Robust altitude control for a small helicopter by considering the ground effect compensation

In this paper, a nonlinear robust control technique is proposed to control the altitude of a small helicopter for hover as well as vertically take-off/landing near ground surface in the presence of strong horizontal wind gusts. A heave motion model of small helicopter is considered to derive the proposed controller for the purposes of capturing dynamic variations of thrust due to the horizontal wind gusts and ground effect. In order to stabilize the vertical dynamics of the UAV helicopter, a recursive (backstepping) design procedure is used to design the robust controller based on Lyapunov approach. Simulation results demonstrate that the proposed robust backstepping controller is capable of controlling the altitude for hover flight of a small helicopter near ground surface in the presence of strong horizontal wind gusts.