本文選題：水下聲源　切入點：激光干涉　出處：《哈爾濱工業(yè)大學(xué)》2017年碩士論文

【摘要】：水下目標(biāo)探測在海洋防務(wù)和海洋工程領(lǐng)域備受關(guān)注。實現(xiàn)水下聲場的探測是突破水下目標(biāo)識別、定位、跟蹤等難題的基礎(chǔ)。目前用于水下目標(biāo)探測的方法眾多,其中“激光-聲”聯(lián)合探測屬于一種前沿基礎(chǔ)研究方法,作者所在實驗室從2008年開始便致力于“激光-聲”聯(lián)合探測水下聲目標(biāo)的研究,并取得了一系列的階段性成果。但是關(guān)于探測信號頻譜混疊情況下的多聲源準(zhǔn)確探測一直是技術(shù)瓶頸。因為當(dāng)水下存在多個聲源,且各聲源頻率接近時,激光相干探測信號的頻譜將混疊在一起,無法直觀的判斷出聲源的個數(shù),也無法利用傳統(tǒng)的方法直接獲取水下各聲源發(fā)聲頻率。本文的研究目的就是解調(diào)出水下多個頻率接近的聲源發(fā)聲頻率。圍繞這一主題,本文主要從以下幾個方面展開研究:建立了水下多聲源頻率解調(diào)的理論模型,并進(jìn)行了仿真驗證。分析水下目標(biāo)輻射噪聲的特性、噪聲在水介質(zhì)中傳播時的衰減特性以及噪聲傳至水表面形成水表面聲波的原理。著重探討水下存在多個聲源,且探測信號頻譜混疊在一起時的頻率解調(diào)方法,提出一種基于Hilbert變換的水下多聲源頻率解調(diào)方法,推導(dǎo)出水下多聲源探測信號經(jīng)處理后的具體數(shù)學(xué)表達(dá)式,并仿真驗證解調(diào)方法的正確性和可行性。研究實測水下多源聲信號頻率提取的頻率解調(diào)實現(xiàn)。根據(jù)理論模型的推導(dǎo)和實際探測實驗的分析,以MATLAB為平臺,研究實測信號的解調(diào)算法實現(xiàn)。結(jié)合五點三次平滑濾波方法對探測信號進(jìn)行預(yù)處理,使得自然水表面波動引起的頻帶對信號解調(diào)的影響降到最低。借助小波包分解與重構(gòu)的方法將有用信號頻帶從干涉信號中剝離出來。通過對信號Hilbert變換及模值計算和平滑濾波等處理使得原來混疊在一起的多個頻帶得以分離,最后通過頻帶中心值搜索計算獲取水下多個聲源的發(fā)聲頻率。設(shè)計并在光學(xué)暗室下搭建一套水下多聲源解調(diào)系統(tǒng)。根據(jù)本課題探測信號的特征,結(jié)合實際探測技術(shù)要求,設(shè)計一套水下多聲源解調(diào)系統(tǒng),根據(jù)實際探測需求對一些關(guān)鍵器件進(jìn)行分析和選擇。在光學(xué)暗室下搭建實驗系統(tǒng)并進(jìn)行調(diào)試,使之能達(dá)到探測要求。為驗證本文提出的解調(diào)方法的可行性和準(zhǔn)確性,利用搭建的激光相干探測系統(tǒng)進(jìn)行發(fā)聲頻率在1kHz-10kHz之間的多個頻率組合的水下目標(biāo)探測,并進(jìn)行水下聲信號頻率信息的探測效率評估。實驗結(jié)果表明本文所提出的信號方法能很好地實現(xiàn)水下復(fù)雜聲信號頻率信息的檢測,為水下聲信號處理提供了新的思路。
[Abstract]:Underwater target detection has attracted much attention in the field of marine defense and marine engineering.The detection of underwater acoustic field is the basis to break through the difficult problems of underwater target identification, positioning and tracking.At present, there are many methods used in underwater target detection, among which "laser-acoustic" joint detection is a kind of advanced basic research method. Since 2008, the author has devoted himself to the research of "laser-acoustic" joint detection of underwater acoustic target.And has obtained a series of stage achievement.Nor can the traditional method be used to directly obtain the sound frequency of underwater sound sources.The purpose of this paper is to demodulate the sound frequency of multiple underwater sound sources.Focusing on this topic, this paper mainly studies the following aspects: the theoretical model of underwater multi-source frequency demodulation is established, and the simulation is carried out.The characteristics of underwater target radiated noise, the attenuation characteristics of noise propagating in water medium and the principle of acoustic wave formation on water surface are analyzed.In this paper, the frequency demodulation method when there are many sound sources under water and the spectrum of detection signals are aliasing together is discussed. A frequency demodulation method based on Hilbert transform for underwater multi-sound sources is proposed.The mathematical expression of the underwater multi-source detection signal is deduced, and the correctness and feasibility of the demodulation method are verified by simulation.In this paper, the frequency demodulation of underwater multi-source acoustic signal is studied.According to the derivation of the theoretical model and the analysis of the actual detection experiment, the demodulation algorithm of the measured signal is studied on the platform of MATLAB.The detection signal is pretreated with 5.3 times smoothing filtering method, which minimizes the influence of frequency band caused by natural water surface fluctuation on signal demodulation.The useful signal band is separated from the interference signal by wavelet packet decomposition and reconstruction.The signal Hilbert transform, modulus calculation and smoothing filtering are used to separate the original overlapping frequency bands. Finally, the sound frequency of multiple underwater sound sources is obtained by searching the center value of the frequency band.A underwater multi-source demodulation system is designed and built under the optical darkroom.According to the characteristics of the detection signal and the requirements of the actual detection technology, a set of underwater multi-source demodulation system is designed, and some key devices are analyzed and selected according to the actual detection requirements.The experimental system is built and debugged under the optical darkroom to meet the detection requirements.In order to verify the feasibility and accuracy of the demodulation method proposed in this paper, a laser coherent detection system is used to detect underwater targets with multiple frequency combinations of sound frequency in 1kHz-10kHz.The detection efficiency of underwater acoustic signal frequency information is evaluated.The experimental results show that the proposed method can detect the frequency information of underwater complex acoustic signals and provide a new idea for underwater acoustic signal processing.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB56

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