基于激光传感器的机器人地图构建方法

针对自主移动机器人局部地图构建问题,分析了几种应用较广的测距传感器的优缺点和地图构建中使用的激光传感器的数学模型及其非线性问题.在给出局部地图构建的一般模型的基础上本文提出了一种机器人局部地图构建的一种新方法,该方法针对传感器数据的不确定问题采用加权最小二乘方法对机器人在导航过程中的局部地图进行构建,具有实现容易、精度较高等特点.仿真和实验结果表明该方法在移动机器人使用激光测距传感器进行环境建模和地图构建过程中可以有效的减小直线拟合误差,进而达到有效建图的目的.     

基于全向移动机器人路径规划的蚁群算法研究

基于一种全向移动的自动导航机器人,分析此机器人的轨迹规划问题.通过栅格法构建所需的环境模型,选用蚁群算法并扩展改进算法背景,将其应用于该机器人的路径规划中.并且对算法中的转移概率,启发式函数进行改进,通过在不同复杂度的多张地图上进行仿真实验,结果证明了该算法的可行性,有效性以及对不同规模地图的适应性.同时基于蚁群算法中关键参数的选取对于路径规划的影响做了相应的对比分析,寻找到最合适的蚁群算法参数.     

基于霍夫变换与模板匹配的栅格地图拼接方法

单个机器人在面对大尺度环境时,建图结果往往存在较大误差.由多个机器人创建出局部地图后进行拼接可以很好地解决这一问题.本文提出了一种基于霍夫变换与模板匹配的地图拼接方法.首先,利用霍夫变换检测局部地图中的直线段,根据最长直线段斜率将局部地图正交方向重对准.然后利用Harris角点检测算法检测局部地图中的角点,并以角点为中...     

基于改进A~*算法的多机器人动态路径规划

为解决智能仓储系统多机器人作业产生的交通拥堵问题,提出了一种基于预约栅格的多机器人动态路径规划算法。首先利用预约栅格与有向图的方法,对机器人之间的碰撞进行预防;然后利用预约栅格生成交通拥堵地图,实时显示当前仓库地图的拥堵状况;最后通过改进A~*算法,实现多机器人的动态路径规划,解决机器人间的交通拥堵问题,提高了系统效率。通过仿真实验,将所提方法与传统方法进行了比较,对多机器人路径规划方法的有效性进行了验证。     

移动机器人的导航定位和地图构建技术综述

在非结构环境或动态环境下,移动机器人必须学会如何导航。目前相关的研究主要集中于机器人定位和地图构建两个方面。本文介绍了移动机器人的主要特征和发展概况,分析了移动机器人定位技术的研究动态,总结了移动机器人地图构建的主流技术和发展趋势,为进一步的研究工作建立了基础平台。     

多机器人对未知环境进行实时在线探测的一种方法

将多机器人协作引入了构建地图的作业任务研究中，将多个范围传感器所探测到的环境信息以概率值的方式表示，利用不确定性证据推理的原理对其进行了Dempster-Shafer数据融合。在协作的基础上，设计了避障策略。系统仿真实验，验证了该方法的可行性。     

基于声纳和摄像头的动态环境地图创建方法

针对动态环境下声纳传感器无法正确检测动态障碍物从而降低移动机器人的地图创建的精度的问题,提出了一种声纳和视觉传感器结合的动态环境地图创建方法.为保持地图信息的完整性,该方法分别建立了动、静态栅格地图,利用前一时刻的静态地图、当前声纳观测信息和摄像头检测的动态障碍物信息的比较来更新地图,并给出了地图更新模型.因视觉信息能成功地解决地图中某些动态障碍物被当成静态障碍物的错误,因而能建立正确的地图.实验验证了该方法正确,可行.     

等值线平滑的噪声地图矢量化优化方法

噪声地图中栅格型噪声云图被放大后会产生失真现象,且占用的存储空间较大,不利于大尺度噪声地图的精细化展示.为提升噪声云图展示效果并降低文件大小,研究双线性插值、双三次卷积插值、栅格图像矢量化方法的优缺点,提出一种基于噪声等值线平滑的矢量化优化方法.该方法利用平滑后的等值线、绘图边界、建筑物轮廓等构建矢量面要素,并根据各面...     

