Piezoelectric Pressing Sensor Drift Inhibition via Subtraction
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Solution Overview
Problem
Conventional pressing force detection devices suffer from drift issues in integral voltage values due to noise, leading to erroneous detection of pressing states, especially when users stop pressing the operation plate.
Innovation Solution
A pressing force detection device with a piezoelectric sensor that generates opposite polarities of output voltage based on deformation, coupled with a calculation unit that calculates a subtraction electrical parameter integral value by subtracting a predetermined value per unit time, preventing drift and accurately detecting pressing states without the need for additional thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the piezoelectric film integrates the difference between output voltage and reference voltage to detect pressing duration, then the device can detect that the user keeps pressing or stops pressing, but drift occurs in the integral value due to noise causing erroneous detection
Solution Approach 1:
The patent introduces a feedback mechanism where the control unit continuously monitors the integral value and compares it against threshold values. When the integral value exceeds a first threshold, the control unit determines pressing state; when it falls below a second threshold, the control unit determines non-pressing state. This feedback loop with threshold comparison eliminates drift-induced false detections while maintaining accurate pressing duration detection.
2Duration of action of moving object
If the device uses integral value of voltage difference to detect pressing duration, then pressing duration can be detected, but the integral value keeps increasing due to noise and does not become 0 when user stops pressing
Solution Approach 1:
The control unit implements feedback by continuously comparing the integral value against predetermined thresholds. The first threshold value establishes the condition for detecting pressing duration, while the second threshold value (lower than the first) establishes the condition for detecting when the user stops pressing. This dual-threshold feedback mechanism ensures the integral value accurately reflects pressing duration without accumulating drift, allowing precise detection of pressing start and end points.
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 effectively inhibits drift in electrical parameter integral values, ensuring accurate detection of pressing states and eliminating erroneous readings, thus improving the reliability of pressing force detection without requiring additional output voltage detection circuits or touch panels.
Implementation Method 1
a piezoelectric film, and a control unit. The piezoelectric film is attached to the operation plate. Moreover, the piezoelectric film outputs an output voltage when the operation plate is pressed by a user.
Data Source
AI summary
A pressing sensor is provided that generates an output voltage of a first polarity by deforming with an operation plate when a part of a user's body touches the operation plate, and generates the output voltage of a second polarity by deforming with the operation plate when the part of the user's body is moved away from the operation plate. Moreover, a calculation unit calculates an electrical parameter integral value by time-integrating an electrical parameter that changes with the output voltage generated by the pressing sensor. The electrical parameter has a third polarity when the output voltage has the first polarity and has a fourth polarity when the output voltage has the second polarity. The calculation unit calculates a subtraction electrical parameter integral value obtained by subtracting a predetermined value having the third polarity per unit time from the electrical parameter integral value.