Washing Machine Dosing Control for Sensor-Delay Concentration
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Solution Overview
Problem
Institutional washing machines, particularly dishwashing machines, face challenges in accurately controlling product concentration due to large distances between the dispenser and concentration sensors, leading to significant over- or undershooting, which is economically and ecologically undesirable, and can cause glass corrosion from alkaline detergents.
Innovation Solution
A method that calculates the minimum opening time of the dispenser's solenoid valve and adjusts the dispensing time based on a moving average of previous dispensing events, ensuring precise concentration control without mechanical modifications, by measuring current concentration and feed rate, and preventing overdosing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a simple control function is used that initiates dispensing when concentration drops below setpoint and stops when setpoint is reached, then the control system is simple and easy to operate, but the final concentration becomes 50% or more above the setpoint causing economic waste, ecological harm, and glass corrosion
Solution Approach 1:
The controller calculates the required dosing time based on the difference between setpoint and current concentration, the feed rate, and the minimum opening time before initiating dispensing. This preliminary calculation prevents overshooting the setpoint concentration by accounting for all system parameters in advance
Solution Approach 2:
The system continuously measures the current concentration in the wash tank and uses this feedback to adjust the dosing time. The controller calculates the concentration difference and modifies the dispensing duration accordingly, creating a closed-loop control system that maintains precise concentration control
2Adaptability or versatility
If the distance between the product reservoir outlet and the sensor is large, then the dispenser can be positioned flexibly in the machine structure, but the concentration control precision deteriorates due to delayed detection and larger overshooting
Solution Approach 1:
The controller acts as an intermediary that compensates for the time delay caused by the large distance between dispenser and sensor. By calculating the minimum opening time and using this as a basis for dosing time calculation, the system compensates for the lag in concentration detection and maintains precise control despite the physical distance
Solution Approach 2:
The system performs preliminary calculation of the dosing time that accounts for the transport time of the product from the reservoir through the feed line to the wash tank. This advance calculation ensures that the dispensing is stopped at the correct moment despite the delayed sensor detection
3Manufacturing precision
If the reversibly closable output device is opened for a very short time to minimize overshooting, then the concentration control precision is improved, but the minimum opening time of the valve cannot be satisfied leading to improper product release
Solution Approach 1:
The controller calculates the minimum opening time required for proper product release and uses this as a foundational parameter for determining the total dosing time. This ensures that the valve is opened long enough to release product properly while still maintaining precise concentration control through accurate dosing time calculation
Solution Approach 2:
The system opens the valve for the minimum required time to ensure proper product release, and if additional dosing is needed, it performs multiple dosing cycles rather than extending the valve opening time excessively. This approach maintains both reliable product release and precise concentration control
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 optimizes product concentration in washing machines, reducing over- and undershooting, ensuring effective cleaning performance while minimizing economic and ecological impacts, and preventing glass corrosion.
Implementation Method 1
a reversibly closable output device, usually a valve... The dispenser is equipped with an reversibly closable output device having a minimum opening time tmin the dispenser has to be opened in order to ensure proper release of the product
Implementation Method 2
a sensor is located for example in the wash tank of such a washing machine measuring a parameter corresponding to the concentration of the product in the washing liquor present in said wash tank
Data Source
AI summary
The present invention relates to a method of controlling a dispenser for dosing a product in a washing machine leading to an optimized dosing result, a dispenser controller programmed with an algorithm to execute the method of the present invention as well as the use of said dispenser for controlling dosing of a product in a washing machine.