【作者】 张晓琳；

【导师】 唐文彦；

【作者基本信息】 哈尔滨工业大学 ， 仪器科学与技术， 2010， 博士

【摘要】 水下目标的特征提取及识别技术是未来海洋工程所要研究的主要技术之一。本文的研究目的是从水表面声波中提取出水下声场信息,为航空遥测潜艇等水下目标的进一步探索奠定技术基础。本文研究基于激光干涉的水表面声波探测技术,从水面散射光和参考光的干涉信号中解调出水表面声波的频率和振幅等信息,从而实现水下目标的探测。围绕这一主题,主要进行如下的研究工作:以基尔霍夫理论为基础,提出水面散射场强度空间分布的理论模型,并进行实验验证。借助格林定理得到水面散射场强度的积分表达,分析水面散射光强与入射角、散射角、入射光强、入射光波长、观测距离、介质折射率等诸多因素的定量关系。着重探讨入射光与散射光的几何条件、水表面声波振幅、波长对散射光强的影响,并进一步研究散射场强度和相位的概率分布问题,进行水下声场信息的探测效率评估。研究激光干涉法探测水表面声波的原理,分析水面散射光与参考光干涉信号的时域和频域图谱特征。分别阐述无水下声源、单一水下声源和多个水下声源时水表面声波频率和振幅信息的计算方法。在光学暗室下建立了一套采用该方法探测水下声信号的实验装置,实现了发声频率在100Hz-18kHz的水下目标的实时探测。为精确获取水下声源的发声频率,研究水下声信号频率提取技术。针对干涉条纹上出现的短时间尺度的高频相位变化,采用局部数据处理技术解调出水下声信号的频率信息,实验结果表明:相对误差为0.7%,标准偏差小于8Hz。由于小波分析在时域和频域都有表征信号局部信息的能力,本文探讨小波及小波包在水声信号检测中的应用,把原始干涉信号的高频载波成分剥离并重构,更加准确的获取水下声场信息。解调出的中高频水下声信号频率相对误差为0.3%,标准偏差小于5Hz。更多还原

【Abstract】 The feature extraction and recognition of underwater objects is one of the major techniques to be studied in future ocean engineering. The purpose of the present study is to extract underwater acoustic information from the acoustic waves on the water surface and lay a technological foundation for the further exploration into the aeronautical telemetering of underwater objects,such as submarines.This paper proposes a water surface acoustic detection technique based on laser inference. The frequency and amplitude information of acoustic waves on the water surface is demodulated from the interference signals of the scattered light and reference light on the water surface in order to detect underwater objects. The following work has been done concerning this topic:A theoretical model for the spatial distribution of the intensity of water-surface scattered field is proposed on the basis of Kirchoff’s theory and the simulation and experimental verification have been conducted. Green’s theorem is used to derive the integral expression of the intensity of the water-surface scattered field and quantitative relations between the intensity of water-surface scattered light and many factors such as incident angle, scattering angle, microscopic fluctuation of the water surface, intensity of incident light, wavelength of incident light, observation distance, and refractive index of medium. Focused discussion is performed about the effects of the geometric conditions of the incident light and scatter light and the amplitude and wavelength of acoustic waves on the water surface on the intensity of scattered light. The further research is done on the probability distribution of the intensity and phase of scattered field. The efficiency of underwater acoustic information detection is evaluated.The basic mechanism by which the laser interference process is used to detect acoustic waves on the water surface is studied, and the time-domain and frequency-domain spectral characteristics of the signals of inference between scattered light and reference light on the water surface are analyzed. Calculation methods for the frequency and amplitude of sound waves on the water surface are explained respectively in the absence of underwater acoustic sources, in the presence of a single underwater acoustic source, and in the presence of multiple underwater acoustic sources. A set of experimental equipment is set up in a photographic laboratory to detect underwater acoustic signals with such methods and the real-time detection is realized for underwater objects with acoustic frequencies ranging 100Hz-18kHz. The underwater signal frequency extraction technique is studied in order to obtain the precise acoustic frequencies of undertaker acoustic sources. For the short-time-scale HF phase changes in the interference fringes, a local data processing technique is used to demodulate the frequency information of underwater acoustic signals. Experimental results show that: the maximum relative error is 0.7% and the standard deviation is smaller than 8Hz. As wavelet analysis is capable of characterizing local information of signals in both the time domain and frequency domain, this paper discusses the application of wavelets and wavelet packets in the detection of underwater sound signals. The components of HF carrier waves of the original inference signals are separated and reconstructed in order to obtain more accurate underground acoustic information. The maximum relative error of the frequencies of demodulated MF and HF underwater sound signals is 0.3% and the standard deviation is smaller than 5Hz.更多还原