【作者】 余赟；

【导师】 惠俊英；

【作者基本信息】 哈尔滨工程大学 ， 水声工程， 2011， 博士

【摘要】 水声技术得到了长足的发展,但同时也面临着新的挑战。随着安静型技术的进步,潜艇的辐射噪声不断地降低,如何远距离探测安静型潜艇成为难点。拖曳线列阵声呐在反潜战中扮演着重要角色,也是最主要的鱼雷报警声呐,是声呐的重要发展方向之一,但此类声呐迄今仍无技术使它们具有被动测距、测速功能。海洋波导的重要特点是低频声场存在稳定可观察的干涉结构,本文欲基于声场的物理本质探索新的目标检测、识别和被动测距技术。声场的干涉结构是目标距离、深度及频率的函数,应通过某种时空变换对其简化,增强有用信息以便应用。文中以浅海低频声场的干涉结构为研究对象,重点关注了线谱甚低频声场干涉结构和连续谱低频声场干涉结构。对于前者,给出了浅海分层介质中波导简正波的矢量场,探讨了复声强的表述及其特征,定量分析了垂直(交互)复声强和水平交互复声强的无功分量和有功分量,并对复声强和交互复声强的相位角分布进行了数值计算。对于后者,基于波导不变量理论框架描述了连续谱低频声场干涉结构(相干函数图或LOFAR图)上的干涉条纹；首次基于相干声场的时空滤波理论用功率响应函数、双频函数、扩展分布函数等推广了连续谱干涉结构的表征手段；通过仿真研究和海试数据分析对上述理论进行了验证并结合波导不变量作了特征分析；并对其他形式的连续谱干涉结构作了简介。对线谱甚低频声场干涉结构的研究表明：当声场中只存在两阶简正波时,合理布放垂直双传感器的深度,可以使声压互谱(或分点测量的声压水平振速互谱)有功分量的正负号在较远距离处与水平距离无关,若定义声压互谱有功分量正负号变号的深度为临界深度,则通过与临界深度比较,可以对目标深度进行分类,即可以判断目标为浅声源(水面舰艇)或航深较大运动平台(潜艇)；声压互谱无功分量正负号分布随水平距离呈周期性变化,利用建模或等效深度近似模型预报水平相干距离,并基于干涉结构测量目标渡越一个水平相干距离尺度的时间,可实现对目标径向运动速度的估计。运用Pekeris波导有效深度的概念建立了声压互谱有功分量正负号分布特性的近似理论分析,加深了对浅海低频声场特性的理解,并推导了双水听器合理的布放深度公式,以指导算法的实际使用。理论分析表明：当两个水听器的布放深度之和近似等于有效深度时,声压互谱有功分量正负号分布才与水平距离无关,值得注意的是,临界深度可调,通过设置一期望的临界深度,则双水听器的布放深度唯一确定。进一步的稳健性分析表明：深度分类算法和距变率估计算法对不同浅海环境是可以适用的。对连续谱低频声场干涉结构的研究表明：浅海低频声场中LOFAR图上的干涉条纹为一族类双曲线,通过干涉条纹方程将波导不变量、最近通过距离与线速度比及最近通过时刻等运动参数联系起来；时空滤波理论的四个系统函数中仅有一个是独立的,每个系统函数均能描述声场连续谱干涉结构的特性,但各个系统函数均能特别突出干涉结构某方面的特征,各有特色。结合LOFAR图和方位时间历程图提出了基于Hough变换的参数估计方法,分有无最近通过距离进行了仿真研究和海试数据分析,验证了算法的正确性和可行性,并表明其有较高的参数估计精度。在参数估计的基础上,提出了四种有最近通过距离时的基于水平双阵(元)的被动测距算法,并进行了定位精度分析,针对算法二稳健性差的缺点,提出了相应的改进算法。提出了两种无最近通过距离的双阵(元)被动测距算法,并进行了仿真研究、定位精度及稳健性分析,随后又提出了相应的改进算法,以提高低信噪比时的测距精度。本文所提出的参数估计和被动测距算法在海洋综合监测、海岸预警系统、航空浮标、潜标、海洋研究、声学测量、鱼雷报警等诸方面有重要应用前景,若要用于工程实际,还需做深入的海试研究。更多还原

