A method of controlling a rotatable-drum laundry dryer and a rotatable-drum laundry dryer implementing the method
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Solution Overview
Problem
Rotatable-drum laundry dryers inaccurately determine dryness when the number of contacts between laundry and electrode sensor is low, leading to incomplete drying or premature cessation of the drying cycle, especially with small loads or irregularly positioned laundry, resulting in inefficient energy use.
Innovation Solution
Implement a method where the electronic control unit detects the presence of moist laundry, starts a drying cycle, measures the cycle time to reach a preset dryness threshold, and if the cycle time is short, continues the drying for a set additional time to ensure adequate drying, and stops the cycle at a predetermined minimum dryness time, while also performing additional detection phases to verify the absence of laundry if not detected initially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electrode sensor is arranged outside the drum to contact laundry during rotation, then dryness detection is enabled, but the frequency of contact between laundry and electrode sensor is reduced when laundry quantity is small or irregularly positioned
Solution Approach 1:
The control unit performs multiple preliminary detection phases before making a final dryness determination. When the laundry load is small or irregularly positioned, the system conducts additional detection cycles to accumulate sufficient contact data, ensuring reliable dryness measurement even with low initial contact frequency.
Solution Approach 2:
The system continuously monitors the contact frequency between laundry and electrode sensor. When contact frequency falls below a threshold (indicating small or irregularly positioned laundry), the control unit adjusts the detection strategy by performing additional detection phases and using feedback from multiple measurements to compensate for the low contact rate.
2Use of energy by moving object
If the drying cycle is stopped when the measured electric parameter reaches a preset value, then energy consumption is reduced, but incomplete dryness condition may occur due to erroneous determination from few contacts
Solution Approach 1:
The control unit uses feedback from multiple voltage signal measurements to determine whether the preset number of effective contacts has been achieved. Only when sufficient contact evidence is accumulated does the system stop the drying cycle, preventing premature termination while still conserving energy by stopping when dryness is truly achieved.
Solution Approach 2:
Before stopping the drying cycle, the system performs preliminary verification by conducting additional detection phases to confirm that the measured electric parameter consistently indicates dryness. This preliminary action ensures accurate dryness determination before energy-saving cycle termination.
3Measurement precision
If additional detection phases are performed to verify laundry presence, then detection accuracy is improved, but the complexity of the control system increases
Solution Approach 1:
The control system dynamically adjusts the number of detection phases based on the detected laundry load characteristics. For small or irregularly positioned laundry where contact frequency is low, additional detection phases are automatically performed. For normal loads, the standard detection procedure is used, keeping the system simple in typical operating conditions.
4Manufacturing precision
If the drying cycle continues for a fixed additional time when cycle time is short, then uniform dryness is ensured, but energy wastage increases for already dry laundry
Solution Approach 1:
The control unit continuously monitors the electric parameter during the additional drying time. If the parameter indicates that dryness has already been achieved, the system stops the drying cycle early, preventing energy wastage. The additional time is only fully utilized when needed to achieve uniform dryness across the laundry load.
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 approach ensures uniform dryness even with low contact frequencies and reduces energy wastage by preventing premature cycle termination and extending drying time as needed for small loads or irregularly positioned laundry.
Implementation Method 1
an electric parameter associated with the laundry moisture is measured by means of an electrode sensor arranged in order to contact with the laundry when drum rotates
Implementation Method 2
the electronic control unit receives a plurality of voltage signals having an amplitude and/or a frequency associated with the electric parameter of the laundry, i.e. impedance or resistance
Data Source
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AI summary
A method of controlling a drying operation of a rotatable-drum laundry dryer (1) comprising a rotatable drum (3) for loading laundry (5) and at least an electrode sensor (22) for sensing dryness of the laundry (5). The method comprises the steps of: detecting the presence/absence of moist laundry (5) inside the rotatable drum (3) by the electrode sensor (22); if presence of moist laundry inside the rotatable drum (3) is detected, starting a drying cycle; sensing dryness of the laundry (5) during the drying cycle; measuring a cycle time (TD) at which the sensed dryness reaches a preset dryness threshold; if the cycle time (TD) is lower than a preset dryness threshold time (Sm), continuing the drying cycle for a first additional time (D1), and stopping the drying cycle at the end of the first additional time (D1).