Fault Tolerant Control Method For Hypersonic Flight Vehicle With State Constraints

The Hypersonic flight vehicle(HFV)has significant advantages such as fast speed and long-range precision strike,which is of great economic and military value.At present,a number of countries have successively carried out relevant ground and flight tests,and HFV has become a research hotspot in the military field.Based on barrier Lyapunov function(BLF)and adaptive backstepping method,this paper researches on the fault-tolerant control(FTC)method for HFV with state constraints.First of all,this paper introduces the development and research significance of HFV,and analyzes the characteristics of HFV model.At the same time,aiming at state constraints and FTC of HFV,the BLF method used to deal with the state constraints is introduced,and the current research of fault-tolerant control for HFV is briefly summarized in this paper.Also,the six degree of freedom(DOF)model,longitudinal model and elevator fault model of HFV required for the controller design are introduced in this paper.Secondly,aiming at the HFV longitudinal model with a redundant elevator,a FTC method which can realize all state constraints is studied.In this paper,the BLF based adaptive backstepping method is used to ensure that the flight path angle,pitch angle and pitch rate are always in the constraint range.Under reasonable assumption,the longitudinal model is divided into altitude subsystem and velocity subsystem,and the controlles are designed separately.In view of the unknown elevator faults that may occur and uncertain parameters of the longitudinal model,this paper designs an adaptive fault-tolerant controller.Also,this paper proves that the designed controller and adaptive laws can guarantee the stability of the system by using Lyapunov stability theory.Thirdly,for the longitudinal model of HFV with state constraints,an adaptive FTC scheme is proposed,which is more suitable for actual requirements.In the process of controller design,the complexity caused by state constraints,aerodynamic uncertainties,external disturbances and flexible dynamics are considered.Different from dividing the longitudinal model into two single input single output(SISO)subsystems,this paper makes appropriate transformation of HFV longitudinal model,so that the adaptive backstepping method based on BLF can be used to deal with the state constraints without neglecting the system coupling.For the unknown fault of elevators,the adaptive FTC mechanism is introduced into the BLF-based controller,which improves the reliability of the system.At last,the lateral motion of HFV model is considered,and the FTC is designed for the six DOF model of HFV.Due to the high complexity of the six DOF model,this paper simplifies the six DOF model of the aircraft under reasonable assumptions.In this paper,radial basis function(RBF)neural network is used to estimate the unknown function in the model.In consideration of the insufficient control torque caused by the fault of the rudder or elevators,a fault-tolerant controller is designed based on the backstepping method,and the angle of attack and the roll angle of the aircraft are constrainted in the preset range.