Front-Loading Washer Door Lock Control With Dual Microcontrollers
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Solution Overview
Problem
Front-loading laundry treatment machines, such as washing machines, often experience safety issues due to program errors or sensor malfunctions, leading to unintended door opening and potential water leakage or damage, as the control device may incorrectly assume safe conditions.
Innovation Solution
A dual-microcontroller system is implemented, where a monitoring microcontroller independently checks the actuator activities and sensor signals to ensure all safety conditions are met before releasing the door lock, using a combination of pressure and temperature sensors, and a logical AND operation with additional safety switches to prevent door opening until safe conditions are confirmed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single control microcontroller is used to manage door locking and laundry treatment programs, then the device complexity is low, but the reliability of door locking control is insufficient due to potential program errors or sensor malfunctions
Solution Approach 1:
The control system is segmented into two independent microcontrollers: a control microcontroller for executing laundry programs and a monitoring microcontroller for independently verifying safety conditions. This segmentation allows each unit to have specialized functions, improving overall reliability while distributing system complexity across separate modules rather than concentrating all control logic in a single device.
Solution Approach 2:
The monitoring microcontroller acts as an intermediary safety layer between the control microcontroller and the door locking mechanism. It independently evaluates sensor signals and actuator states, and only permits door unlocking when all safety conditions are confirmed. This intermediary function prevents direct control errors from causing unsafe door opening, thereby improving reliability without requiring complete redesign of the control architecture.
2Object-affected harmful factors
If safety checks are performed only by the control microcontroller, then the ease of operation is maintained, but the object-generated harmful factors increase due to potential water leakage from incorrect door release
Solution Approach 1:
The monitoring microcontroller performs preliminary safety verification before allowing door unlocking. It continuously monitors water level, drum rotation speed, and temperature conditions, and only permits door opening when all parameters indicate safe conditions. This preliminary check prevents water leakage by ensuring the door is only unlocked when the tub is sufficiently drained and the drum is stationary, without requiring additional user actions or complicating the operating procedure.
3Reliability
If redundant monitoring systems are implemented to prevent control errors, then the reliability of door locking is improved, but the device complexity increases due to additional microcontrollers and switches
Solution Approach 1:
The monitoring microcontroller combines multiple safety verification functions into a single integrated unit. It simultaneously monitors water level sensors, temperature sensors, drum rotation sensors, and actuator states, then consolidates this information to make a unified decision about door locking. This merging approach improves reliability through comprehensive monitoring while avoiding the complexity of implementing separate dedicated monitors for each safety parameter.
Data Source
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AI summary
The washing machine has actuating unit that actuates locking device (21) for unlocking or opening door. A control unit is connected to sensors (17b) to disable a function of detected sensor signal. The control unit is provided with microcontroller (22) for controlling actuators for executing laundry treatment program and for enabling or disabling the locking device in response to detected signals. The operation of microcontroller is monitored by monitoring microcontroller (23) to activate the operation of locking device.