基于局部子地图方法的多机器人主动同时定位与地图创建

研究了多机器人在未知环境下以主动的方式协作完成同时定位与地图创建(SLAM)的问题.引入局部子地图方法,由每个机器人建立自身周围局部区域的子地图,使多个机器人之间的地图创建相互独立,从而对全局环境的SLAM问题进行分解.而每个机器人在建立局部子地图时将主动SLAM问题转化为多目标优化问题;机器人选取最优的控制输入,使定位与地图创建的准确性、信息增益以及多机器人之间的协调关系得到综合优化.最后,通过扩展的卡尔曼滤波器(EKF)对子地图进行融合得到全局地图.仿真结果验证了该方法的有效性.

基于子地图的智能车辆同步定位与地图创建

为使智能车辆能在无法预先确定环境范围的条件下创建环境栅格地图并实时定位,提出了一种基于子地图框架的同步定位与地图创建方法。在子地图中设置重合区域与切换区域,以避免相邻子地图间的连续切换。实验结果表明,该方法可保证车辆在同步定位与地图创建过程中地图范围的动态增长和子地图间的稳定切换,具有较高的实时性和定位精度。

基于签名向量与路标定位的子地图匹配算法

在移动机器人的分层同时定位和地图构建SLAM算法中,通过签名元素实现局部子地图的匹配存在计算复杂性的问题,提出了通过构建签名元素向量的方法来解决子地图匹配的问题;由于机器人在重复访问某一个区域的时候,两次的运动轨迹不可能完全重合,因此在该方法中结合了基于路标进行定位的技术,从而实现可靠的回路闭合确认计算。另外,讨论了在获得全局地图的后处理过程中存在两个或者多于两个的闭合回路共享部分路径时,实现全局优化的算法中限制条件的修改问题。最后,通过一个算例说明子地图匹配过程的具体操作。

一种适用于激光SLAM大尺度地图的闭环检测方法

针对2D激光SLAM在大尺度地图的闭环检测中,存在匹配候选集数量庞大和容易发生误检的问题,提出了基于子地图匹配的闭环检测方法。该方法首先使用连续几帧的激光数据构建子地图,并用构建的子地图生成压缩表;然后结合机器人的位姿估计,利用压缩表进行粗扫描匹配,筛选出闭环检测的匹配候选集,提升匹配速度;最后用经筛选的匹配候选集进行细扫描匹配来检测闭环,以满足SLAM在大尺度地图下闭环检测的速度和准确率要求。实验结果表明,该算法可有效提高闭环检测的可靠性并显著减少匹配候选集数量。

基于改进GICP配准的激光-惯性SLAM算法

激光点云配准性能是影响激光-惯性SLAM系统精度和实时性的重要因素,对于多线激光雷达,大量的待配准点虽然能提高配准精度,但是也会降低系统运行效率。针对该问题,提出了一种基于改进广义迭代最近点(GICP)配准的激光-惯性SLAM算法。首先,用改进的GICP算法进行点云配准,通过减少待配准点数量提高配对点的质量,增加迭代目标,提高了定位精度。其次,针对改进的GICP算法提出了一个高效的子地图模型,提高了系统运行效率。在KITTI数据集上的实验结果表明,与改进前的算法相比,所提算法的定位误差降低了69.98%;与Le GO-LOAM、LIO-SAM算法相比,所提算法的平均定位误差分别降低了88.44%和62.42%。同时进行了实测实验验证,与LeGO-LOAM、LIOSAM算法相比,所提算法的平均定位误差分别降低了21.02%和24.77%,且具有更高的系统运行效率。

