A Review on Sensor Network Issues and Robotics <s> Coverage. <s> This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an... <s> BIB001 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Motor schemas serve as the basic unit of behavior specifica tion for the navigation of a mobile robot. They are multiple concurrent processes that operate in conjunction with asso ciated perceptual schemas and contribute independently to the overall concerted action of the vehicle. The motivation be hind the use of schemas for this domain is drawn from neuro- scientific, psychological, and robotic sources. A variant of the potential field method is used to produce the appropriate velocity and steering commands for the robot. Simulation re sults and actual mobile robot experiments demonstrate the feasibility of this approach. <s> BIB002 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> This paper considers the problem of deploying a mobile sensor network in an unknown environment. A mobile sensor network is composed of a distributed collection of nodes, each of which has sensing, computation, communication and locomotion capabilities. Such networks are capable of self-deployment; i.e., starting from some compact initial configuration, the nodes in the network can spread out such that the area ‘covered’ by the network is maximized. In this paper, we present a potential-field-based approach to deployment. The fields are constructed such that each node is repelled by both obstacles and by other nodes, thereby forcing the network to spread itself throughout the environment. The approach is both distributed and scalable. <s> BIB003 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Wireless ad-hoc sensor networks have recently emerged as a premier research topic. They have great long-term economic potential, ability to transform our lives, and pose many new system-building challenges. Sensor networks also pose a number of new conceptual and optimization problems. Some, such as location, deployment, and tracking, are fundamental issues, in that many applications rely on them for needed information. We address one of the fundamental problems, namely coverage. Coverage in general, answers the questions about quality of service (surveillance) that can be provided by a particular sensor network. We first define the coverage problem from several points of view including deterministic, statistical, worst and best case, and present examples in each domain. By combining the computational geometry and graph theoretic techniques, specifically the Voronoi diagram and graph search algorithms, we establish the main highlight of the paper-optimal polynomial time worst and average case algorithm for coverage calculation. We also present comprehensive experimental results and discuss future research directions related to coverage in sensor networks. <s> BIB004 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> This paper describes an incremental deployment algorithm for mobile sensor networks. A mobile sensor network is a distributed collection of nodes, each of which has sensing, computation, communication and locomotion capabilities. The algorithm described in this paper will deploy such nodes one-at-a-time into an unknown environment, with each node making use of information gathered by previously deployed nodes to determine its deployment location. The algorithm is designed to maximize network ‘coverage’ while simultaneously ensuring that nodes retain line-of-sight relationships with one another. This latter constraint arises from the need to localize the nodes in an unknown environment: in our previous work on i>team localization (A. Howard, M.J. Mataric, and G.S. Sukhatme, in i>Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems, EPFL, Switzerland, 2002s i>IEEE Transactions on Robotics and Autonomous Systems, 2002) we have shown how nodes can localize themselves by using i>other nodes as landmarks. This paper describes the incremental deployment algorithm and presents the results from an extensive series of simulation experiments. These experiments serve to both validate the algorithm and illuminate its empirical properties. <s> BIB005 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> The effectiveness of cluster-based distributed sensor networks depends to a large extent on the coverage provided by the sensor deployment. We propose a virtual force algorithm (VFA) as a sensor deployment strategy to enhance the coverage after an initial random placement of sensors. For a given number of sensors, the VFA algorithm attempts to maximize the sensor field coverage. A judicious combination of attractive and repulsive forces is used to determine virtual motion paths and the rate of movement for the randomly-placed sensors. Once the effective sensor positions are identified, a one-time movement with energy consideration incorporated is carried out, i.e., the sensors are redeployed to these positions. We also propose a novel probabilistic target localization algorithm that is executed by the cluster head. The localization results are used by the cluster head to query only a few sensors (out of those that report the presence of a target) for more detailed information. Simulation results are presented to demonstrate the effectiveness of the proposed approach. <s> BIB006 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> We consider the problem of self-deployment of a mobile sensor network. We are interested in a deployment strategy that maximizes the area coverage of the network with the constraint that each of the nodes has at least K neighbors, where K is a user-specified parameter. We propose an algorithm based on artificial potential fields which is distributed, scalable and does not require a prior map of the environment. Simulations establish that the resulting networks have the required degree with a high probability, are well connected and achieve good coverage. We present analytical results for the coverage achievable by uniform random and symmetrically tiled network configurations and use these to evaluate the performance of our algorithm. <s> BIB007 