【摘要】：在分布式光纖傳感系統(tǒng)中,數(shù)據(jù)采樣速率及探測(cè)脈沖光的脈寬會(huì)影響到系統(tǒng)的空間分辨率,而高空間分辨率又是系統(tǒng)所追求的;同時(shí)傳感信號(hào)極其的微弱,信噪比非常低,常常被淹沒在噪聲中不能直接被識(shí)別,需要對(duì)數(shù)據(jù)進(jìn)行一定的處理。因此,設(shè)計(jì)出一套不僅可以自由設(shè)置探測(cè)脈沖光的脈寬、能夠進(jìn)行高速數(shù)據(jù)采集保證系統(tǒng)空間分辨率,而且能夠進(jìn)行大容量緩存,還能實(shí)時(shí)對(duì)數(shù)據(jù)進(jìn)行處理提高信噪比的系統(tǒng)非常的有意義。本文以基于瑞利散射的分布式光纖傳感技術(shù)原理為基礎(chǔ),結(jié)合系統(tǒng)性能需求,選用Altera公司型號(hào)為EP4CE15F17C8N的FPGA芯片作為系統(tǒng)的主控制器兼處理器,負(fù)責(zé)系統(tǒng)的時(shí)序、邏輯控制和信號(hào)調(diào)理,設(shè)計(jì)了基于FPGA的分布式光纖傳感系統(tǒng)。該系統(tǒng)的設(shè)計(jì)方案為模塊化設(shè)計(jì),把整個(gè)系統(tǒng)分為五個(gè)關(guān)鍵功能模塊,分別為:脈沖光生成模塊、數(shù)據(jù)采集模塊、數(shù)據(jù)緩存模塊、數(shù)據(jù)處理模塊及數(shù)據(jù)傳輸模塊。對(duì)各個(gè)模塊的主要功能及器件的選擇進(jìn)行了說明:脈沖光生成模塊產(chǎn)生適合系統(tǒng)要求的探測(cè)脈沖光,可實(shí)現(xiàn)最小脈寬5ns、最大頻率100MHz的脈沖光生成;數(shù)據(jù)采集模塊采用高速AD6645芯片對(duì)傳感信號(hào)進(jìn)行A/D轉(zhuǎn)換,FPGA對(duì)轉(zhuǎn)換后的數(shù)據(jù)進(jìn)行采集,ADC轉(zhuǎn)換速率可達(dá)80MSPS;采用兩塊SDRAM芯片以乒乓操作的形式進(jìn)行數(shù)據(jù)緩存;數(shù)據(jù)處理模塊主要是針對(duì)傳感信號(hào)極其微弱和時(shí)變特性,先采用滑動(dòng)累加平均算法對(duì)數(shù)據(jù)進(jìn)行處理提高信號(hào)的信噪比,再對(duì)提高信噪比后的信號(hào)進(jìn)行小波變換處理以提取信號(hào)的細(xì)節(jié)部分;通過USB傳輸模塊實(shí)現(xiàn)FPGA與上位機(jī)間的數(shù)據(jù)傳輸。本文詳細(xì)敘述了系統(tǒng)各個(gè)功能模塊設(shè)計(jì)的關(guān)鍵技術(shù)及實(shí)現(xiàn)方式,同時(shí)分析了影響系統(tǒng)空間分辨率和信噪比的相關(guān)因素并提出了相應(yīng)的改進(jìn)措施,同時(shí)對(duì)設(shè)計(jì)的各個(gè)功能模塊進(jìn)行功能驗(yàn)證。最后把各個(gè)功能模塊組合在一起實(shí)現(xiàn)整個(gè)系統(tǒng)功能,并對(duì)整個(gè)系統(tǒng)進(jìn)行驗(yàn)證測(cè)試,成功測(cè)試到了光纖連接點(diǎn)及光纖尾端處的菲涅爾反射信號(hào),測(cè)試結(jié)果表明本文設(shè)計(jì)的基于FPGA的分布式光纖傳感系統(tǒng)性能良好,設(shè)計(jì)方案可行有效,達(dá)到預(yù)期效果,對(duì)分布式光纖傳感信號(hào)的采集和處理效果明顯。
[Abstract]:In the distributed optical fiber sensing system, the data sampling rate and the pulse width of the detection pulse light will affect the spatial resolution of the system, and the resolution between high altitude is pursued by the system. At the same time, the sensing signal is extremely weak and the signal-to-noise ratio is very low, so it is often inundated in the noise and can not be recognized directly, so it is necessary to process the data to a certain extent. Therefore, it is very meaningful to design a set of systems which can not only freely set the pulse width of the detected pulse light, can carry out high-speed data acquisition to ensure the spatial resolution of the system, but also can cache the data in large capacity, and can also process the data in real time to improve the signal-to-noise ratio (SNR). In this paper, based on the principle of distributed optical fiber sensing technology based on Rayleigh scattering, combined with the performance requirements of the system, the FPGA chip of Altera company model EP4CE15F17C8N is selected as the main controller and processor of the system, which is responsible for the timing, logic control and signal conditioning of the system, and a distributed optical fiber sensing system based on FPGA is designed. The design scheme of the system is modular design, the whole system is divided into five key functional modules, namely: pulse light generation module, data acquisition module, data cache module, data processing module and data transmission module. The main functions of each module and the selection of devices are explained as follows: the pulse light generation module produces the detection pulse light suitable for the system requirements, which can realize the pulse light generation of the minimum pulse width of 5 ns and the maximum frequency 100MHz, the data acquisition module uses the high speed AD6645 chip to convert the sensing signal, FPGA collects the converted data, and the ADC conversion rate can reach 80 100MHz. Two SDRAM chips are used to cache the data in the form of ping-pong operation. The data processing module mainly aims at the extremely weak and time-varying characteristics of the sensing signal. Firstly, the sliding accumulation average algorithm is used to process the data to improve the signal-to-noise ratio, and then the signal after improving the signal-to-noise ratio is processed by wavelet transform to extract the details of the signal. The data transmission between FPGA and the upper computer is realized by USB transmission module. In this paper, the key technologies and implementation methods of each functional module of the system are described in detail, and the related factors affecting the spatial resolution and signal-to-noise ratio of the system are analyzed, and the corresponding improvement measures are put forward. At the same time, the function of each functional module is verified. Finally, each functional module is combined to realize the whole system function, and the whole system is verified and tested, and the Fresnel reflection signal at the optical fiber connection point and the end of the optical fiber is successfully tested. The test results show that the distributed optical fiber sensing system based on FPGA has good performance, the design scheme is feasible and effective, and the expected effect is achieved, and the acquisition and processing effect of the distributed optical fiber sensing signal is obvious.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TP212

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