Modeling and attitude control of aircraft with variations in mass and center of gravity

Large scale variations in the mass or center of gravity (C.G.) pose serious problems for the control of aircraft in situations as heavy load airdrop on cargo aircraft, the airliners which employ the active C.G. control technology, aircraft with structural damages during the flight. To solve the problem of attitude control of such aircraft, a general model for the aircraft is established and a disturbance rejection attitude controller is proposed. The proposed model comprises of a 6-DOF dynamics model and the mass and C.G. variation model, which can handle various mass or C.G. variations and can reflect the dynamic couplings introduced by such variations. For the attitude control of such aircraft, based on the framework of observation and compensation, an explicit model following controller with the extension of extended state observer (ESO) is established. Real-time simulations demonstrate that the proposed model can accurately reflect the aircrafts dynamic responses during the variations, and with the compensation from the ESO, the model following controller can improve the performance and meet the requirements of precision attitude control.