Fault Tolerant Control Of Interconnected Multibody System And Its Space Application

Due to the increasing scale of mechanical control systems in the field of aviation,aerospace and robot,large-scale system has been unable to be modeled by single-body modeling method.However,methods of multibody systems or interconnected systems can effectively deal with such nonlinear coupled systems,improving control accuracy greatly.Since large-scale consists of a lot of subsystems,a fault occurring in any subsystem will affect the stability of the whole system.Therefore,it is an urgent need to carry out research on fault tolerant control(FTC)of multibody systems and interconnected systems in the field of major engineering.To begin with,this paper makes an introduction of the background and significance of this research,and summarizes the modeling,control and fault tolerant control problems of multibody systems.Modeling and fault tolerant control methods of interconnected systems are also listed.Afterwards,this paper considers the fault tolerant control problem for a class of interconnected systems modeled by a family of port-Hamiltonian systems with energy conserving interconnections.The control goal is to maintain the energy conservation of the interconnected system in the presence of faults.A cooperative fault tolerant strategy is proposed to suppress the change of energy due to faults by comprehensively designing external controls of subsystems and internal controls at interconnection ports.To validate the effectiveness of the proposed control scheme,a system in which three blocks connected by controllable spring mechanisms is considered in the simulation.Simulation results show the feasibility of the control strategy.Furthermore,this paper presents a novel control scheme for the tethered spacecraft formation,based on a simplified model around the equilibrium point.The decentralized control law of each spacecraft utilizes its own state information only.The formation stability is analyzed by using an interconnected system approach called the small gain theorem,which deeply reveals the coupling characteristic among three spacecraft.When the coupling between spacecraft satisfies the condition of small gain theorem,the stability of the system will be guaranteed.Although the requirement of coupling conditions for the decentralized control law is high,this control scheme can greatly reduce the communication burden between spacecraft.Simulation results show the effectiveness of these control schemes.At last,three other control strategies called centralized control,semi-centralized control and distributed control are proposed.The fault tolerant control problem is considered with four fault tolerant control laws based on the above methods being presented.Due to the coupling between spacecraft,fault propagation behavior is also discussed.In the simulation analysis,we compare the system performance under the decentralized control law and other methods both in the fault-free situation and faulty situation and analyze the advantages and drawbacks of four control algorithms.