一种基于多层代价地图的移动机器人导航方法

当前移动机器人导航方法大多数是改善局部路径规划的反应式导航而没有充分考虑全局环境中的行人,借助全局范围的行人感知,提出并实现一种基于多层代价地图的全局路径规划方法。首先基于行人感知进行个人空间和群组交互的社会代价建模,基于行人轨迹预测生成包含预测阶段社会代价的多层动态代价地图,提供预测阶段的社会约束信息。全局路径规划器在动态代价地图基础上定义代价函数进行最优状态的启发式搜索,引入“规划-预测-执行”时序周期进行动态规划。最后通过和传统路径规划器在行人运动、群组交互等仿真、实际场景下进行对比试验,该方法对应路径长度、执行时间更短,和人/群组保持的距离更符合社会性。     

Mobile robot navigation using motor schema and fuzzy context dependent behavior modulation

This paper presents a novel technique to autonomously select different motor schemas using fuzzy context dependant blending of robot behaviors for navigation. First, a set of motor schemas is formed as behaviors. Both strategic and reactive type schemas have been employed in order to facilitate both the aspects of global and local motion planning. While strategic schemas are formed using the prior knowledge of the environment, the reactive schemas are activated using current sensory data of the robot. For global path planning, a safe path is first created using a Voronoi diagram. For local planning, the Voronoi vertices are treated as immediate subgoals and are used to form schemas leading to achieve optimized traveled distance and goal oriented robot navigation. Two motor schemas are formed as reactive behaviors for obstacle avoidance. The unknown obstacles are modeled using the sensory data. The coordinated behavior is achieved while employing weighed vector summation of the schemas. The adaptation of weights are achieved through a fuzzy inference system where fuzzy rules are used to dynamically generate the weights during navigation. A novel approach is proposed for fuzzy context-dependent blending of schemas. Fuzzy rules are formed using two main criteria into account: the first criterion reasons out the context dependent activity of a schema for achieving goal and the second criterion reasons out cooperative activity of strategic schemas with high priority reactive schemas. Comprehensive results validate that the proposed technique eliminates the existing drawbacks of motor schema approaches available in literature and provides collision free goal oriented robot navigation.     

动态环境下多重A*算法的机器人路径规划方法

传统的A*算法仅适用于全局的静态环境,在求解路径规划问题时存在搜索效率低,路径不平滑等不足。针对这些问题,进行了以下改进：优化全局路径节点,引入删除冗余点准则与新增节点准则,使得全局路径更加平滑,更符合机器人运动学规律;结合滚动窗口法的思想,在每个滚动窗口内进行局部路径规划,首先根据前一步的节点信息确定局部子目标区域,然后在局部子目标区域内引入避障控制策略进行实时避障。最后通过Matlab软件建立多种栅格地图仿真,从路径轨迹的平滑度、搜索效率与局部规划能力方面将改进后的算法与原算法进行对比,并在动态环境下进行仿真分析,仿真结果表明改进后算法拥有良好局部规划能力,且路径轨迹更加平滑,在复杂环境下搜索效率更高。     

基于模型预测控制与改进人工势场法的多无人机路径规划

模型预测控制(model predictive control,MPC)已成功地应用于无人机集群的路径规划.但其存在计算量大及单步运算时间长等不足,在实时运行中往往难以获得较高的控制频率.而离线的MPC需要准确的地图信息,难以处理地图中无法预测的动态障碍物.对此,提出一种结合离线MPC全局规划与在线改进人工势场法局部规划的方法.在利用MPC方法生成安全、平滑轨迹的同时,提高无人机在动态障碍物影响下的避障能力.通过引入调节力来处理传统人工势场法的局部极小值问题,并将目标与无人机的相对距离引入斥力函数,同时改进引力函数,以改善无人机在目标点处低速徘徊的问题.此外,设计一种事件触发的无人机轨迹变更与轨迹恢复策略,使无人机仅在必要时实施动态避障行为.在此基础上,最大化利用原来的规划轨迹.仿真验证结果表明,所提出的路径规划方法能够使无人机集群安全飞行至目标点,并且具有良好的动态避障能力.     

