大场景宽测绘带高分辨合成孔径声纳运动补偿与成像方法研究

Synthetic Aperture Sonar (SAS) is a new type of high resolution underwater imaging sonar, which can obtain some constant two-dimensional high resolution images with full range. For this reason, SAS is widely used in underwater topography and geomorphology mapping, small target detection and high resolution reconnaissance in recent years. Motion compensation (MOCO) is a key step in SAS imaging process, which must be carried out if the motion trajectory of sonar deviates from the ideal trajectory more than 1/8 of the working wavelength. Otherwise the imaging quality will be seriously affected. In order to further improve the image quality of SAS, optimize the performance of SAS system, and enhance the practical application ability, the research on motion compensation and imaging method of large scene, wide mapping swath and high resolution synthetic aperture sonar is carried out in this application. Through the research, (i) a general method is proposed firstly to accurately calculate the actual positions of different array elements of sonar array based on the output data of high-resolution sensors, and some best two-dimensional high-resolution images in theory are obtained combining the point-by-point motion compensation and imaging method;(ii) base on the output data of high-resolution sensors, the six-freedom degrees motion errors are estimated, which are compensated by the line-by-line MOCO method fully and rapidly proposed in this application;(iii) when the resolution of sensors installed in SAS carrier is too low to meet the MOCO requirements, some motion error estimation methods are proposed based on the echo data received by the sonar receiver, and some reasonable line-by-line motion compensation and imaging methods are established, which are very meaningful to realize real-time motion compensation and high resolution imaging independent of high-precision sensors.

合成孔径声纳（SAS）是一种新型高分辨水下成像声纳，能够获得全距离恒定的二维高分辨图像，广泛应用于水下地形地貌测绘、小目标探测及高分辨侦察等领域。运动补偿是SAS成像过程中极为关键的步骤，当声纳载体的运动轨迹偏离理想航迹超过工作波长的1/8时，必须进行运动补偿，否则会严重影响成像质量。为进一步提高SAS图像质量、优化SAS系统性能、提升SAS系统实际应用能力，本申请拟开展大场景宽测绘带高分辨SAS运动补偿与成像方法研究。通过研究，既能在SAS安装高精度传感器时，充分利用传感器输出数据推算声纳基阵不同阵元的实际位置，结合逐点运动补偿与成像方法，获取更高质量的二维高分辨图像，结合逐线运动补偿与成像方法，实现快速运动补偿与图像重建；又能在SAS安装的传感器测量精度不高时，基于回波数据快速准确地估计运动误差，建立合理的逐线运动补偿与成像方法，实现不依赖于高精度传感器的实时运动补偿与高分辨成像。

合成孔径声纳（SAS）是一种新型高分辨水下成像声纳，能够获得不依赖于工作频率和作用距离的二维高分辨图像，在水下地形测绘、小目标探测、水下考古、猎雷以及高分辨侦察等领域有着广泛应用。运动补偿是SAS成像过程中极为关键的步骤，对于提升SAS图像质量有着重要意义。本项目开展大场景宽测绘带高分辨SAS运动补偿与成像方法研究，提出多因素影响下基于高精度传感器的逐点运动补偿与成像方法，可根据高精度传感器数据利用空间直角坐标转换原理准确推算出非停走停模式下声纳基阵不同阵元在不同脉冲收发时刻的实际位置和声纳基阵的六自由度运动误差，结合准精确的声纳基阵实际位置和逐点算法，可以获得理论最优的二维图像；提出方位空不变六自由度运动补偿与成像快速算法，结合传统距离多普勒算法和线频调变标算法，可在保证图像质量的基础上，有效提高逐点运动补偿与成像的运算效率；提出六阶方位空变运动补偿与成像快速算法，考虑六自由度运动误差的六阶方位空变特性，可在进一步优化图像质量的同时，保证运动补偿与成像效率；提出大场景宽测绘带情形基于回波数据的逐线运动补偿与成像方法，利用偏置相位中心阵元法推导侧摆和偏航误差，提出三角函数拟合的运动误差修正方法，综合利用子孔径运动补偿、单基等效处理以及传统单阵逐线成像算法，实现运动补偿和高分辨成像。仿真分析和实测数据成像验证了上述所提算法的有效性。通过本项目研究，可以保证无论SAS系统是否安装高精度传感器，均可以利用本项目所提方法有效解决多子阵SAS的运动补偿和成像问题。因此，本项目研究成果可为进一步优化SAS系统性能、提升SAS系统实际应用能力提供重要的理论支撑。