Circle motion control of Trirotor UAV via discrete output zeroing

In this paper, a nonlinear controller is designed for an underactuated UAV having three inputs to realize “circle motion”, the motion that the attitude of UAV points to the center of circle while the center of mass moves on a circle orbit. The proposed method is redesigning the time-varying output zeroing controller discretely. This method allows output functions to be kept zero even though output functions are changed. In other words, zero dynamics can be controlled by this method. Finally, numerical simulation shows the validity of the proposed nonlinear controller.