Coordinated Tracking Control For Nonlinear Multi-agent Systems With Communication Constraints

In recent years,due to the development of control science,computer science,communication engineering and other fields of science research,the research of coordinated tracking control has attracted increasing attention in the academic and engineering community.With the deepening of research,the application of coordinated tracking control of multi-agent systems has a wide range of impacts in the fields of aerospace,military,industry and life.The key of multi-agent system coordinated tracking control research is how to propose a suitable distributed control scheme based on consensus theory and network communication information,so that the multi-agents system can accomplish specific tasks in a complex environment.During this process,the different coordination control status will be presented,such as realization of formation tracking,namely the agents will form a given formation shape and track a set target or reference signal.In this paper,the problem of coordinated tracking control for nonlinear multi-agent systems with communication constraints is discussed.Considering that many agent models in the actual system are nonlinear,the thesis mainly focuses on nonlinear multi-agent systems.Based on this,it also considers the communication constraints between agents,such as communication delay,discontinuous communication,and directed communication topology which influence the performance of the coordinated tracking control system.Furthermore,the stability of the entire coordinated tracking control system is analyzed using matrix theory,nonlinear system theory and algebraic graph theory.The main research work in this thesis is as follows:1.For the second-order multi-agent system model with nonlinear dynamics,the problem of coordinated tracking control under directed communication topology with communication delay and partly intermittent communication is studied.By introducing the formation vector and target tracking signal,a coordinated tracking control protocol based on the consensus theory is proposed,which makes the distance between agents converge to the desire distance and ensures the followers to track the state of the leader.Furthermore,Lyapunov theory and matrix theory are used to prove stability of the system,and the sufficient conditions for the convergence of the system are given.2.The problem of distributed coordinated tracking control for nonholonomic chained systems with directed communication topology is studied,the adaptive parameter estimator is designed based on the state information of neighboring agents,so that the global information of the graph is not to be known and the leader's state information is partially reachable to other neighboring agents.Under the directed communication graph containing a directed spanning tree,the design of coordinated tracking control protocol is divided into two steps:the first step is to design the control protocol of the linear subsystem part by the discontinuous adaptive control strategy,and the second step is to construct another control subprotocol by the backstepping method.The stability of the system is proved based on the stability theory and the nonlinear analysis tool,the state of nonholonomic chained multi-agent system will eventually track the desired reference signal by selecting the appropriate control protocol parameters.Finally,the results of coordinated tracking control of nonholonomic chained multi-agent system are applied in the wheeled vehicle model with the nonholonomic constraints,when the states of nonholonomic chained system reach an agreement and track the desired reference signal,the wheeled vehicle will form the desired formation and track a desired reference target under a corresponding control protocol.3.The adaptive coordinated tracking control problem for a group of nonholonomic chained systems has been discussed.Firstly,adaptive control gains are employed in the linear subsystem based on the state information of neighboring agents,thus the global information of the topology graph is not required to be known in the control laws.Furthermore,the back-stepping strategy is applied in the rest of chained-form subsystems such that the state of all robots converges to the desired reference trajectory.And then the connectivity maintenance for an initially connected communication graph is guaranteed by use of navigation function method.Finally,the asymptotic stability of nonholonomic chained systems is proved by Lyapunov method and non-smooth analysis method.