Attitude Dynamic Modeling And Control For Flexible Flight Vehicle

With the continuous development of modern aircraft,hypersonic vehicles(Hypersonic Vehicles)to become the current design trend of the aircraft in order to make the aircraft in the limited fuel conditions to obtain higher flight speed and range.Large slender ratio,light weight,structural quality is the main feature of small.These characteristics determine that the aircraft has a very obvious elastic characteristic.Therefore,this paper takes the subject of China Aerospace Science and Industry Group as the research background,and deeply studies the modeling and attitude tracking control problem of hypersonic vehicle with elastic effect.The main contents of this paper are summarized as follows:Aiming at the significant elastic vibration problem,the elastic model of the aircraft is established considering the coupling between the elastic effect and the rigid body.Based on the rigid body attitude dynamics equation of the aircraft,the simplified Euler-Bernoulli beam model is used to simplify the aircraft fuselage model.And the elastic vibration of the aircraft is modeled by the hypothetical modal method.Considering the direct effect and indirect effect of the elastic effect on the aircraft,two rigid and flexible coupling models of the elastic vehicle are obtained respectively.The elastic vibration of the aircraft is analyzed based on the aerodynamic attitude model of the elastic aircraft.Finally,the optimal installation position of the measuring element is obtained by numerical simulation.Aiming at the attitude angle tracking problem of the aircraft,a back-stepping attitude tracking controller and a sliding mode attitude tracking controller are designed based on the rigid body model of the aircraft,and the expected pitch angle is effectively tracked.Considering the influence of elastic vibration,it is regarded as the interference of the system model.Based on the mixed sensitivity method,the robust controller is designed to suppress the elastic disturbance.And the design of the controller is applied to the elastic model of the aircraft to carry out numerical simulation,which verifies the effectiveness of the designed attitude control system.Based on the elastic model of the aircraft,considering the elastic effect of the elastic effect,the elastic vibration is introduced into the control system circuit by the measurement element.By designing the nonlinear disturbance observer and the sliding mode disturbance observer,Estimation of vibration.The effect of two kinds of observer on elastic vibration is compared by numerical simulation.Considering the effect of disturbing observer on the disturbance,the effect of estimating the disturbance is weakened with the increase of the frequency.In order to obtain better estimation effect,the filter is introduced in the measurement link,and then the filtered low frequency elastic disturbance is observed.Considering the non-matching uncertainty of the system,the anti-attitude tracking controller based on the disturbance observer is designed,and the interference estimation value is introduced into the virtual control quantity to realize the compensation for the elastic disturbance.Considering the robustness of the system for elastic disturbances,a sliding mode attitude tracking controller based on the disturbance observer is designed.The estimated value of the disturbance observer is introduced into the designed sliding surface and the elastic disturbance is compensated.The validity of the two control schemes based on disturbance observer is verified by numerical simulation.