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Monitoring of environmental phenomena with embedded networked sensing confronts the challenges of both unpredictable variability in the spatial distribution of phenomena, coupled with demands for a high spatial sampling rate in three dimensions. For example, low distortion mapping of critical solar radiation properties in forest environments may require two-dimensional spatial sampling rates of greater than 10 samples/m2 over transects exceeding 1000 m2. Clearly, adequate sampling coverage of such a transect requires an impractically large number of sensing nodes. This paper describes a new approach where the deployment of a combination of autonomous-articulated and static sensor nodes enables sufficient spatiotemporal sampling densityo ver large transects to meet a general set of environmental mapping demands. To achieve this we have developed an embedded networked sensor architecture that merges sensing and articulation with adaptive algorithms that are responsive to both variabilityin environmental phenomena discovered bythe mobile sensors and to discrete events discovered byst atic sensors. We begin byde scribing the class of important driving applications, the statistical foundations for this new approach, and task allocation. We then describe our experimental implementation of adaptive, event aware, exploration algorithms, which exploit our wireless, articulated sensors operating with deterministic motion over large areas. Results of experimental measurements and the relationship among sampling methods, event arrival rate, and sampling performance are presented. <s> BIB008 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> We consider the problem of coverage and exploration of an unknown dynamic environment using a mobile robot(s). The environment is assumed to be large enough such that constant motion by the robot(s) is needed to cover the environment. We present an efficient minimalist algorithm which assumes that global information is not available (neither a map, nor GPS). Our algorithm deploys a network of radio beacons which assists the robot(s) in coverage. This network is also used for navigation. The deployed network can also be used for applications other than coverage. Simulation experiments are presented which show the collaboration between the deployed network and mobile robot(s) for the tasks of coverage/exploration, network deployment and maintenance (repair), and mobile robot(s) recovery (homing behavior). We present a theoretical basis for our algorithm on graphs and show the results of the simulated scenario experiments. <s> BIB009 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Previous work on the coverage of mobile sensor networks focuses on algorithms to reposition sensors in order to achieve a static configuration with an enlarged covered area. In this paper, we study the dynamic aspects of the coverage of a mobile sensor network that depend on the process of sensor movement. As time goes by, a position is more likely to be covered; targets that might never be detected in a stationary sensor network can now be detected by moving sensors. We characterize the area coverage at specific time instants and during time intervals, as well as the time it takes to detect a randomly located stationary target. Our results show that sensor mobility can be exploited to compensate for the lack of sensors and improve network coverage. For mobile targets, we take a game theoretic approach and derive optimal mobility strategies for sensors and targets from their own perspectives. <s> BIB010 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Recently there has been a great deal of research on using mobility in sensor networks to assist in the initial deployment of nodes. Mobile sensors are useful in this environment because they can move to locations that meet sensing coverage requirements. This paper explores the motion capability to relocate sensors to deal with sensor failure or respond to new events. We define the problem of sensor relocation and propose a two-phase sensor relocation solution: redundant sensors are first identified and then relocated to the target location. We propose a Grid-Quorum solution to quickly locate the closest redundant sensor with low message complexity, and propose to use cascaded movement to relocate the redundant sensor in a timely, efficient and balanced way. Simulation results verify that the proposed solution outperforms others in terms of relocation time, total energy consumption, and minimum remaining energy. <s> BIB011 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Sensor deployment is an important issue in designing sensor networks. We design and evaluate distributed self-deployment protocols for mobile sensors. After discovering a coverage hole, the proposed protocols calculate the target positions of the sensors where they should move. We use Voronoi diagrams to discover the coverage holes and design three movement-assisted sensor deployment protocols, VEC (vector-based), VOR (Voronoi-based), and minimax based on the principle of moving sensors from densely deployed areas to sparsely deployed areas. Simulation results show that our protocols can provide high coverage within a short deploying time and limited movement. <s> BIB012 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> Mobile sensor has enabled many new applications in wireless sensor networks where coverage is one of the most important problems to support those applications. Previous research works of coverage issue mainly focus on the static sensor network, which can not handle the significant challenge brought by the node mobility. In this paper, we consider the coverage problem in mobile sensor networks under a very general framework, in which all the sensors are moving all the time with any specified movement model. We propose a scheme that can provide a Real-time Coverage-Map According to Probability (RC- MAP) of the mobile sensor networks. By introducing probability into coverage, RC-MAP provides three different types of coverage map in real-time, including probability to be covered, expected number