Piezoelectric Sensor Element for Common Mode Signal Cancellation
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Solution Overview
Problem
Piezoelectric sensors, such as those made from PVDF, often generate false signals due to temperature changes, which can be problematic in environments with significant temperature fluctuations, leading to inaccurate touch or pressure detection.
Innovation Solution
A piezoelectric sensor element is designed with a layered structure that includes conductive regions and non-conductive voids to reduce thermally-induced voltage changes, allowing for effective cancellation of pyroelectric signals caused by temperature changes, thereby improving the accuracy of force and pressure detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric materials with large pyroelectric coefficient are used for touch detection, then the sensitivity to mechanical force is improved, but false signals are generated due to temperature changes
Solution Approach 1:
The piezoelectric layer is divided into multiple segments with different orientations. Specifically, the piezoelectric layer includes first, second, third, and fourth segments where the second and third segments are oriented to detect mechanical force while the first and fourth segments are oriented to detect temperature changes. This segmentation allows the sensor to distinguish between mechanical stimuli and thermal interference by comparing signals from differently oriented segments.
2Ease of manufacture
If conventional piezoelectric sensor structures are used, then manufacturing simplicity is maintained, but thermal interference cannot be effectively cancelled
Solution Approach 1:
Multiple functional segments are merged into a single integrated piezoelectric layer structure. The first, second, third, and fourth segments are all part of one continuous piezoelectric layer, allowing simultaneous detection of both mechanical force (via second and third segments) and temperature changes (via first and fourth segments) without requiring separate sensor elements or complex assembly processes.
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
This solution effectively reduces thermally-induced signals, enhancing the reliability and accuracy of touch and pressure sensors by minimizing the impact of temperature fluctuations, allowing for more precise detection of mechanical stimuli while maintaining cost-effectiveness and design flexibility.
Implementation Method 1
Piezoelectric impact detectors formed from polymeric materials such as polyvinylidene fluoride (PVDF) offer cost effective and high performance detection of momentary forces
Implementation Method 2
many piezoelectric materials such as PVDF have the disadvantage that they also respond to temperature changes, often with pyroelectric coefficients that rival their piezo coefficients
Data Source
AI summary
Certain implementations of the disclosed technology may include systems, methods, and apparatus for common mode signal cancellation in force change detectors. An example embodiment of the disclosed technology includes a press sensor element configured to reduce or eliminate thermally induced signals. The sensor element includes a piezoelectric layer that includes a first surface in communication with a first layer. The first layer includes a first conductive region. The piezoelectric layer includes a second surface in communication with a second layer. The second layer includes a second conductive region, a third conductive region, and a non-conductive void region separating the second conductive region and the third conductive region. The second and third conductive regions are configured to substantially reduce a thermally-induced voltage change between two or more of the first, second and third conductive regions responsive to a corresponding temperature change of at least a portion of the piezoelectric layer.