Planning collision-free trajectories in time-varying environments: a two-level hierarchy

We propose a two-level hierarchy for planning collision-free trajectories in time varying environments. Global geometric algorithms for trajectory planning are used in conjunction with a local avoidance strategy. Simulations have been developed for a mobile robot in the plane among stationary and moving obstacles. Essentially, the robot has a global geometric planner that provides a coarse global trajectory (the path and velocity along it), which may be locally modified by the low-level local avoidance module if local sensors detect any obstacles in the vicinity of the robot. This hierarchy makes effective use of the complementary aspects of the global trajectory planning approaches and the local obstacle avoidance approaches.     

基于BIM的建筑机器人自主路径规划及避障研究

针对建筑机器人进入施工位置全局路径规划最优且可实时避障的要求,提出了一种新型的导航地图建立方法,通过建筑物BIM（Building Information Modeling）模型建立导航地图,通过优化A*算法搜索点选取策略,以及删除了路径上的冗余转折点,缩短算法运行时间,且规划出的全局路径不会紧贴着建筑物墙壁,有效降低了机器人与墙体发生碰撞的可能性。结合动态窗口算法进行局部路径规划,在全局路径关键点之间使用动态窗口法,且加入了新的刹车判定条件,使得机器人的运动连续化。实验结果表明改进后的A*算法运行时间相较于原始算法减少50%以上,每去除一个冗余转折点路径长度减少0.4?m,路径与障碍物之间的距离比原始算法增加了2倍,结合了动态窗口法之后能够较好地避开障碍且输出的控制参数连续化。     

Autonomous Navigation for Micro Aerial Vehicles in Complex GNSS-denied Environments

Micro aerial vehicles, such as multirotors, are particular well suited for the autonomous monitoring, inspection, and surveillance of buildings, e.g., for maintenance in industrial plants. Key prerequisites for the fully autonomous operation of micro aerial vehicles in restricted environments are 3D mapping, real-time pose tracking, obstacle detection, and planning of collision-free trajectories. In this article, we propose a complete navigation system with a multimodal sensor setup for omnidirectional environment perception. Measurements of a 3D laser scanner are aggregated in egocentric local multiresolution grid maps. Local maps are registered and merged to allocentric maps in which the MAV localizes. For autonomous navigation, we generate trajectories in a multi-layered approach: from mission planning over global and local trajectory planning to reactive obstacle avoidance. We evaluate our approach in a GNSS-denied indoor environment where multiple collision hazards require reliable omnidirectional perception and quick navigation reactions.     

一种内河海事无人艇路径规划算法设计与仿真

为了解决内河海事无人艇路径规划问题,提出了一种基于电子江图的路径遍历算法。该算法以分层的电子江图为基础,运用全局路径规划和局部路径规划的方法寻找近似可航路径。运用栅格法在复杂多变的内河环境中选择可航区域,运用Voronoi图对动态物标或可视为质点的碍航物建立航行路径集;将可航区域（或轻微碍航区域）与航行路径集公共区域记为可航路径;并运用贝塞尔曲线和二次规划数学方法进行优化。Matlab仿真结果表明,当障碍物位置坐标不同或目的地位置坐标不同时均可以生成近似可航路径;生成的不同近似可航路径均能被优化为最优安全可航路径,所以建立的环境模型以及使用的路径规划算法是有效、可行的。     

Experience Learning From Basic Patterns for Efficient Robot Navigation in Indoor Environments

In this paper we propose a machine learning technique for real-time robot path planning for an autonomous robot in a planar environment with obstacles where the robot possess no a priori map of its environment. Our main insight in this paper is that a robot’s path planning times can be significantly reduced if it can refer to previous maneuvers it used to avoid obstacles during earlier missions, and adapt that information to avoid obstacles during its current navigation. We propose an online path planning algorithm called LearnerRRT that utilizes a pattern matching technique called Sample Consensus Initial Alignment (SAC-IA) in combination with an experience-based learning technique to adapt obstacle boundary patterns encountered in previous environments to the current scenario followed by corresponding adaptations in the obstacle-avoidance paths. Our proposed algorithm LearnerRRT works as a learning-based reactive path planning technique which enables robots to improve their overall path planning performance by locally improving maneuvers around commonly encountered obstacle patterns by accessing previously accumulated environmental information. We have conducted several experiments in simulations and hardware to verify the performance of the LearnerRRT algorithm and compared it with a state-of-the-art sampling-based planner. LearnerRRT on average takes approximately 10% of the planning time and 14% of the total time taken by the sampling-based planner to solve the same navigation task based on simulation results and takes only 33% of the planning time, 46% of total time and 95% of total distance compared to the sampling-based planner based on our hardware results.     

