基于免疫自适应遗传算法的机器人栅格地图融合

融合各机器人独自创建的环境地图,实现信息共享,是提高分布式多移动机器人系统环境探索效率的关键.研究了在没有公共参考坐标系及机器人相对位置信息未知情况下的栅格地图融合问题,提出了一种基十免疫自适应遗传算法的栅格地图融合方法,该算法把反映两个栅格地图重叠区域相异程度的优化函数作为抗原,每个可能的平移、旋转平面转换对应一个抗体.仿真结果表明了该算法可以较快的收敛速度和较强的全局搜索能力,搜索到两个栅格地图的最佳重叠区域,实现地图融合.     

多机器人地图融合方法研究

多机器人建图是实现机器人自主导航,完成复杂智能任务的关键.其中如何将不同机器人采集的数据融合到全局地图中,成了多机器人建图中的一个核心问题.文中采用独立探索、集中建图的探索策略,提出一种基于改进差异进化算法的多机器人概率栅格地图的融合.该算法在地图相似度的概念基础上,建立相异度函数,利用改进的进化算法搜索策略快速地搜索各局部地图之间的最大重叠部分,实现了多机器人系统栅格地图的融合,有效的解决了相对位置未知情况下的地图创建问题.通过实验验证了该方法正确、可行.     

基于超声波的移动机器人的同时定位和地图构建

为了在移动机器人SLAM过程中得到更精确的定位和二维地图构建,对一种利用超声波传感器信息进行栅格地图创建的方法提出了改进;该方法利用Bayes法则对信息进行融合,利用粒子滤波和航位推算相结合的方法对机器人进行精确定位和创建地图,然后利用移动的栅格法进行地图的全局更新,提出了一种地图的校验方法;通过实验,在粒子数为200的情况下分别得到了算法改进前和改进后的地图构建结果,通过比较,证明了使用该算法进行移动机器人定位和地图构建更加精确。     

基于声纳传感器的移动机器人地图创建方法研究*

提出了一种改进的基于声纳传感器信息进行栅格地图创建的方法。将Bayes法则用于移动机器人地图创建,对多个声纳传感器信息进行融合,解决信息间的冲突问题,并根据声纳模型将测量数据集成到局部地图中,改变栅格被障碍物占有的概率。经过坐标变换后,利用Bayes法则更新全局地图中的栅格信息,实现从局部地图到全局地图的更新。实验验证了该算法的可行性与有效性。     

面向复杂障碍场的电力巡检机器人局部动态融合路径规划

为解决电力巡检机器人在复杂障碍场中，常与障碍物碰撞、避障效率低等问题，提出面向复杂障碍场的电力巡检机器人局部动态融合路径规划方法。使用基于栅格法的复杂障碍场地图生成方法，构建面向复杂障碍场的电力巡检环境地图；结合所构建地图信息，由改进遗传算法寻优获取巡检所用全局最短路径后，经时间弹性带算法，结合不同时刻机器人位姿信息，由距离阈值判断机器人与动态障碍物碰撞可能性，以全局规划路径弹性拉伸的方式，完成局部动态融合的避障运行，且需分析局部动态规划路径中，机器人运行方向与全局规划路径一致性，动态调节规划机器人巡检路径。经测试，此方法使用后，机器人未出现碰撞问题，且避障速度提升约300%。     

