Dryer Drum Moisture Control Using Torque and Air Temperature
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Solution Overview
Problem
Existing control methods for rotatable drum washer-dryers lack accuracy in determining laundry moisture, particularly during specific drying cycles like the 'iron drying cycle', where high moisture precision is required for subsequent ironing, due to architectural limitations that prevent the arrangement of measuring sensors inside the drum.
Innovation Solution
An electronic control system that uses temperature and torque signals to determine the end of a drying cycle by comparing the temperature difference between the airflow output and inside the drum with a threshold value, ensuring accurate moisture control through a linear function based on motor torque and temperature data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If temperature-based control methods are used in rotatable drum washer-dryers, then the control system can be implemented without internal drum sensors, but the moisture determination accuracy deteriorates for specific drying cycles like iron drying
Solution Approach 1:
The patent combines multiple existing sensors (temperature sensors in airflow circuit, torque sensor from motor) to create a composite moisture determination system. By merging data from these different sensor sources with a linear function algorithm, the system achieves high measurement precision without requiring internal drum sensors, thus resolving the contradiction between ease of implementation and moisture determination accuracy.
Solution Approach 2:
The patent introduces a linear function algorithm as an intermediary that processes temperature difference and torque data to indirectly determine laundry moisture. This intermediary computation layer enables accurate moisture measurement without direct contact sensors in the drum, maintaining ease of implementation while achieving high precision through mathematical mediation of sensor data.
2Measurement precision
If multiple sensor measurements and complex algorithms are used to improve moisture determination accuracy, then moisture precision improves, but the device complexity increases
Solution Approach 1:
The patent utilizes sensors and data that already exist in the washer-dryer system (temperature sensors for airflow control, motor torque for drum operation) and repurposes them for moisture determination. This self-service approach allows the system to achieve high measurement precision without adding external complex sensing equipment, thereby improving moisture accuracy while minimizing increases in device complexity.
Solution Approach 2:
The patent changes the parameters being measured from direct moisture content to indirect parameters (temperature difference and torque) that can be obtained from existing sensors. By transforming the measurement approach to use available system parameters with a linear function algorithm, the system achieves high precision moisture determination without the complexity of direct moisture sensors or complex multi-sensor arrays.
3Ease of operation
If the drying cycle is stopped based on threshold temperature comparison, then the control method is simple to implement, but the final moisture precision deteriorates for cycles requiring high accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the linear function algorithm continuously processes temperature difference and torque data to dynamically determine when the laundry has reached the desired moisture level. This feedback-based approach maintains the simplicity of threshold-based control while achieving high final moisture precision by using multiple feedback parameters (temperature and torque) rather than a single temperature threshold.
Solution Approach 2:
The patent uses a linear function that combines temperature difference and torque measurements, where the contribution of each parameter can be adjusted through the linear function coefficients. This partial action approach allows the system to achieve high moisture precision by selectively weighting the importance of different measurement parameters, maintaining control simplicity while improving accuracy through multi-parameter consideration.
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 accurate determination of laundry moisture at the end of a drying cycle, improving precision and reliability across various drying cycles and load quantities, ensuring the laundry is sufficiently humid for ironing.
Implementation Method 1
a signal which is indicative of the torque value TE that the electric motor 9 provides to the drum 3
Implementation Method 2
the temperature difference ΔT between a drying airflow output-temperature TOUT sensed by means of a second temperature sensor 28 arranged on the output air-duct 25 and a sensed inside-temperature TW of the drying airflow inside the rotatable drum 3
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Laundry drying machine (1) comprising a rotatable laundry drum (3), an electric motor (9) for rotating said rotatable laundry drum (3) about its axis of rotation (6), hot air generator means (11) configured to supply a drying airflow to the drum (3) during a drying cycle, an electronic control system (16) configured to: provide a signal (S) indicative of torque (TE) that said electric motor (9) provides to the rotatable laundry drum (3), sense the inside-temperature (TW) of the drying airflow inside the drum (3), sense the output-temperature (TOUT) of the airflow which flows out from the rotatable drum 3, determine a comparison threshold (THC) based on the sensed signal (S), determine a temperature-difference (ΔT) between the sensed output-temperature (TOUT) and the sensed inside-temperature (TW), compare the determined temperature-difference (ΔT) with the determined comparison threshold (THC) and stop the drying cycle according to the result of the comparison.