Adaptive Sliding Mode Controller for Attitude and Position of Quadrotor UAV

Abstract

In recent years Unmanned Aerial Vehicles (UAVs) have become increasingly popular research topic due to their wide applications and advantages. The quadrotor is a highly non-linear and coupled system which requires a good controller. In this research work, an adaptive law-based Sliding Mode Control (SMC) is proposed for attitude and position of quadrotor UAVs under external disturbance and internal parameter uncertainty, considered mass in this study. Since quadrotor dynamics is highly non-linear and strongly coupled, the system dynamics is given first and open loop verification is done to show that the system functions according to the given input signal properly. The Adaptive Sliding Mode Control (ASMC) is then designed and the chattering effect on the proposed controller performance is decreased by adding a boundary layer around the sliding surface by tanh function. Lyapunov stability analysis is used to achieve asymptotic stability. The system has inner and outer loop which controls attitude and position respectively. The outer loop output responses, X and Y positions, are given as a desired trajectory for inner loop, Phi and Theta, while an arbitrary reference trajectory is given for Psi angle. The controller and the system dynamics is integrated and simulated using MATLAB/Simulink environment. The simulation result shows, the system performs very well while exhibiting robustness on the set point path with less than 2 second settlement and 0% overshoot. To confirm the robustness of the control method, uncertain parameter value of mass and external step wind disturbance is applied on the system. Finally, the proposed controller is compared with classical SMC to show the performance of both controllers. The proposed controller has good tracking and better disturbance rejection ability.