A distributed motion coordination strategy for multiple nonholonomic mobile robots in cooperative hunting operations

This paper presents a distributed smooth time-varying feedback control law for coordinating motions of multiple nonholonomic mobile robots of the Hilare-type to capture/enclose a target by making troop formations. This motion coordination is a cooperative behavior for security against invaders in surveillance areas. Each robot in this control law has its own coordinate system and it senses a target/invader, other robots and obstacles, to achieve this cooperative behavior without making any collision. Each robot especially has a two-dimensional control input referred to as a “formation vector” and the formation is controllable by the vectors. The validity of this control law is supported by computer simulations.     

A framework for the collective movement of mobile robots based on distributed decisions

A novel framework for the control of the collective movement of mobile robots is presented and analyzed in this article. It allows a group of robots to move as a unique entity performing the following functions: obstacle avoidance at group level, speed control and modification of the inter-robot distance. Its flocking controller is distributed among the robots, allowing them to move in the desired common direction and maintain a desired inter-robot distance. The framework is made up of different modules that modify the behavior of the group thus allowing different functions. They are based on consensus algorithms that allow the robots to agree on different parameters, taking into account which robot has more relevant information. New modules can be easily designed and incorporated into the framework in order to augment its capabilities. It can be easily implemented on any mobile robot capable of measuring the relative positions of neighboring robots and communicating with them. It has been successfully tested using 8 real robots and in simulation with up to 40 robots, demonstrating experimentally its scalability with an increasing number of robots.     

基于移动Agent的分布式数据库的协同安全模型

随着各种分布式计算的广泛应用,移动Agent技术引起了人们越来越多的关注.在移动Agent的应用环境中,数据传输、服务器资源.移动Agent运行环境和移动Agent自身安全等方面的安全性问题日益突出.同时移动Agent应用系统中各个数据处理Agent之间的自主进行协商和协调也是一个有待解决的问题.针对这些问题,提出了一种基于移动Agent的分布式数据库的协同安全模型,来初步解决移动Agent的分布式数据库安全性和Agent之间协调工作的问题.     

Line and circle formation of distributed physical mobile robots

The formation problem of distributed mobile robots was studied in the literature for idealized robots. Idealized robots are able to instantaneously move in any directions, and are equipped with perfect range sensors. In this study, we address the formation problem of distributed mobile robots that are subject to physical constraints. Mobile robots considered in this study have physical dimensions and their motions are governed by physical laws. They are equipped with sonar and infrared range sensors. The formation of lines and circles is investigated in detail. It is demonstrated that line and circle algorithms developed for idealized robots do not work well for physical robots. New line and circle algorithms, with consideration of physical robots and sensors, are presented and validated through extensive simulations. © 1997 John Wiley & Sons, Inc.     

Cooperative adaptive consensus tracking for multiple nonholonomic mobile robots

This paper addresses the cooperative adaptive consensus tracking for a group of multiple nonholonomic mobile robots, where the nonholonomic robot model is assumed to be a canonical vehicle having two actuated wheels and one passive wheel. By integrating a kinematic controller and a torque controller for the nonholonomic robotic system, a cooperative adaptive consensus tracking strategy is developed for the uncertain dynamic models using Lyapunov-like analysis in combination with backstepping approach and sliding mode technique. A key feature of the developed adaptive consensus tracking algorithm is the introduction of a directed network topology into the control constraints based on algebraic graph theory to characterise the communication interaction among robots, which plays an important role in realising the cooperative consensus tracking with respect to a specific common reference trajectory. Furthermore, a novel framework is proposed for developing a unified methodology for the convergence analysis of the closed-loop control systems, which can fully ensure the desired adaptive consensus tracking for multiple nonholonomic mobile robots. Subsequently, illustrative examples and numerical simulations are provided to demonstrate and visualise the theoretical results.     

Robust place recognition based on omnidirectional vision and real-time local visual features for mobile robots

Topological localization is especially suitable for human–robot interaction and robot’s high level planning, and it can be realized by visual place recognition. In this paper, bag-of-features, a popular and successful approach in pattern recognition community, is introduced to realize robot topological localization. By combining the real-time local visual features proposed by ourselves for omnidirectional vision and support vector machines, a robust and real-time visual place recognition algorithm based on omnidirectional vision is proposed. The panoramic images from the COLD database were used to perform experiments to determine the best algorithm parameters and the best training condition. The experimental results show that the robot can achieve robust topological localization with high successful rate in real time by using our algorithm.     

Nash-optimization distributed model predictive control for multi mobile robots formation

This paper investigates the distributed model predictive control (DMPC) problem for multi mobile robots. The distributed system model is obtained by the kinematic model of single mobile robot. By including the coupling terms in the cost function, cooperation between subsystems can be incorporated in the distributed control problem. Then, each robot has its own optimal control problem, and neighboring subsystems can exchange information with one another by using wireless communication. The distributed model predictive control problem is formulated by the local cost function and solved by using Nash-optimization algorithm. The convergence condition of the proposed algorithm is presented. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed method.     

