Capacitance Input Device Reference Value Stabilization
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Solution Overview
Problem
Conventional capacitance-type input devices malfunction due to temperature changes and fail to return to normal operation after erroneous detection caused by foreign substances.
Innovation Solution
An input device with a control unit that performs weighted averaging of capacitance measurement signals and reference values, adjusting weights based on difference values compared to touch and abnormal correction thresholds, allowing for continuous correction and quick reset of reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capacitance-type input device uses a fixed reference value for touch detection, then the device can operate with simple detection logic, but the device malfunctions when temperature changes cause capacitance fluctuations
Solution Approach 1:
The patent applies the dynamics principle by making the reference value dynamic instead of fixed. The reference value is continuously updated based on recent measurement data, allowing the system to adapt to temperature changes and capacitance fluctuations. This dynamic adjustment maintains detection accuracy without requiring complex detection logic, as the system automatically compensates for environmental variations.
Solution Approach 2:
The patent implements feedback by using detected capacitance values to continuously update the reference value. The system monitors measurement data, calculates appropriate reference values based on statistical characteristics (such as median or average of recent measurements), and applies these updated references back to the detection process. This closed-loop feedback mechanism ensures reliable detection under varying temperature conditions while keeping the overall system relatively simple.
2Reliability
If the reference value is continuously updated to adapt to temperature changes, then detection accuracy is maintained, but the device cannot return to normal operation after erroneous detection caused by foreign substances
Solution Approach 1:
The patent applies periodic action by implementing a time-based update mechanism for the reference value. Instead of continuously updating the reference value without restriction, the system updates it periodically or at specific intervals. This periodic approach allows the system to adapt to temperature changes over time while preventing foreign substances from permanently corrupting the reference value. The system can reset or discard corrupted reference values after predetermined time periods, enabling recovery from erroneous states.
Solution Approach 2:
The patent implements preliminary action by establishing validation criteria before updating the reference value. The system checks whether measured capacitance values fall within expected ranges before incorporating them into the reference value calculation. This preliminary validation prevents foreign substances from corrupting the reference value in the first place. Additionally, the system prepares recovery mechanisms in advance, such as maintaining historical reference values or implementing reset functions, that can be activated when erroneous detection is detected.
3Speed
If the reference value updates quickly to track capacitance changes, then the device responds rapidly to temperature variations, but the device may incorrectly interpret normal capacitance variations as touch operations
Solution Approach 1:
The patent applies dynamics by implementing an adaptive update rate for the reference value. The system dynamically adjusts how quickly the reference value changes based on the observed capacitance variation patterns. During rapid temperature changes, the reference value updates more frequently to track the changes. During normal operation with stable capacitance, the update rate slows down to prevent normal variations from being misinterpreted as touch operations. This dynamic adjustment of update speed resolves the contradiction between rapid response and false detection.
Solution Approach 2:
The patent implements parameter changes by modifying the update threshold and time constants based on operational conditions. The system changes parameters such as the weighting factor in reference value calculation, the time window for statistical analysis, and the threshold for triggering reference updates. These parameter adjustments allow the system to respond quickly to genuine temperature changes while filtering out normal capacitance variations that could be mistaken for touch operations. The parameters are tuned to distinguish between environmental variations and actual user interactions.
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
The device effectively stabilizes reference values during touch operations and quickly returns to normal operation by adjusting weight magnitudes, enabling accurate detection and preventing prolonged erroneous signals.
Implementation Method 1
a capacitance measurement unit that measures capacitance for each of the plurality of capacitance detection units
Data Source
AI summary
Provided is an input device including a coordinate input unit having plural capacitance detection units, a capacitance measurement unit that measures capacitance for each of the plural capacitance detection units, and performs an AD conversion on the measured capacitance to output the converted capacitance as a measurement signal, and a control unit that controls the capacitance measurement unit, calculates a data signal by arithmetically operating the measurement signal, stores the data signal in association with coordinate information of the capacitance detection unit, and outputs a control signal. The control unit calculates a difference value between a predetermined reference value and the data signal at a constant time interval, performs a weighted average process on the data signal and the predetermined reference value to update and store a value on which the process is performed as a new reference value, and changes a weight given to the weighted average process.