基于扩展卡尔曼滤波的轮式移动机器人定位技术

针对单一传感器或现有多传感系统在信息传递提取上的不足,应用一种信息融合方法,对机器人进行相对定位与绝对定位的融合分析,得出机器人的最优位置信息,最终实现了移动机器人的精确定位。首先,采用码盘、陀螺仪进行机器人相对定位,采用激光雷达进行机器人绝对定位;其次,建立环境地图、传感器及机器人运动模型;最后,以扩展卡尔曼滤波作为多传感器融合技术,建立多传感器信息融合模型,实现精确定位。     

未知环境下基于意图推理的多机器人编队控制

设计了一种未知环境下基于意图推理的多机器人编队控制方法.该方法在机器人自身移动局部坐标系中通过观察其领航机器人,采用限定记忆最小二乘多步递推策略对领航机器人的运动趋势进行预测,估计出领航机器人的运动信息及机器人之间的相关信息,结合已有的编队控制律以及切线避障策略使机器人安全躲避潜在危险的同时实现多机器人之间的协调.该方法扩展性较好,仿真验证了其可行性.     

Quantitative evaluation of high temperature deformation mechanisms: a specific microgrid extensometry technique coupled with EBSD analysis

A microgrid extensometry method has been developed and used to obtain information about intragranular and intergranular creep mechanisms. An oxide grid was deposited on a creep specimen using an electron lithography technique. This oxide grid offers high backscattered electron contrast and can withstand long duration creep tests under vacuum in the 700–850 °C range without degradation. Specific methods were used to measure in-plane displacements at the grid nodes or at the grain boundaries using correlation of grid images taken before and after the creep test. The local strain and grain boundary sliding (GBS) data were then calculated. Combined information about grain boundary crystallography and GBS has been obtained by superimposing the electron backscattered diffraction (EBSD) map on the deformation maps. To illustrate the potential of this set of processes, two examples of application on a nickel-base disc superalloy are presented. The first one concerns the influence of the creep temperature on the local strain and the GBS. The second application quantitatively shows the influence of grain boundary character on GBS of this material.     

Integration of colour and affine invariant feature for multi-view depth video estimation

Although many depth map estimation methods have been developed, depth map estimation still has some difficulties in low-texture regions and occlusion. This paper presents a novel approach for multi-view depth video estimation which adopts an adaptive matching scheme for high-texture regions and low-texture regions, respectively. For low-texture regions, the proposed method integrates affine invariant features with colour to make the matching more robust. Furthermore, according to the smoothness assumption of depth maps, a refinement is then performed on the estimated depth maps. Experimental results show that the proposed method can achieve better or comparable performances than the state-of-the-art method in the category of local methods even with the less running time.     

Image retargeting approach for ranging cameras

This paper presents a novel image retargeting approach for ranging cameras. The proposed approach first extracts three feature maps: depth map, saliency map and gradient map. Then, the depth map and the saliency map are used to separate the main contents and the background and thus compute a map of saliency objects. After that, the proposed approach constructs an importance map which combines the four feature maps by the weighted sum. Finally, the proposed approach constructs the target image using the seam carving method based on the importance map. Unlike previous approaches, the proposed approach preserves the salient object well and maintains the gradients and visual effects in the background. Moreover, it protects the salient object from being destroyed by the seam carving algorithm. The experimental results show that the proposed approach performs well in terms of the resized quality.     

