Washing Machine Motor Current Sensing for Laundry Load Detection
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Solution Overview
Problem
Conventional washing machines face challenges in precisely determining the amount of laundry, especially with sensorless motors, leading to inefficiencies in spin-drying operations, increased washing time, and energy consumption.
Innovation Solution
A washing machine equipped with a motor, a motor-driving unit, a current-sensing unit, and a controller that repeatedly accelerates and decelerates the motor's rotational speed within a predetermined range to analyze current values during maintenance, acceleration, and deceleration periods, allowing for precise calculation of laundry amount and unbalance sensing to adjust speed accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the amount of laundry is determined at the time of starting the motor, then the measurement process is simple, but it is difficult to determine a small amount of laundry and the measured value varies due to initial position and motor movement
Solution Approach 1:
The patent applies preliminary action by rotating the drum at a predetermined speed before measuring the current value to ensure laundry is properly distributed. This preliminary rotation eliminates the effects of initial laundry position and settling, providing a consistent baseline for accurate measurement of even small amounts of laundry.
Solution Approach 2:
The patent uses periodic action by repeatedly rotating the drum at a predetermined speed multiple times and measuring current values at each rotation. The final laundry amount is determined by averaging these multiple measurements, which reduces variation and improves measurement precision.
2Productivity
If the motor is rotated at high speed for spin drying, then spin drying efficiency is improved, but laundry tangling causes unbalance and potential damage to the washing machine
Solution Approach 1:
The patent applies feedback by continuously monitoring current values during drum rotation and calculating unbalance levels. When unbalance exceeds a predetermined threshold, the system automatically adjusts the rotational speed or terminates spin drying, preventing damage while maintaining efficient operation when conditions are favorable.
Solution Approach 2:
The patent uses dynamics by making the rotational speed adjustable based on real-time laundry distribution conditions. The system dynamically changes the spin drying speed according to the measured unbalance level, optimizing both efficiency and safety rather than operating at a fixed high speed.
3Productivity
If the rotational speed is adjusted based on laundry amount, then spin drying performance is optimized, but determining the laundry amount accurately is difficult with sensorless motors
Solution Approach 1:
The patent replaces mechanical sensors with an electrical measurement approach. By measuring the current value consumed by the motor during drum rotation and correlating it with laundry amount through calibration, the system achieves accurate measurement without requiring additional mechanical sensing components.
Solution Approach 2:
The patent applies self-service by using the motor's own current consumption characteristics to determine laundry amount. The motor's electrical properties serve as the measurement mechanism, eliminating the need for separate sensing systems and reducing overall device complexity.
4Measurement precision
If multiple measurements are taken to reduce variation, then measurement accuracy improves, but the time required for determination increases
Solution Approach 1:
The patent applies partial action by performing a fixed number of predetermined rotations for measurement rather than continuing until absolute precision is achieved. This predetermined limited action balances measurement accuracy with time efficiency, avoiding excessive measurement 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 method enables rapid and accurate determination of laundry quantity, reducing spin-drying time and energy consumption while preventing motor unbalance and damage.
Implementation Method 1
a current-sensing unit for measuring current of the motor during operation of the motor
Implementation Method 2
In the spin-drying operation, a motor is rotated at a high speed. As a result, centrifugal force is applied to the laundry in the drum, whereby water is removed from the laundry.
Implementation Method 3
a motor-driving unit for supplying operating power to the motor to operate or stop the motor and to control a rotational speed of the motor
Data Source
Figure 1
Figure 2
Figure 3~4(d)
AI summary
A washing machine and a method of controlling the same are disclosed. The amount of laundry that is introduced into the washing machine is measured using gravity and inertia applied during the operation of the motor (270), whereby it is possible to precisely calculate the amount of laundry and to minimize the effects of the initial position of the laundry and the movement of the laundry. In addition, the current value of the motor that is operated is used to measure the amount of laundry without a sensor. Furthermore, the amount of laundry is measured at the rotational speed of the motor at which the laundry clings to the drum (134), whereby it is possible to minimize error due to the movement of the laundry to thus improve accuracy. Moreover, it is possible to determine the amount of laundry within a short time. Consequently, it is easy to commence the spin-drying operation, thereby reducing washing time and saving energy.