Design Of Offshore Platform Structure Vibration Detection System Based Wireless Network

The bearing capacity of offshore platform structure is reduced gradually and the hidden trouble of safety is exposed by the long-term effects of environmental load, accidental disasters, corrosion and other factors. The structural health monitoring technology applied to offshore platform structure, can diagnose the damage situation of the structure to a certain extent. Structural health monitoring system consist of sensing, data acquisition and pre processing and transmission, damage diagnosis and safety evaluation, model updating and data management, in which the initial phase of sensing, data acquisition and preprocessing is crucial for the later structural modal identification and damage diagnosis and safety evaluation. In this paper, the former are collectively referred to as the vibration detection system, and wireless network technology was introduced into the design of the vibration detection system applied to offshore platform structures.Starting from the low frequency vibration characteristics of offshore platform, the paper determines the main measurement object and the sensor of vibration detection system. This paper analyzes and compares the mature short distance wireless transmission technology, has determined the ZigBee technology and Wi-Fi technology combining scheme, and designes using method of scheme through calculation of bandwidth requirements. In order to ensure the authenticity and reliability of sensor data, this paper discusses installation and fixation of sensors, and determines the fixed modes of magnetic adsorption method. This paper analyzes and designs the operation scheme of data acquisition node with low power consumption from many aspects. In order to meet the needs of the later structure modal parameter identification, this paper presents method of extracting posture acceleration sensor from 3 axis accelerometer data. This article also discusses how to ensure the reliability of the system operation from the electric parameter monitoring, temperature and humidity monitoring, wireless encryption and other aspects.Embarked from the application demand and the current master of technology, this paper designs the overall framework of the vibration detection system, and put forward the performance index. The design of vibration detection system includes hardware design of acquisition nodes, software design of acquisition nodes and software design of the monitoring host. Hardware circuit takes FPGA minimum system as the core, with the acceleration signal acquisition circuit, low power supply management circuit, wireless module, USB interface circuit, SD card interface circuit, GPS receiver and digital temperature and humidity sensors, to achieve the basic function of data acquisition, data storage, power management, GPS timing, temperature and humidity data acquisition, power monitoring, USB communication etc. Inside the FPGA, based on the AVALON bus architecture, digital logic parts with NiosⅡ processor as the core are designed. The software part of the acquisition node based on Nios Ⅱ processor as the operation platform is divided into the driver layer, base layer and application layer according to hierarchy. Among them, this article focuses on the implementation method of SD storage, wireless data upload and GPS timing and the application layer of the ZigBee wireless communication protocol. In addition, this paper also briefly introduces the monitoring host software architecture and function.In the end of this thesis, research and design of the vibration detection system are summarized and the improvement scheme is put forward, in order to meet the need of engineering application for vibration of offshore platform structure detection.