Simultaneous localization of multiple unknown CSMA-based wireless sensor network nodes using a mobile robot with a directional antenna

We use a single mobile robot equipped with a directional antenna to simultaneously localize unknown carrier sensing multiple access (CSMA)-based wireless sensor network nodes. We assume the robot can only sense radio transmissions at the physical layer. The robot does not know network configuration such as size and protocol. We formulate this new localization problem and propose a particle filter-based localization approach. We combine a CSMA model and a directional antenna model using multiple particle filters. The CSMA model provides network configuration data while the directional antenna model provides inputs for particle filters to update. Based on the particle distribution, we propose a robot motion planning algorithm that assists the robot to efficiently traverse the field to search radio source. The final localization scheme consists of two algorithms: a sensing algorithms that runs in O(n) time for n particles and a motion planning algorithm that runs in O(nl) time for l radio sources. We have implemented the algorithm, and the results show that the algorithms are capable of localizing unknown networked radio sources effectively and robustly.     

Sensor planning for mobile robot localization using Bayesian network inference

We propose a new method of sensor planning for mobile robot localization using Bayesian network inference. Since we can model causal relations between situations of the robot's behavior and sensing events as nodes of a Bayesian network, we can use the inference of the network for dealing with uncertainty in sensor planning and thus derive appropriate sensing actions. In this system we employ a multi-layered-behavior architecture for navigation and localization. This architecture effectively combines mapping of local sensor information and the inference via a Bayesian network for sensor planning. The mobile robot recognizes the local sensor patterns for localization and navigation using a learned regression function. Since the environment may change during the navigation and the sensor capability has limitations in the real world, the mobile robot actively gathers sensor information to construct and reconstruct a Bayesian network, and then derives an appropriate sensing action which maximizes a utility function based on inference of the reconstructed network. The utility function takes into account belief of the localization and the sensing cost. We have conducted some simulation and real robot experiments to validate the sensor planning system.     

Sensor planning with Bayesian decision theory

In this paper ongoing work on an approach for planning sensing actions and controlling intelligent, purposive robotic systems is presented. The method uses Bayesian decision analysis (BDA) for deciding what sensing actions should be performed. This offers a probabilistic framework that provides a more dynamic and modular behaviour than traditional rule based planners. Experiments show that the Bayesian sensor planning strategy is capable of controlling an autonomous mobile robot operating in partly known environments.     

Cooperative localization for disconnected sensor networks and a mobile robot in friendly environments

Localization for a disconnected sensor network is highly unlikely to be achieved by its own sensor nodes, since accessibility of the information between any pair of sensor nodes cannot be guaranteed. In this paper, a mobile robot (or a mobile sensor node) is introduced to establish correlations among sparsely distributed sensor nodes which are disconnected, even isolated. The robot and the sensor network operate in a friendly manner, in which they can cooperate to perceive each other for achieving more accurate localization, rather than trying to avoid being detected by each other. The mobility of the robot allows for the stationary and internally disconnected sensor nodes to be dynamically connected and correlated. On one hand, the robot performs simultaneous localization and mapping (SLAM) based on the constrained local submap filter (CLSF). The robot creates a local submap composed of the sensor nodes present in its immediate vicinity. The locations of these nodes and the pose (position and orientation angle) of the robot are estimated within the local submap. On the other hand, the sensor nodes in the submap estimate the pose of the robot. A parallax-based robot pose estimation and tracking (PROPET) algorithm, which uses the relationship between two successive measurements of the robot's range and bearing, is proposed to continuously track the robot's pose with each sensor node. Then, tracking results of the robot's pose from different sensor nodes are fused by the Kalman filter (KF). The multi-node fusion result are further integrated with the robot's SLAM result within the local submap to achieve more accurate localization for the robot and the sensor nodes. Finally, the submap is projected and fused into the global map by the CLSF to generate localization results represented in the global frame of reference. Simulation and experimental results are presented to show the performances of the proposed method for robot-sensor network cooperative localization. Especially, if the robot (or the mobile sensor node) has the same sensing ability as the stationary sensor nodes, the localization accuracy can be significantly enhanced using the proposed method.     