CBBR: enabling distributed shared memory-based coordination among mobile robots

Coordinating mobile robots are widely used in commercial and industrial settings to fulfill various tasks. However, to program the coordination among mobile robots is challenging. A coordination framework is needed to shield the programmer from handling low-level details of robot control and communication, while supporting flexible and cost-effective coordination at the same time. The coordination framework should also be able to well coexist with the underlying robot control. To this end, we propose the Coordination-enabled Behavior-Based Robotics (CBBR) framework. CBBR employs Distributed Shared Memory (DSM) to support coordination. The shared memory illusion built by the DSM greatly simplifies the coordination logic. Moreover, the flexible access patterns of the DSM and the rich consistency semantics of the DSM reads and writes enable flexible and cost-effective coordination. With the coordination support from the DSM, CBBR naturally extends the classical Behavior-Based Robotics (BBR) for robot control. From the perspective of robot control using BBR, the shared variables in the DSM act as the logical sensors capturing the status of coordination. The coordination algorithms are encapsulated into coordination behaviors. Thus, the physical environment status and the coordination status may trigger the physical and the coordination behaviors. The scheduling of both types of behaviors integrates coordination into robot control. We conduct a case study to demonstrate the use of CBBR. The performance measurements show the cost-effectiveness of coordinating mobile robots based on CBBR, in terms of time, space, and energy consumption.     

基于模糊控制的移动机器人FPGA实现

针对轮式移动机器人寻线行走的跟踪控制要求,提出一种通用的移动机器人行走模糊控制设计方法,并以FPGA为核心器件,通过硬件描述语言(VHDL)实现移动机器人模糊控制系统,充分发挥模糊控制及可编程逻辑器件的优点。实验表明,该移动机器人具有自动纠偏、寻线准确、高集成度和高可靠性的特点。     

A distributed multi-agent production planning and scheduling framework for mobile robots

Inspired by the new achievements in mobile robotics having as a result mobile robots able to execute different production tasks, we consider a factory producing a set of distinct products via or with the additional help of mobile robots. This particularly flexible layout requires the definition and the solution of a complex planning and scheduling problem. In order to minimize production costs, dynamic determination of the number of robots for each production task and the individual robot allocation are needed. We propose a solution in terms of a two-level decentralized Multi-Agent System (MAS) framework: at the first, production planning level, agents are tasks which compete for robots (resources at this level); at the second, scheduling level, agents are robots which reallocate themselves among different tasks to satisfy the requests coming from the first level. An iterative auction based negotiation protocol is used at the first level while the second level solves a Multi-Robot Task Allocation (MRTA) problem through a distributed version of the Hungarian Method. A comparison of the results with a centralized approach is presented.     

基于聚类匹配的移动机器人地图实时创建算法

提出了一种基于模式识别聚类思想的数据点集匹配算法.该匹配算法具有传统迭代匹配算法和非迭代匹配算法的优点,匹配速度快,精度高.结合上述匹配算法,给出了一种基于激光测距仪的移动机器人环境地图实时创建方法.该方法使用从环境数据中提取出的特征点来完成两组激光数据点集的匹配,进而完成环境地图的创建.利用本实验室自主研发的救援机器人平台对该算法进行了验证,实验结果表明,该算法能够完成室内环境下移动机器人实时准确有效的环境地图创建.     

Formations of minimalist mobile robots using local-templates and spatially distributed interactions

In this paper we address the problem of synthesizing simple rules and local interactions at the individual level so that pre-specified complex behavior emerges at the group level of a collection of autonomous mobile agents. Usually, the emergent collective behavior is used to perform certain spatial group-tasks. Specifically, we consider self-assembling of a group of mobile robots into grid, line, and wedge patterns. We introduce the notion of local-templates in which each mobile agent – capable of simple forward/backward movements and a clock-wise/counter clock-wise spin – actively encodes distinctive information into multiple non-overlapping sectorial regions of the surrounding environment in order to form pose-specific virtual links with similar minimalist agents in a local neighborhood. The resulting local patterns around each agent lead to the desired global formation. In order to take mobile robots closer to their biological counterparts, there is a need to further simplify the manner in which they currently perceive their surroundings, communicate with their neighbors, and compute their actions. We have built a robotic platform consisting of four wheeled-mobile robots that are christened as Kinbots. They are similar in principle to Braitenberg Vehicles and use simple perception/interaction/actuation techniques to achieve individual vehicle complexity and produce effective group behavior through cooperation. To validate the proposed approach, we demonstrate a column-formation task in computer simulations and physical experiments. We illustrate an experiment which is representative of various prominent stages in a group-formation task such as formation-achievement, maintenance, and response of formation movement to the presence of obstacles.     

