Sliding Mode Control Design For Variable Structure Near Space Vehicles Based On Switched Disturbance Observer

Near space vehicle(NSV)has great military value in future integrated joint operations due to its advantages such as persistent space capability,large-range maneuvering capability during long flight and rapid access to adjacent space response capability,and has become the focus of attention and research of various military powers at present.The special flight environment and great flight envelope of the near-space vehicle make it have the features of complex nonlinearity,fast time-varying and strongly coupling,also present the characteristics of multiple flight states and multiple flight modes in the flight process.Therefore,it is a significant and extremely challenging work to study the control system of the NSV.Centering on this scientific problem,this paper mainly studies the sliding mode control problem of variable structure near space vehicle(VSNSV)with the model uncertainty and external disturbance based on the switching model of 6-dof and 12-variable which based on winged-cone model.Firstly,the attitude tracking control problem of VSNSV with time-varying composite disturbance is studied.When the VSNSV perform different tasks,for the problem of composite disturbance change caused by the structure change,a switched nonlinear disturbance observer which can be switched synchronously with VSNSV is designed.Based on the switching disturbance observer,a switching sliding mode controller is designed for VSNSV by using the sliding mode control strategy.Then,considering the actuator dynamics in practice,a new switched sliding mode method is proposed.Also,according to the common Lyapunov function method,it is proved that uniformly boundedness of all signals for the systems can be guaranteed under arbitrary switchings.The simulation results show that the switched nonlinear disturbance observer can effectively observe unknown discontinuous composite disturbance,and the proposed control method can satisfy the tracking control requirement of VSNSV.Secondly,an attitude tracking control problem based on a switched sliding surface of VSNSV is studied.The control design of the switched system is limited because the subsystems share a same sliding surface,that is,the sliding surface can not be designed according to the requirement of each subsystem.Therefore,in order to solve this problem,the suitable sliding surface is designed for each subsystem of VSNSV under a basic condition of satisfying the stability requirement of switched system,then,a common coordinate transform is constructed and the switched sliding mode controller is designed.Also,using the average dwell time method,it is proved that the mentioned control strategy can guarantee the boundedness of all signals of the system.Simulation results show that the proposed control method can satisfy the tracking control requirement of VSNSV.Finally,the conclusions and perspectives are presented.