Cooperative Coverage Control and Formation Control of Networked Mobile Agents

Abstract

Networked mobile agents have wide engineering applications. Cooperative control and motion coordination of mobile agents has prompted much research interest especially coverage and formation control for mobile agents. Cooperative coverage control of mobile agents aims at driving a group of agents to an optimal configuration in a mission region to maximize the likelihood of detecting an event of interest. Formation control of multiple agents is to make a team of agents move with a featured group motion and maintain a desired geometric pattern. Though much progress has been made on coverage and formation control of multiple mobile agents in the past decades, yet velocity constraints, environmental uncertainty and communication noise, absence of global information, limited local measurements, and complicated collective motions still give rise to numerous challenges. This thesis focuses on the cooperative coverage control and formation control problems of networked mobile agents.

The cooperative coverage control problem for mobile agents in a one dimensional mission space is worth studying due to its wide potential applications such as environmental boundary monitoring and target tracking. The first part of the thesis addresses the one-dimensional coverage control problem of networked mobile agents subject to different actuation or velocity constraints and position measurement errors, with the objective to minimize the largest time required for the agents to reach any point in the one-dimensional space. The main results of this part are summarized as follows:

1. The nonuniform coverage control for networked mobile agents with different actuation limits on a line is studied. The roughness of each point on the line is assumed to be different. A distributed coverage control law with input constraint is developed for each agent using the position information of its neighbors and local roughness information. Under the proposed control law, the agents converge to the optimal position configuration such that the largest time required for the agents to reach any point on the line is minimized. Meanwhile, the spatial ordering of the agents on the line is preserved throughout the evolution and thus collision between mobile agents is avoided.

2. The coverage control for networked mobile agents subject to different velocity constraints and bounded measurement errors on a circle is studied. The effect of measurement errors on the coverage cost function, which is defined as the largest time for the mobile agents to arrive at any point on the circle, is considered. Distributed coverage control laws with input constraints are developed via low gain feedback approach based on local noisy position measurements among agents, under which the networked agents converges to a neighborhood of the optimal configuration. Furthermore, the conditions for the agents to preserve their spatial order on the circle are derived in order to avoid collision among agents. An upper bound on the limit of the coverage cost function as time goes to infinity is also given.

In the second part of the thesis, cooperative formation control for moving-target enclosing by networked mobile agents is investigated. The objective is to design a distributed control law under which a group of mobile agents can converge to the desired circular formation around the moving target, that is, the agents travel along a common circle centered at the target and maintain a desired spaced formation. The neighboring topology of the agents may dynamically switch dependent on their positions relative to the target at each time instant. In practice, the target enclosing problem can find its application in surveillance, satellite orbit maintenance and entrapping or attacking a target object. The main results of this part are summarized as follows:

1. The localization and enclosing control of an unknown moving target by networked mobile agents in a plane is considered. Each agent is assumed to know its own position and the bearing angle to the target, based on which an estimator is proposed for each agent to estimate the target position, and a distributed control law is then designed. For a moving target with a bounded velocity, networked mobile agents globally converge to a neighborhood of the desired circular formation around the target under the proposed control law. For a moving target with a time-varying velocity which might be unbounded, under the assumption that one of the agents has access to the velocity information of the target, the localization algorithm and control law are modified by utilizing the estimate of the target’s velocity for each agent. It is shown that under the proposed control strategy, the agents globally converge to the desired circular formation around the moving target.

2. The enclosing control of a moving target with an unknown velocity by a group of mobile agents in a plane is studied. The target’s velocity is a time-varying exogenous signal and assumed to be generated by an exogenous linear system. Based on the relative positions, a dynamic control law is proposed for the agents to cooperatively estimate the velocity of the target. Under the proposed control law, the agents eventually move along a common circle of the desired radius around the moving target and also achieve any desired spaced pattern along the circle. Furthermore, conditions are derived under which the collision among the agents and the target can be avoided throughout the evolution.

Date of Award	3 Jul 2019
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Lu LIU (Supervisor) & Xiaofan Wang (External Supervisor)