基于重叠区域融合的多无人机实时视觉稠密地图构建

针对提高多无人机平台执行协同环境感知任务时的精度与效率问题,开展了多无人机视觉稠密建图与地图融合技术的研究。首先,针对建图误差和传感器误差导致生成无效地图点和局部重影的问题,提出了一种基于视觉的稠密点云地图构建算法,该算法在对点云进行滤波之后通过基于KD-Tree的广义最近邻迭代和体素滤波结合完成稠密点云地图的构建。随后,提出了基于重叠区域的稠密地图融合算法,算法进行增长子地图的融合判断,通过获取重叠区域并查找正确的匹配点对,实现稠密地图的融合。最后,搭建了一个双无人机验证平台,并通过在室外场景下进行协同环境感知验证了所提出的方法可以保证地图构建误差在5%以内的同时有效降低地图点的数量,并且实现了精确的地图融合。

通讯范围受限条件下的多机器人主动SLAM

针对机器人通讯范围受限的问题,提出一种新的多机器人协作同时定位与建图(simultaneous locali-zation and mapping,SLAM)方法。多个机器人采用基于最优控制的主动探索策略,创建自身周围区域的子地图,在每个建图周期内使用扩展的卡尔曼滤波器(extended Kalman filter,EKF)估计和维护子地图状态,并在一个周期结束后联络其通讯范围内的其他机器人,进行子地图的传递与融合。同时,为避免由通讯范围受限带来的地图过度融合问题,每个机器人保存每个建图周期内的局部子地图,待与其他机器人相遇时只传递并融合子地图的增量部分。仿真实验验证了该方法的有效性。

最短路径搜索算法的几种优化改进

介绍了GIS领域最短路径搜索的一种优化模式。在Dijkstra’s算法的基础上,从三个方面改进了最短路径的计算。首先引入了多级路线图,在读取线路数据时,根据路线的级别有所选择;其次,在计算最短距离时考虑速度的影响;最后,在道路的转弯处,引入虚拟路径来估算转弯对汽车行驶的影响。应用以上三种方法的实验,取得了很好的效果。

The Organization of Multimedia Information in Electronic Map

On the basis of an electronic map_based hypermedia data model (EMBHDM),this paper makes a study on the technologies of nonlinear storage,organization,management and browsing of information as well as organization of data on the basis of the relationship between multimedia information of electronic maps. This paper first analyzes some features of electronic maps and hypermedia technology,and then illustrates the creation of EMBHDM with some examples.The tests show that this model can efficiently organize and express multimedia data.

Guide Rules for Electronic Atlas Project in China

Electronic atlas project (E-atlas project) plays a n important role in the procedure of popularizing maps and is diversifying its a pplication widely in China. Practice for E-atlas projects is a basic approach f or achieving public accessibility to national spatial data infrastructure (N SDI) and meets people’s inherent needs of updated maps. This paper provides a d escription and assessment of an integration of E-atlas projects, analyzes curre nt progress and characters of E-atlas project, summarizes basic guide rules, an d provides solution and interpretation. It depicts a conceptual framework of an authoring toolkit that is driven by application of E-atlas on the basis of succ essful instances. The toolkit which improves interactive interface, decreases op erational difficulties is developed in Visual C++ and used widely in China.

Dynamic analysis of granite rockburst based on the PIV technique

This paper describes the deep rockburst simulation system to reproduce the granite instantaneous rockburst process.Based on the PIV(Particle Image Velocimetry)technique,quantitative analysis of a rockburst,the images of tracer particle,displacement and strain fields can be obtained,and the debris trajectory described.According to the observation of on-site tests,the dynamic rockburst is actually a gas–solid high speed flow process,which is caused by the interaction of rock fragments and surrounding air.With the help of analysis on high speed video and PIV images,the granite rockburst failure process is composed of six stages of platey fragment spalling and debris ejection.Meanwhile,the elastic energy for these six stages has been calculated to study the energy variation.The results indicate that the rockburst process can be summarized as:an initiating stage,intensive developing stage and gradual decay stage.This research will be helpful for our further understanding of the rockburst mechanism.

Dynamics of Quantum Entanglement in Reservoir with Memory Effects

The non-Markovian dynamics of quantum entanglement is studied by the Shabani-Lidar master equation when one of entangled quantum systems is coupled to a local reservoir with memory effects.The completely positive reduced dynamical map can be constructed in the Kraus representation.Quantum entanglement decays more slowly in the non-Markovian environment.The decoherence time for quantum entanglement can be markedly increased with the change of the memory kernel.It is found out that the entanglement sudden death between quantum systems and entanglement sudden birth between the system and reservoir occur at different instants.

