Miniaturizing On Ground Settlement Optical Sensing System By Using The FPGA Technique

With the acceleration of urbanization in our country,urban infrastructure is is getting better and better.In particular,the structural health monitoring of large infrastructures,such as railways,tunnels,bridges,has become very professional.And the problem of ground settlement is one of the important contents.Therefore,the methods for ground settlement monitorings are also in need of diversification and hierarchy.These needs can be roughly classified as: the monitoring during constructing period and servicing.This paper focuses on the latter.The ground settlement monitoring during servicing period is generally a combination of two aspects,they are regular routine inspections and the safety assessment of the structure in some specific areas,where some abnormal states have been perceived.With the development of the technology such as internet of things(Io T),both the two aspects get to develop in the direction of miniaturization,automation,intelligence,and remote etc.This dissertation was carried out under the background of this demand,in order to make a compact fiber-optic white light Michelson interference ground settlement monitoring(FIGS)systemto meet th eneed of portability,low cost,multi-channel multiplexing etc.A Filed Programmable Gate Array(FPGA)technique was employed and the main achievements were list as the below:(1)The data acquisition and processing of the FIGS based on the FPGA technique was realized in the development environment of Verilog HDL.Specificly,the modules of data transmission,control command,filtering,data storage,white light interference peak-seeking and clock etc.,were designed and tested well in experiments.(2)Two peak-seeking algorithms for the FIGS have been proposed as the position averaging method and the center-of-mass algorithm.The combination of the two algorithms could improve the accuracy of the FIGS system even if the white light interference peaks became distorted.The experiments with a comparison of a 50μm standard-thickness rule demonstraed that the maximum error was 3.71μm and proved the effectiveness of the algorithms.And it allows the FIGS to meet the exceptional accuracy index for foundation settlement monitoring(3)In order to realize a compact FIGS system in teh aspect of miniaturization,power consumption,cost etc.,a specific data acquisition and processing hardware board had been designed.The board was composed of the modules of the FPGA core chip,serial port,Analog digital converter(ADC),and power supply.With a verification of the waveform generator,the desigend board worked well.And after testing,the average power consumption of the FIGS using this hardware board is only 23 W.