Washing Machine Motor Back-EMF Pulse Counting for Laundry Weight Sensing
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Solution Overview
Problem
Current laundry weight sensing methods in washing machines are inefficient, leading to inaccurate weight measurement and increased water consumption due to limited sensitivity in detecting counter electromotive force, which affects the performance and energy efficiency of the washing process.
Innovation Solution
The method involves counting pulses indicating counter electromotive force generated when the motor is turned off, with specific motor control periods to maintain and alter rotation rates, and repeated operations to accumulate accurate pulse counts, enhancing the sensitivity of laundry weight detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motor is turned off immediately after reaching maximum rotation rate, then the sensing time is short, but the counter electromotive force difference is insufficient for accurate weight detection
Solution Approach 1:
The motor is controlled to rotate periodically with multiple on-off cycles during the sensing period. The motor rotates to maximum rate, is turned off to generate counter electromotive force, then rotated again, repeating this cycle several times. This periodic rotation allows accumulation of pulse counts from multiple counter electromotive force events, improving measurement precision while managing the total sensing time.
Solution Approach 2:
The motor is pre-driven to maximum rotation rate before each measurement phase. This preliminary acceleration ensures that when the motor is turned off, sufficient counter electromotive force is generated for accurate detection. The preliminary action of accelerating the motor creates the conditions necessary for reliable weight sensing without requiring extended measurement time.
2Measurement precision
If the motor is driven continuously to maximum rate, then sufficient counter electromotive force is generated, but energy consumption increases
Solution Approach 1:
Instead of continuous operation, the motor operates in periodic cycles of acceleration and deceleration. The motor is driven to maximum rate, then turned off to generate counter electromotive force for measurement, then driven again. This periodic operation generates sufficient counter electromotive force for accurate detection while minimizing energy consumption by allowing the motor to coast during measurement phases rather than maintaining continuous high-speed operation.
Solution Approach 2:
The useful action of generating counter electromotive force is maintained through multiple repeated cycles rather than requiring continuous high-energy operation. Each on-off cycle produces a pulse of counter electromotive force that contributes to the total measurement, allowing the system to accumulate sufficient signal over time while using less total energy than continuous operation would require.
3Device complexity
If simple voltage measurement is used, then the device complexity is low, but the weight sensing performance is insufficient
Solution Approach 1:
The patent replaces simple voltage measurement with a method based on counting electrical pulses generated from counter electromotive force events. Instead of measuring continuous voltage levels, the system detects discrete pulse signals that occur when the motor decelerates. This substitution of measurement approach improves sensing performance by providing more distinct and countable signals while maintaining relatively simple circuit implementation.
Solution Approach 2:
The measurement approach changes from measuring voltage magnitude to counting the number of pulse events. By changing the measured parameter from continuous voltage to discrete pulse count, the system achieves better weight sensing performance. The parameter change allows for more precise differentiation of weight values through cumulative pulse counting over multiple rotation cycles.
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
This approach significantly improves the accuracy of laundry weight sensing by increasing the counter electromotive force difference, resulting in better water management and energy efficiency in washing machines.
Implementation Method 1
a voltage is measured according to a drive capacitor of a motor... there is a corresponding voltage and a time duration between rising edges of a first pulse and a third pulse of the voltage is measured... sensing of the laundry weight using the counter electromotive force
Data Source
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AI summary
A laundry weight sensing method. A motor is consecutively turned on and off plural times, the number of pulses output from a counter electromotive force detector according to counter electromotive force of the motor when the motor is finally turned off is counted, and a laundry weight is sensed using the counted number of pulses.