基于新型栅格启发式算法的矿井机器人路径规划

在传统正方形栅格地图中,存在机器人遇到障碍物时沿对角线方向移动易与障碍物碰撞,其绕障和平稳性等方面的能力较差且实时探测过程中每步消耗的时间无法唯一确定等问题。针对上述问题,提出了以正六边形栅格化的工作环境为基础,采用改进的启发式路径搜索算法对多个并行移动的矿井机器人进行路径优化的方法。从绕障转角、绕障能力及最优路径3个方面,对单个机器人在正方形和正六边形栅格建模环境中的运动性能进行比较分析,结果表明:就单个机器人来说,正六边形栅格地图下的路径长度代价小于正方形栅格地图的路径长度代价;从单个机器人的路径规划来看,正六边形栅格地图更有利于获得最短路径,从而得出正六边形栅格比传统正方形栅格更适合于机器人工作环境的建模。针对多个协同操作的机器人并行移动的路径规划问题,在正六边形栅格化的工作空间建模基础上,采用改进的启发式路径搜索算法对多个机器人的路径进行优化:采用改进的启发式估计函数规划多个协同操作的机器人路径,该函数决定了当前机器人所在位置周围所有相邻栅格中哪一个即将被机器人遍历。依据机器人已经遍历的栅格数和候选栅格与该机器人目标栅格之间的变形曼哈顿距离,该启发式估计函数可评估出相邻栅格的适应度值。仿真结果表明:正六边形栅格地图在路径总长及算法运行时间上均比正方形栅格地图减少了10%以上,且有效避免了机器人与静态障碍物之间及机器人之间发生碰撞,提高了机器人的安全性;随着机器人数量的增多,改进的启发式路径搜索算法对正六边形栅格地图的机器人路径和算法运行时间的优化作用更加明显。     

基于蜂窝地图的步进式机器人路径规划

针对在智能空间中步进式机器人的移动问题,本论文对基于蜂窝地图的步进式机器人路径规划问题进行了较为深入的研究。在硬件系统设计与实现的基础上,重点研究了1.蜂窝栅格地图创建,给出由步进式机器人运动量推算出其所在栅格编码值计算方法,极大方便了系统中机器人蜂窝地图构建。2.基于蜂窝栅格地图的局部路径规划,分析并解决了由于蜂窝地图高度对称性带来的"死角"和"死圈"问题,总结了局部路径规划具有减小所需存储空间、提高系统实时性的优势,和规结果往往只是局部最优这一不足。3.基于蜂窝栅格地图的全局路径规划,根据整个步进式机器人系统定位精度要求,利用遗传算法规划出全局最优路径,并在仿真平台上得以实现。最后还分析了不同空间复杂度的栅格地图对于全局路径规划结果的影响。     

基于分布式感知的移动机器人同时定位与地图创建

为了创建大规模环境的精确栅格地图,提出一种基于分布式感知的两层同时定位与地图创建（SLAM）算法．在局部层,机器人一旦进入了一个新的摄像头视野,便依据机器人本体上的激光和里程计信息,采用Rao-Blackwellized粒子滤波方法创建一个新的局部栅格地图．与此同时,带有检测标志的机器人在摄像头视野内以曲线方式运动,以解决该摄像头的标定问题．在全局层,一系列的局部地图组成一个连接图,局部地图间的约束对应于连接图的边．为了生成一个准确且全局一致的环境地图,采用随机梯度下降法对连接图进行优化．实验结果验证了所提算法的有效性．     

栅格地图中多机器人协作搜索目标

目标搜索是多机器人领域的一个挑战.本文针对栅格地图中多机器人目标搜索算法进行研究.首先,利用Dempster-Shafer证据理论将声纳传感器获取的环境信息进行融合,构建搜索环境的栅格地图.然后,基于栅格地图建立生物启发神经网络用于表示动态的环境.在生物启发神经网络中,目标通过神经元的活性值全局的吸引机器人.同时,障碍物通过神经元活性值局部的排斥机器人,避免与其相撞.最后,机器人根据梯度递减原则自动的规划出搜索路径.仿真和实验结果显示本文提及的算法能够实现栅格地图中静态目标和动态目标的搜索.与其他搜索算法比较,本文所提及的目标搜索算法有更高的效率和适用性.     

温室移动机器人复合栅格地图构建方法研究

针对温室环境中机器人依靠自身携带的传感器无法获取全面的环境信息,从而常导致路径规划错误的问题,提出了一种结合外部传感器系统获取温室环境信息,构建复合栅格地图的方法。首先,利用无线传感器网络定时采集对机器人通过性有影响的温度、湿度环境信息,并发送给机器人;其次,当温度或湿度数据的变化率达到设定阈值时,机器人利用阈值分割和插值法分别建立温度和湿度栅格地图;最后,将温度栅格地图、湿度栅格地图和室内障碍物物栅格地图相结合,构建动态更新的复合栅格地图。经测试,采用常规A*算法规划路径时,基于环境数据变化率阈值设定为±10%的复合栅格地图的成功率和完成时间,分别是基于普通栅格地图成功率的2.5倍,和1.05倍。结果表明,复合栅格地图能提高路径规划的成功率,并且不会由于动态更新复合栅格地图,导致机器人响应时间明显增加,实时性能满足系统的实际需求。     

