Piezoelectric Force Sensing via Voltage Transition Time
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Solution Overview
Problem
Conventional piezoelectric elements are limited in measuring constant pressure and distinguishing absolute pressure values due to their dynamic nature, and they face challenges in preventing high haptic feedback voltages from discharging into sensitive low-voltage amplifier electronics used for pressure sensing.
Innovation Solution
A system that measures the transition time of voltage pulses applied to a piezoelectric element, utilizing the capacitance affected by applied pressure to determine absolute pressure, while also enabling haptic feedback using larger voltage pulses without disrupting pressure sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional piezoelectric elements are used for dynamic pressure sensing, then they can measure pressure changes effectively, but they cannot measure constant pressure or determine absolute pressure values
Solution Approach 1:
The patent measures the transition time (rise time or fall time) of voltage pulses applied to the piezoelectric element. This transition time is affected by the capacitance of the piezoelectric element, which in turn is affected by the amount of pressure currently being applied. By measuring transition time rather than voltage magnitude, the system can determine absolute pressure values including constant pressure, not just dynamic pressure changes.
2Power
If high driving voltages are used for haptic feedback, then effective haptic feedback is achieved, but high voltages stored in the piezoelectric element can discharge into sensitive low-voltage amplifier electronics
Solution Approach 1:
The patent generates haptic feedback voltage pulses in alternation with or coinciding with measurement pulses. By using periodic pulsed action rather than continuous high voltage, the system achieves effective haptic feedback while minimizing the risk of voltage discharge into the amplifier electronics during measurement phases.
Solution Approach 2:
The patent uses the transition time measurement method as an intermediary approach that allows the system to handle both high voltages for haptic feedback and low voltages for measurement without direct conflict. The capacitance-based transition time measurement provides a buffer that prevents direct voltage discharge into the amplifier electronics.
3Adaptability or versatility
If the piezoelectric element is used for both pressure sensing and haptic feedback, then device functionality is enhanced, but the two very different voltage ranges create practical problems
Solution Approach 1:
The patent makes the piezoelectric element serve dual functions: pressure sensing and haptic feedback. By using the same element for both purposes and managing voltage application through periodic pulsing, the system reduces overall device complexity while maintaining versatile functionality.
Solution Approach 2:
The patent alternates between measurement pulses for pressure sensing and haptic feedback pulses, allowing the same piezoelectric element to handle both low-voltage measurement and high-voltage feedback operations at different time intervals, thereby simplifying the overall device architecture.
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
Enables the measurement of absolute pressure and simultaneous haptic feedback, allowing for more advanced applications such as absolute pressure-sensitive computer user interfaces without voltage interference issues.
Implementation Method 1
A piezoelectric element generates an electric field (and a measurable voltage from the field) in response to applied pressure
Implementation Method 2
Piezoelectric elements also change shape in response to a dynamic electrical field
Implementation Method 3
The transition time (such as the rise time and/or fall time of the voltage pulse) is affected by the capacitance of the piezoelectric element, which in turn is affected by the amount of pressure currently being applied to the piezoelectric element
Data Source
AI summary
A system and method for measuring absolute pressure applied to a piezoelectric element by measuring a transition time of a voltage pulse applied to a piezoelectric element. The transition time (such as the rise time and/or fall time of the voltage pulse) is affected by the capacitance of the piezoelectric element, which in turn is affected by the amount of pressure currently being applied to the piezoelectric element. The system may also provide haptic feedback via the same piezoelectric element.