面向ARV的视觉辅助水下对接方法研究     

魏志祥  吴超 《海洋工程》2021,39(1):91-99,152

针对水下机器人作业过程中的近距离引导水下对接问题,以自治缆控水下机器人(ARV)为研究对象,为实现快速、高精度的水下对接,设计了基于反射光源识别的单目视觉辅助水下对接方法。通过在对接口布置反光带并将其作为目标图像,设计了图像处理和特征点提取的算法,经过图像特征信息的分析处理,优化算法的时间复杂度,提高了特征点提取的准确率和识别效率。最后设计了传统的引导灯方案与反光带方案的对比试验,验证算法的可行性,证明在水下环境下识别反射光源的方法极大提升了位置估计的准确率,同时在计算速度上也有显著提高,弥补了传统水下对接方法中精度不足或计算量大的缺陷,更好地满足了ARV水下对接的需求,能为潜水器实现水下自主对接提供参考依据。  相似文献   

A binocular parallel rendering method for VR globes     

Wumeng Huang 《International Journal of Digital Earth》2020,13(9):998-1016

ABSTRACT

The scene-rendering mechanism based on binocular vision is one of the key techniques for the VR globe to achieve immersion-type visualization of global 3D scenes. However, this special rendering mechanism also requires that the 3D scene is continuously drawn twice within one frame, which significantly affects the rendering efficiency of VR globes. Therefore, we propose a binocular parallel rendering method. This method first improves the current rendering process of VR globes by assigning the rendering tasks for the left and right camera of VR to be processed on different CPU cores, thereby achieving parallel rendering of binocular scenes. Second, due to the problem of inconsistent resolution of binocular scenes caused by different viewpoints for the left and right cameras, we propose a resolution synchronize algorithm. this algorithm conducts real-time synchronization on the resolution of scene in the rendering process and thus avoids the problem of erroneous binocular stereo matching. Finally, we validate the effectiveness of the method in this paper through experiments. The results of experiments indicate that while the method in this paper can ensure the consistency of binocular scene resolution, it can decrease the frame time of VR globes by approximately 27% on average.  相似文献   

IMU辅助下的单目视觉坐标传递     

郭若南  蒋郡祥  牛小骥  史俊波 《测绘通报》2020,(3):7-11

针对管线测量中由于GNSS RTK卫星信号遮挡或测站不易架设等原因无法提供坐标的场景,本文提出了一种IMU辅助下的单目视觉坐标传递方法,用于延伸RTK测得的精密坐标。首先在两个已知的RTK点上架设相机拍摄图像,同时采集IMU数据;然后对图像进行特征提取和匹配,恢复帧间旋转、平移及尺度;最后三角化待测点,以获得待测点在真实尺度的相机坐标系下的坐标。受IMU静基座初始对准方法的启发,本文利用重力矢量和相机光心间矢量分别在地理坐标系和相机坐标系下的投影求解这两个坐标系间的旋转矩阵,进而求得待测点在地理坐标系下的三维坐标。相对于其他测量手段,本文方法灵活便捷、设备轻便、操作简单,且一次采集即可获取相机视场中的任意共视点坐标。试验结果表明,本文提出的坐标传递方法所得的平面坐标的误差平均值为0.12 m,高程误差的平均值为0.2 m。  相似文献   

Computer vision applied to wave flume measurements     

G. Iglesias  O. Ibáñez  J.R. Rabuñal 《Ocean Engineering》2009,36(14):1073-1079

A new measurement system for laboratory wave flumes is presented, based on the analysis of digital images by means of computer vision techniques. Unlike conventional wave gauges, the system detects the motions of the free surface along the flume section of interest as opposed to a point. A further advantage lies in that no sensors are necessary within the flume. The system is particularly useful in the case of wave flume tests of floating bodies, such as an oil boom—the motions of the model boom are measured without any sensors in contact with it, which otherwise might place constraints on its displacements. The new method is validated based on free surface measurements carried out with a conventional wave gauge, with excellent results.  相似文献   

多媒体电子地图界面视觉感受实验设计     

柳佳佳  王浏毅  王海龙 《测绘科学》2009,34(3)

现时的电子地图与以往的相比,可以说是品种繁多、技术成熟、界面精美,而且正在向3D地图的方向迈进。电子地图除功能表现出灵活性、多样性以外,图上信息获取的方式也更加人性化,因此,电子地图的界面设计要在强化原有视觉效果的基础上,力求以更强的视觉冲击来提高电子地图的表现力。为此获取真实的用户体验数据是有必要的也是必须的。从使用者对地图界面及其要素的视觉感受特点出发,通过物理—心理—生理学的方法对电子地图界面怎样设计才能为使用者所接受的问题进行实验研究,改进地图界面的设计方法,是实验系统设计和制作的实际意义所在。  相似文献   

