Nonlinear observers applied to fixed-wing UAVs

This paper presents a comparison of two types of robust observers algorithms: the sliding-mode observer (SMO) and the nonlinear extended state observer (NESO). For some controllers design, it is necessary the use of observers in order to estimate the states which are not directly available. We present several simulations for the sliding-mode observer and the nonlinear extended state observer. In order to validate the robustness of such observers, we have developed a fixed-wing UAV platform, and we have designed a Proportional-Derivative (PD) control law which uses the output signals of the observer as state feedback. The analyzed movements are the altitude, roll and yaw.