Robotics and Autonomous Systems 59 (2011) 497–507 Contents lists available at ScienceDirect Robotics and Autonomous Systems journal homepage: www.elsevier.com/locate/robot Decentralized control of a group of mobile robots for deployment in sweep coverage ✩ Teddy M. Cheng ∗ , Andrey V. Savkin, Faizan Javed School of Electrical Engineering and Telecommunications, The University of New South Wales, Sydney, NSW 2052, Australia article info Article history: Received 18 May 2009 Received in revised form 14 September 2010 Accepted 1 March 2011 Available online 29 March 2011 Keywords: Agents and autonomous systems Decentralized control Mobile robots Sweep coverage Sensor deployment abstract This paper addresses a problem of sweep coverage by deploying a network of autonomous mobile robots. We propose a decentralized control algorithm for the robots to accomplish the sweep coverage. The sweep coverage is achieved by coordinating the robots to move along a given path that is unknown to the vehicles a priori. The motion coordination algorithm is developed based on simple consensus algorithms. The effectiveness of the algorithm is demonstrated via numerical simulations. The proposed algorithm would have applications to military and civilian operations. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Movement-assisted sensors are deployed to achieve or improve coverage of a sensor network in tasks, such as surveillance and tracking [1,2]. A network of movement-assisted sensor is typically implemented by deploying a group of mobile sensor-equipped robots or vehicles, and each robot can be viewed as a sensing node. Coverage is an important issue in a sensor network, and is usually treated as a measure of quality of service. Regarding multi-robot systems, an important type of coverage was originally defined by Gage [3], namely, sweep coverage. By definition, sweep coverage means that by moving a number of nodes across a sensing field, such that it addresses a specified balance between maximizing the detection rate of events and minimizing the number of missed detections per unit area. As indicated in [3], sweep coverage could be used in a num- ber of tasks, such as reconnaissance, maintenance inspection, ship hull cleaning and multi-agent minesweeping. Among them, minesweeping [4–6] is an extremely challenging and dangerous task. Therefore, in this paper, our effort is to address a problem of sweep coverage by deploying a network of autonomous robots that could resemble a minesweeping operation. In order to reduce the ✩ This work was supported by the Australian Research Council. ∗ Corresponding author. Tel.: +61 2 93854778; fax: +61 2 9385993. E-mail addresses: t.cheng@ieee.org (T.M. Cheng), a.savkin@unsw.edu.au (A.V. Savkin), f.javed@unsw.edu.au (F. Javed). cost of operation, it is desired that the robots have limited commu- nication and detection capabilities. Hence, the autonomous robots should work in a distributed and unsupervised mode. The control of such autonomous robots is a decentralized control problem, as only local information is available to each robot for the control. To address the abovementioned issues, our aim is to develop a set of simple decentralized control laws that steers a group of sensor- equipped robots autonomously to form a sensor barrier and, at the same time, move along a given path at a given speed. As a re- sult, any object that lies in the path of this sensor barrier will be detected. The potential applications of the sweep coverage we study here are not limited to minesweeping, it can also be applied to, e.g., boarder patrolling [7], environmental monitoring of disposal sites on the deep ocean floor [8], and sea floor surveying for hydrocarbon exploration [9]. Particularly, in the case of sea exploration, the United Nations Convention on the Law of the Sea [10] states that a coastal nation has sole exploitation rights over all natural resources within her Exclusive Economic Zone (EEZ) that starts at the coastal baseline and extends 200 nautical miles (370.4 km) out into the sea. When exploring a nation’s EEZ, one can easily imagine the magnitude of the operation. In fact, this type of operation is analogous to the sweep coverage addressed in this paper. To accomplish the operation, we could simply deploy a large number of low-cost, sensor-equipped autonomous underwater and/or surface vessels, and let them autonomously sweep the EEZ as they move along the coastline. 0921-8890/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.robot.2011.03.001