Piezoelectric Load Sensor Assembly for Static and Dynamic Strain Measurement
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Solution Overview
Problem
Traditional piezoelectric sensors face challenges in measuring static or quasi-static strain due to finite electric input impedance, which causes charge leakage and disables the measurement of slow change voltage.
Innovation Solution
A piezoelectric sensor assembly with an electronic processor that utilizes both dynamic and static sensing modes, employing an LRC circuit model to process voltage data from piezoelectric sensors, allowing for measurement of force quantities across a broad frequency range, including low frequencies through resonant frequency modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional piezoelectric sensors are used to measure static or quasi-static strain, then the sensor produces an electric charge in proportion to the strain, but the finite electric input impedance of the meter causes charge leakage over time, disabling the measurement of static or slow change voltage
Solution Approach 1:
The patent replaces traditional voltage measurement methods with frequency measurement methods. Instead of directly measuring the voltage signal from the piezoelectric sensor (which suffers from charge leakage through finite input impedance), the system measures the resonant frequency of the sensor-structure system. The resonant frequency shifts in response to static and quasi-static strain, providing a measurement mechanism that is immune to charge leakage problems.
Solution Approach 2:
The patent changes the measurement parameter from voltage amplitude to resonant frequency. By exciting the piezoelectric sensor-structure system at its resonant frequency and measuring the frequency shift rather than the voltage magnitude, the system overcomes the charge leakage issue. The resonant frequency is determined by the mechanical properties of the system rather than the electrical charge state, making it stable for static and quasi-static measurements.
2Measurement precision
If piezoelectric sensors operate in dynamic mode with high frequency signals, then the measurement is reliable, but the sensor cannot effectively measure static or low frequency loads
Solution Approach 1:
The patent makes the piezoelectric sensor multifunctional by enabling it to measure both dynamic and static/quasi-static loads using the same sensor element. The system uses resonant frequency measurement techniques that work across the entire frequency spectrum. By measuring the resonant frequency of the sensor-structure system and its shifts under various loading conditions, the sensor can accurately measure static, quasi-static, and dynamic loads without requiring separate sensing 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
Enables accurate measurement of static and dynamic loads by overcoming the limitations of traditional sensors, providing sensitive strain monitoring from static/quasi-static to ultrasonic frequencies without the need for external excitation or precise power supplies.
Implementation Method 1
Piezoceramic components, such as plates, disks and rings, are known to convert quantities, such as force, pressure, strain, and acceleration, into electrical voltage
Implementation Method 2
a tuned and unloaded resonant frequency, and a measured and loaded resonant frequency is associated with the combined element and structure, and a difference between the tuned resonant frequency and the measured resonant frequency is directly proportional to the force quantity value
Data Source
AI summary
A piezoelectric sensor assembly for measuring a force quantity on a structure includes at least one piezoelectric sensor, each including an element and two electrodes each projecting outward from the element. An electronic processor of the assembly is configured to receive data from the sensor, wherein the data includes a voltage with a magnitude that is indicative of a dynamic load (i.e., amplitude modulation mode) placed upon the structure. The processor may be configured to interrogate the piezoelectric sensor for its resonant frequency change which is indicative of the load applied to the structure at low operation frequency and to which the piezoelectric sensor would not otherwise respond well. The dual mode operation of the piezoelectric sensor extends the frequency range of the strain measurement from the dynamic range to static or quasi-static range.