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题名	多子阵SAS三维模型仿真与数据处理算法研究
作者	刘维
学位类别	博士
答辩日期	2008-05-30
授予单位	中国科学院声学研究所
授予地点	声学研究所
关键词	合成孔径声纳 多子阵 三维模型仿真 成像算法 运动补偿
其他题名	Research on Multiple-Receiver SAS Three Dimensional Model Simulation and Data Processing Algorithms
学位专业	信号与信息处理
中文摘要	合成孔径声纳(Synthetic Aperture Sonar, SAS)利用小孔径基阵移动形成虚拟大孔径，通过信号相干处理获取高分辨声图像。为了提高测绘效率和进行运动补偿，应用型合成孔径声纳系统普遍采用多子阵配置。高效的多子阵成像算法和高精度运动补偿算法是合成孔径声纳高分辨成像的关键。 因为多子阵合成孔径声纳方位向采样不均匀，单子阵频域算法不能直接应用于多子阵成像。受水中作用力的影响，合成孔径声纳基阵很难保持理想航迹，因此需要进行运动误差补偿。目前普遍采用的相位中心重叠运动补偿方法(Displaced Phase Center,DPC)对首向角估计精度较差，存在较大的累积误差；而高精度水下导航设备价格昂贵，另外由于图像坐标系和运动坐标系并不完全相同，导航数据需要映射到图像坐标系才能应用于合成孔径声纳运动补偿。无论是合成孔径成像算法的研究，还是高精度运动补偿算法的研究，都需要各种场景的成像数据作为基础。合成孔径声纳湖海试实验的成本非常高，而且成像场景非常有限。通过模型仿真获取研究数据可以降低实验成本，并得到多种成像场景的数据，为算法研究提供便利。本文的研究内容围绕这些问题展开，重点对合成孔径声纳三维模型仿真、多子阵合成孔径声纳快速成像算法、合成孔径声纳运动补偿方法进行了研究。 第一章和第二章阐明了本文研究工作的概况、意义和基础模型，是本文的研究基础。 第三章中，提出了一种基于三角面元和点目标混合建模的合成孔径声纳三维数据仿真模型，此仿真模型考虑了声纳基阵的三维六自由度运动、目标三维回波模型、阴影特征、目标后向散射特性、发射波束形状、发射和接收指向性等因素。使用本文提出的三维数据仿真模型可以实现对点目标和面目标的仿真。 第四章中，针对时域算法计算效率比较低的特点，研究了一种快速时域成像算法(FFBP 算法)并对该算法进行了一定的改进(不均匀图像分裂策略)；针对频域算法面临的不均匀采样问题，将NSFFT 和NFFT 方法引入到合成孔径声纳频域成像中来，并针对ω - k 和CS 算法进行了改进，使之可以适用于多子阵合成孔径声纳。最后对各种算法的计算效率进行对比分析。 第五章中推导了基于方向矢量的相位中心重叠运动补偿方法的递推关系式，并分析相位中心重叠方法存在的主要问题即重叠相位中心对的估计、首向角估计精度差和累积误差。针对重叠相位中心对估计的问题，文中提出采用Radon 变换提高相位中心对估计的精度；针对方向矢量估计精度差的问题，文中提出一种采用BDPC 和姿态传感器的运动误差补偿方法；针对累积误差的问题，文中提出一种采用BDPC 和图像数据相关的联合运动补偿方法；最后，文中还提出一种利用三维运动数据进行运动补偿的方法。 文中所有研究都给出了与之对应的仿真数据和湖海试数据的分析结果。 最后对全文的工作进行了总结。
英文摘要	Synthetic Aperture Sonar forms large virtual aperture by the movement of small physical aperture and produces high resolution sonar image by signal coherent processing in along-track direction. To increase mapping rate and compensate motion errors, almost all synthetic aperture sonar systems in practice deploy multiple receivers. High efficient multiple-receiver image reconstruction algorithms and high precision motion compensation algorithms are pivotal for high resolution SAS imaging. Standard image reconstruction algorithms in frequency domain can’t adapt to multiple-receiver SAS systems because of their non-uniform sampling in azimuth direction. With disturbances of water, carriers of sonar array can hardly maintain the ideal track. So motion compensation (MC) should be implemented to remove the motion errors. Displace phase center algorithm (DPCA), which is normally used in multiple-receiver SAS system, has disadvantages of low precision heading estimation and large accumulative error. High precision underwater navigation sensors are expensive. Besides these, there is difference between two dimensional image coordinate and three dimensional array motion coordinate. To utilize underwater navigation sensors’ data for motion compensation, projection algorithm should be developed. Both research of SAS image reconstruction and that of motion compensation need datasets of various situation. Lake-trial or sea-trial means a large expense of money and time. Simulation is an economical way to get data, by which we can create various datasets at will and present convenience for algorithm research. The thesis is trying to solve these problems and pays more attention to three dimensional model simulation, fast image reconstruction methods for multiple-receiver and SAS MC algorithms. The general situation、significance and basic mathematic model of the research work are introduced in the first and second chapter, which are the foundation of this thesis. In the next chapter, a 3-D SAS data simulating model is brought out. In this model, targets in simulated scene are composed of triangle faces and points. Important factors are considered in the model such as 3-D six degree motion、3-D echo model、shadow、backscattered characteristic、shape of transmitting beam、beam pattern of transmitter and receivers, and etc. By this simulation model, datasets of point-targets and 3-D targets can be generated. In the fourth chapter, attention is paid on increasing efficiency of SAS image reconstruction algorithms. A fast time domain SAS image reconstruction algorithm (FFBP) is researched. Improvement like non-uniform image factorizing along range direction is carried out to adapt the algorithm to synthetic aperture sonar imaging. Besides that, NSFFT and NFFT are applied to SAS frequency image reconstruction algorithms s like ω - k and CS. The improvements can adapt ω - k and CS algorithms to multiple-receiver synthetic aperture sonar, the samples of which are non-uniform in along track direction. Contents of the last chapter concerned with SAS motion compensation algorithms. Most of the pages in the chapter are focused on eliminating accumulative errors, estimation of displaced phase center pairs and three dimensional motion compensation methods. In the chapter, a recursive expression of DPC based on direction vector is presented. After that, the method is presented using Radon Transform to estimate displaced phase center pairs and along track velocity. Then two methods are presented to eliminate accumulating errors of DPC SAS motion compensation algorithm. One method is based on BDPC and altitude sensor data and the other is based on BDPC and image data correlation. At last, a new compensation method using three dimension motion data is brought out. All research works or methods in the thesis are validated by simulating data or trial data. Summarization is done in the end.
语种	中文
公开日期	2011-05-07
页码	166
内容类型	学位论文
源URL	[http://159.226.59.140/handle/311008/364]
专题	声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文
推荐引用方式 GB/T 7714	刘维. 多子阵SAS三维模型仿真与数据处理算法研究[D]. 声学研究所. 中国科学院声学研究所. 2008.

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