基于传感器信息的智能移动机器人导航评述

导航是研究智能移动机器人技术中的一个重要领域,对自主导航技术的关键问题——路径规划进行了评述。路径规划一般可分为基于模型的环境信息完全知道的全局路径规划和基于传感器的环境信息完全未知或部分未知的局部路径规划2种类型。分别对各种方法的发展现状进行了总结,指出了各种方法的优点和不足。     

Improvement of group performance of job distributed mobile robots by an emotionally biased control system

This paper deals with the implementation of emotions in mobile robots performing a specified task in a group in order to develop intelligent behavior and easier forms of communication. The overall group performance depends on the individual performance, group communication, and the synchronization of cooperation. With their emotional capability, each robot can distinguish the changed environment, can understand a colleague robot’s state, and can adapt and react with a changed world. The adaptive behavior of a robot is derived from the dominating emotion in an intelligent manner. In our control architecture, emotion plays a role to select the control precedence among alternatives such as behavior modes, cooperation plans, and goals. Emotional interaction happens among the robots, and a robot is biased by the emotional state of a colleague robot in performing a task. Here, emotional control is used for a better understanding of the colleague’s internal state, for faster communication, and for better performance eliminating dead time. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

VCS-based motion planning for distributed mobile robots: collision avoidance and formation

This paper addresses decentralized motion planning among a homogeneous set of feedback-controlled mobile robots. It introduces the velocity obstacle, which describes the collision between robot and obstacle, and the hybrid interactive velocity obstacles are designed for collision checking between interacting robots. The (sub)goal selection algorithm is also studied for formation control, then the preferred velocity is designed for robot tracking its desired (sub)goal. Furthermore, the rules for the size regulation of obstacle are presented to avoid conservative motion planning and enhance the safety. Then, we establish a novel Velocity Change Space (VCS), map the velocity obstacles, the desired (sub)goal and the reachable velocity change window before collision in this space, and directly get the new velocity by a multi-objective optimization method. We apply VCS-based motion planning methods to distributed robots, and simulation is used to illustrate the good performances with respect to the un-conservative, foresighted and multi-objective optimal motion planning, especially the successful application in the formation control of the multi-robot system.     

Teleoperation of a platoon of distributed wheeled mobile robots with predictive display

We propose a novel teleoperation framework for multiple distributed non-holonomic mobile robots (WMR), each equipped with onboard sensing and computing using peer-to-peer communication. One of the WMRs is designated as the leader with the first-person view camera and SLAM, while the other WMRs maintain a certain desired formation relative to their respective fore-running WMR in a distributed manner. For this, we first utilize nonholonomic passive decomposition to split the platoon kinematics into that of the formation-keeping aspect and the collective tele-driving aspect. We then design the controls for these two aspects individually and distribute them into each WMR while incorporating their nonholonomic constraint and distribution requirement. We also propose a novel predictive display, which, by providing the user with the estimated current and predicted future pose of the platoon and future possibility of collision while incorporating the uncertainty inherent to the distribution, can significantly enhance the tele-driving performance. Experiments and user study are also performed.     

基于ARM的移动机器人测距传感器设计

为实现移动机器人安全避障,设计了一种基于S3C44BOX微控制器的8路超声波测距系统.具体介绍了该超声波测距传感器的软、硬件设计及工作原理.系统利用ARM外围丰富的I/O接口和内部定时器精确控制选通开关芯片CD4066的使能端,以消除多路超声波传感器之间回波干扰和直接串扰的问题,并采用最小二乘法对测量数据进行了分析和修正.实验研究结果表明,该系统具有良好的测距性能.     

基于视觉字典的移动机器人闭环检测方法研究

针对移动机器人同步定位和地图构建(SLAM)的闭环检测问题,提出了一种基于视觉字典的闭环检测方法。该方法首先使用SURF算法对每一帧图像进行特征提取,生成视觉单词,构建视觉字典树,再基于"词袋"(Bag of Words,Bo W)对场景建模,通过计算图像视觉单词的匹配度估计图像间的相似度。为提高闭环检测的成功率,运用贝叶斯滤波与相似度来计算闭环假设的后验概率分布。同时,为提高系统的实时性,引入了内存管理机制。实验结果显示该方法是有效的。     

改进的遗传算法无线视频传感器网络协作路由技术研究

提出了适用于无线视频传感器网络的基于能量感知的跨层交互多路径协作路由技术.该技术首先采用了基于视频传感器节点感知距离的遗传优化算法,预测传输视频数据的能耗和剩余能量,结合无线信道质量和视频编码算法建立一种跨层协同的工作体系,优化节点传输视频数据的能耗、时延和带宽等因素;然后建立应用层、网络层和物理层跨层协同工作体系.仿真实验和数学分析表明,该技术不仅能够较好地满足视频传感器网络应用业务的多样性QoS数据传输性能需求,而且可以充分利用视频传感器网络受限的计算、存储能力和能量等资源.