【Abstract】 Underwater acoustic technology has made great progress recently, but it also faces new challenges. With the development of quiet submarine, whose radiated noise has been greatly reduced, how to detect the quiet submarines in long range becomes difficult. Towed line array sonar is one of the important sonar developing directions, because it has been playing an important role in anti-submarine warfare and torpedo alarm. However, until now there is no any technology making this sonar possessing the functions of passive ranging and velocity estimation. The important feature of the ocean waveguide is that the stable interference structure can be observed in the low-frequency sound field. The purpose of this paper is to explore new target detection, identification and passive ranging techniques based on the physical nature of the sound field.Sound field interference structure is the function of the range, the depth and the radiated noise frequency of the target, so it should be simplified by adopting space-time transformation to enhance useful information for application. The interference structures in shallow water low-frequency sound field have been researched and many attentions are paid to the line spectrum interference structures in the very low frequency sound field and the continuous spectrum interference structures in the low-frequency sound field. For the former, the vector field of normal modes in shallow water stratified medium waveguide is concerned, the expression of complex acoustic intensity, especially the analysis of their characteristics are proposed; the reactive component and active component of the vertical (interactive) or horizontal interactive complex sound intensity are analyzed quantitatively; Further more, the phase angle of complex acoustic intensity is discussed and its distribution regularities are analyzed numerically. For the latter, the interference striations on the continuous spectrum interference structures, also called LOFARgram or coherent function records, in the low-frequency sound field are described based on the theoretical framework of waveguide invariants; Other than coherent function, the power response function, dual-frequency function and spread function from the space-time filtering theory of coherent sound field are adopted to promote the characterization means for continuous spectrum interference structures; The coincidence of the results from the simulation and sea trial, which are analyzed combined waveguide invariants, suggests the correctness of the theory; Then continuous spectrum interference structures in other scenarios are introduced briefly.Researches on the line spectrum interference structure in very low frequency sound field show that:the sign of the sound pressure cross-spectrum (or cross-spectrum between sound pressure and horizontal velocity) active component is independent of range by placing the receiving transducers in appropriate depths when only two normal modes trapped in the waveguide, so the target can be classified by comparing its depth with the critical depth on which the sign of the sound pressure cross-spectrum active component changed oppositely, in other words, the sound pressure cross-spectrum active component can be used to tell whether the sound source is near the surface (surface ship) or underwater (submarine); while the active component sign of the sound pressure cross-spectrum changes periodically with the horizontal range, and the period is defined as horizontal coherence distance which can be obtained by acoustic field modeling or predicting using effective depth approximate model, then the target radial velocity can be estimated by measuring the time during which the moving target passes one horizontal coherence distance scale. Approximate theoretic analysis of sound pressure cross-spectrum active component characteristics which deepens the understanding to the characteristic of shallow water low-frequency acoustic field is proposed in the paper combined with the concept of effective depth, and the prediction formula of appropriate deploying depth of transducers is presented which can be used to guide the actual application of the algorithm. The theoretic analysis indicates that the sum of the bi-hydrophone depths should be equal to the waveguide effective depth, then the sign distribution of the sound pressure cross-spectrum active component is independence on the horizontal range, and bi-hydrophone deploying depth is uniquely determined by setting a expected critical depth which is adjustable. Further stability analysis shows that the depth classification algorithm and radial velocity estimation algorithm are applicable to the different shallow water environment.Researches on the continuous spectrum interference structure in low frequency sound field show that:the interference striations on the LOFARgram obtained in the shallow water low-frequency acoustic field are a family of quasi hyperbolas, and the waveguide invariant, the range of the closest point of approach and the corresponding time are linked by the interference striation equation; Among the four system functions of the space-time filter theory, there is only one independent, every function can be adopted to describe the characteristics of the continuous spectrum interference structure, however, each system function owns special characteristics, which can give prominence to certain features of the interference structure. Hough transform based parameter estimation algorithms are proposed combining the image processing to LOFARgram and bearing-time records, and the correctness and feasibility of the parameter estimation algorithms under two scenarios that is whether there is closest point of approach have been validated by the simulation researches and sea trial data analysis, which also show its high accuracy of parameter estimation. For the scenario including the closest point of approach, four dual-array (element) based passive ranging algorithms are proposed when the estimated parameters are as the prerequisite, and the positioning accuracy is analyzed for the four algorithms. And the improved positioning algorithm is studied to overcome the poor stability of the second algorithm. For the scenario without the closest point of approach, two dual-array (element) based passive ranging algorithms are proposed, and then the corresponding simulation researches, accuracy analysis and stability analysis are finished. Furthermore, the improved positioning algorithms for both passive ranging algorithms are proposed to improve the positioning accuracy when the SNR is low.The parameter estimation algorithms and passive ranging algorithms proposed in this paper have important application prospect in many aspects, such as marine integrated monitoring, coastal forecasting and alarming system, airborne sonobuoy, marine research, acoustic measurement, torpedo alarm and so on. Further researches by sea trial will be needed for their practical engineering applications.更多还原