Altitude control improvement for a Quadrotor UAV using integral action in a sliding-mode controller

In this paper, a robust altitude control scheme is proposed for a mini-Quadrotor UAV system based on sliding mode controller with an integral action to eliminate the steady-state error induced by the boundary layer in order to achieve asymptotic convergence to the desired altitude with continuous control input. The proposed integral sliding mode controller is chosen to ensure the stability and robustness of overall dynamics during the altitude control at a desired height reference on the z-axis. Furthermore, we propose a Control Lyapunov Function (CLF) via Lyapunov theory in order to construct the robust stabilizing controller and demonstrate the stability of the z-dynamics of our system. A suitable sliding manifold is designed to achieve the control objective. At last, the theoretical results are supported by different simulation tests to verify the robustness and effectiveness of proposed robust control scheme in presence of bounded external disturbances.