Electrostatic Touch Sensing with Phase Hopping Against Noise
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Solution Overview
Problem
Existing operation detection devices face reduced detection accuracy due to noise frequencies close to the drive frequency, leading to erroneous touch detection when noise and touch signals are similar.
Innovation Solution
An operation detection device with an electrostatic sensor, drive circuit, and control unit that outputs a drive signal with a periodic waveform, changing its phase in non-detection periods to distinguish noise from operational signals through frequency hopping, thereby reducing noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive frequency is changed to avoid noise frequencies, then the detection accuracy is improved, but the detection device may erroneously determine touch operations when noise and touch signals are similar
Solution Approach 1:
The patent applies periodic action by dividing the operation cycle into alternating detection periods and non-detection periods. During non-detection periods, the drive frequency is changed to avoid noise frequencies, while during detection periods, the original drive frequency is restored for accurate touch detection. This periodic switching resolves the contradiction by temporarily avoiding noise frequencies without affecting overall detection accuracy.
Solution Approach 2:
The patent implements preliminary action by changing the drive frequency in advance during non-detection periods before actual touch detection occurs. This allows the system to proactively avoid noise frequencies that would interfere with detection, while ensuring the original frequency is restored before detection begins, thus preventing erroneous detections while maintaining measurement precision.
2Object-affected harmful factors
If the drive frequency is changed during detection period, then noise effects are reduced, but the detection accuracy decreases due to property changes in the detection circuit
Solution Approach 1:
The patent uses periodic action to switch between detection periods and non-detection periods. Frequency changes are performed exclusively during non-detection periods when the detection circuit properties are not being measured, thus reducing noise effects without compromising detection accuracy during the detection periods when the circuit operates at its original frequency.
Solution Approach 2:
The system performs frequency changes in advance during non-detection periods, before the detection period begins. This preliminary frequency adjustment allows noise effects to be minimized without affecting the detection circuit's operating characteristics during actual detection, thereby maintaining measurement precision while reducing harmful noise factors.
3Measurement precision
If the detection period is extended to improve detection accuracy, then the ability to change frequency for noise avoidance is reduced
Solution Approach 1:
The patent implements periodic action by creating a cyclic pattern of detection periods and non-detection periods. This allows the system to maintain adequate detection periods for accurate measurement while interspersing non-detection periods that provide opportunities for frequency changes to avoid noise, thus balancing detection accuracy with frequency adaptability.
Solution Approach 2:
The system applies partial action by performing frequency changes only during non-detection periods rather than continuously. This partial frequency adjustment approach maintains detection accuracy during detection periods while providing sufficient frequency adaptability during non-detection periods to avoid noise interference, resolving the contradiction between extended detection needs and frequency changing capability.
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 solution enhances detection accuracy by differentiating noise-induced changes from operational changes, ensuring accurate touch detection even when noise frequencies are close to the drive frequency.
Implementation Method 1
an electrostatic sensor; a drive circuit configured to output a drive signal to the electrostatic sensor in order to detect an operator's operation on the electrostatic sensor
Data Source
AI summary
Operation detection device having high detection accuracy based on reduced effects of noise is provided. Operation detection device includes electrostatic sensor, drive circuit to output a drive signal to electrostatic sensor to detect operator's operation on electrostatic sensor, and control unit to determine presence or absence of operation based on output value of electrostatic sensor, and to control drive waveform of drive signal. Control unit controls drive waveform according to a cycle that is a predetermined period of time including both detection period in which detection of operation is performed and non-detection period in which detection of operation is not performed. The drive waveform has a shape that is based on periodic function that repeats a constant pattern for an entirety of the cycle. The control unit changes the phase of the drive signal in the detection period by controlling a property of the drive waveform in the non-detection period.