Application of A* algorithm for real-time path re-planning of an unmanned surface vehicle avoiding underwater obstacles

This paper describes path re-planning techniques andunderwater obstacle avoidance for unmanned surface vehicle （USV）based on multi-beam forward looking sonar （FLS）. Near-optimalpaths in static and dynamic environments with underwaterobstacles are computed using a numerical solution procedure basedon an A algorithm. The USV is modeled with a circular shape in 2degrees of freedom （surge and yaw）. In this paper, two-dimensional（2-D） underwater obstacle avoidance and the robust real-time pathre-planning technique for actual USV using multi-beam FLS aredeveloped. Our real-time path re-planning algorithm has beentested to regenerate the optimal path for several updated frames inthe field of view of the sonar with a proper update frequency of theFLS. The performance of the proposed method was verifiedthrough simulations, and sea experiments. For simulations, theUSV model can avoid both a single stationary obstacle, multiplestationary obstacles and moving obstacles with the near-optimaltrajectory that are performed both in the vehicle and the worldreference frame. For sea experiments, the proposed method for anunderwater obstacle avoidance system is implemented with a USVtest platform. The actual USV is automatically controlled andsucceeded in its real-time avoidance against the stationary underseaobstacle in the field of view of the FLS together with the GlobalPositioning System （GPS） of the USV.     

海底障碍物探测技术

从障碍物探测的方法原理、基本状况、应用实例效果等方面分析目前国内外常用的海底障碍物探测技术方法,探讨各种方法的优缺点及适用条件,总结海底障碍物探测现状及发展趋势。     

美国潜艇拖曳阵声呐技术特点及发展趋势

根据现有公开技术资料,对美国潜艇拖曳阵声呐的发展情况、技术特点进行阐述,并预测了拖曳阵声呐的发展趋势。     

Underwater digital terrain model with GPS-aided high-resolution profile-scan sonar images

The whole procedures of underwater digital terrain model (DTM) were presented by building with the global positioning system (GPS) aided high-resolution profile-scan sonar images. The algorithm regards the digital image scanned in a cycle as the raw data. First the label rings are detected with the improved Hough transform (HT) method and followed by curve-fitting for accurate location; then the most probable window for each ping is detected with weighted neighborhood gray-level co-occurrence matrix; and finally the DTM is built by integrating the GPS data with sonar data for 3D visualization. The case of an underwater trench for immersed tube road tunnel is illustrated.     

基于统计量的声呐图像目标检测算法

水下声呐图像目标检测问题是一项重要而困难的工作,采用滑动窗计算图像中各像素点处邻域像素灰度的统计量,利用最大熵图像分割算法确定检测阈值,并利用均值、标准差、偏态和峰度等统计量对算法进行了仿真验证,对声呐图像中的目标回波区和阴影区域均可实现较好的检测效果。结果表明,该方法具有原理简单、运算效率高、实时性好等特点,具有较强的工程应用价值。     

拖曳线列阵声呐判断左右舷模糊方法研究

潜艇性能的不断提高,促进了拖曳线列阵声呐的快速发展.拖曳线列阵声呐有其独特的优点,但它的左右舷模糊问题靠其本身是无法克服的.本文分析了判断左右舷所用的转向法及与其他声呐协同法的不足之处,同时提出了2部拖曳线列阵声呐协同使用的方法.     

地下连续墙接缝渗漏检测及防治技术

为高效解决深基坑工程地下连续墙渗漏水问题,依托南宁地铁3 号线金湖广场站富水深基坑工程,开展声呐渗流检测技术应用研究。首先,对65 幅地下连续墙止水帷幕实施声呐渗流检测,得到相应位置流速、流向、流量和渗透系数等数据,反演绘制三维可视化渗流场,准确定位地下连续墙薄弱部位; 然后,据此进行局部袖阀管注浆防渗漏处理; 最后,复测检验注浆效果,基坑渗漏水量得到有效控制。该技术能够为深基坑地下连续墙的渗流流速检测预警、渗漏风险控制管理、渗水事故应急处置提供完整可行的解决方案。     

拖曳声纳搜潜使用方法研究

水面舰船拖曳线列阵声纳在对潜远程警戒与搜索中起着重要作用。但由于拖曳声纳物理结构的特殊性,其对水面舰艇的机动性也有一定的限制。据此,讨论了使用拖曳声纳的三种可行搜索方式,给出了各自使用的限制条件,并根据具体的海洋环境,计算了搜索效率。     

某型声纳测距工况误差分析

被动测距声纳由于其不主动发射声波被广泛应用于潜艇。国产某型声纳在用户使用过程中发现测距精度偏低。笔者在对被动测距声纳测距原理分析的基础上,结合多年维修经验,给出了几项措施,能够最大限度的保证该型声纳的测距精度。     

宽带宽波束SAS成像研究

宽带宽波束合成孔径声呐（WBSAS）成像不同于传统的窄带合成孔径声呐成像存在自身特有的问题。适用于传统窄带合成孔径成像声呐成像的菲涅耳近似和其它一些简化不再适用于WBSAS成像处理。大距离徙动给成像、运动补偿和自聚焦提出了严峻的挑战。着重探讨WBSAS与传统的窄带合成孔径声呐成像的区别。