Research On Dynamic Modeling And Backstepping Control Design For Airship

Airships,also known as lighter-than-air(LTA)aerial vehicles,have some remarkable advantages compared to fixed-wing vehicles(airplanes)and rotary-wing aircrafts(helicopters).Because of low speed,long endurance and hovering,a wide range of applications have recently been proposed for airships,such as advertising,surveillance,environmental monitoring,planetary exploration,stratospheric observation and so on.Recently,with the development of the airship application in most fields,there is a great need in accurate dynamic modeling.In order to fulfill the tasks perfectly,control system is remarkable important.Comprehensive analyses show that the main problems in controlling are airship landing,actuator saturation and flexible dynamics.Considering the nonlinear six-degree-of-freedom dynamic modeling of airship,we discussed the design and derivation of a constrained adaptive backstepping controller for airship landing on the runway in the presence of wind gust.What's more,the design and derivation of an adaptive backstepping approach to control airships with minimal knowledge of airship aerodynamics and the engine thrust limits has been discussed.At last,based on the precise flexible dynamic model,a novel backstepping nonlinear controller with integral action is proposed for motion control systems.The main work of the thesis is as follows:1)Based on the nonlinear six-degree-of-freedom(6DOF)rigid model,the quantification motion sensitivity of the airship to geometric parameters was investigated through turning circles and horizontal/vertical zigzag maneuvers,which will guide the design of airship very well.2)Based on the nonlinear six-degree-of-freedom flexible model,the influence of the elastic deformation of the airship on the motion of the airship was analyzed.In circling motion,different types of airships including different hull length and different bending stiffness were simulated to show the effect of elastic deformation.The accurate model for future control was built.3)Considering the nonlinear six-degree-of-freedom dynamic modeling of airship,we discussed the design and derivation of a constrained adaptive backstepping controller for airship landing on the runway in the presence of wind gust.Throughout the design procedure of constrained adaptive backstepping controller,the airship modeling errors are taken into account.The command filter is used to deal with the dynamic characteristics and constraints for preventing the aggressive adaptation.The results show that the proposed backstepping control algorithm could stabilize the whole system and drive an airship to the desired landing trajectory of position.4)The design and derivation of an adaptive backstepping approach to control airships with minimal knowledge of airship aerodynamics and the engine thrust limits has been discussed.The adaptive control was used to estimate the dynamic characteristics on line,which guaranteed the system to be robust even model characteristics uncertainty.Lyapunov function has been used to stabilize the system even in the presence of thrust saturation.The proposed backstepping control algorithm could stabilize the whole system and drive an airship to the desired trajectory of position and yaw angle,which show the good performance of the adaptive backstepping approach.5)Based on the precise flexible dynamic model,a novel backstepping nonlinear controller with integral action is proposed for motion control systems.To make the model more accurate for reality,the strict restriction of actuators,such as limitations in magnitude and rate of change of rudder,was considered.For the accurate control object,an improved backstepping control method with integral action was used.The resulting feedback controller is able to adapt to strict restriction of actuators.The method reduces the conservatism of the controller design and has wider applications.With the deformation considered,the presented controller could resist the flexible uncertainty effect,and the system's trajectory tracking ability is significantly improved.The approach guarantees exponential stability of a compensated tracking error in the sense of Lyapunov.