Piezoelectric Force Localisation for Glove- and Liquid-Resistant Input
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Solution Overview
Problem
Existing user input control technologies, such as capacitive sensing, face limitations in accuracy and robustness, especially in the presence of liquids and when users wear thicker gloves, and are prone to false triggers due to the lack of pressure requirement and material restrictions for the casing.
Innovation Solution
A piezoelectric sensor system with a layer of piezoelectric material between sensing electrodes and a counter electrode, featuring primary and secondary electrodes arranged to form active regions, allows for accurate localization of applied forces by comparing primary and secondary piezoelectric charges to determine if the force centroid is within a defined perimeter, enhancing reliability and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If capacitive sensing electrodes are used for buttonless input panels, then mechanical complexity is reduced, but measurement precision deteriorates when liquids are present or users wear thicker gloves
Solution Approach 1:
The patent replaces capacitive sensing (electrical field-based) with piezoelectric sensing (mechanical stress-based). The piezoelectric sensor detects applied forces directly through mechanical stress on the piezoelectric material, eliminating dependence on electrical fields that are blocked by liquids or thick gloves. This substitution resolves the contradiction by maintaining simplicity while improving precision in challenging environments.
Solution Approach 2:
The patent changes the detection parameter from electrical capacitance to mechanical piezoelectric charge. By measuring piezoelectric charges generated in response to applied forces rather than capacitive coupling, the system becomes insensitive to liquids and glove thickness while maintaining robust input detection capability.
2Ease of operation
If capacitive sensing is used without pressure requirement, then ease of operation is improved, but reliability deteriorates due to easy false triggers
Solution Approach 1:
The patent implements a conditional integration process where capacitive detection serves as a preliminary trigger that activates piezoelectric monitoring. The system first detects capacitive coupling to determine a user interaction period, then conditionally integrates piezoelectric signals during this period. This two-stage approach ensures genuine user interaction while filtering out false triggers from unrelated conductive objects.
Solution Approach 2:
The patent uses capacitive sensing feedback to control piezoelectric signal processing. The capacitive detection provides feedback about user presence, which gates the piezoelectric measurement process. This feedback mechanism distinguishes between intentional user input and spurious signals, maintaining ease of operation while improving reliability.
3Ease of operation
If electric fields are used for capacitive sensing, then ease of operation is improved, but adaptability deteriorates due to material restrictions for casing
Solution Approach 1:
The patent replaces electrical field-based capacitive sensing with mechanical stress-based piezoelectric sensing. This substitution removes the requirement for electric field penetration through the casing, allowing any mechanically robust material to be used for the casing and cover, thereby dramatically improving adaptability while maintaining ease of operation.
Solution Approach 2:
The patent changes the physical parameter used for sensing from electrical field coupling to mechanical stress. This parameter change eliminates the constraint on casing material electrical properties, allowing versatile material selection including metals and conductive materials that would block capacitive fields but are perfectly suitable for piezoelectric sensing.
4Measurement precision
If piezoelectric sensor with multiple electrodes is used, then measurement precision is improved for force localization, but device complexity increases
Solution Approach 1:
The patent segments the sensing area into multiple discrete electrodes arranged in a grid pattern. Each electrode independently measures piezoelectric charge, allowing the system to determine which specific electrode(s) are activated and calculate the force centroid location. This segmentation enables precise force localization while maintaining a relatively simple electrode structure.
Solution Approach 2:
The patent extends the sensing capability from single-point detection to two-dimensional localization by arranging electrodes in a grid across the sensing surface. This dimensional expansion allows the system to determine both x and y coordinates of applied forces, achieving accurate force centroid localization without excessive complexity.
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 system provides accurate and reliable user input detection, resistant to liquids and glove thickness, with improved mechanical robustness and reduced false triggers, enabling effective use in various applications without the need for pressure-sensitive materials.
Implementation Method 1
A piezoelectric sensor includes a layer of piezoelectric material disposed between a number of sensing electrodes and at least one counter electrode
Data Source
AI summary
A device (15) including a piezoelectric sensor (16). The piezoelectric sensor (16) includes a layer of piezoelectric material (7) disposed between a number of sensing electrodes (4, 12, 13) and at least one counter electrode (3). The device (15) also includes a controller (17) connected to the piezoelectric sensor (16). The sensing electrodes (4, 12, 13) are arranged to form one or more active regions (19). Each active region (19) includes one or more primary sensing electrodes (4,12) and one or more secondary sensing electrodes (4, 13). The secondary sensing electrodes (4, 13) are separated from the primary sensing electrodes (4, 12) by a perimeter (14). The controller (17) is configured, for each active region (19), to monitor primary piezoelectric charges induced on each primary sensing electrode (4, 12) and to monitor secondary piezoelectric charges induced on each secondary sensing electrode (4, 13). The controller (17) is also configured, in response to detecting one or more primary and/or secondary piezoelectric charges, to determine whether a corresponding applied force has a centroid within the perimeter (14) based on comparing the primary piezoelectric charges to the secondary piezoelectric charges.