大幅面地图的三维地形重建

研究完成了一个实用的可用于大幅面像素地图的三维地形重建系统.提出一个实用的 等高线内插算法,算法克服了网格绘制等值线方法和三角网绘制等值线方法因只考虑了点的位 置属性、未考虑等高线的线属性而使插出的等高线常常会与母线相交的弱点;同时提出了一个 实用的等高线高程识别算法和一个可用于大幅面地图的三维规则数据场建立算法,算法充分利 用了等高线的先验知识,不仅建立的数据场的质量很高,而且算法的时间复杂性与数据点数 (m)和网格点数(n)成线性关系O(m+n),因此计算速度很快.最后利用三维规则数据场生成真 实感图形.     

地图构建中动态障碍干扰滤除的一种方法

在移动机器人环境建图中,动态障碍物的存在直接影响传感器的读数,导致产生不一致的环境地图,因此,移动机器人构建地图必须滤除动态障碍物干扰。采用直线插补的方法在先前的局部图上搜寻机器人与目标点之间是否存在障碍物,若存在障碍,则可判定该障碍物已移走(即为动态障碍),应该予以滤除。实验结果证明,该方法能在建图过程中有效地滤除动态障碍,并能有效减少静态障碍物探测的误差累积,算法复杂度小。     

Efficient Path Routing Over Road Networks in the Presence of Ad-Hoc Obstacles

Nowadays, the path routing over road networks has become increasingly important, yet challenging, in many real-world applications such as location-based services (LBS), logistics and supply chain management, transportation systems, map utilities, and so on. While many prior works aimed to find a path between a source and a destination with the smallest traveling distance/time, they do not take into account the quality constraints (e.g., obstacles) of the returned paths, such as uneven roads, roads under construction, and weather conditions on roads. Inspired by this, in this paper, we consider two types of ad-hoc obstacles, keyword-based and weather-based obstacles, on road networks, which can be used for modeling roads that the returned paths should not pass through. In the presence of such ad-hoc obstacles on roads, we formulate a path routing query over road networks with ad-hoc obstacles (PRAO), which retrieves paths from source to destination on road networks that do not pass ad-hoc keyword and weather obstacles and have the smallest traveling time. In order to efficiently answer PRAO queries, we design effective pruning methods and indexing mechanism to facilitate efficient PRAO query answering. Extensive experiments have demonstrated the efficiency and effectiveness of our approaches over real/synthetic data sets.     

An efficient dynamic system for real-time robot-path planning.

This paper presents a simple yet efficient dynamic-programming (DP) shortest path algorithm for real-time collision-free robot-path planning applicable to situations in which targets and barriers are permitted to move. The algorithm works in real time and requires no prior knowledge of target or barrier movements. In the case that the barriers are stationary, this paper proves that this algorithm always results in the robot catching the target, provided it moves at a greater speed than the target, and the dynamic-system update frequency is sufficiently large. Like most robot-path-planning approaches, the environment is represented by a topologically organized map. Each grid point on the map has only local connections to its neighboring grid points from which it receives information in real time. The information stored at each point is a current estimate of the distance to the nearest target and the neighbor from which this distance was determined. Updating the distance estimate at each grid point is done using only the information gathered from the point's neighbors, that is, each point can be considered an independent processor, and the order in which grid points are updated is not determined based on global knowledge of the current distances at each point or the previous history of each point. The robot path is determined in real time completely from the information at the robot's current grid-point location. The computational effort to update each point is minimal, allowing for rapid propagation of the distance information outward along the grid from the target locations. In the static situation, where both the targets and the barriers do not move, this algorithm is a DP solution to the shortest path problem, but is restricted by lack of global knowledge. In this case, this paper proves that the dynamic system converges in a small number of iterations to a state where the minimal distance to a target is recorded at each grid point and shows that this robot-path-planning algorithm can be made to always choose an optimal path. The effectiveness of this algorithm is demonstrated through a number of simulations.     

