A survey of multi-agent formation control

Time-varying formation tracking analysis and design problems for second-order Multi-Agent systems with switching interaction topologies are studied, where the states of the followers form a predefined time-varying formation while tracking the state of the leader. A formation tracking protocol is constructed based on the relative information of the neighboring agents. Necessary and sufficient conditions for Multi-Agent systems with switching interaction topologies to achieve time-varying formation tracking are proposed together with the formation tracking feasibility constraint based on the graph theory. An approach to design the formation tracking protocol is proposed by solving an algebraic Riccati equation, and the stability of the proposed approach is proved using the common Lyapunov stability theory. The obtained results are applied to solve the target enclosing problem of a multiquadrotor unmanned aerial vehicle (UAV) system consisting of one leader (target) quadrotor UAV and three follower quadrotor UAVs. A numerical simulation and an outdoor experiment are presented to demonstrate the effectiveness of the theoretical results.

Time-Varying Formation Tracking for Second-Order Multi-Agent Systems Subjected to Switching Topologies With Application to Quadrotor Formation Flying

This paper addresses the distributed formation control problem of a networked multi-agent system (MAS) subject to limited communication resources. First, a dynamic event-triggered communication mechanism (DECM) is developed to schedule inter-agent communication such that some unnecessary data exchanges among agents can be reduced so as to achieve better resource efficiency. Different from most of the existing event-triggered communication mechanisms, wherein threshold parameters are fixed all the time, the threshold parameter in the developed event triggering condition is dynamically adjustable in accordance with a dynamic rule. It is numerically shown that the proposed DECM can achieve a better tradeoff between reducing inter-agent communication frequency and preserving an expected formation than some existing ones. Second, an event-triggered formation protocol is delicately proposed by using only locally triggered sampled data in a distributed manner. Based on the formation protocol, it is shown that the state formation control problem is cast into an asymptotic stability problem of a reduced-order closed-loop system. Then, criteria for designing desired formation protocol and communication mechanism are derived. Finally, the effectiveness and advantages of the proposed approach are demonstrated through a comparative study in multirobot formation control.

Distributed Formation Control of Networked Multi-Agent Systems Using a Dynamic Event-Triggered Communication Mechanism

Time-varying formation tracking problems for linear multiagent systems with multiple leaders are studied, where the states of followers form a predefined time-varying formation while tracking the convex combination of the states of multiple leaders. Followers are classified into well-informed ones and uninformed ones, where the neighbor set of the former contains all the leaders, whereas the latter contains no leaders. A formation tracking protocol is constructed using only neighboring relative information. Necessary and sufficient conditions for multiagent systems with multiple leaders to achieve time-varying formation tracking are proposed by utilizing the properties of the Laplacian matrix, where the formation tracking feasibility constraints are also given. An approach to design the formation tracking protocol is presented by solving an algebraic Riccati equation. The obtained results can be applied to deal with time-varying formation tracking problems, target enclosing problems, and consensus tracking problems for linear multiagent systems with one or multiple targets/leaders. Numerical simulations are provided to demonstrate the effectiveness of the theoretical results.

Time-Varying Formation Tracking for Linear Multiagent Systems With Multiple Leaders

Time-varying formation control for general linear multi-agent systems with switching directed topologies

Distributed stabilization control of rigid formations with prescribed orientation

This paper proposes distance-based adaptive formation control laws for the leader-follower system. The developed controller makes all the agents maintain the formation group and move with a constant reference velocity in a plane. It is assumed that there are one leading and two following agents. The leading agent knows the reference velocity whereas the follower does not know the velocity of other agents. Thus, to move in a group, the controller for the follower estimates the reference velocity. An adaptive method is used in the estimation process. The stability and boundedness of the formation are proved by using Lyapunov stability analysis and Barbalat's lemma. Simulations results are included to illustrate the validity of the developed theories.

Distance-based formation control with a single moving leader

Summary

We propose a control strategy that could steer the group of mobile agents in the plane to achieve a specified formation. The control law could be implemented in a fully decentralized manner so that each agent moves on their own local reference frame. Under the acyclic minimally persistent graph topology, each agent measures the relative displacements of neighboring agents and then adjusts the distances between them to achieve the desired formation. As well as achieving a fixed formation, we could resize the formation only by changing the leader edge, which connects the leader with the first-follower in acyclic minimally persistent graph, without changing the structures of the control law. Copyright © 2014 John Wiley & Sons, Ltd.

Formation stabilization and resizing based on the control of inter-agent distances

In this paper, distributed formation control for multi-agent systems is considered. The proposed control laws are designed to globally obtain and keep the desired formation in a two-dimensional space. It is assumed that the local frames of the agents are not aligned with each other and each agent does not know the orientation of others’ coordinate frames. Further, the agent measures only relative positions of neighbors with respect to the local reference frame. Therefore, the control of the system is completely decentralized and the global convergence is achieved without the global reference frame. The stability and convergence of the system are analyzed mathematically and the experiment using quadcopters is performed to verify the results of the theoretical analysis. In addition, the ambiguity problem and time-varying velocity case are also handled and discussed.

Myoung-Chul Park

Papers

A survey of multi-agent formation control

Distributed stabilization control of rigid formations with prescribed orientation

Distance-based formation control with a single moving leader

Formation stabilization and resizing based on the control of inter-agent distances

Distance-Based Cycle-Free Persistent Formation: Global Convergence and Experimental Test With a Group of Quadcopters