Reactive navigation of underwater mobile robot using ANFIS approach in a manifold manner

Learning and self-adaptation ability is highly required to be integrated in path planning algorithm for underwater robot during navigation through an unspecified underwater environment. High frequency oscillations during underwater motion are responsible for nonlinearities in dynamic behavior of underwater robot as well as uncertainties in hydrodynamic coefficients. Reactive behaviors of underwater robot are designed considering the position and orientation of both target and nearest obstacle from robot’s current position. Human like reasoning power and approximation based learning skill of neural based adaptive fuzzy inference system (ANFIS) has been found to be effective for underwater multivariable motion control. More than one ANFIS models are used here for achieving goal and obstacle avoidance while avoiding local minima situation in both horizontal and vertical plane of three dimensional workspace. An error gradient approach based on input-output training patterns for learning purpose has been promoted to spawn trajectory of underwater robot optimizing path length as well as time taken. The simulation and experimental results endorse sturdiness and viability of the proposed method in comparison with other navigational methodologies to negotiate with hectic conditions during motion of underwater mobile robot.     

Reactive navigation in dynamic environment using a multisensorpredictor

A reactive navigation system for an autonomous mobile robot in unstructured dynamic environments is presented. The motion of moving obstacles is estimated for robot motion planning and obstacle avoidance. A multisensor-based obstacle predictor is utilized to obtain obstacle-motion information. Sensory data from a CCD camera and multiple ultrasonic range finders are combined to predict obstacle positions at the next sampling instant. A neural network, which is trained off-line, provides the desired prediction on-line in real time. The predicted obstacle configuration is employed by the proposed virtual force based navigation method to prevent collision with moving obstacles. Simulation results are presented to verify the effectiveness of the proposed navigation system in an environment with multiple mobile robots or moving objects. This system was implemented and tested on an experimental mobile robot at our laboratory. Navigation results in real environment are presented and analyzed.     

An open‐source system for vision‐based micro‐aerial vehicle mapping,planning, and flight in cluttered environments

We present an open‐source system for Micro‐Aerial Vehicle (MAV) autonomous navigation from vision‐based sensing. Our system focuses on dense mapping, safe local planning, and global trajectory generation, especially when using narrow field‐of‐view sensors in very cluttered environments. In addition, details about other necessary parts of the system and special considerations for applications in real‐world scenarios are presented. We focus our experiments on evaluating global planning, path smoothing, and local planning methods on real maps made on MAVs in realistic search‐and‐rescue and industrial inspection scenarios. We also perform thousands of simulations in cluttered synthetic environments, and finally validate the complete system in real‐world experiments.     

动态环境下机器人多目标路径规划蚂蚁算法

研究了一种新颖的动态复杂不确定环境下的机器人多目标路径规划蚂蚁算法。该方法首先根据蚂蚁觅食行为对多个目标点的组合进行优化,规划出一条最优的全局导航路径。在此基础上,机器人按照规划好的目标点访问顺序根据多蚂蚁协作局部路径算法完成局部路径的搜索。机器人每前进一步都实时地进行动态障碍物运动轨迹预测以及碰撞预测,并重新进行避碰局部路径规划。仿真结果表明,即使在障碍物非常复杂的地理环境,用该算法也能使机器人沿一条全局优化的路径安全避碰的遍历各个目标点,效果十分令人满意。     

基于稀疏A*搜索和改进人工势场的无人机动态航迹规划

针对不同属性的障碍物所构成的威胁分布模型, 本文提出了一种基于稀疏A*搜索算法预规划和改进人工势场相结合的无人机动态避障算法. 该算法首先对威胁分布建立栅格化模型; 然后根据静态威胁, 基于稀疏A*搜索算法进行全局航迹规划; 最后结合预规划路径和动态威胁分布, 利用改进人工势场法完成无人机的动态避障. 仿真结果表明, 该方法能够规划出给定威胁指标下的全局最优路径并达到良好的动态规避性能.     