基于模糊模式识别的车辆定位地图匹配算法

针对传感器给出的车辆定位信息的不确定性,提出了基于模糊模式识别技术获得匹配道路的算法。给出的算法不需要车辆行驶的速度、方向参数,利用车辆定位轨迹与电子地图道路网之间的相似性,结合车辆实际行驶情况,得出定位点到候选道路之间的距离、相邻采样时刻定位点连线与候选道路之间的夹角、候选道路与历史匹配道路连通性的隶属函数,按照最大隶属原则选择匹配道路。通过实验验证,表明该算法具有可靠性,适用面广,能有效地提高车辆定位的精度。     

栅格地图环境下机器人速度势实时路径规划

针对智能制造工程环境中移动机器人的自动避障问题,提出一种基于栅格地图的移动机器人速度势实时避障路径规划方法。利用栅格法二值化移动机器人的工作场景,从机器人中心出发向不同方向进行栅格搜索。基于障碍物对移动机器人有排斥作用以及目标点对机器人有吸引作用的思想,通过栅格数的累加计算机器人到障碍物之间的实时距离,并以此为参数,考虑障碍物的形状、最小安全距离等因素的影响来建立负的速度增量函数;以机器人当前位置与目标点的实时距离和角度为参数建立正向速度增量函数。进而在机器人运动学模型基础上,定义速度势函数来对移动机器人进行实时速度驱动。通过设置最小速度增量,避免在零势点处的局部极小点问题;通过设立距离阈值,避免在目标点附近速度增量趋于无穷的问题。通过仿真对所提出的算法进行验证。     

对网格中间区域矫正更优的图像矫正算法

常规放疗中模拟定位机影像增强器采集的图像常存在失真,为了保证放疗的精度,必须进行矫正,为此提出一种以点到直线距离为目标函数的图像矫正算法.在综合考虑矫正的速度、精度、平滑性的前提下,先采用基于一次线性基的移动最小二乘法对图像进行了矫正,取得了比较理想的结果;进一步,利用矫正后各线条应该为直线这一特征增加了参考点的数量,使交叉点中间区域也有了参考点.矫正结果显示,矫正之后各网格线呈现更理想的直线,交叉点之间的区域矫正比只考虑交叉点的矫正算法理想.当参考点增加到2 000多个点时,算法运行时间仍然较短.     

基于无线数传技术的无人船控制系统设计与实现

针对于现有的无人船(unmanned surface vehicle)存在的问题,为提高其控制行驶最大距离,设计一种以无线数据传输模块为传输介质的系统,传输下位机与上位机之间的数据;从激光雷达的二维扫描图像信息,根据SLAM (simultaneous localization and mapping)算法制作出水面环境的栅格地图圈定卫星地图盲区,组合多种传感器定位的方式估算无人船相对位置并定位在卫星离线地图,以达到按路径规划行进的目的;设计了上位机软件和基于STM32的控制器;无人船位姿信息发送到上/下位机,上位机得到信息向下位机传输实现远程遥控行驶的目的;实验结果表明,与常规的网络信号发射和接收传输数据不一样,在无网络基站环境中仍能够在1 200 m以内保持良好的远程控制,证实了系统的可靠性和准确性。     

Drawing road networks with focus regions

Mobile users of maps typically need detailed information about their surroundings plus some context information about remote places. In order to avoid that the map partly gets too dense, cartographers have designed mapping functions that enlarge a user-defined focus region--such functions are sometimes called fish-eye projections. The extra map space occupied by the enlarged focus region is compensated by distorting other parts of the map. We argue that, in a map showing a network of roads relevant to the user, distortion should preferably take place in those areas where the network is sparse. Therefore, we do not apply a predefined mapping function. Instead, we consider the road network as a graph whose edges are the road segments. We compute a new spatial mapping with a graph-based optimization approach, minimizing the square sum of distortions at edges. Our optimization method is based on a convex quadratic program (CQP); CQPs can be solved in polynomial time. Important requirements on the output map are expressed as linear inequalities. In particular, we show how to forbid edge crossings. We have implemented our method in a prototype tool. For instances of different sizes, our method generated output maps that were far less distorted than those generated with a predefined fish-eye projection. Future work is needed to automate the selection of roads relevant to the user. Furthermore, we aim at fast heuristics for application in real-time systems.     