A Sensor Placement Algorithm for a Mobile Robot Inspection Planning

In this paper, we address the inspection planning problem to ??see?? the whole area of the given workspace by a mobile robot. The problem is decoupled into the sensor placement problem and the multi-goal path planning problem to visit found sensing locations. However the decoupled approach provides a feasible solution, its overall quality can be poor, because the sub-problems are solved independently. We propose a new randomized approach that considers the path planning problem during solution process of the sensor placement problem. The proposed algorithm is based on a guiding of the randomization process according to prior knowledge about the environment. The algorithm is compared with two algorithms already used in the inspection planning. Performance of the algorithms is evaluated in several real environments and for a set of visibility ranges. The proposed algorithm provides better solutions in both evaluated criterions: a number of sensing locations and a length of the inspection path.     

一种普适机器人系统同时定位、标定与建图方法

机器人定位、传感器网络标定与环境建图是普适机器人系统中三个相互耦合的基本问题, 其有效解决是普适机器人系统提供高效智能服务的前提. 本文提出了普适机器人系统同时机器人定位、传感器网络标定与环境建图的概念, 通过分析三者之间的耦合关系, 给出同时定位、标定与建图问题的联合条件概率表示, 基于贝叶斯公式和马尔科夫特性将其分解为若干可解项, 并借鉴Rao-Blackwellized粒子滤波的思想分别求解. 首先, 联合传感器网络对机器人的观测、机器人对已定位环境特征的观测以及机器人自身控制量,设计了位姿粒子的采样提议分布和权值更新公式; 其次, 联合传感器网络对机器人运动轨迹及已定位环境特征的观测,设计了传感器网络标定的递推公式; 然后, 联合传感器网络和机器人对(已定位或新发现)环境特征的观测,设计了环境建图的递推公式. 给出了完整的同时定位、标定与建图算法, 并通过仿真实验验证了该算法的有效性.     

New Entropy-Based Adaptive Particle Filter for Mobile Robot Localization

Over the last decade, particle filters have been applied with great success to a variety of state estimation problem. The standard particle filter suffers poor efficiency during the estimation process, especially in the global localization and kidnapped problem. In this paper, we proposed a novel information entropy-based adaptive approach to improve the efficiency of particle filters by adapting the number of particles. The information entropy-based adaptive particle filter approaches use the information entropy to present the uncertainty of a mobile robot to the environment. By continuously obtaining the sensor information, the robot gradually reduces the uncertainty to the environment and, therefore, reduces the particle number for the estimation process. We derived the mathematic equation relating the information entropy with particle number. Extensive localization experiments using a mobile robot showed that our approach yielded drastic improvements and efficiency performance over a standard particle filter with fixed particles and over other adaptive approaches.     

基于红外传感皮肤的多关节机器人自主运动方法研究

本文研究了障碍环境下多关节机器人自主实时避碰运动理论、技术与方法. 研制的新型红外传感皮肤, 可以为多关节机器人提供所需要的周围环境信息. 针对非结构化环境下的多关节机器人实时避障问题, 提出了一种未知环境下的机器人模糊路径实时规划新方法. 实验结果表明: 基于研制的红外传感皮肤和模糊运动规划算法, 多关节机器人可以在未知或时变环境下自主工作.     

霍夫空间中多足球机器人协作目标定位算法

针对嵌入式仿人足球机器人提出一种霍夫空间中的多机器人协作目标定位算法。机器人利用实验场地中的标志物采用基于三角几何定位方法进行自定位,把机器人多连杆模型进行简化,通过坐标系位姿变换把图像坐标系转换到世界坐标系中,实现机器人目标定位;在多机器人之间建立ZigBee无线传感器网络进行通信,把多个机器人定位的坐标点进行霍夫变换,在霍夫空间中进行最小二乘法线性拟合,获取最优参数,然后融合改进后的粒子滤波实现对目标小球的跟踪;最后在21自由度的仿人足球机器人上进行仿真和实验。数据结果表明,这种多机器人协作的定位算法的精度提高了约48%,在满足实时性的前提下,对目标的跟踪效果也得到了改善。     

