SECOND ORDER SLIDING MODE CONTROLLER DESIGN WITH OPTIMUM CHARACTERISTIC EQUATION FOR FOUR ROTOR UAV

Nowadays, small structured micro unmanned aerial vehicles (UAV’s) with four-rotor appears in military and civilian applications. As the usage of these vehicles becomes widespread, the development of controller structures which allow the UAV’s to follow a specified trajectory precisely is a new area of interest for researchers. In this work, nonlinear mathematical model of a four-rotor UAV is obtained. In order to obtain the mathematical model of UAV Newton-Euler equations are used. In the trajectory tracking system of this vehicle, second order sliding mode controller (SOSMC) is designed. Inside of the controller, control process is divided into two subsystems in order to provide position and attitude control. SOSMC is applied to the fully actuated and under actuated subsystems individually. In the next step, coefficients of the SOSMC is determined with optimum characteristic equation. Based on the reference study, boundaries of the predefined characteristic equation is obtained. Later, appropriate values are observed. In final part, simulation results are obtained, and the results are compared with the reference study. As a result, Optimum Characteristic equation results proved its robustness according to the smaller steady state error and more precise flight performance in trajectory. In this study simulation results are obtained using Simulink/MATLAB environment.