等高线树构建及高保真DEM构建

研究正负地貌等高线（含未闭合等高线）的空间关系。首先将未闭合等高线分为完全开放等高线和贴边等高线,分别进行自动闭合处理。然后使用多边形叠加分析的方法判断闭合等高线之间的关系,构建等高线树。通过对等高线树结构的遍历,获取格网点高程值的上下界,将上下界输入到高精度曲面建模区域优化控制方法进行约束优化控制模拟,能保证模拟结果的回放等高线与原始等高线的最大距离不超过一个栅格的宽度。最后对高斯合成曲面和扫描矢量化等高线两个实例进行论证。     

Finding the right pixel size

This paper discusses empirical and analytical rules to select a suitable grid resolution for output maps and based on the inherent properties of the input data. The choice of grid resolution was related with the cartographic and statistical concepts: scale, computer processing power, positional accuracy, size of delineations, inspection density, spatial autocorrelation structure and complexity of terrain. These were further related with the concepts from the general statistics and information theory such as Nyquist frequency concept from signal processing and equations to estimate the probability density function. Selection of grid resolution was demonstrated using four datasets: (1) GPS positioning data—the grid resolution was related to the area of circle described by the error radius, (2) map of agricultural plots—the grid resolution was related to the size of smallest and narrowest plots, (3) point dataset from soil mapping—the grid resolution was related to the inspection density, nugget variation and range of spatial autocorrelation and (4) contour map used for production of digital elevation model—the grid resolution was related with the spacing between the contour lines i.e. complexity of terrain. It was concluded that no ideal grid resolution exists, but rather a range of suitable resolutions. One should at least try to avoid using resolutions that do not comply with the effective scale or inherent properties of the input dataset. Three standard grid resolutions for output maps were finally recommended: (a) the coarsest legible grid resolution—this is the largest resolution that we should use in order to respect the scale of work and properties of a dataset; (b) the finest legible grid resolution—this is the smallest grid resolution that represents 95% of spatial objects or topography; and (c) recommended grid resolution—a compromise between the two. Objective procedures to derive the true optimal grid resolution that maximizes the predictive capabilities or information content of a map are further discussed. This methodology can now be integrated within a GIS package to help inexperienced users select a suitable grid resolution without doing extensive data preprocessing.     

Generalizing self-organizing map for categorical data

The self-organizing map (SOM) is an unsupervised neural network which projects high-dimensional data onto a low-dimensional grid and visually reveals the topological order of the original data. Self-organizing maps have been successfully applied to many fields, including engineering and business domains. However, the conventional SOM training algorithm handles only numeric data. Categorical data are usually converted to a set of binary data before training of an SOM takes place. If a simple transformation scheme is adopted, the similarity information embedded between categorical values may be lost. Consequently, the trained SOM is unable to reflect the correct topological order. This paper proposes a generalized self-organizing map model that offers an intuitive method of specifying the similarity between categorical values via distance hierarchies and, hence, enables the direct process of categorical values during training. In fact, distance hierarchy unifies the distance computation of both numeric and categorical values. The unification is done by mapping the values to distance hierarchies and then measuring the distance in the hierarchies. Experiments on synthetic and real datasets were conducted, and the results demonstrated the effectiveness of the generalized SOM model.     

Improved Evaluation and Generation Of Grid Layouts Using Distance Preservation Quality and Linear Assignment Sorting

Images sorted by similarity enables more images to be viewed simultaneously, and can be very useful for stock photo agencies or e-commerce applications. Visually sorted grid layouts attempt to arrange images so that their proximity on the grid corresponds as closely as possible to their similarity. Various metrics exist for evaluating such arrangements, but there is low experimental evidence on correlation between human perceived quality and metric value. We propose distance preservation quality (DPQ) as a new metric to evaluate the quality of an arrangement. Extensive user testing revealed stronger correlation of DPQ with user-perceived quality and performance in image retrieval tasks compared to other metrics. In addition, we introduce Fast linear assignment sorting (FLAS) as a new algorithm for creating visually sorted grid layouts. FLAS achieves very good sorting qualities while improving run time and computational resources.     

考虑LVRT能力的风电场联络线距离保护研究

具备低电压穿越(LVRT)能力的风电场能够在系统故障及电网电压跌落期间连续运行,因此,对具备LVRT能力的风电场联络线距离保护配置时,要综合考虑风电场LVRT时间。本文采用卸荷保护电路措施来提高永磁直驱风机(PMSG)的LVRT的能力,通过分析风电场LVRT与风机低电压保护动作时间配合关系,提出风电场联络线的距离保护时间配合的改进方案,最后仿真验证了提出方案的有效性和可行性。     

