Study On Active Disturbance Rejection Attitude Control For A Variable-Structure VTOL Aircraft

The vertical takeoff and landing(VTOL)aircraft which possesses both the advan-tages of the fixed-wing aircraft and helicopter such as vertical takeoff and landing,hover,high speed,long voyage and so on,will have great research value and enor-mous development potential in future.A new type of variable-structure VTOL aircraft is introduced in this thesis including its structure and how it works.The biggest control problem of the new type aircraft is that its dynamic model will change much during the flight,which makes controller design extremely difficult.The variable-structure VTOL aircraft has three modes which are VTOL mode,fixed-wing mode and mode conversion.Based on its dynamic model,an active dis-turbance rejection controller(ADRC)is designed for attitude control of the aircraft.Based on the dynamic model,attitude control problem of the VTOL mode of the aircraft is analyzed,which confirms power and control object of the aircraft.An active disturbance rejection attitude controller is designed,which consists of tracking differen-tiator,extended state observer,state error feedback and control decoupler.Simulation results show that the proposed method has outstanding advantages in stability,rapidity,robustness and so on.Based on the dynamic model,attitude control problem of the fixed-wing mode of the aircraft is analyzed,which confirms power and control object of the aircraft.An active disturbance rejection attitude controller is designed through projecting different control loops for forward speed and attitude angle.The control instruction of actuators which is obtained by the control decoupler is used for attitude control.Simulation re-sults show that the proposed method has remarkable advantages in stability,rapidity,robustness and so on.Attitude control problem of the mode conversion of the aircraft is analyzed,which divided the mode conversion into two parts.According to the change of the engine thrust tilting angle,active disturbance rejection control algorithms are presented.Aiming at the problem that the control instruction of actuators will change too much while control algorithms switch,a method of transition control is proposed to make the system stable.Simulation results show that the desighed controller could make the aircraft accomplish mode conversion steadily.