基于多机器人自组织协作的多目标跟踪

提出了一种基于局部区域内的机器人和目标密度的多机器人分布式控制算法。运用这种算法,多机器人在跟踪多目标过程中,每个机器人能在每次调整速度和方向之前,根据最新的通讯信息和感知信息,计算通讯范围内相邻机器人和感知范围内移动目标的数量及位置坐标,然后按照所受人工势场(APF)力的合力决定下一次移动的新位置坐标,这个合力乘以一个基于机器人和目标密度的可变加权系数,以适应不同状态,然后按照动力学和运动学方程计算速度及方向。通过仿真实验对该算法进行了验证,实验结果表明,多机器人可以根据多目标的移动进行自主协作跟踪观测,算法的性能优于无可变加权系数的APF法和静态感知节点(SN)法。此方法对于实时监测和目标跟踪具有实际应用意义。     

A neural network approach for safety and collision avoidance in robotic systems

A major factor which has limited the application of robots in industrial and human service applications has been the lack of robust sensing and control algorithms for detection and prevention of collision conditions. This paper discusses an approach to the collision avoidance control of robots using a neural network methodology for the integration of sensory input data from the robot's environment. The paper presents a formulation of the collision avoidance problem using the occupancy grid formulation, and discusses the use of a combination of Dempster-Shafer inference and neural networks in fusing the sensory information and making robot movement decisions. Initial studies have shown this approach to be both robust and computationally tractable in providing enhanced safety capabilities.     

Parameter estimation with correlated outputs using fidelity maps

This paper introduces a new approach for parameter estimation and model update based on the notion of fidelity maps. Fidelity maps refer to the regions of the parameter space within which the discrepancy between computational and experimental data is below a user-defined threshold. It is shown that fidelity maps provide an efficient and rigorous approach to approximate likelihoods in the context of Bayesian update or maximum likelihood estimation. Fidelity maps are constructed explicitly in terms of the parameters and aleatory uncertainties using a Support Vector Machine (SVM) classifier. The approach has the advantage of handling numerous correlated responses, possibly discontinuous, without any assumption on the correlation structure. The construction of accurate fidelity map boundaries at a moderate computational cost is made possible through a dedicated adaptive sampling scheme. A simply supported plate with uncertainties in the boundary conditions is used to demonstrate the methodology. In this example, the construction of the fidelity map is based on several natural frequencies and mode shapes to be matched simultaneously. Various statistical estimators are derived from the map.     

Path-independent phase unwrapping of subsampled phase maps

A technique for unwrapping subsampled phase maps is presented. The subsampled phase map is obtained by standard phase-shifting methods that use subsampled interferograms. The technique then estimates the wrapped local curvature of the subsampled phase map. This local curvature is then low-pass filtered with a free-boundary low-pass filter to reduce phase noise. Finally the estimated local curvature of the wave front is integrated by the use of a least-squares technique to obtain the searched continuous wave front.     

Mapping the backbone of science

Summary This paper presents a new map representing the structure of all of science, based on journal articles, including both the natural and social sciences. Similar to cartographic maps of our world, the map of science provides a bird’s eye view of today’s scientific landscape. It can be used to visually identify major areas of science, their size, similarity, and interconnectedness. In order to be useful, the map needs to be accurate on a local and on a global scale. While our recent work has focused on the former aspect,1 this paper summarizes results on how to achieve structural accuracy. Eight alternative measures of journal similarity were applied to a data set of 7,121 journals covering over 1 million documents in the combined Science Citation and Social Science Citation Indexes. For each journal similarity measure we generated two-dimensional spatial layouts using the force-directed graph layout tool, VxOrd. Next, mutual information values were calculated for each graph at different clustering levels to give a measure of structural accuracy for each map. The best co-citation and inter-citation maps according to local and structural accuracy were selected and are presented and characterized. These two maps are compared to establish robustness. The inter-citation map is then used to examine linkages between disciplines. Biochemistry appears as the most interdisciplinary discipline in science.     

Image resizing based on strengthened edges

Image resizing techniques based on image content have been extensively studied. Most of these approaches evaluate the importance of each pixel to preserve more critical regions and discard less critical regions for achieving a target image size. This study proposes an image resizing algorithm based on strengthened edges. First, we created two feature maps: an improved gradient map and an enhanced saliency map. We then computed a strengthened edge map on the basis of these two feature maps. Finally, the target image was constructed using a seam carving method on the basis of the strengthened edge map. More accurate results can be obtained using the proposed approach rather than previous methods.