Washing Machine Laundry Weighing With Temperature and Unbalance Correction
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Solution Overview
Problem
Existing automatic weighing methods for laundry in washing machines are inaccurate due to the lack of correction factors for engine temperature and inertia, leading to inefficiencies in water, energy, and detergent consumption, especially in industrial settings with varying temperatures and unbalanced loads.
Innovation Solution
An automatic weighing method that determines the engine temperature using a frequency modulator, measures current during different angular speeds, and calculates the weight of laundry by accounting for unbalance and temperature effects, without requiring additional sensors, using a formula that incorporates the sum of current during acceleration and temperature to determine the weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing weighing methods based on drum acceleration are used, then the system structure remains simple, but measurement precision deteriorates due to lack of temperature and inertia correction
Solution Approach 1:
The system uses existing sensors (current sensor, rotation sensor) to automatically determine temperature and unbalance factors without adding dedicated temperature sensors or complex measurement devices. The control unit self-calibrates by measuring current during idle periods to calculate resistance and temperature, and by measuring current at specific rotation speeds to determine unbalance, thereby improving accuracy while maintaining simple structure.
Solution Approach 2:
The system changes the operating parameters of the drum (rotation speed, acceleration phases) to extract multiple pieces of information from the same sensor data. By measuring current during different phases (idle, acceleration, constant speed), the system derives temperature, unbalance, and weight information from the same electrical measurements, avoiding additional sensors while improving measurement precision.
2Loss of substance
If no weighing system is used, then device complexity remains low, but loss of substance increases due to excessive water and detergent consumption
Solution Approach 1:
The weighing function is integrated into the existing motor control system using the same current and rotation sensors already present for motor control. The control unit processes motor current data to derive laundry weight, eliminating the need for separate weighing sensors and keeping the system simple while enabling precise water and detergent dosing based on actual laundry load.
3Measurement precision
If temperature correction is not applied, then device complexity remains low, but measurement precision deteriorates in industrial settings with varying temperatures
Solution Approach 1:
The system determines temperature by measuring the electrical resistance of the motor winding during idle periods and comparing it to reference resistance values at known temperatures. This self-diagnosis approach uses existing current measurement capabilities to infer temperature without adding temperature sensors, maintaining simple structure while improving measurement accuracy under varying temperature conditions.
Solution Approach 2:
The system replaces mechanical or thermal temperature sensing with an electrical measurement approach. By measuring the electrical resistance of the motor winding (which varies with temperature) and using this to calculate temperature correction factors, the system substitutes a simple electrical measurement for complex thermal sensing, reducing device complexity while improving temperature compensation.
4Measurement precision
If unbalance measurement is not performed, then device complexity remains low, but measurement precision deteriorates due to high energy consumption during drum acceleration
Solution Approach 1:
The system determines unbalance by measuring the motor current during constant speed rotation and comparing it to expected current values. The control unit calculates unbalance factors from the same current data already being collected for weight measurement, using the motor's electrical response to detect mechanical unbalance without adding vibration sensors or complex mechanical detection devices.
Solution Approach 2:
The system combines unbalance detection and weight measurement functions into a single measurement process. By analyzing motor current characteristics during drum rotation, the system simultaneously extracts information about both the laundry weight and the unbalance condition, eliminating the need for separate detection mechanisms while improving overall measurement precision.
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 provides accurate weighing of laundry, optimizing water and energy consumption by enabling precise dosing of water and detergent, potentially saving over 50% of water and reducing electrical energy usage, while maintaining cost-effectiveness by not increasing the system's price.
Implementation Method 1
determination of the temperature of the engine is processed by a frequency modulator based on a value of calculated resistance of a winding of the engine
Implementation Method 2
measuring of energy absorbed by engine to drive the drum of the washing machine during acceleration
Implementation Method 3
a value of current is measured on the winding of the engine during its inaction
Data Source
Figure 1
AI summary
Automatic weighing method for washing machine, where determination of temperature of an engine by frequency modulator is processed, during that measuring of amount of current passing through the winding of the engine of the washing machine during its inaction is done, and afterwards calculation of resistance of the winding of the engine of the washing machine based on amount of measured current is effected, afterwards angular speed of the drum of the washing machine is increased up to distribution angular speed (ω0), which is intended to distribute laundry in the drum of the washing machine, afterwards angular speed of the drum of the washing machine is increased up to medium angular speed (ω1), which is intended to spread the laundry on the inner surface of the drum of the washing machine, afterwards angular speed of the drum of the washing machine is decreased up to measuring angular speed (ω2), during that a value of unbalance of the drum of the washing machine is determined, afterwards angular speed of the drum of the washing machine is increased up to maximal angular speed (ω3), during that energy consumed for acceleration of the drum of the washing machine is measured, afterwards weight of the laundry in the drum of the washing machine is calculated by determined resistance of the winding of the engine, by value of unbalance of the laundry in the drum of the washing machine, and by sum of electrical energy consumed during acceleration of the drum of the washing machine up to the maximal angular speed (ω3).