浅谈错视及其纠正与地质制图     

黄德纯 《湖南地质》1998,17(3):197-200

本文侧重论述了错视,错视的表现及其利用与纠正,同时举例论述了正确运用错视对提高地质制图质量的重要性。  相似文献   

基于双目视觉的双臂协作教学机器人研究与设计     

温秀兰  胡仰  姚波  赵艺兵  宋爱国  崔伟祥 《南京气象学院学报》2021,13(3):304-310

为弥补智能制造、机器人工程等新专业实验装置短缺、学生创新实践能力亟待提升等问题,本文设计了一种基于双目视觉的双臂协作教学机器人.双臂机械部分设计呈对称结构,底座大而稳定,可以降低制造成本及协作抓取难度;研究设计的示教动作还原算法和重投影误差最小化算法,可以提升机器人末端位姿数据采集精度,使双臂协作抓取更准确稳定.该系统不仅能够通过上位机拖动控制双臂运动完成示教编程及动作组实验,而且还能够进行基于视觉引导的图像处理及单臂抓取实验、运动分析实验、在线编程与协调抓取开放实验.该系统成本低、功能丰富、综合性强,且兼具拖动示教与开放性特点,有助于提升学生创新实践能力,非常适合在智能制造、机器人工程等专业实验教学过程中推广应用.  相似文献   

Uncertainty,entropy, scaling and hydrological stochastics. 2. Time dependence of hydrological processes and time scaling / Incertitude,entropie, effet d'échelle et propriétés stochastiques hydrologiques. 2. Dépendance temporelle des processus hydrologiques et échelle temporelle     

《水文科学杂志》2013,58(3)

Abstract

The well-established physical and mathematical principle of maximum entropy (ME), is used to explain the distributional and autocorrelation properties of hydrological processes, including the scaling behaviour both in state and in time. In this context, maximum entropy is interpreted as maximum uncertainty. The conditions used for the maximization of entropy are as simple as possible, i.e. that hydrological processes are non-negative with specified coefficients of variation and lag-one autocorrelation. In the first part of the study, the marginal distributional properties of hydrological processes and the state scaling behaviour were investigated. This second part of the study is devoted to joint distributional properties of hydrological processes. Specifically, it investigates the time dependence structure that may result from the ME principle and shows that the time scaling behaviour (or the Hurst phenomenon) may be obtained by this principle under the additional general condition that all time scales are of equal importance for the application of the ME principle. The omnipresence of the time scaling behaviour in numerous long hydrological time series examined in the literature (one of which is used here as an example), validates the applicability of the ME principle, thus emphasizing the dominance of uncertainty in hydrological processes.  相似文献   

A Modified Neural Network for Improving River Flow Prediction/Un Réseau de Neurones Modifié pour Améliorer la Prévision de L'Écoulement Fluvial     

《水文科学杂志》2013,58(2)

Abstract

Artificial neural network (ANN) models provide huge potential for simulating nonlinear behaviour of hydrological systems. However, the potential of ANN is yet to be fully exploited due to the problems associated with improving the model generalization performance. Generalization refers to the ability of a neural network to correctly process input data that have not been used for calibrating the neural network model. In the hydrological context, better generalization performance implies higher precision of forecasting. The primary objectives of this study are to explore new measures for improving the generalization performance of an ANN-based rainfall–runoff model, and to evaluate the applicability of the new measures. A modified neural network model (entitled goal programming (GP) neural network) for modelling the rainfall–runoff process has been developed, in which three enhancements are made as compared to the widely-used backpropagation (BP) network. The three enhancements are (a) explicit integration of hydrological prior knowledge into the neural network learning; (b) incorporation of a modified training objective function; and (c) reduction of network sensitivity to input errors. Seven watersheds across a range of climatic conditions and watershed areas in China were selected for examining the alternative networks. The results demonstrate that the GP consistently outperformed the BP both in the calibration and verification periods and three proposed measures yielded improvement of performance.  相似文献   

Coupling between weather radar rainfall data and a distributed hydrological model for real-time flood forecasting / Couplage de données pluviométriques issues de radars météorologiques et d’un modèle hydrologique distribué pour la prévision de crue en temps réel     

《水文科学杂志》2013,58(6)

Abstract

Abstract After the destructive flood in 1998, the Chinese government planned to build national weather radar networks and to use radar data for real-time flood forecasting. Hence, coupling of weather radar rainfall data and a hydrological (Xinanjiang) model became an important issue. The present study reports on experience in such coupling at the Shiguanhe watershed. After having corrected the radar reflectivity and the attenuation data, the weather radar rainfall was estimated and then corrected in real time using a Kalman filter. In general, the precipitation estimated from weather radar is reasonably accurate in most of the catchment investigated, after corrections as above. Compared to the results simulated by raingauge data, the simulations based on the weather radar data are of similar accuracy. Present research results show that rainfall estimated from the weather radar, the radar data correction method, the method of coupling, and the Xinanjiang model lend themselves well to application in operational real-time flood forecasting.  相似文献