Capacitive Humidity Sensing for Reliable Drying Cycle Information
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Solution Overview
Problem
Existing drying cycle information systems in appliances like tumble dryers are unreliable due to unpredictable factors and sensor biases, leading to inaccurate load humidity detection and cycle duration estimation.
Innovation Solution
An appliance equipped with a capacitive sensing arrangement and control unit that estimates load mass, residual humidity, and cycle end using electric signals from conductive pads, applying linear regression models to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If temperature sensors are used to provide temperature signals for drying information, then temperature measurement is achieved, but the response time is slow due to thermal inertia and the measurements are sensitive to drying air flow dynamics
Solution Approach 1:
The patent replaces temperature-based sensing (thermal system) with capacitive sensing (electrical system). The capacitive sensor measures humidity directly through electrical capacitance changes, eliminating the thermal inertia problem and providing immediate response without being sensitive to air flow dynamics.
Solution Approach 2:
The patent changes the measurement parameter from temperature to electrical capacitance. By measuring the capacitive effect of humidity on conductive pads rather than temperature, the system achieves fast response time and eliminates the drawbacks of thermal sensing.
2Measurement precision
If motor torque signals are used for drying information, then indirect humidity detection is achieved, but the signals show strong appliance-to-appliance variations due to flexible belts and drum sealing variations
Solution Approach 1:
The patent replaces mechanical sensing (motor torque measurement) with electrical sensing (capacitive measurement). The capacitive sensor directly measures humidity effects on electrical capacitance, eliminating mechanical variations from belts and drum sealing that cause signal inconsistency.
Solution Approach 2:
The patent introduces conductive pads as an intermediary sensing element that directly contacts or nears the laundry load. These pads serve as a stable reference that measures humidity through capacitance changes, eliminating the need to infer humidity from motor torque variations.
3Ease of operation
If drying cycle assumptions based on case of policies are used to provide drying information, then cycle management is simplified, but the drying information becomes unreliable as it does not account for actual appliance and load conditions
Solution Approach 1:
The patent implements feedback by continuously measuring actual humidity conditions through capacitive sensors and using this information to adjust and determine drying cycle status. The control unit receives real-time capacitive signals and makes decisions based on actual load conditions rather than pre-programmed assumptions.
Solution Approach 2:
The capacitive sensing arrangement enables the system to self-monitor its actual operating conditions. The sensor automatically detects humidity levels and provides direct feedback to the control unit, allowing the appliance to adapt to actual load conditions without external intervention or complex assumptions.
4Productivity
If measurements are carried out upon occurrence of predetermined drying cycle conditions or events, then cycle control is structured, but the drying information fails to provide reliable data as the conditions have low and inconstant correlation with actual drying information
Solution Approach 1:
The patent implements continuous humidity monitoring through the capacitive sensing arrangement that operates throughout the drying cycle. Instead of discrete measurements at predetermined events, the sensor continuously tracks humidity changes, providing reliable data at all times and enabling precise determination of drying cycle status.
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
Provides reliable drying information by accurately estimating load humidity and cycle duration, enhancing user experience and efficiency.
Implementation Method 1
a capacitive sensing arrangement arranged for generating an electric signal indicative of a degree of humidity of a load contained in the drying chamber
Data Source
AI summary
An appliance having a drying chamber for performing a drying cycle, a capacitive sensing arrangement within the drying chamber and configured to generate an electric signal indicative of a degree of humidity of a load contained in the drying chamber, and a control unit arranged for carrying out at least one among: estimating a mass of the load; estimating a residual humidity of the load; estimating a residual time to the end of the drying cycle, and detecting an end of the drying cycle according to the electric signal.