Research On Structural Strain On-line Monitoring System Using Piezoelectric Material

Structural strain is the most important parameter in ship and marine structures healthmonitor. Therefore, establishment of structure strain on-line monitoring system is being moreand more necessary. A structural strain on-line monitoring system using piezoelectric materialis developed in this thesis. The system can monitor the stress and strain of ship and marinestructures on-line for long period, and preliminary warning function is available. At the sametime, the probed data can be uploaded and saved to the host computer. The wirelesscommunication mode effectively avoids wire disposal on the ship and marine structures, andreduces heavy workload. The system has obvious advantages such as small volume, lowpower consumption, simple circuit board and so on.The thesis studies the composition of the structural strain on-line monitoring system,hardware structure design and software design method in detail. The thesis also introduces therole of all the parts. The main research work of the thesis is shown as follows:Firstly, the hardware of system is designed. Based on MSP430 single chip microcomputerand nRF905 wireless transceiver this system is designed with PVDF film that is used as strainsensor. This system consists of three modules: data acquisition module, data emission module,and data receiving module. The structural stress and strain is probed with PVDF film in dataacquisition module. ADC12, the analog-to-digital converter internal integration in themicrocontrollcr, is used to analog-digital conversion of voltage data. The probed data are sentby data emission module, and received by data receiving module. At the same time the probeddata can be uploaded and saved to the host computer.Secondly, the software of system is designed. The software design of system consists oftwo parts: the data sending part and the data receiving part. The functional module ofMSP430 single chip microcomputer is set and each register of nRF905 wireless transmittalmodule is confected through programming, and then hardware is controlled by software. Thefunctions such as data acquisition, data emission, data receiving and uploading to the hostcomputer are available. At the same time, early warning value can be set in the software.Lastly, experimental examination is done. Through the research in this thesis, thefollowing relationships are further verified: the relationship between the stress frequency (f)and the output voltage of host computer (V) when the stress amplitude (T) at the surface of the plate keeps constant; the relationship between (T) and (V) while the stress frequency (f)keeps constant; The relationship between the area of PVDF (A) and (V). Also, the thesis teststhe wireless data acquisition module and the on-line monitoring module through comparingthe voltage waveform from the host computer and the voltage waveform from the dataacquisition module.