| In modern society, all kinds of large and flexible construction and engineeringstructure have emerged; the importance of real-time structural health monitoring hasbecome increasingly prominent. Piezoelectric material, as a high-performance mechanicalstress-the electric field energy conversion medium, is very suitable for the sensing field.Great need to work long hours and the number of monitoring points, the structure of thearea of monitoring, the structure of the piezoelectric sensor, power, difficult toelectromagnetic interference and easy processing and integration characteristics ofpiezoelectric materials has broad application prospects in the field of monitoring sensor.Cantilever piezoelectric sensing element, the establishment of the finite element model ofthe piezoelectric material and experimental verification, the piezoelectric sensing elementhas been optimized for low frequency vibration sensitivity, and to design the supportingelectrical and software components. A full-featured surveillance system was developed andthe system is tested and validated. The detailed contents are as follows:(1) A kind of low-frequency piezoelectric test equipment was proposedOn the basis of summing up the structural health monitoring system status quo, it isproposed to design a high sensitivity, low-cost low-frequency piezoelectric sensing elementto improve the structural health monitoring system for the monitoring of large-scalestructure in the low-frequency performance. Success stories through in-depth study at homeand abroad in the history of engineering disasters, and effective monitoring, combined withthe advantages of piezoelectric material in the sensing aspects and looking forward to theprospect of the piezoelectric sensor in structural health monitoring technology.(2) Properties of piezoelectric sensor materialsThe piezoelectric vibrator is the core component of the piezoelectric sensor, its performance will directly affect the performance of the piezoelectric sensing devices. In thispaper, the piezoelectric sensing element, the basic theory of piezoelectric materials as thepiezoelectric vibration midnight the relationship between the microscopic cell polarizationdirection and the direction of vibration, combined with the vibration modes and structuralfeatures to determine the chip piezoelectric sensing element. Chip piezoelectric oscillatorsupport, working principle and the equivalent circuit for the final structural design of thesensing element ideas.(3) Design and analysis of the piezoelectric sensing elementStudy the basic structure of the piezoelectric sensing element program to determinethe use of chip-type cantilever structure, the rectangular piezoelectric design variables anddesign principles, including a clamping manner, piezoelectric cutting shape, substratethickness. In which the main line of improvement ideas for the stress state of thepiezoelectric material to uniform distribution of the effective use of every inch ofpiezoelectric ceramics can. Combined with finite element simulation technology, simulationanalysis for a variety of design variables, and have been a number of structural variables ofsimulation best value and best solution. Experimental approach in its conclusions based onthe conclusions of the Finite Element Analysis of the experimental verification, the resultsof the simulation analysis is expected. Designed and fabricated chip piezoelectric sensingelement of the monitoring system based on variable analysis.(4) The electrical structure of the piezoelectric test equipment designIn order to effectively collect the weak signal of the piezoelectric sensor output designa stable and efficient amplifier section. Amplifier circuit with low power consumption andhigh input impedance of the IC and the low-pass filter circuit in order to adapt to thepiezoelectric element signal power, and low-frequency characteristics of low signal intensity.Analyze and validate the performance of the finished amplifier circuit, and has provided aguarantee for the analog to digital converter input signal quality. Design Communicationbetween PC and the signal acquisition circuit, which uses ultra-compact low-power tiny45multifunction microcontroller atmel-to complete the task of the analog to digital converterand data acquisition. And acquisition interfaces with versatile, easy to install and supply capacity of the USB interface. The entire monitoring system power supply and data transferfrom the plug and play USB interface of the PC side. The driver of the host computer wasusing C#to integrated windows Windows operating system USBHID Device Interfacedriver to get data from the microcontroller and real-time display on the screen, real-timerecording to the hard disk of the host computer. The circuit and software design of themonitoring system to make it portable is better, easier installation and operation.(5) The actual performance test of piezoelectric structural health monitoringsystem test deviceTest and validate the actual performance of the piezoelectric test device. Piezo testequipment at the laboratory indoor and outdoor large-scale structure of monitoring test.Sinusoidal mechanical vibrations in the room to test the sensitivity of the monitoring systemfor the different frequencies, and measured the linear range and sensitivity of the scope ofthe monitoring system. Mixed-frequency identification tests, the use of mixed breathing andheartbeat frequency to test the recognition capabilities of the monitoring system for mixedvibrations of different frequencies. Outdoor monitoring experiment tested the piezo testequipment to verify the real-time monitoring capability of the piezoelectric test devices inpractical applications in real large-scale structure. |
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