基于MEMS激光雷达的智能轮椅SLAM研究

轮椅是残障人士和老年人的重要代步工具,传统的电动、手动轮椅移动方式单一,需要他人辅助完成,且无法主动保证使用者的安全。研究了基于机器人操作系统(ROS)的轮椅室外场景建模、路径规划与导航算法。在轮椅上安装MEMS激光雷达,融合体素网格滤波器和LeGO-LOAM算法完成点云处理和室外场景建模;设计了融合百度地图和激光雷达的轮椅导航方式,使用者可根据百度地图提供的路径规划信息遥控轮椅,在建图完毕后,可仅依靠激光雷达完成路径导航和自主移动;结合激光雷达智能感知算法,实现了道路信息的实时感知,使轮椅具备主动安全功能。通过实验验证了建模、感知算法的功能,并完成了融合导航仿真实验,研究内容能够大幅提升智能轮椅使用过程中的安全性能。     

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.     

Monocular Vision for Mobile Robot Localization and Autonomous Navigation

This paper presents a new real-time localization system for a mobile robot. We show that autonomous navigation is possible in outdoor situation with the use of a single camera and natural landmarks. To do that, we use a three step approach. In a learning step, the robot is manually guided on a path and a video sequence is recorded with a front looking camera. Then a structure from motion algorithm is used to build a 3D map from this learning sequence. Finally in the navigation step, the robot uses this map to compute its localization in real-time and it follows the learning path or a slightly different path if desired. The vision algorithms used for map building and localization are first detailed. Then a large part of the paper is dedicated to the experimental evaluation of the accuracy and robustness of our algorithms based on experimental data collected during two years in various environments.     

Autonomous Navigation of UAV in Foliage Environment

This paper presents a navigation system that enables small-scale unmanned aerial vehicles to navigate autonomously using a 2D laser range finder in foliage environment without GPS. The navigation framework consists of real-time dual layer control, navigation state estimation and online path planning. In particular, the inner loop of a quadrotor is stabilized using a commercial autopilot while the outer loop control is implemented using robust perfect tracking. The navigation state estimation consists of real-time onboard motion estimation and trajectory smoothing using the GraphSLAM technique. The onboard real-time motion estimation is achieved by a Kalman filter, fusing the planar velocity measurement from matching the consecutive scans of a laser range finder and the acceleration measurement of an inertial measurement unit. The trajectory histories from the real-time autonomous navigation together with the observed features are fed into a sliding-window based pose-graph optimization framework. The online path planning module finds an obstacle-free trajectory based the local measurement of the laser range finder. The performance of the proposed navigation system is demonstrated successfully on the autonomous navigation of a small-scale UAV in foliage environment.     

基于ROS的无人配送车导航系统的设计与实现

针对无人配送车在自主导航过程中存在的寻路效率低、避障能力弱、转折幅度过大等问题,该文采用搭载机器人操作系统(ROS)的Turtlebot3机器人作为无人配送车,设计并实现了高效稳定的无人配送车自主导航系统。ROS是专门用于编写机器人软件的灵活框架,对其集成的SLAM算法进行改进,以完成无人配送车在封闭园区环境中的即时定位与地图构建,同时对ROS导航功能包集成的路径规划算法进行改进,使无人配送车在已知环境地图中规划生成出适合无人配送车工作的路径和有效避开障碍物。最后在Gazebo仿真环境中对无人配送车自主导航系统进行测试与验证。仿真试验结果表明,设计实现的无人配送车导航系统能够很好地满足无人配送车在封闭园区中的自主导航功能。     

Real-time hierarchical POMDPs for autonomous robot navigation

This paper proposes a new hierarchical formulation of POMDPs for autonomous robot navigation that can be solved in real-time, and is memory efficient. It will be referred to in this paper as the Robot Navigation–Hierarchical POMDP (RN-HPOMDP). The RN-HPOMDP is utilized as a unified framework for autonomous robot navigation in dynamic environments. As such, it is used for localization, planning and local obstacle avoidance. Hence, the RN-HPOMDP decides at each time step the actions the robot should execute, without the intervention of any other external module for obstacle avoidance or localization. Our approach employs state space and action space hierarchy, and can effectively model large environments at a fine resolution. Finally, the notion of the reference POMDP is introduced. The latter holds all the information regarding motion and sensor uncertainty, which makes the proposed hierarchical structure memory efficient and enables fast learning. The RN-HPOMDP has been experimentally validated in real dynamic environments.     

