Design of robust controller of fixed-wing UAV for transition flight

Abstract

We propose the flight control system of a fixed-wing small UAV for a transition flight in consideration of nonlinearity on its dynamics. The control system consists of controllers for translational motion and rotational motion. The effect of its nonlinear dynamics on a control performance cannot be disregarded when designing a flight control system because it is difficult to linearize the motion with consideration of an equilibrium transition between vertical and horizontal flight modes. Moreover, the attitude of the small UAV is particularly affected by disturbances such as a gust of wind. Therefore, we employ the dynamic inversion method to take nonlinearity of the motion into account for a flight control design. A robust controller is applied to control the attitude of the UAV. It is necessary to use an observer based on the disturbance accommodating control (DAC) method to estimate of unknown parameter of nonlinear equations. We present preliminary results of numerical simulations and experiments of the UAV testbed that uses the proposed control system.