Drum Dryer Moisture Control With Time-Variable Impedance Thresholds
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Solution Overview
Problem
Existing rotatable-drum laundry dryers fail to achieve precise and stable final moisture levels regardless of laundry quantity/weight, particularly with cotton and synthetic fabrics, due to the use of time-constant impedance measurement thresholds.
Innovation Solution
A control method that memorizes a variable comparison threshold in time according to a predetermined profile, measuring electric quantities like resistance or impedance to determine the end of the drying cycle, and adjusts the cooling stage duration based on calculated laundry quantity/weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a time-constant impedance comparison threshold is used to control the drying cycle, then the control method is simple and low-cost, but the final moisture varies significantly with laundry quantity/weight
Solution Approach 1:
The patent applies the dynamics principle by transforming the static, time-constant comparison threshold into a dynamic, time-variable comparison threshold. The threshold now changes over time according to a predetermined profile, allowing the control system to adapt to different drying stages and laundry quantities without requiring complex weight sensors or multiple sensors. This dynamic adjustment enables consistent final moisture across varying load sizes while maintaining system simplicity.
Solution Approach 2:
The patent implements parameter changes by modifying the comparison threshold parameter from a constant value to a time-variable value. The threshold is stored in memory as a function of time and is updated during the drying cycle based on the predetermined profile. This parameter transformation allows the system to compensate for the effects of different laundry quantities on moisture evaporation rates, achieving consistent drying results without adding hardware complexity.
2Manufacturing precision
If weight sensors are added to measure laundry quantity and adjust the comparison threshold, then precise final moisture can be achieved, but the system becomes expensive and complicated
Solution Approach 1:
The patent applies the taking out principle by removing the weight sensors and related complex measurement systems from the design. Instead of measuring laundry quantity directly through sensors, the invention extracts the essential control function by using a time-variable comparison threshold that indirectly compensates for quantity variations. This extraction eliminates the need for expensive and complex hardware while maintaining drying precision.
Solution Approach 2:
The patent uses copying by creating a predetermined profile in memory that represents the relationship between time, laundry quantity, and optimal comparison threshold values. Rather than physically measuring each parameter in real-time with sensors, the system copies the expected behavior patterns into a lookup table or functional relationship stored in memory, allowing the microprocessor to retrieve and apply the appropriate threshold based on elapsed time without additional sensing hardware.
3Measurement precision
If the comparison threshold is adjusted based on laundry quantity, then precise moisture control is achieved, but additional sensors and control complexity are required
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the optimal comparison threshold values for different time points and laundry quantities in memory before the drying cycle begins. The predetermined profile contains all the necessary adjustment data that would otherwise require complex real-time calculations and sensor inputs. During operation, the system simply retrieves the appropriate threshold value based on elapsed time, achieving precise moisture control through pre-prepared control parameters rather than complex real-time adaptation.
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 a precise and stable final moisture level, independent of laundry quantity/weight, without the need for weight sensors, reducing complexity and cost while maintaining consistent drying performance across different loads.
Implementation Method 1
measuring an electric quantity indicating the moisture in the laundry at the drying time
Data Source
AI summary
A method for controlling a rotatable-drum laundry drier to dry laundry in a drum is provided. The control method includes the steps of memorizing, in a memory device of the laundry drier, a comparison threshold variable in time according to a predetermined profile, and, at predetermined drying times in the laundry drying cycle, measuring an electric quantity indicating the moisture in the laundry at the drying time; comparing, at each drying time, the measured electric quantity with the memorized comparison threshold corresponding to the drying time; and determining the end of drying cycle time on the basis of this comparison.