Planning the motions of a mobile robot in a sensory uncertaintyfield

Failures in mobile robot navigation are often caused by errors in localizing the robot relative to its environment. This paper explores the idea that these errors can be considerably reduced by planning paths taking the robot through positions where pertinent features of the environment can be sensed. It introduces the notion of a “sensory uncertainty field” (SUF). For every possible robot configuration q, this field estimates the distribution of possible errors in the robot configuration that would be computed by a localization function matching the data given by the sensors against an environment model, if the robot was at q. A planner is proposed which uses a precomputed SUF to generate paths that minimize expected errors or any other criterion combining, say, path length and errors. This paper describes in detail the computation of a specific SUF for a mobile robot equipped with a classical line-striping camera/laser range sensor. It presents an implemented SUF-based motion planner for this robot and shows paths generated by this planner. Navigation experiments were conducted with mobile robots using paths generated by the SUF-based planner and other paths. The former paths were tracked with greater precision than the others. The final section of the paper discusses additional research issues related to SUF-based planning     

一种低计算量移动机器人自定位方法

移动机器人定位问题就是通过传感器数据来确定自己的位姿。本文介绍了几种基于概率的自定位算法。针对蒙特卡罗定位算法需要精确概率模型以及计算量大的问题,本文提出了一种均匀蒙特卡罗算法。该算法假设运动模型和感知模型都是均匀分布的,采样点在运动过程中不变,而且不需要精确的概率模型,计算量小,稳定性高。试验表朗,该算法能在室内环境下很好的对机器人定位。     

From pixels to multi-robot decision-making: A study in uncertainty

Mobile robots must cope with uncertainty from many sources along the path from interpreting raw sensor inputs to behavior selection to execution of the resulting primitive actions. This article identifies several such sources and introduces methods for (i) reducing uncertainty and (ii) making decisions in the face of uncertainty. We present a complete vision-based robotic system that includes several algorithms for learning models that are useful and necessary for planning, and then place particular emphasis on the planning and decision-making capabilities of the robot. Specifically, we present models for autonomous color calibration, autonomous sensor and actuator modeling, and an adaptation of particle filtering for improved localization on legged robots. These contributions enable effective planning under uncertainty for robots engaged in goal-oriented behavior within a dynamic, collaborative and adversarial environment. Each of our algorithms is fully implemented and tested on a commercial off-the-shelf vision-based quadruped robot.     

Localization methods for a mobile robot in urban environments

This paper addresses the problems of building a functional mobile robot for urban site navigation and modeling with focus on keeping track of the robot location. We have developed a localization system that employs two methods. The first method uses odometry, a compass and tilt sensor, and a global positioning sensor. An extended Kalman filter integrates the sensor data and keeps track of the uncertainty associated with it. The second method is based on camera pose estimation. It is used when the uncertainty from the first method becomes very large. The pose estimation is done by matching linear features in the image with a simple and compact environmental model. We have demonstrated the functionality of the robot and the localization methods with real-world experiments.     

Distance-Optimal Navigation in an Unknown Environment Without Sensing Distances

This paper considers what can be accomplished using a mobile robot that has limited sensing. For navigation and mapping, the robot has only one sensor, which tracks the directions of depth discontinuities. There are no coordinates, and the robot is given a motion primitive that allows it to move toward discontinuities. The robot is incapable of performing localization or measuring any distances or angles. Nevertheless, when dropped into an unknown planar environment, the robot builds a data structure, called the gap navigation tree, which enables it to navigate optimally in terms of Euclidean distance traveled. In a sense, the robot is able to learn the critical information contained in the classical shortest-path roadmap, although surprisingly it is unable to extract metric information. We prove these results for the case of a point robot placed into a simply connected, piecewise-analytic planar environment. The case of multiply connected environments is also addressed, in which it is shown that further sensing assumptions are needed. Due to the limited sensor given to the robot, globally optimal navigation is impossible; however, our approach achieves locally optimal (within a homotopy class) navigation, which is the best that is theoretically possible under this robot model.     

