Study On Multiple Sub-array Beam-space High Resolution Uncerwater Acoustic Imaging Technology

The precondition of the efficient research in ocean exploring resource, ocean engineering and other correlated fields is acquiring the credible information of underwater scene. As the most obvious measure to reflecting the information is underwater acoustic image, the multibeam bathymetry system with the capability of 3-D imaging and the side scan sonar with the capability of 2-D imaging become the ocean survey instruments used in above fields most broadly. And internationally the two kinds of instruments are all developing toward the direction that they can combine and provide information of terrain and physiognomy at the same time. The background of this paper is the project supported by National High Technology Research and Development Program of China, "Shallow Water Wide-coverage Multibeam Bathymetry System" and the project supported by Small and Medium-sized Enterprise Innovation Funds of Heilongjiang province, "High Resolution Shallow Water Multibeam Bathymetry System", etc. The purpose of this paper is to develop a set of high resolution seafloor terrain and physiognomy detection system that has the ability of underwater scene 2-D/3-D imaging on the basis of the theory of multibeam bathymetry system, and to research the correlated techniques. So the paper can be divided into two parts that theory research and engineering realization. The theory research includes:estimation of direction of arrival (DOA) and intensity of arrival (IOA) of seabed backscattering using multiple sub-array beam-space seafloor detection algorithm and the usability of the algorithm in the seafloor terrain and physiognomy detection system and sonar image segmentation algorithm based on Markov random field model. The engineering realization includes:the real-time realization of multiple sub-array beam-space seafloor detection algorithm and the design, realization and test proof of high resolution seafloor bathymetry and physiognomy detection system. Firstly, based on analysis of researching course of the correlated fields of underwater acoustic image processing, the key problems, which need to be resolved when realizing the high resolution seafloor terrain and physiognomy detection system, are discussed. And then to solve the problem of the estimation of DOA and IOA of the seabed backscattering signal, two kinds of new algorithm of signal processing, Multiple Sub-array Beam-space CAATI and Multiple Sub-array Beam-space Root-MUSIC, have been proposed. The estimation performance of two kinds of algorithm in the case of low SNR and few snaps has also been studied by computer simulation. And the processing of the sea test data and the simulation underwater scene data according to the IHO standard confirms the usability of the algorithm further more.In the part of sonar image processing, to the problem of traditional image segmentation algorithm based on Markov random field model, such as inaccurate model parameter, long resolving time and easy to trap in local optimum solution etc, a simplified model with fixed parameters is proposed. By applying the algorithm to the synthesized texture image and actual side scan sonar image, the practicability and segmentation performance of the algorithm have been analyzed theoretically.At the aspect of the architecture of the parallel processing platform, a new direct interconnect networks topology, generalized K-ary n-cubes networks based on k-ary n-cubes networks is proposed and the topological properties and routing algorithms have been researched too. After analyzing the algorithm computation load, a theory has been known that the Eigenvalue decomposition (EVD) of average covariance matrix is the part in which most computation load concentrates. So the method of EVD based on parallel Jacobi and the realization on FPGA have been studied. A parallel signal process system based on FPGA and DSP has also been designed and actualized.At last, the engineering realization and performance testing of high resolution seafloor terrain and physiognomy detection system have been completed.