 2:
The system performs preliminary detection and alarm actions before executing the door opening action. The weight sensor detects the object, triggers an alarm, and waits for user response before automatically opening the door. This preliminary action sequence ensures safety while providing user awareness and control opportunities.
3Ease of manufacture
If the back electromotive force detection is used to detect objects, then the manufacturing precision and cost are reduced, but the measurement precision deteriorates compared to direct sensing
Solution Approach 1:
The back electromotive force acts as an intermediary indicator of drum rotation and object presence. Instead of directly sensing objects, the system measures the electrical characteristic (back EMF) of the motor, which indirectly reflects the mechanical state of the drum and any objects affecting its rotation. This intermediary measurement approach reduces cost while maintaining functional detection capability.
Solution Approach 2:
The system uses the back electromotive force waveform as a copy or proxy for direct mechanical sensing data. By analyzing the electrical signature of the motor under different load conditions (with or without objects), the system infers object presence without direct physical contact sensing, reducing manufacturing complexity while preserving detection functionality.
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
The system effectively prevents drowning accidents by alerting users or automatically opening the door when a child or pet is detected inside the washing machine, ensuring their safety during operation.
Implementation Method 1
detecting a back electromotive force of a washing motor, and analyzing a periodicity of a waveform period of the back electromotive force
Data Source
AI summary
A washing machine and a method for controlling the same are disclosed. The washing machine detects a back electromotive force of a washing motor, and controls output of an alarm sound by analyzing periodicity of a waveform period of the back electromotive force. The washing machine determines whether a child or pet is in a drum washing machine on the basis of the back electromotive force generated from the washing motor, and informs a user or guardian of the determined result.