Nonlinear attitude control using extended state observer for tilt-rotor aircraft

A tilt-rotor has a rotor on each side of its airframe and each rotor can be tilted to provide lift or thrust. With the tilt on rotors, the model of tilt-rotor has a significant change. Conventional control methods based on linearized model need extensive gain scheduling with the nacelle angle and flight condition. In order to alleviate this requirement, a design of attitude control based on ESO(Extended State Observer) is developed. The kernel of this method is the estimation and compensation of the disturbance on model. The disturbance includes the model error and coupling between different channels. By the compensation of the disturbance, the controller achieves the decoupling of the system and the compensation of model error and other disturbance at the same time. This control architecture is based on the nonlinear model of the aircraft and the parameters of the controller are available in wide ranges. Nonlinear feedback law is designed for outer loop controller to guarantee the dynamic performances. Simulation results in different flight conditions show that the design of attitude control is feasible.