基于地图的移动机器人自定位与导航系统

针对地图已知情况下的移动机器人大范围导航问题,研制了一个由地图编辑器模块、地图匹配与定位模块以及多层递阶规划模块三部分组成的移动机器人导航系统．地图编辑器负责导航地图的编辑;地图匹配与定位模块利用里程计和激光雷达数据实现基于地图匹配的自定位;多层递阶规划模块将基于拓扑地图的全局规划、基于栅格地图的局部规划和底层的行为控制功能有机结合．通过室内定位和大范围导航实验评估了本系统的有效性和准确性．     

A New Mobile Robot Toolbox for Matlab

In this study, a wheeled mobile robot navigation toolbox for Matlab is presented. The toolbox includes algorithms for 3D map design, static and dynamic path planning, point stabilization, localization, gap detection and collision avoidance. One can use the toolbox as a test platform for developing custom mobile robot navigation algorithms. The toolbox allows users to insert/remove obstacles to/from the robot’s workspace, upload/save a customized map and configure simulation parameters such as robot size, virtual sensor position, Kalman filter parameters for localization, speed controller and collision avoidance settings. It is possible to simulate data from a virtual laser imaging detection and ranging (LIDAR) sensor providing a map of the mobile robot’s immediate surroundings. Differential drive forward kinematic equations and extended Kalman filter (EKF) based localization scheme is used to determine where the robot will be located at each simulation step. The LIDAR data and the navigation process are visualized on the developed virtual reality interface. During the navigation of the robot, gap detection, dynamic path planning, collision avoidance and point stabilization procedures are implemented. Simulation results prove the efficacy of the algorithms implemented in the toolbox.     

移动机器人自主导航系统及上位机软件设计与实现

针对移动机器人自主导航系统,采用C++语言设计了一款基于Qt的跨平台实时数据可视化上位机软件;该软件执行SLAM技术和路径规划算法,实现可视化移动机器人建图与导航过程以及实时读取数据参数等功能;首先介绍移动机器人的硬件结构和功能;其次给出了自主导航所运用到的改进RRT*算法和动态窗口法;在详细叙述上位机软件工作流程的基础上,开发和设计了实时话题显示、读取以及界面可视化等功能;最后基于ROS系统完成移动机器人自主导航功能,并通过实时地图与数据可视化来验证所设计上位机软件功能的有效性。     

基于双目视觉的无人船障碍物探测与地图构建

在无人船的巡航过程中，如何探测和躲避障碍物是必须解决的问题。由于无人船自主巡航依赖于其自身对所处环境的精确探测，而目前一般采用的超声波或雷达技术探测距离和精度较低，避障功能弱，因此需引入视觉方法来提升避障精度，并用于轨迹生成、定位或路径规划。本文为无人船搭建双目视觉系统，提出采用双目直接稀疏里程计算法构建无人船所处三维空间模型，将构建的三维点云图转化为二维网格图并标记障碍物，为避障系统进行路径规划提供障碍物数据。实验结果表明，该系统对真实河流环境进行了地图构建，并解决了水上环境构建存在的“虚拟障碍”等问题。     

A robust navigation system for robotic wheelchairs

A landmark based navigation system for robotic wheelchairs is developed. The proposed navigation system is robust in the localization procedure which is the major problem in robotic navigation systems. Every landmark is composed of a segment of metallic path and a radio-frequency identification (RFID) tag. The odometry information is used for localization, which is corrected on-line every time the robotic wheelchair is over a landmark. A topological map is generated using such landmarks to compute the shortest path. A technique to generate the topological map for this navigation system and an obstacle avoidance strategy are also developed.     

保证智能轮椅平滑通过狭窄通道的路径曲率优化算法

为了使用户更感舒适,智能轮椅应该能在具有复杂几何约束的室内环境下平滑地通过狭窄通道.本文提出一个基于路径曲率优化的算法以确保智能轮椅平滑地通过狭窄过道.考虑到路径平滑度取决于路径曲率及其变化率,在通过传感器数据计算出狭窄通道相对于轮椅的位置后,算法以贝塞尔曲线的曲率及其变化率最小为优化目标,以轮椅过通道时的方向及贝塞尔多边形应为凸多边形作为约束,规划出一条平滑的最优路径,然后控制轮椅实时跟踪这条路径.上述过程动态循环运行,实现了智能轮椅平滑通过狭窄通道.仿真中将本文算法同基于A*的路径规划导航算法进行了对比,结果表明本文提出的基于曲率优化的算法可以实现比A*算法路径曲率更小且更加平滑的过狭窄通道过程,并且即使在没有全局地图和定位信息情况下,算法也能控制轮椅平滑地通过狭窄过道.实验中详细阐述了算法的实现过程,实验结果也证实了算法的有效性.     

基于多传感器信息融合的移动机器人导航综述

综述了自主式移动机器人导航技术,对其中的同步定位与地图创建、路径规划以及多传感器信息融合等技术进行了详细的分析,并从基于地图、基于环境和基于行为3个方面全面地阐述了移动机器人路径规划技术的研究现状.对当前的研究热点SLAM技术、遗传算法和基于行为的规划算法等进行了较为详细的介绍和分析.同时,展望了移动机器人导航技术的发展趋势.     

