Adaptive backstepping controller for altitude control of a small scale helicopter by considering the ground effect compensation

In this paper, a nonlinear adaptive control technique is proposed to control the altitude of a small-scale helicopter for hovering as well as vertically take-off/landing near ground surface in the presence of strong horizontal wind gusts. In general, the control of small scale helicopter is a difficult task, because the helicopter system is highly nonlinear, coupled and sensitive. For simplicity, only vertical flight motion is focused on here. This type of system has only two degrees of freedom, including helicopter altitude and collective pitch angle of blade. A vertical dynamics motion model of small-scale 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 small-scale helicopter, a recursive (backstepping) design procedure is used to design the adaptive controller based on Lyapunov approach. Simulation results demonstrate that the proposed adaptive backstepping controller is capable of controlling the altitude for hovering flight of a small-scale helicopter near ground surface in the presence of strong horizontal wind gusts.