Gust Disturbance Analysis And Stability Control For Very Flexible Aircraft

The Very Flexible Aircraft is a kind of High Altitude Long Endurance aircraft,with a large aspect ratio wing.It can cruise for a long time above twenty thousand meters altitude,and play an important role in both military and civil fields,such as intelligence collection,reconnaissance and surveillance,network relay and meteorological information collection.The wing of a Very Flexible Aircraft is long and flexible,and it is prone to deformation in the normal flight state,which affects the flight performance of the aircraft.So it is necessary to carry out the structure and dynamics modeling,the analysis of motion characteristics,the stability analysis and the design of control system.First of all,the Euler Bernoulli beam for modeling flexible wing is derived using the theory of finite element and Lagrange equation;strip assumption is introducted for aerodynamic modeling of aircraft;finally the nonlinear model coupling of aeroelasticity and dynamics is derived.Secondly,a new trim theory is proposed for the Very Flexible Aircraft.The time domain response of the aircraft with load is analyzed.The gust response of the aircraft under discrete gust,continuous turbulence and specific wind field is emphatically analyzed,and the critical value of gust for stabilizing the flight of aircraft is preliminarily obtained.Then,the Very Flexible Aircraft becomes unstable system when its centered loads exceed the critical value,so the size of the null controllable region is discussed under the different load,the different control constraints,the different damping factor and different stiffness,using the radius of stability to quantitatively measure.Finally,the nonlinear model of the Very Flexible Aircraft is linearized and the balance truncation method is used to reduce the order.The output is compared.A model reference adaptive controller based on LQR controller is designed for Very Flexible Aircraft under gust disturbance.The simulation results show that the controller can track longitudinal instructions well under gust disturbance.