Research On Reentry Fault Diagnosis And Fault Tolerant Control Of Hypersonic Vehicle

Hypersonic vehicle has the characteristics of high speed,large range,strong maneuverability and fast response,which is the key research direction of aerospace power.However,compared with the traditional aircraft,the harsh flight environment of the hypersonic vehicle makes its actuator prone to failure,which seriously affects the stability of the control system,and even directly leads to flight mission failure.Therefore,this paper will carry out in-depth research on the flight characteristics of hypersonic vehicles,focusing on the problem of fault diagnosis and fault-tolerant control under actuator fault.Firstly,the research status of hypersonic vehicles,fault diagnosis methods and fault-tolerant control methods at home and abroad are fully investigated,and the existing methods are systematically analyzed and summarized.Then,the actuator layout and overall parameters of the aircraft are introduced.The reentry dynamics model of the aircraft is established based on flight dynamics and aerodynamics.At the same time,the typical failure modes of the actuator are fully analyzed,and the mathematical model for control system design is established,which lays the foundation for the follow-up research.In order to solve the problem of fault-tolerant control under actuator fault,an adaptive backstepping fault-tolerant controller is designed based on fuzzy theory.Firstly,a tracking differentiator based on hyperbolic sine function is designed to reduce the change rate of attitude command,which makes it easier for the control system to track attitude command.Then,the control system is divided into o uter loop angle subsystem and inner loop angular velocity subsystem,and the total disturbance including actuator fault is estimated by fuzzy system approximation,The weights of the fuzzy system are updated in real time by adaptive law.In order to further improve the attitude control accuracy and disturbance rejection ability,an adaptive inversion fault-tolerant controller based on finite time extended observer is proposed.Firstly,based on the finite time convergence theory,a new type of finite time extended observer is designed to observe the state of the system and the lumped disturbances including faults in real time.Then,a dual loop attitude controller is designed based on the idea of backstepping control.The lumped disturbances are compensated in the controller,and an adaptive term is introduced to estimate the upper bound of the observation error,Thus,the attitude tracking accuracy of the control system is further improved.In order to accurately determine the fault location and estimate the rudder deflection angle,a super-twisting sliding mode fault-tolerant controller based on multi model filter is proposed.Firstly,the rudder angle is extended to the state vector to establish the state space equation.Based on the established state space equation,a multi model unscented Kalman filter fault diagnosis scheme is proposed.The state estimation ability of the filter is used to estimate the rudder angle,and the residual chi square detection method is used to determine the fault location.Then,a fast nonsingular terminal sliding mode surface is designed to improve the convergence speed of the control system,and a multivariable super-twisting sliding mode controller is designed based on the super-twisting theory.At the same time,a control allocation strategy based on fault diagnosis information is given to realize highly reliable active fault-tolerant control.