Research On Wireless Measurement Mechanism Of Flexible Piezoelectric Composite Strain Sensor

The hazard caused by vibration exists in all aspects of life,and the wireless measurement of structural vibration is of great significance.In this paper,with the positive electrical characteristics of the polyvinylidene fluoride(PVDF)flexible piezoelectric composite film sensor,it is possible to achieve the conversion of the structure vibration information into an electrical signal,and the electrical signal is realized by the wireless measurement system so that the vibration frequency and the strain size of the structure are revised.The research contents are as follows:First,this paper has a self-made PVDF flexible piezoelectric composite film sensor,and the simple preparation process is initial film-stretch-high pressure polarization.The self-made PVDF piezoelectric properties of the self-made flexible piezoelectric composite film sensors is analyzed using XRD,SEM and open-circuit voltmeter.Second,in this paper,a wireless measuring system of PVDF flexible piezoelectric composite film sensor is designed: 1)Based on the equivalent circuit of the flexible piezoelectric composite film sensor,the corresponding front-end interface circuit is designed,which includes charge amplifying circuits,low-pass filter circuits and power frequency trapping circuits.And front-end interface circuit is proved to meet the design requirements with circuit simulation.2)Combined with the transmission equation of front-end interface circuit and the first type of piezoelectric equation of the flexible piezoelectric composite film sensor,the signal transfer function of the wireless measurement system is derived.the relationship between the system acquisition voltage and the strain is established,and a method of solving structural strain by means of electrical signals collected by wireless measurement system is proposed.3)Piezoelectric signal acquisition modules are drawn by PCB drawing software,and modules mainly include front-end interface circuit modules,AD acquisition modules,data processing modules,and wireless transmission modules.Finally,a wireless test experiment is carried out in a wireless measurement system for the PVDF flexible piezoelectric composite film sensor that is pasted on the vibration of the cantilever beam.The received wireless measurement signal is revised by the derived wireless measurement system signal transfer function,and the strain measured by the wired measurement system is compared.The comparison results show that the wireless measurement system enables accurate measurement of the cantilever beam vibration frequency and structural strain,and its wireless measurement distance of the system can reach 150 meters.Therefore,it can partially replace the traditional wired measuring system,which has broad engineering application prospects.