Washing Machine Motor Braking With Zero-Current Noise Control
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Solution Overview
Problem
Conventional washing machines experience noise issues during motor braking due to high current flow, especially with belt-type brushless direct current (BLDC) motors, and may incorrectly detect tub vibrations leading to movement or frame contact due to improperly fixed vibration sensors.
Innovation Solution
A washing machine with a controller that checks the fixation state of a vibration sensor using measurement data and performs zero-current control during motor braking, reducing noise and preventing incorrect vibration detection by setting the command current value to 0 A, thereby minimizing noise and ensuring proper sensor fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a short brake method is used to brake the motor during spin-drying, then the motor can be stopped quickly, but a large amount of current flows causing noise
Solution Approach 1:
The patent changes the current parameter during braking from high current (short brake method) to zero current (zero-current control method). By setting the command current value to 0A during braking, the motor stops without generating the large current that causes noise, thus resolving the contradiction between quick stopping and noise reduction
Solution Approach 2:
The patent implements periodic braking control by alternating between acceleration and braking phases during the spin-drying cycle. The controller performs weight detection by instantaneous acceleration, then brakes when vibration exceeds thresholds, creating a periodic pattern of acceleration-braking cycles that reduces overall noise while maintaining functionality
2Measurement precision
If the vibration sensor is fixedly attached to the tub, then vibration can be detected, but the sensor may not be properly detected during spin-drying causing incorrect vibration detection
Solution Approach 1:
The patent performs preliminary weight detection by instantaneous acceleration at the beginning of spin-drying before normal operation. This preliminary action serves dual purposes: detecting laundry weight and verifying sensor fixation. By checking sensor response during this preliminary phase, the system ensures reliable vibration detection throughout the spin-drying cycle
Solution Approach 2:
The patent uses feedback from the vibration sensor during instantaneous acceleration to determine both laundry weight and sensor fixation status. The controller compares vibration measurement data against reference data to verify proper sensor attachment, creating a feedback mechanism that ensures measurement reliability before proceeding with normal spin-drying operations
Data Source
AI summary
A washing machine and a control method thereof, capable of reducing noise by performing a zero-current control during the braking of a motor, and checking whether a vibration sensor is installed on a tub in a weight detection state in the beginning of a spin-drying. The zero-current control is performed by driving a current regulator with a command current set to “0 A”, so that the current flowing at the motor decreases and thus noise is reduced. In a washing machine having a vibration sensor fixedly attached to a tub, a fixation state of the vibration sensor with respect to the tub is checked in advance by use of measurement data of the vibration sensor at a weight detection stage in the beginning of the spin drying so that the frame touch caused by an erroneous detection of vibration or a failure of vibration detection may be prevented.