基于激光雷达的动态障碍物实时检测

动态障碍的存在直接影响到环境地图的构建精度,可靠实时地检测出动态障碍物是未知环境下移动机器人构建环境地图的根本前提。基于2D激光雷达传感器,提出了一种移动机器人在未知环境下实时检测动态障碍物的方法。将激光雷达的观测数据经过滤波映射到世界坐标系,构建相邻采样时刻的三幅栅格地图;判断相邻时刻三幅栅格地图上对应栅格的占用状态,确定环境中的静态障碍物,以静态障碍物为参考,根据当前的栅格地图可以检测出环境中的动态障碍物。基于激光雷达时空关联性分析,采用八邻域滚动窗口的方法处理不确定性因素。在实际移动机器人MORCS-1上进行的实验结果表明,该方法可使移动机器人准确有效地检测出未知环境中的动态障碍物,实时性好,可靠性高。     

实时更新的全局一致三维栅格建图

在未知的三维环境中,移动机器人自主导航通常需要实时构建与环境全局一致的栅格地图,而现有大部分系统缺少地图更新策略,构建的栅格地图与实际环境不一致.文中将同步定位与建图模块获得的环境信息以点云形式提供给栅格建图模块处理,同时提出基于关键帧的高效数据结构和地图实时更新策略,实时构建可用于移动机器人自主导航的全局一致的地图.室内动态的实验数据测试表明,文中方法可以有效实时更新地图,生成与环境一致的三维栅格地图,支持其后续的自主导航操作.     

基于视觉注意的移动机器人环境3D建模

人类的视觉注意具有高度的选择性.模仿这些机制可以使得机器人对其周围环境建模更具高效、智能和鲁棒特性.本文采用视觉注意提出了一种移动机器人环境3D建模方法.该方法采用障碍物距离势函数的变化率作为显著度的度量函数,利用移动机器人提取到的场景中的特征点并结合快速均值漂移算法,实现了移动机器人周围环境中物体显著性检测,并以其为栅格先验模型,结合传感器模型、投影方法采用贝叶斯估计方法构建了环境的栅格模型.建立的模型在室内和室外环境进行了实验验证和性能评估.     

Learning Occupancy Grid Maps with Forward Sensor Models

This article describes a new algorithm for acquiring occupancy grid maps with mobile robots. Existing occupancy grid mapping algorithms decompose the high-dimensional mapping problem into a collection of one-dimensional problems, where the occupancy of each grid cell is estimated independently. This induces conflicts that may lead to inconsistent maps, even for noise-free sensors. This article shows how to solve the mapping problem in the original, high-dimensional space, thereby maintaining all dependencies between neighboring cells. As a result, maps generated by our approach are often more accurate than those generated using traditional techniques. Our approach relies on a statistical formulation of the mapping problem using forward models. It employs the expectation maximization algorithm for searching maps that maximize the likelihood of the sensor measurements.     

Probabilistic terrain classification in unstructured environments

Autonomous navigation in unstructured environments is a complex task and an active area of research in mobile robotics. Unlike urban areas with lanes, road signs, and maps, the environment around our robot is unknown and unstructured. Such an environment requires careful examination as it is random, continuous, and the number of perceptions and possible actions are infinite.We describe a terrain classification approach for our autonomous robot based on Markov Random Fields (MRFs ) on fused 3D laser and camera image data. Our primary data structure is a 2D grid whose cells carry information extracted from sensor readings. All cells within the grid are classified and their surface is analyzed in regard to negotiability for wheeled robots.Knowledge of our robot’s egomotion allows fusion of previous classification results with current sensor data in order to fill data gaps and regions outside the visibility of the sensors. We estimate egomotion by integrating information of an IMU, GPS measurements, and wheel odometry in an extended Kalman filter.In our experiments we achieve a recall ratio of about 90% for detecting streets and obstacles. We show that our approach is fast enough to be used on autonomous mobile robots in real time.     

