Sliding Mode Control Of Non-Minimum Phase Hypersonic Vehicle Based On Disturbance Observer

Due to the unique structure and complex flight environment of hypersonic flight vehicle(HFV),the dynamics model of HFV has the characteristics of non-minimum phase(NMP),strong uncertainty,strong nonlinear,which brings certain challenges to the design of HFV control system.In this paper,the stable tracking control of HFV is taken as the goal,and the influence of external disturbance(ED),actuator fault and NMP on HFV is studied and the control scheme is proposed.The main research contents are as follows:Firstly,a sliding mode(SM)control strategy based on B-I is proposed for tracking and controlling NMP HFV under the influence of ED.The nonlinear disturbance observer(DO)is used to estimate the ED and the disturbance estimation error(DEE)is guaranteed to be bounded stable(BS).Based on the B-I standard of HFV,the sigmoid function is introduced to construct a dynamic SM controller to stabilize the internal dynamics(IDs).Meanwhile,a dynamic inverse controller is designed to stabilize the external dynamics(EDs).A SM controller is designed for the velocity subsystem.Lyapunov theory is used to prove the asymptotic stability of the IDs,the practical finite time stability(PFTS)of the velocity tracking error and the BS of the EDs.The effectiveness of the control strategy is verified by simulation.Secondly,a new integral SM surface and a new reaching law are designed,and a robust SM controller is constructed to ensure the asymptotic stability of IDs.Meanwhile,the non-singular terminal sliding mode(TSM)controllers are designed respectively to ensure the PFTS of the velocity tracking error and the BS of the EDs.Considering the influence of ED,a TSM DO is designed.The PFTS of DEE is proved by Lyapunov theory,and the effectiveness of the control strategy is verified by simulation.Finally,the tracking control problem of NMP HFV under the influence of ED and actuator fault is studied.a nested SM controller based on a finite-time DO and a new reaching law is proposed for the velocity subsystem to realize the PFTS of EDD and the velocity tracking error.For the attitude subsystem,a nested SM fault-tolerant controller based on output redefinition is proposed,and an adaptive law is designed to estimate the fault parameters and ED.The PFTS of the new output tracking error is proved by Lyapunov theory,and the tracking performance of the control system is verified by simulation.