Touch Panel Force Sensing With Fixed Reference Voltage
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Solution Overview
Problem
Existing touch type operation input devices face instability in detecting pressing force due to external noise disturbances affecting the reference voltage, leading to inaccurate output voltages when detecting finger presses on the touch panel.
Innovation Solution
A touch type operation input device with a piezoelectric sensor and a pressing force detection unit that fixes the reference voltage when a pressing force is applied, allowing for accurate detection by calculating the difference between the output voltage and the fixed reference voltage, and includes a polylactic acid piezoelectric film for increased sensitivity and reduced pyroelectricity effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference voltage is applied to the piezoelectric element and an amplification circuit is used to amplify the output voltage, then the pressing force detection sensitivity is improved, but the reference voltage becomes unstable due to external noise disturbances
Solution Approach 1:
The system performs preliminary detection using the touch sensor to determine whether a finger is actually pressing the touch panel before enabling pressing force detection. This preliminary action prevents the amplification circuit from being activated during non-pressing states, thereby avoiding noise interference while maintaining detection sensitivity when needed.
Solution Approach 2:
The system uses feedback from the touch sensor to control the operation of the pressing force detection circuit. When the touch sensor detects no pressing operation, the system disables the pressing force detection, creating a feedback mechanism that adapts the detection system to actual usage conditions and eliminates unnecessary noise susceptibility.
2Measurement precision
If the amplification circuit continuously amplifies the output voltage for pressing force detection, then the detection sensitivity is improved, but power consumption increases and noise interference worsens
Solution Approach 1:
The system implements periodic action by enabling the amplification circuit only during periods when pressing force detection is actually needed (when touch sensor detects a press). The circuit remains inactive during non-pressing periods, creating a periodic operation pattern that reduces power consumption while maintaining detection sensitivity when required.
Solution Approach 2:
The touch sensor serves a dual function: it detects both the presence of a pressing operation and controls the activation of the pressing force detection circuit. This self-service mechanism allows the system to automatically manage its own power consumption and detection sensitivity requirements without external control.
3Adaptability or versatility
If the amplification circuit is activated to detect small pressing forces, then the detection range is expanded, but the system becomes more susceptible to noise and external disturbances
Solution Approach 1:
The system performs preliminary verification using the touch sensor to confirm that a pressing operation is actually occurring before activating the high-sensitivity amplification circuit. This preliminary action ensures that the expanded detection range is only utilized when genuinely needed, preventing noise from being misinterpreted as valid pressing force signals.
Solution Approach 2:
The touch sensor acts as an intermediary between the user's finger and the pressing force detection system. It provides a preliminary indication of pressing intent, allowing the system to selectively activate the sensitive amplification circuit only when the intermediary confirms a valid pressing operation, thereby filtering out noise before it can affect detection.
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 corrects pressing force detection errors and enhances sensitivity, providing accurate and stable detection of pressing forces regardless of touch position, while reducing power consumption and eliminating the need for complex heat correction mechanisms.
Implementation Method 1
a piezoelectric sensor configured to generate an output voltage in accordance with pressing force
Implementation Method 2
includes a polylactic acid piezoelectric film for increased sensitivity and reduced pyroelectricity effects
Data Source
AI summary
A touch type operation input device capable of accurately detecting pressing force with which an operator presses is provided. The touch type operation input device includes a touch panel including a piezoelectric sensor and a touch sensor, and a pressing force detection unit. Until the pressing force detection unit detects a position detection signal given by the touch sensor, the pressing force detection unit causes a reference voltage of the pressing force detection to follow an output voltage of the piezoelectric sensor to be the same as the output voltage of the piezoelectric sensor. When the pressing force detection unit obtains the position detection signal given by the touch sensor, the pressing force detection unit fixes the reference voltage. The pressing force detection unit calculates a pressing force detection voltage from the difference between the output voltage and the fixed reference voltage, and detects the pressing force.