High-Resolution Threshold Photoelectron Spectroscopy by Vacuum Ultraviolet Laser Velocity-Map-Imaging Method

We have obtained the high-resolution threshold photoelectron （TPE） spectra of chlorobenzene C6HaCl （X1A1）, propargyl radical C3H3 （X2B1）, and allyl radical C3H5 （X2A1） by employing the vacuum ultraviolet （VUV） laser velocity-map-imaging-TPE （VUV-VMI-TPE） method. The photoelectron energy resolution of 1-2 cm^-1 observed for the VUV-VMI-TPE method is comparable to that achieved in VUV laser pulsed-field ionization-photoelectron （VUV-PFI-PE） measurements. Similar to VUV-PFI-PE measurements, the energy resolutions for VUV-VMI-photoelectron （VUV-VMI-PE） and VUV-VMI-TPE measurements are found to depend on the dc electric field F in V/cm used at the photoionization region for electron extraction. The decrease of the ionization thresholds of C6H5Cl and C3H3 observed as a function of F shows that the Stark shift correction for VUV-VMI-TPE measurements is governed by the formula -3.1√F in cm^-1, which is half of the classical prediction of -6.1v/F in cm^-1. We have also measured the VUV-VMI-PE spectra of C6H5Cl and C3H5 at VUV energies near their ionization thresholds. The cationic vibrational bands observed in the VUV-VMI-PE measurements were assigned to be the vibrational progression, nv7＋ （n=0-3）, for C3H＋. The higher experimental sensitivity and similar energy resolutions achieved in VUV-VMI-TPE compared to VUV-PFI-PE measurements make the VUV-VMI- TPE method an excellent alternative for high-resolution VUV-PFI-PE measurements.

A New Software for GIS Image Pixel Topographic Fac－tors in Remote Sensing Monitoring of Soil Losses

Based on the new algorithm for GIS image pixel topographic factors in remote sensing monitoring ofsoil losses, a software was developed for microcomputer to carry out computation at a medium river basin(county). This paper lays its emphasis on algorithmic skills and programming techniques as well as applicationof the software.

Mobile robot simultaneous localization and map building based on improved particle filter

We present an investigation into the use of pan tilt zoom camera and sonar sensors for simuhaneous localization and mapping with artificial colored landmarks. An improved particle filter is applied to estimate a posterior of the pose of the robot, in which each particle has associated it with an entire map. The distributions of landmarks are also represented by particle sets, where separate particles are used to represent the robot and the landmarks. Hough transform is used to extract line segments from sonar observations and build map simultaneously. The key advantage of our method is that the full posterior over robot poses and landmarks can be nonlinearly approximated at every point in time by particles. Especially the landmarks are affixed on the moving robots, which can reduce the impact of the depletion problem and the impoverishment problem produced by basic particle filter. Experimental results show that this approach has advantages over the basic particle filter and the extended Kalman filter.

Information Organization and Visualization Mechanism of Electronic Map

Based on research on information organization and visualization mechanism of multimedia electronic map, this paper proposes an organization method about spatial information and multimedia information of multimedia electronic map: seamless spatial data were organized and managed by stratified expansion R-tree and Quad-tree hierarchy; and multimedia information data were organized and managed by hypermedia model based on an electronic map. Considering electronic map features, the paper also proposes a method for spatial date organization, which integrates Digital Landscape Model and Digital Cartographic Model, and a hybrid model between vector and raster spatial data. Then, the paper studies information visualization mechanism of multimedia electronic map. Finally, the paper certifies the results via a case of multimedia electronic map authoring tools software—Atlas2005.