基于生物认知的移动机器人路径规划方法

针对移动机器人在非结构环境下的导航任务,受哺乳动物空间认知方式的启发,提出一种基于生物认知进行移动机器人路径规划的方法．结合认知地图特性,模拟海马体的情景记忆形成机理,构建封装了场景感知、状态神经元及位姿感知相关信息的情景认知地图,实现了机器人对环境的认知．基于情景认知地图,以最小事件距离为准则,提出事件序列规划算法用于实时导航过程．实验结果表明,该控制算法能使机器人根据不同任务选择最佳规划路径．     

基于模糊神经网络算法的智能轮椅沿墙走行为研究

为了解决移动机器人在户外自主导航移动过程中的局部路径规划问题,提出了一种更为实用的模糊神经网络算法来进行局部路径规划。利用多个声纳和一个摄像头来采集外部环境信息,使智能轮椅在移动过程中可以得到较全面的外部环境信息,使用模糊神经网络算法来对得到的环境信息进行融合,应用的神经网络模型为Takagi-Sugeno(T-S)型,通过融合的结果来控制轮椅的沿墙走行为。通过计算机仿真和实验,验证了该方法的可行性和有效性,轮椅沿墙行走的路径得到了优化。     

室外自主移动机器人AMOR的导航技术

在非结构化环境,移动机器人行驶运动规划和自主导航是非常挑战性的问题。基于实时的动态栅格地图,提出了一个快速的而又实效的轨迹规划算法,实现机器人在室外环境的无碰撞运动导航。AMOR是自主研发的室外运动移动机器人,它在2007年欧洲C-ELROB大赛中赢得了野外自主侦察比赛的冠军。它装备了SICK的激光雷达,用来获取机器人运动前方的障碍物体信息,建立实时动态的环境地图。以A*框架为基础的改造算法,能够在众多的路径中快速地找到最佳的安全行驶路径,实现可靠的自主导航。所有的测试和比赛结果表明所提方案是可行的、有效的。     

Driving on Point Clouds: Motion Planning,Trajectory Optimization,and Terrain Assessment in Generic Nonplanar Environments

We present a practical approach to global motion planning and terrain assessment for ground robots in generic three‐dimensional (3D) environments, including rough outdoor terrain, multilevel facilities, and more complex geometries. Our method computes optimized six‐dimensional trajectories compliant with curvature and continuity constraints directly on unordered point cloud maps, omitting any kind of explicit surface reconstruction, discretization, or topology extraction. We assess terrain geometry and traversability on demand during motion planning, by fitting robot‐sized planar patches to the map and analyzing the local distribution of map points. Our motion planning approach consists of sampling‐based initial trajectory generation, followed by precise local optimization according to a custom cost measure, using a novel, constraint‐aware trajectory optimization paradigm. We embed these methods in a complete autonomous navigation system based on localization and mapping by means of a 3D laser scanner and iterative closest point matching, suitable for both static and dynamic environments. The performance of the planning and terrain assessment algorithms is evaluated in offline experiments using recorded and simulated sensor data. Finally, we present the results of navigation experiments in three different environments—rough outdoor terrain, a two‐level parking garage, and a dynamic environment, demonstrating how the proposed methods enable autonomous navigation in complex 3D terrain.     

基于RGB-D信息的移动机器人SLAM和路径规划方法研究与实现

移动机器人在各种辅助任务中需具备自主定位、建图、路径规划与运动控制的能力。本文利用RGB-D信息和ORB-SLAM算法进行自主定位,结合点云数据和GMapping算法建立环境栅格地图,基于二次规划方法进行平滑可解析的路径规划,并设计非线性控制器,实现了由一个运动底盘、一个RGB-D传感器和一个运算平台组成的自主移动机器人系统。经实验验证,这一系统实现了复杂室内环境下的实时定位与建图、自主移动和障碍物规避。由此,为移动机器人的推广应用提供了一个硬件结构简单、性能良好、易扩展、经济性好、开发维护方便的解决方案。     

Optimal Multi-Criteria Waypoint Selection for Autonomous Vehicle Navigation in Structured Environment

This paper deals with autonomous navigation of unmanned ground vehicles (UGV). The UGV has to reach its assigned final configuration in a structured environments (e.g. a warehouse or an urban environment), and to avoid colliding neither with the route boundaries nor any obstructing obstacles. In this paper, vehicle planning/set-points definition is addressed. A new efficient and flexible methodology for vehicle navigation throughout optimal and discrete selected waypoints is proposed. Combining multi-criteria optimization and expanding tree allows safe, smooth and fast vehicle overall navigation. This navigation through way-points permits to avoid any path/trajectory planning which could be time consuming and complex, mainly in cluttered and dynamic environment. To evaluate the flexibility and the efficiency of the proposed methodology based on expanding tree (taking into account the vehicle model and uncertainties), an important part of this paper is dedicated to give an accurate comparison with another proposed optimization based on the commonly used grid map. A set of simulations, comparison with other methods and experiments, using an urban electric vehicle, are presented and demonstrate the reliability of our proposals.