Research Of The Trackinh Control Methods Of A Hypersonic Vehicle

Compared with traditional aircraft,the flight trajectory of hypersonic vehicle has the characteristics of high speed,high altitude and high maneuverability.Therefore,hypersonic vehicle has important strategic significance in both military and civil fields.Hypersonic vehicle has the characteristics of strong coupling,strong time-varying and strong nonlinear.These characteristics make hypersonic vehicles face severe challenges in modeling and control system design.The advanced aerodynamic shape,integrated fuselage / engine design,large flight envelope and drastic change of flight environment of hypersonic vehicle make the stability of hypersonic vehicle poor,the model uncertainty is high,and the coupling between rigid body and flexible body is serious.Therefore,it is necessary to design a stable and reliable robust controller for hypersonic vehicles.In order to understand the flight characteristics of hypersonic vehicle more comprehensively,this paper first deduces the suitable rigid/elastic coupling dynamic model for the vehicle in the longitudinal channel based on Lagrange method and virtual work principle,and applies the model to analyze the flight characteristics of hypersonic vehicle,including the characteristics of hypersonic vehicle in the longitudinal channel Stability analysis and modal analysis of hypersonic vehicle.Based on the rigid/elastic coupling model of hypersonic vehicle in longitudinal channel,the control-based model is derived and decomposed into altitude subsystem and velocity subsystem.In view of the external disturbance and model parameter uncertainty of hypersonic vehicle in the process of motion,the flexible mode,external disturbance and model parameter uncertainty are considered as bounded lumped disturbance.Then,based on the backstepping control method and adaptive theory,adaptive robust backstepping controllers are designed for the altitude and velocity subsystems of the vehicles,respectively.Under certain conditions,the controller can be stable in the sense of Lyapunov,and the effectiveness of the controller is proved by the simulation results.The controller derived in the previous chapter can make the system track the desired input in the presence of external interference,but the magnitude of the disturbance cannot be measured by effective means.In fact,under the condition of actual system operation,there are a large number of disturbances,so the idea of suppressing the interference by observing the external interference is produced,that is,the design of interference observer.In this chapter,by introducing the disturbance observer,based on the theory of the previous chapter,the disturbance of the aircraft is observed,and the equivalent disturbance is introduced into the controller to suppress the disturbance,so that the system has stability.The elastic deformation of hypersonic vehicle in flight significantly increases the possibility of actuators’ generation saturation.When the actuator works in saturated state,the vehicle can not be effectively controlled.In order to solve the problem of actuator input saturation,an adaptive backstepping saturation tracking controller is designed based on backstepping control method,adaptive tracking differentiator and hyperbolic tangent function of appropriate saturation equation.The simulation results show that the algorithm can make the equilibrium point of state convergence and has good stability.Furthermore,aiming at the actuator fault in the flight process.Based on the passive fault-tolerant theory,the adaptive backstepping saturation fault-tolerant tracking controller is designed for the altitude subsystem and velocity subsystem of the aircraft by using backstepping control theory,command filter,signal compensation and auxiliary system.The stability of the system is proved based on Lyapunov stability theory,and the effectiveness of the designed controller is proved by the results of mathematical policy.Finally,considering the input saturation,actuator fault and state constrained tracking control problems encountered in the flight process of an flexible hypersonic vehicle,based on the passive fault-tolerant idea,using the new barrier Lyapunov function,adaptive technology and first-order filter,adaptive saturation fault tolerance is designed for the velocity subsystem and altitude subsystem respectively The controller can deal with input saturation and state constraints by introducing hyperbolic tangent function and new barrier Lyapunov function.Finally,the Lyapunov function is used to prove the above controller strictly,which shows that the system state is ultimately uniformly bounded,and the effectiveness of the proposed control strategy is verified by digital simulation.The controller provides an effective method to deal with a series of practical problems encountered in the actual flight process of a flexible hypersonic vehicle.