Periodicity and map for discovery of new ionic liquids

There is virtually no limit in the number of ionic liquids. How to select proper ones or discover new ones with desirable properties in such a large pool of ionic liquids? It has become a bottleneck in the researches and applications of ionic liquids. Mendeleev’s periodic law states that the properties of the elements vary periodically. Whether the similar regularity exists among ionic or mo-lecular fragments of compounds is an interesting topic. In this work, we attempted to establish a pe-riodicity and draw a “map” of ionic liquids for providing definite guidance to discover, design, and se-lect the proper ionic liquids rather than trial-and-error. If a complete regularity of the system of ionic liquids can be finally established in the future, we are near an epoch in understanding the existing differences and the reasons for the similarity of the ions or molecular fragments.

Quantitative analysis of nanoscale deformation fields of a crack-tip in single-crystal silicon

A mode II crack in single-crystal silicon was investigated experimentally using high-resolution transmission electron microscopy.Geometric phase analysis and numerical moiré method were employed to map the deformation fields of the crack-tip area.The normal strain field maps of the crack-tip area indeed showed the deformation occurs primarily in the vicinity of the dislocations and the normal strains are near zero in the crack-tip area.The shear strain field map shows that the relatively large shear strain is in the crack-tip area.The experimental results were compared with the predictions of linear elastic fracture mechanics.The comparison shows that measured strain distribution ahead of the crack-tip agrees with the predictions of linear elastic fracture mechanics up to 1 nm from the crack-tip.

Intra-individual comparison of different gadolinium-based contrast agents in the quantitative evaluation of C6 glioma with dynamic contrast-enhanced magnetic resonance imaging

This experiment aimed to compare the ionic （Gadodiamide, Gd-DTPA-BMA） and non-ionic （Gadopentetate dimeglumine, Gd-DTPA） gadolinium-based contrast agents （GBCA） in the quantitative evaluation of C6 glioma with dynamic contrast-enhanced magnetic resonance imaging （DCE-MRI）. A C6 glioma model was established in 12 Wistar rats, and magnetic resonance （MR） scans were performed six days after tumor implantation. Imaging was performed using a 3.0-T MR scanner with a 7-inch handmade circular coil. Pre-contrast T1 mapping and dynamic contrast-enhanced T1WI after a bolus injection （0.2 mL s 1） of GBCA at 0.4 mmol kg-1 were performed. Each rat received two DCE-MRI scans, 24 h apart. The first and second scans were performed using Gd-DTPA-BMA and Gd-DTPA, respectively. Image data were processed using the Patlak model. Both Kns and Vp maps were generated. Tumors were manually segmented on all 3D K and Vp maps. Pixel counts and mean values were recorded for use in a paired t-test. Three radiologists independently performed the tumor segmentation and value calculation. The agreements from different observers were subjective to the intra-class correlation coefficient （ICC）. Readers demonstrated that the pixel counts of tumors in/Crns maps were higher with Gd-DTPA-BMA than with Gd-DTPA （P〈0.001, all readers）. Although the/（r,,s values were higher with Gd-DTPA-BMA than with Gd-DTPA, there was no statistical significance （P〉0.05, all readers）. The pixel counts of tumors in Vp maps, as well as Vp values, showed no obvious difference between the two agents （P〉0.05, all readers）. Excellent interobserver measurement reproducibility and reliability were demonstrated in the ICC tests. The Gd-DTPA-BMA contrast agent had significantly higher pixel counts of glioma in the maps, and an increased tendency for average/Us values, indicating that DCE-MRI with Gd-DTPA-BMA may be more suitable and sensitive for the evaluation of glioma.

World Expo 2010 Pavilions Clustering Analysis Based on Self-Organizing Map

This paper reports the classification of 90 sample pavilions in Shanghai World Expo. An artificial intelligence based nonlinear clustering method known as Self-Organizing Map(SOM) has been used to classify expo pavilions. SOM is an efficient tool for visualization of multidimensional data. To conduct the classification, four characteristics namely Hurst exponent for queue length, Hurst exponent for waiting time, mean queue length and mean waiting time have been applied. The classification results show that Shanghai World Expo pavilions can be optimally classified into four classes. This result will shed light on further studies that how to manage the queue of World Expo pavilions in the future.