of sensors to cover, and expected waiting time before being covered. Extensive simulation results demonstrate the high accuracy and effectiveness of the proposed scheme. <s> BIB013 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> More and more researches focus on the development of mobile wireless sensor networks (MWSNs) due to the favorable advantages and applications of MWSNs. However, there is not a comprehensive survey about the research issues on MWSNS for the state of art. In this paper, we survey the communication and data management issues on MWSNs and provide extensible research directions of MWSNs. <s> BIB014 </s> A Review on Sensor Network Issues and Robotics <s> Coverage. <s> We study the dynamic aspects of the coverage of a mobile sensor network resulting from continuous movement of sensors. As sensors move around, initially uncovered locations may be covered at a later time, and intruders that might never be detected in a stationary sensor network can now be detected by moving sensors. However, this improvement in coverage is achieved at the cost that a location is covered only part of the time, alternating between covered and not covered. We characterize area coverage at specific time instants and during time intervals, as well as the time durations that a location is covered and uncovered. We further consider the time it takes to detect a randomly located intruder and prove that the detection time is exponentially distributed with parameter 2λrvs where λ represents the sensor density, r represents the sensor's sensing range, and vs denotes the average sensor speed. For mobile intruders, we take a game theoretic approach and derive optimal mobility strategies for both sensors and intruders. We prove that the optimal sensor strategy is to choose their directions uniformly at random between (0, 2π). The optimal intruder strategy is to remain stationary. This solution represents a mixed strategy which is a Nash equilibrium of the zero-sum game between mobile sensors and intruders. <s> BIB015
In the sensor networks, coverage can be seen as the measure of quality of service. The quality of surveillance that the network can provide also depends upon the coverage of a sensor network BIB004 BIB015 . It can be seen that, for all the applications of mobile sensor networks, coverage is one of the most fundamental issues BIB013 . It will decrease due to sensor failure and undesirable sensor deployment. Gage (Gage 92) defines coverage as the maintenance of spatial relationship which adjusts to exact local conditions to optimize the performances of some functions. Gage describes three coverage behavior types. Blanket coverage: its objective is to achieve a static arrangement of nodes that minimizes the total detection area. Barrier coverage: the main goal of the barrier coverage is to reduce the probability of unnoticed penetration through the barrier. Sweep coverage: the concept of sweep coverage is from robotics which is more or less equivalent to moving barrier. The lifetime of sensors is strongly affected by hardware defects, battery depletions, some harsh external environments (e.g., fire, wind), and so forth BIB014 . In MSNs, previously uncovered areas became covered when sensors move through them and when sensors move away, the already covered areas become uncovered. As a result, the areas covered by sensors change over time, and more areas will be covered at least once as time continues. For robotic applications Khatib BIB001 was the first one to describe potential field techniques for tasks like local navigation and obstacle avoidance. Similar concept of "motor schemas" was also introduced which uses the superposition of spatial vectors to generate behavior BIB002 . Howard et al. BIB003 also used potential fields, but for the deployment problem, they consider the problem of arranging mobile sensors in an unknown environment, where fields are constructed such that each node is repelled by other nodes and also throughout the environment obstacles forces the network to spread. Reference BIB007 also proposed potential field technique which is distributed and scalable and does not require prior map of the environment. In BIB005 , for the uncovered areas by the sensor network, new nodes are always placed on the boundary of those areas. It is also able to find a suboptimal deployment solution and also makes it sure that each node must be in line of sight with another node. In order to increase the coverage BIB012 proposed algorithms to calculate the desired target positions where sensors should move and identify the coverage holes existing in the network. To find out the coverage holes Voronoi diagram was used by Wang et al. BIB012 and he also designed three movement-assisted sensor deployment protocols, namely, VEC (vector based), VOR (Voronoi-based), and Minimax, based on the principle of sensors moving from densely deployed areas to sparsely deployed areas. A virtual force algorithm (VFA) was proposed by BIB006 to increase sensor field coverage by combining repulsive forces and attractive forces to determine randomly deployed sensors movement and virtual motion paths. Reference BIB008 deals with both static and mobile sensors and within the sensor field the job is to be served by mobile sensors which appear at random locations. The static sensors then guide the mobile sensors to the position where the task occurs when they get aware about the arrival of tasks. Researchers deal with the dynamic aspects of coverage in mobile sensor networks and also characterized area coverage at specific time instants and during time interval and detection time of the randomly located target BIB010 . The problem of coverage and exploration through the utilization of deployed network was considered and the algorithm which assumes that the global information is not available was also presented BIB009 . In BIB011 the problem of sensor relocation is being focused and two-phase sensor relocation solution has been proposed in which redundant sensors are identified first using Grid-Quorum and then are relocated in a cascaded movement in a timely, efficient, and balanced way BIB014 .