A new parameterization of digital straight lines

A 1:1 correspondence is established between digital straight lines which start at a fixed point and a simple set of quadruples of integer parameters. Such a representation by parameters is useful for enumeration, First, the authors show a 1:1 correspondence between point pairs in a planar set of points and the linear dichotomies of this set. Then, from the equivalence between digital lines and linear dichotomies of points on the digitization grid, they prove a 1:1 and 'onto' correspondence between digital straight lines starting at a fixed point and a well-defined set of pairs of grid points. It follows that four parameters uniquely represent any given digital line with a fixed starting point. An O(N) algorithm is given for determining the parameters from the digital line, as well as O(log N) algorithms for transforming between these parameters and the parameters suggested by L. Dorst and A.W.M. Smeulders (1984)     

激光—相机系统语义栅格建图和路径规划

目的 SLAM（simultaneous localization and mapping）是移动机器人在未知环境进行探索、感知和导航的关键技术。激光SLAM测量精确，便于机器人导航和路径规划，但缺乏语义信息。而视觉SLAM的图像能提供丰富的语义信息，特征区分度更高，但其构建的地图不能直接用于路径规划和导航。为了实现移动机器人构建语义地图并在地图上进行路径规划，本文提出一种语义栅格建图方法。方法 建立可同步获取激光和语义数据的激光-相机系统，将采集的激光分割数据与目标检测算法获得的物体包围盒进行匹配，得到各物体对应的语义激光分割数据。将连续多帧语义激光分割数据同步融入占据栅格地图。对具有不同语义类别的栅格进行聚类，得到标注物体类别和轮廓的语义栅格地图。此外，针对语义栅格地图发布导航任务，利用路径搜索算法进行路径规划，并对其进行改进。结果 在实验室走廊和办公室分别进行了语义栅格建图的实验，并与原始栅格地图进行了比较。在语义栅格地图的基础上进行了路径规划，并采用了语义赋权算法对易移动物体的路径进行对比。结论 多种环境下的实验表明本文方法能获得与真实环境一致性较高、标注环境中物体类别和轮廓的语义栅格地图，且实验硬件结构简单、成本低、性能良好，适用于智能化机器人的导航和路径规划。     

A very simple spiking neuron model that allows for modeling of large, complex systems

This letter introduces a biologically inspired very simple spiking neuron model. The model retains only crucial aspects of biological neurons: a network of time-delayed weighted connections to other neurons, a threshold-based generation of action potentials, action potential frequency proportional to stimulus intensity, and interneuron communication that occurs with time-varying potentials that last longer than the associated action potentials. The key difference between this model and existing spiking neuron models is its great simplicity: it is basically a collection of linear and discontinuous functions with no differential equations to solve. The model's ability to operate in a complex network was tested by using it as a basis of a network implementing a hypothetical echolocation system. The system consists of an emitter and two receivers. The outputs of the receivers are connected to a network of spiking neurons (using the proposed model) to form a detection grid that acts as a map of object locations in space. The network uses differences in the arrival times of the signals to determine the azimuthal angle of the source and time of flight to calculate the distance. The activation patterns observed indicate that for a network of spiking neurons, which uses only time delays to determine source locations, the spatial discrimination varies with the number and relative spacing of objects. These results are similar to those observed in animals that use echolocation.     

A*算法在AGV路径规划上的改进与验证

针对单AGV路径规划时,A^*算法的启发函数采用曼哈顿距离时遇到障碍物会出现局部绕行这一问题,将带有障碍物的栅格地图作为环境模型,研究出两种改进A^*算法的路径规划方法。第一种方法是在遇到障碍物时将启发函数中曼哈顿距离换成欧氏距离,利用欧氏距离规划路径代价最小的特性避免绕行;第二种方法通过比较AGV遇到障碍物的位置与障碍物左右两端距离大小,通过规定行驶方向避免绕行。仿真结果表明,两种方法均可以在单AGV遇到障碍物时避免绕行,有效地减少了行驶时间,也使得路径更加平滑,提高了AGV的运行效率。     

大型油库消防救援寻路算法改进

大型油库区的地形不同于城市、山地等复杂的地形,虽然范围较大,但是油库区地形十分规整,油罐等建筑排列整齐,且在储油罐区的道路是笔直畅通的.根据这些特点,将标准的A^*寻路算法进行改进.一方面,根据油库地形结构简单,搜索节点相对少的特点,对A^*算法中搜索Open表中节点的数据结构进行改进,采用排序算法提高了搜索效率;另一方面,根据储油罐区道路笔直畅通的特点,将道路分为有障碍路段和无障碍路段,分而治之,提高整体的寻路效率.实验证明,将两种改进方法进行结合,寻路时间明显缩短,平均搜索效率提高6.86%.