An innovative fuzzy backstepping sliding mode controller for a Tri-Rotor Unmanned Aerial Vehicle

The dynamical model of a Tri-Rotor Unmanned Aerial Vehicle (UAV) is presented in this paper. The Tri-Rotor has three rotors with two fixed-pitch propellers and a tiltable propeller to control the yaw displacement. The model is obtained via the Newton–Euler approach and a nonlinear control strategy called fuzzy backstepping sliding mode control is proposed for the attitude stabilization and altitude tracking of the vehicle. The designed controller consists of a backstepping sliding mode controller and a fuzzy logic controller. For the problem of determining the backstepping sliding mode control coefficients, an optimization method of gradient descent algorithm has been used. However, the control precision of the backstepping sliding mode is intimately dependent on the precision of coefficients. Besides, the uncertain unmodeled coefficients as well as the characteristics of the complex electromechanical system could cause the coefficients not be invariable. Therefore, a fuzzy logic controller is proposed to compensate the coefficients uncertainty to improve the robustness. The effectiveness of the proposed control algorithm is demonstrated via certain simulation results based on the actual parameters of UAV, and its advantages are indicated in comparison with the backstepping sliding mode control without fuzzy logic control.