Map evaluation using matched topology graphs

Mapping is an important task for mobile robots. The assessment of the quality of maps in a simple, efficient and automated way is not trivial and an ongoing research topic. Here, a new approach for the evaluation of 2D grid maps is presented. This structure-based method makes use of a topology graph, i.e., a topological representation that includes abstracted local metric information. It is shown how the topology graph is constructed from a Voronoi diagram that is pruned and simplified such that only high level topological information remains to concentrate on larger, topologically distinctive places. Several methods for computing the similarity of vertices in two topology graphs, i.e., for performing a place-recognition, are presented. Based on the similarities, it is shown how subgraph-isomorphisms can be efficiently computed and two topology graphs can be matched. The match between the graphs is then used to calculate a number of standard map evaluation attributes like coverage, global accuracy, relative accuracy, consistency, and brokenness. Experiments with robot generated maps are used to highlight the capabilities of the proposed approach and to evaluate the performance of the underlying algorithms.     

Integrating fuzzy topological maps and fuzzy geometric maps for behavior‐based robots

In behavior‐based robots, planning is necessary to elaborate abstract plans that resolve complex navigational tasks. Usually maps of the environment are used to plan the robot motion and to resolve the navigational tasks. Two types of maps have been mainly used: metric and topological maps. Both types present advantages and weakness so that several integration approaches have been proposed in literature. However, in many approaches the integration is conducted to build a global representation model, and the planning and navigational techniques have not been fitted to profit from both kinds of information. We propose the integration of topological and metric models into a hybrid deliberative‐reactive architecture through a path planning algorithm based on A^* and a hierarchical map with two levels of abstraction. The hierarchical map contains the required information to take advantage of both kinds of modeling. On one hand, the topological model is based on a fuzzy perceptual model that allows the robot to classify the environment in distinguished places, and on the other hand, the metric map is built using regions of possibility with the shape of fuzzy segments, which are used later to build fuzzy grid‐based maps. The approach allows the robot to decide on the use of the most appropriate model to navigate the world depending on minimum‐cost and safety criteria. Experiments in simulation and in a real office‐like environment are shown for validating the proposed approach integrated into the navigational architecture. © 2002 Wiley Periodicals, Inc.     

Map merging for multiple robots using Hough peak matching

Navigation in a GPS-denied environment is an essential requirement for increased robotics autonomy. While this is in some sense solved for a single robot, the next challenge is to design algorithms for a team of robots to be able to map and navigate efficiently.The key requirement for achieving this team autonomy is to provide the robots with a collaborative ability to accurately map an environment. This problem is referred to as cooperative simultaneous localization and mapping (SLAM). In this research, the mapping process is extended to multiple robots with a novel occupancy grid map fusion algorithm. Map fusion is achieved by transforming individual maps into the Hough space where they are represented in an abstract form. Properties of the Hough transform are used to find the common regions in the maps, which are then used to calculate the unknown transformation between the maps.Results are shown from tests performed on benchmark datasets and real-world experiments with multiple robotic platforms.     

Adaptive occupancy grid mapping with clusters

In this article, we describe an algorithm for acquiring occupancy grid maps with mobile robots. The standard occupancy grid mapping developed by Elfes and Moravec in the mid-1980s decomposes the high-dimensional mapping problem into many one-dimensional estimation problems, which are then tackled independently. Because of the independencies between neighboring grid cells, this often generates maps that are inconsistent with the sensor data. To overcome this, we propose a cluster that is a set of cells. The cells in the clusters are tackled dependently with another occupancy grid mapping with an expectation maximization (EM) algorithm. The occupancy grid mapping with an EM algorithm yields more consistent maps, especially in the cluster. As we use the mapping algorithm adaptively with clusters according to the sensor measurements, our mapping algorithm is faster and more accurate than previous mapping algorithms. This work was presented in part at the 10th International Symposium on Artificial Life and Robotics, Oita, Japan, February 4–6, 2005