Research On Cooperative Fault-Tolerant Control For Multi-Agent Systems

With the rapid development and integration of computer network technology,infor-mation technology,automation technology and artificial intelligence technology,more and more attention is paid to multi-agent systems(MASs),which has been considered as one of the most important and active fields in the research.Also,due to complicated tasks can be accomplished by a group of agents with simple structure by cooperation,the coordination control for MASs has potential applications in broad areas including the aerospace,distributed sensor network,formation of mobile robots,industrial produc-tion process and so forth.Unfortunately,such complex distributed architecture of MASs is vulnerable to the local system faults and the unreliable communication networks in practical applications.The faulty components in some subsystems may cause the local performance deterioration and lead to agent instability,even affect the coordination goal achievement of agent networks.Therefore,the requirement of system security and relia-bility is relatively high for MASs,which also makes the cooperative fault-tolerant control problem for MASs become a challenging research topic with great theoretical and practi-cal significance.But,almost no results on such issues have been reported up to now.On the basis of the previous work,this dissertation,combining communication topol-ogy of multi-agent networks and distributed adaptive control technique and using their advantages,presents a systematically new framework of cooperative fault-tolerant con-trol design.For the linear MASs with actuator failures and undirected communication networks,the cooperative fault-tolerant controller is proposed via distributed adaptive technique.Moreover,for a class of uncertain MASs with acltuator failures,heterogeneous matching uncertainties,disturbances and time-varying undirected topology,a constructive cooperative adaptive fault compensation methodology is established on the basis of the multiple Lyapunov functions(MLFs)method and algebraic graph theory.Meanwhile,the distributed reliable H? consensus problem for a class of Lipschitzian nonlinear MASs with actuator faults and switching undirected topology is investigated.On the other hand,for the linear MASs under switching directed communication networks,the two-step de-sign approach for constructing the distributed fault-tolerant consensus protocol is devel-oped,which is applied to decouple the asymmetric network topology structure from the local controller gains design.Finally,for a class of nonlinear MASs with intermittent communications and actuator failures,a new constructive adaptive reliable coordination control methodology is established on the basis of the distributed adaptive technique,topology connectivity allocation,MLFs method and algebraic graph theory.All the main results are verified by simulation and part of the developed theories is applied to the sim-ulation studies of networked aircraft model.The main research contents are outlined as follows:Chapters 1-2 summarize and analyze the background and the development of coop--erative control for MASs.Preliminaries about the considered problems are also given.Chapter 3 studies the cooperative fault-tolerant tracking control problem for linear MASs subject to external disturbances and actuator faults including loss of effectiveness,bias,outage and stuck.The communication network is an undirected connected graph with a fixed topology.Different from the traditional centralized fault-tolerant tracking control problem,only part of the follower nodes can obtain the information of leader di-rectly.Based on the local state information of neighboring agents,a novel cooperative fault-tolerant tracking control scheme by using adaptive mechanism is proposed.By in-troducing the estimates of controller parameters driven by neighborhood tracking errors,it is shown that not only the actuator faults in the follower nodes can be compensated,but also the global tracking objective can be achieved.Furthermore,it is proved that all closed-loop signals are bounded and all follower nodes asymptotically tracking to the leader can be achieved in the presence of actuator faults and matched external disturbances mismatched parameter uncertainties.Finally,a numerical example is given to show the effectiveness of the proposed control scheme.In Chapter 4,based on the results in Chapter 3,the distributed fault-tolerant track-ing control problem for a class of high-order agent networks with switching undirected topology,heterogeneous matching uncertainties,disturbances and actuator faults is con-sidered.Based on the relative information of neighbors,a novel fault-tolerant consensus tracking protocol is designed for each follower node via distributed adaptive mechanism.By utilizing the MLFs method and algebraic graph theory,a sufficient condition for con-sensus tracking is established.Furthermore,it is proved that if the topology dwell time is larger than a positive threshold,the state of each follower node synchronizes to that of the leader with a bounded residual error.Finally,the simulations illustrate the advantages of our approaches compared with the existing results.Chapter 5 studies the problem of distributed reliable H? consensus control for MASs with actuator faults and switching undirected topology.The Lipschitzian nonlinearities,several types of actuator faults and exogenous disturbances are considered in subsystems.By utilizing the relative state information of neighbors,a new distributed adaptive re-liable consensus protocol is presented for actuator failure compensations in individual nodes.By applying the topology-based average dwell time approach and Lyapunov the-ory,the distributed controller design condition is given in terms of linear matrix inequal-ities(LMIs).It is shown that the proposed scheme can guarantee that the reliable H?consensus problem is solvable in the presence actuator faults and external disturbance.Finally,two numerical examples are given to show the effectiveness of the proposed the-oretical results.Chapter 6 investigates the cooperative fault-tolerant tracking control linear net-worked agent systems with actuator faults and switching directed networks.Suppose the interaction network of all subsystems may switch among finite digraphs,which con-tains some non-identical directed spanning trees.Based only on the state information of neighboring agents,the two-step design methodology for constructing the distributed consensus protocol is developed.First,by using the neighborhood information,the dis-tributed reference model observer is designed to estimate the state information of leader agent.Next,on the basis of the estimation and states of subsystems,the decentralized adaptive fault-tolerant controller is proposed to compensate the actuator failures.Also,the closed-loop consensus tracking can still be guaranteed to asymptotically converge to zero in the presence of actuator faults and switching directed networks.Finally,an exam-ple is given to illustrate the effectiveness of the proposed method.Chapter 7 studies the adaptive reliable coordination control problem for a class of MASs under switching undirected topology in the presence of intermittent communi-cation constraints and actuator faults.A new fault-tolerant consensus tracking control scheme is presented by utilizing distributed adaptive technique.In contrast to the exist-ing results on cooperative tracking control problem against intermittent communications,no assumption on zero input of the leader is made in the discussions.By introducing the estimates to account for the unknown faulty efficiency factors and the bounds of the leader's control input signal,the local controller parameters are updated in individual nodes.Also,a novel topology-connectivity-dependent average dwell time approach is proposed to deal with network switching jumps effectively.By combining MLFs method and algebraic graph theory,it is shown that the global tracking errors are uniformly ulti-mately bounded even in the cases of intermittent communication constraints and actuator failures.Simulation results are given to illustrate the effectiveness of the proposed coop-erative fault-tolerant control method.Finally,the results of the dissertation are summarized and further research topics are pointed out.