Robust Controller Design And Simulation For A Tri-Rotor Aircraft

Tri-Rotor UAV is a kind of simple, unique UAV, which has availabilities in vertical takeoff andlanding. So it has broad applications in both military and civilian areas. In recent years, the researchon small rotor UAVs is becoming more and more mature. Especially, the mathematical modeling andthe control system design of the UAV are the main problems.In this paper, a small Tri-Rotor UAV has been considered. Firstly, the dynamic equations for thethree linear translations and three angular rotations are established according to the Newton’s lawsand Euler Equations. Particularly its control strategies are discussed. Then, the final control model ofthe UAV is derived. After that, the classic PID controller is designed, which includes two parts—theangular rotation controller and the translational position controller. The feasibility of the controlmethod is verified by the simulation.Considering that the Tri-Rotor UAV is an under-actuated MIMO system and it has nonlinear andcoupling dynamic features, so a robust control system is designed in order to get more efficient andmore accurate control effects. This controller combines the dynamic inversion and robust controlmethod. First, use the dynamic inversion method to design the angular and position controllerrespectively, ensuring the decoupling and stability of the system. Since the dynamic inversioncontroller has bad robust performance and can’t satisfy the control requirements, the robustcontroller based on that is presented, and the angular and position robust controllers are designed.Through selecting the weighing functions, improve the frequency characteristics of the system’s openloop singular functions. Substantially, calculate the robust stability controller, which makes the systemachieve great robust stability and robust performance. The results of the simulation show that theclosed system has great performance in fixed hovering, trajectory tracking, interference suppressionand robust.