摘要
应力应变信号是船舶与海洋工程结构健康监测技术最为重要的参数之一。因此，建立结构应变在线监测系统就成为必要。本文开发一种基于压电材料的结构应变在线监测系统。本系统可以长期在线监测船舶与海洋结构的应力应变，并具有预警功能；同时可以将采集到的数据上传至上位机进行存储；无线通信方式有效的避免了在船舶与海洋结构物上进行布线，减少了繁重的工作量。系统具有体积小、功耗低、电路构造简单等特点。
论文研究了结构应变在线监测系统的组成、硬件结构设计和软件开发方法，并介绍了各个模块在系统中的作用。主要包括以下内容：
首先，系统的硬件设计。本系统主要采用PVDF压电薄膜作为传感器，以MSP430单片机为核心，利用nRF905无线收发芯片设计构成。整个系统分为三个模块：数据采集模块、数据发射模块、数据接收模块。数据采集模块使用PVDF压电薄膜进行结构应力应变信号采集，使用微控制器内部集成的模数转换器ADC12进行电压数据的模数转换，再通过数据发射模块将采样数据发射出去，数据接收模块负责接收数据并将数据通过串口上传至上位机进行分析和处理，上位机还可以将数据保存下来以备后用。
其次，系统的软件设计。系统软件设计分为两大部分：数据发送部分和数据接收部分。通过编程对MSP430单片机的功能模块进行设置并配置nRF905无线模块的各寄存器，然后由软件控制硬件，完成数据的采集、发射、接收和上传至上位机的功能。同时可以在软件中设置预警值。
最后，实验验证工作。通过本文实验研究，进一步验证了如下关系：当钢板上表面应力的幅值T相同时，应力的频率f与上位机输出电压V的关系；当钢板上表面应力的频率f相同时，T与V的关系；PVDF薄膜面积A与V的关系。并且通过对比上位机软件显示的电压波形图与数据采集模块的输出电压波形图的方法对系统的无线数据采集及在线监测功能进行了验证。
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.
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