Bipolar Piezoelectric Haptic Device for Bidirectional Surface Deflection
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Solution Overview
Problem
Haptic signalizing devices using piezoelectric elements face challenges in enhancing haptic sensitivity, deployability, and manufacturing efficiency, particularly in effectively utilizing the converse piezoelectric effect to drive device surfaces in both directions and managing temperature-dependent depolarization limits.
Innovation Solution
A haptic signalizing device employing piezoelectric elements arranged beneath a device surface, driven by a bipolar alternating electric field, with mechanical and electrical connections using adhesive for efficient movement and temperature-adaptive electric field control to prevent depolarization, maximizing deflection amplitude and sensitivity across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If piezoelectric elements are driven in a monopolar fashion, then the device structure is simpler, but haptic sensitivity is reduced due to unidirectional movement only
Solution Approach 1:
The patent implements bipolar driving that dynamically switches the electric field direction between same-direction and opposite-direction phases, enabling the piezoelectric element to move bidirectionally. This dynamic approach maximizes deflection amplitude in both directions, significantly improving haptic sensitivity compared to static monopolar driving while maintaining reasonable circuit complexity through systematic voltage switching.
Solution Approach 2:
The driving circuit employs periodic bipolar voltage application with alternating phases (same-direction and opposite-direction electric fields). This periodic action creates rhythmic bidirectional movement of the piezoelectric element, optimizing haptic feedback delivery. The periodic switching between voltage polarities enables the element to explore its full mechanical range, enhancing perceived haptic sensitivity.
2Manufacturing precision
If piezoelectric elements are driven with high electric field strength, then deflection amplitude increases, but depolarization occurs at elevated temperatures reducing reliability
Solution Approach 1:
The patent dynamically adjusts the electric field strength parameter based on temperature conditions. At elevated temperatures, the system reduces the magnitude of the opposite-direction electric field to stay below the depolarization threshold, while maintaining effective haptic operation. This parameter adaptation allows the device to achieve high deflection amplitude at normal temperatures while ensuring reliability across the full operating temperature range.
Solution Approach 2:
The system incorporates temperature monitoring and adaptive control that adjusts electric field application based on real-time temperature feedback. When temperature exceeds thresholds that risk depolarization, the control circuit automatically modulates the opposite-direction voltage to prevent damage. This feedback mechanism ensures long-term reliability while maintaining optimal haptic performance across varying thermal conditions.
3Ease of operation
If piezoelectric elements are mechanically connected to device surface, then haptic signal transmission is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functions into the adhesive layer: it simultaneously provides mechanical bonding between the piezoelectric element and device surface, establishes electrical connection for driving signals, and enables bidirectional force transmission for haptic feedback. This merging of structural, electrical, and mechanical functions into a single material layer simplifies assembly while maintaining superior haptic signal transmission compared to separate connection mechanisms.
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 improves haptic sensitivity by enabling bidirectional surface movement, reduces manufacturing complexity, and extends device functionality across a wider temperature range by optimizing electric field strength and minimizing energy loss due to depolarization.
Implementation Method 1
The piezoelectric effect causes the piezoelectric element to change polarization in the crystal lattice in response to mechanical stress, producing a measurable signal.
Implementation Method 2
Piezo haptics is possible due to the converse piezoelectric effect, where the application of an electrical field over the crystal lattice creates a mechanical deformation in the crystal.
Data Source
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AI summary
A haptic signalizing device (10) comprises a number of piezoelectric elements (6b) arranged below a device surface (1) such that mechanical deformations caused by the converse piezoelectric effect in the at least one piezoelectric element (6b) make the device surface (1) to move such that the device surface (1) follows the piezoelectric element (6b) and a driving circuit (20, 30) configured to cause the converse piezoelectric effect on the at least one piezoelectric element (6b) by generating an alternating electric field over the piezoelectric element (6b) in a bipolar fashion, that is, consecutively in both the same and the opposite direction with respect to the polarization of the piezoelectric element (6b), to make the piezoelectric element (6b) to move beyond its initial position consecutively in both directions. The piezoelectric element (6b) is arranged i) to locally move the device surface (1) inwards when the mechanical deformation in the piezoelectric element (6b) is a deflection directed away from the device surface (1), and ii) to locally move the device surface (1) outwards when the mechanical deformation in the piezoelectric element (6b) is a deflection that is directed towards the device surface (1).