一种基于假设检验的机器人所处区域类型识别方法

为实现机器人对其所处区域的有效识别,提出一种基于假设检验的区域类型识别方法。首先考虑观测误差影响提出一种基于概率的未知障碍物识别方法。进而将观测信息视为对周围环境的采样,假设机器人所处区域类型,利用观测信息中的未知障碍物数对其验证,实现对区域类型的识别。该方法考虑了实际中观测误差的影响,限制了误判的概率。实验证明,该方法能够在观测误差影响下有效识别机器人所处区域类型,并成功将其应用于部分未知环境的路径规划中。     

Learning Concepts from Sensor Data of a Mobile Robot

Machine learning can be a most valuable tool for improving the flexibility and efficiency of robot applications. Many approaches to applying machine learning to robotics are known. Some approaches enhance the robot's high-level processing, the planning capabilities. Other approaches enhance the low-level processing, the control of basic actions. In contrast, the approach presented in this paper uses machine learning for enhancing the link between the low-level representations of sensing and action and the high-level representation of planning. The aim is to facilitate the communication between the robot and the human user. A hierarchy of concepts is learned from route records of a mobile robot. Perception and action are combined at every level, i.e., the concepts are perceptually anchored. The relational learning algorithm GRDT has been developed which completely searches in a hypothesis space, that is restricted by rule schemata, which the user defines in terms of grammars.     

Probabilistic guarantees for high-level robot behavior in the presence of sensor error

This paper presents an approach for reasoning about the effects of sensor error on high-level robot behavior. We consider robot controllers that are synthesized from high-level, temporal logic task specifications, such that the resulting robot behavior is guaranteed to satisfy these specifications when assuming perfect sensors and actuators. We relax the assumption of perfect sensing, and calculate the probability with which the controller satisfies a set of temporal logic specifications. We consider parametric representations, where the satisfaction probability is found as a function of the model parameters, and numerical representations, allowing for the analysis of large examples. We also consider models in which some parts of the environment and sensor have unknown transition probabilities, in which case we can determine upper and lower bounds for the probability. We illustrate our approach with two examples that provide insight into unintuitive effects of sensor error that can inform the specification design process.     

A stereo matching approach based on particle filters and scattered control landmarks

In robot localization, particle filtering can estimate the position of a robot in a known environment with the help of sensor data. In this paper, we present an approach based on particle filtering, for accurate stereo matching. The proposed method consists of three parts. First, we utilize multiple disparity maps in order to acquire a very distinctive set of features called landmarks, and then we use segmentation as a grouping technique. Secondly, we apply scan line particle filtering using the corresponding landmarks as a virtual sensor data to estimate the best disparity value. Lastly, we reduce the computational redundancy of particle filtering in our stereo correspondence with a Markov chain model, given the previous scan line values. More precisely, we assist particle filtering convergence by adding a proportional weight in the predicted disparity value estimated by Markov chains. In addition to this, we optimize our results by applying a plane fitting algorithm along with a histogram technique to refine any outliers. This work provides new insights into stereo matching methodologies by taking advantage of global geometrical and spatial information from distinctive landmarks. Experimental results show that our approach is capable of providing high-quality disparity maps comparable to other well-known contemporary techniques.     

Sensor Planning for 3D Object Search

In this paper, we provide a systematic study of the task of sensor planning for object search. The search agent's knowledge of object location is encoded as a discrete probability density which is updated whenever a sensing action occurs. Each sensing action of the agent is defined by a viewpoint, a viewing direction, a field-of-view, and the application of a recognition algorithm. The formulation casts sensor planning as an optimization problem: the goal is to maximize the probability of detecting the target with minimum cost. This problem is proved to be NP-Complete, thus a heuristic strategy is favored. To port the theoretical framework to a real working system, we propose a sensor planning strategy for a robot equipped with a camera that can pan, tilt, and zoom. In order to efficiently determine the sensing actions over time, the huge space of possible actions with fixed camera position is decomposed into a finite set of actions that must be considered. The next action is then selected from among these by comparing the likelihood of detection and the cost of each action. When detection is unlikely at the current position, the robot is moved to another position for which the probability of target detection is the highest.