Washing Machine Detergent Dosing Control for Sensor Delay
Find Innovative SolutionsGenerate Solutions
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, and the decrease in product block size over time, leading to significant over- or undershooting of detergent concentration, which is economically and ecologically undesirable.
Innovation Solution
A method that accounts for the minimum opening time of the dispenser's solenoid valve and calculates the current feed rate based on a moving average of previous dispensing events, adjusting the dispensing time to maintain optimal concentration within user-defined limits, avoiding excessive overdosing or undershooting by considering the distance and solubility of the product.
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 severe overdosing
Solution Approach 1:
The controller calculates the required dosing time based on the concentration difference between setpoint and measured value, and the current feed rate, before actually initiating dispensing. This preliminary calculation allows the system to stop dispensing exactly when the setpoint is reached, preventing the 50% or more overdosing that occurs with simple on/off control.
Solution Approach 2:
The system dynamically adjusts the dosing time based on real-time measurements of concentration and feed rate. Instead of using a fixed dosing duration, the controller continuously adapts the dispensing parameters to match the current system state, enabling precise concentration control while maintaining operational simplicity.
2Ease of manufacture
If the distance between the outlet of the product reservoir (dosing point) and the sensor is large, then the dispenser can be positioned conveniently in the machine structure, but significant over- or undershooting of product concentration occurs
Solution Approach 1:
The controller performs preliminary calculations of the required dosing time based on the known distance between dosing point and sensor, the current feed rate, and the concentration difference. This allows the system to compensate for the time delay inherent in large distances, ensuring the setpoint is reached precisely despite the physical separation between dosing and measurement points.
Solution Approach 2:
The controller acts as an intermediary that processes information from the sensor and translates it into appropriate dosing commands, accounting for the time delay caused by the distance between dosing point and sensor. This intermediary calculation layer enables accurate concentration control despite the physical separation in the machine structure.
3Duration of action of stationary object
If the product block size decreases over time, then the detergent is gradually consumed as intended, but the feed rate changes leading to inaccurate dosing
Solution Approach 1:
The system continuously measures the actual feed rate by monitoring the concentration change over time and uses this feedback to adjust subsequent dosing operations. This feedback mechanism compensates for variations in feed rate caused by the decreasing product block size, maintaining accurate dosing throughout the entire product lifetime.
Solution Approach 2:
The controller dynamically adapts the dosing parameters based on the current feed rate, which changes as the product block size decreases. By continuously updating the dosing calculation to reflect the current system state, the system maintains precise concentration control throughout the entire consumption period of the detergent block.
4Device complexity
If dispensing continues until the sensor measures reaching of the setpoint, then the control logic is simple, but the final concentration typically exceeds the setpoint by 50% or more causing economic and ecological waste
Solution Approach 1:
The controller calculates the precise dosing time required to reach the setpoint concentration before initiating dispensing, based on the measured concentration difference and current feed rate. This preliminary calculation enables the system to stop dispensing exactly when the setpoint is reached, eliminating the 50% or more overdosing waste associated with simple continue-until-reached control logic.
Solution Approach 2:
Instead of continuing dispensing until the sensor measures the setpoint (which causes excessive action and overdosing), the system uses a calculated partial dosing duration that stops exactly when the setpoint is reached. This partial action approach prevents the harmful excessive dispensing while maintaining simple control logic.
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 ensures precise control of product concentration in washing machines, optimizing cleaning performance and reducing economic and ecological impacts by minimizing over- or undershooting, without requiring mechanical modifications to the machines.
Implementation Method 1
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
Figure 1
Figure 2
Figure 3
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 to the use of said dispenser for controlling dosing of a product in a washing machine.