基于无人机自标定的表面流场测量方法

针对无人机图像标定及配准等关键技术问题,提出了一种基于无人机自标定的表面流场测量方法。该方法基于运动恢复结构(SFM)三维重建技术完成无人机图像自标定,采用加速稳健特征变换(SURF)方法对无人机图像进行配准。将该方法应用于南京市三汊河河口闸下游表面流场测量,结果表明,基于SFM的三维重建精度可以满足自标定的要求,不需要另外设置地面控制点对无人机图像进行标定,简化无人机标定过程,SURF方法可有效地消除无人机位置飘移对表面流场测量结果的影响。

石化危险事故搜救移动机器人SLAM问题研究

石油化工火灾火势发展快,火情易变,且时有突发险情,后果难以预料。因此,需要充分利用耐高温高压的移动机器人,进行内部侦查,查找有无人员伤亡,查明燃烧位置、形式以及面积,然后再投入充足的救援力量,以快制快,确定进攻和撤退路线。针对危险现场复杂环境,噪声大,救援迫切性要求,文章提出一套具有高鲁棒性、快速定位的单目视觉SLAM系统。主要内容是,首先,为减少危险环境中图像存在大噪声,论文提出一种基于双向匹配机制的SURF方法,在快速提取图像的点特征的同时保证了稳定可靠性。然后,在这些提取得点特征基础上,因为救援任务的迫切性,论文设计了一种融合互信息和图像信息的路标和位置更新方法,它通过不同时刻路标的互信息增益判断是否进行状态更新,来提高定位的快速性。在此基础上,设计和实现基于扩展卡尔曼滤波技术（Extended Kalman Filter,EKF）的单目视觉SLAM系统。最后,通过实验验证了所设计的SLAM系统具有较高可靠性和定位速度快等优点。

结合角点和局部特征描述的标版广告检测算法

针对媒体中广告元素检测需求的多样化,通常需要检测视频或图像中是否存在相应的标版类广告,提出了一种结合Harris角点和SURF描述子的广告图标检测算法。算法利用了Harris角点物理意义明确、稳定性、鲁棒性好、提取用时较快等优点,用于提取图像的特征点;并利用SURF描述子具有的良好的特征描述作用,以及对旋转、亮度等变换的适应性,对特征点生成多个不同尺度的SURF描述子,以用于特征描述和图像间的比较,从而解决图像匹配中的尺度变化适应性问题。使用实际用例对方法进行验证,结果表明方法较之于SURF算法具有更好的快速性,且效果良好,检测结果准确。

Correction of Wave Surge Forces to Improve Surf-Riding/Broaching Vulnerability Criterion Check Accuracy

Surf-riding/broaching is one of the five stability failure modes to be included into the International Maritime Organization (IMO) second generation intact stability criteria (which are risk-based stability criteria) that can ensure the safety of ships in actual seaways more effectively. This study focuses on the influence of wave surge force prediction accuracy on surf-riding/broaching vulnerability criterion check result. Firstly, it is demonstrated that the wave surge force prediction method adopted in the current vulnerability criterion check procedure is not accurate and may lead to wrong conclusions. The experimental data from captive model test and the numerical result based on 3D panel method both indicate that the diffraction effect must be considered to correctly predict the wave surge forces. Besides, sophisticated methods are not suitable for Level 2 vulnerability criterion check due to their complexity. Therefore, an empirical formula for wave surge force correction based on sample ship calculation results is proposed. The proposed empirical correction formula can effectively improve the vulnerability criterion check accuracy and thus contribute to the design and safety of the ships which are vulnerable to this stability failure mode. © 2017, Shanghai Jiaotong University and Springer-Verlag GmbH Germany.