一种动态环境下移动机器人的路径规划方法

本文提出了在动态环境中，移动机器人的一种路径规划方法，适用于环境中存 在已知和未知、静止和运动障碍物的复杂情况．采用链接图法建立了机器人工作空间模型， 整个系统由全局路径规划器和局部路径规划器两部分组成．在全局路径规划器中，应用遗传 算法规划出初步全局优化路径．在局部路径规划器中，设计了三种基本行为：跟踪全局路径 的行为、避碰的行为和目标制导的行为，采用基于行为的方法进一步优化路径．其中，避碰 的行为是通过强化学习得到的．仿真和实验结果表明所提方法简便可行，能够满足移动 机器人导航的高实时性要求．     

Speed Planning for a Maneuvering Motion

Collision-free motion among moving objects is an on-going research topic. Based on the concept of a modified path-velocity decomposition and application of the interface propagation method, a strategy for trajectory planning is proposed in this paper. In the proposed method, the global navigation paths for robots are assumed to have already been planned without any static obstacle crossing their paths. Each subtask along the global path of each controlled object contains a desired goal position and desired arrival time for reaching the position. Based on the information about each subtask, Space/Time Graphs (STGs) for the robots are created. By shifting the speed path from corresponding forbidden regions on the STG, potential collisions can be avoided. Optimal speed paths with least velocity alterations for controllable objects are derived automatically by applying the interface propagation method in the STGs. The applicability of the proposed approach is demonstrated and the results show that controllable and uncontrollable moving objects can work together in a shared environment by avoiding collisions.     

一种新的基于切线的路径规划方法

提出了一种崭新的基于切线的路径规划方法.它在二维离散姿态空间中,用障碍物的边界线建立环境模型,用凸壳和切线构造局部最短路径,复杂地形能被主干线结构有效地分解.跳跃式扫描技术和按需扩展搜索图的策略使它优于切线图法.它能非常有效地利用稀疏环境和处理较大的规划空间,并且能适应未知和动态的环境, 这使它成为远距离漫游的理想导航方法. 仿真表明,本文算法通常都能得到全局最优路径,并且规划速度快、内存需求小，非常适合于实时应用.􀁱     

融合改进A*算法和Morphin算法的移动机器人动态路径规划

在动态未知环境下对机器人进行路径规划,传统A*算法可能出现碰撞或者路径规划失败问题。为了满足移动机器人全局路径规划最优和实时避障的需求,提出一种改进A*算法与Morphin搜索树算法相结合的动态路径规划方法。首先通过改进A*算法减少路径规划过程中关键节点的选取,在规划出一条全局较优路径的同时对路径平滑处理。然后基于移动机器人传感器采集的局部信息,利用Morphin搜索树算法对全局路径进行动态的局部规划,确保更好的全局路径的基础上,实时避开障碍物行驶到目标点。MATLAB仿真实验结果表明,提出的动态路径规划方法在时间和路径上得到提升,在优化全局路径规划的基础上修正局部路径,实现动态避障提高机器人达到目标点的效率。     

A Novel Approach for Mobile Robot Navigation with Dynamic Obstacles Avoidance

This paper proposes a new approach for trajectory optimization of a mobile robot in a general dynamic environment. The new method combines the static and dynamic modes of trajectory planning to provide an algorithm that gives fast and optimal solutions for static environments, and generates a new path when an unexpected situation occurs. The particularity of the method is in the representation of the static environment in a judicious way facilitating the path planning and reducing the processing time. Moreover, when an unexpected obstacle blocks the robot trajectory, the method uses the robot sensors to detect the obstacle, finds a best way to circumvent it and then resumes its path toward the desired destination. Experimental results showed the effectiveness of the proposed approach.     

实现机器人动态路径规划的仿真系统

针对机器人动态路径规划问题,提出了在动态环境中移动机器人的一种路径规划方法,适用于环境中同时存在已知和未知,静止和运动障碍物的复杂情况。采用栅格法建立机器人空间模型,整个系统由全局路径规划和局部避碰规划两部分组成。在全局路径规划中,用快速搜索随机树算法规划出初步全局优化路径,局部避碰规划是在全局优化路径的同时,通过基于滚动窗口的环境探测和碰撞规则,对动态障碍物实施有效的局部避碰策略,从而使机器人安全顺利地到达目的地。仿真实验结果说明该方法具有可行性。