Robust altitude control of an unmanned autonomous helicopter using backstepping

In this paper, a nonlinear robust control technique is proposed to control heave motion for hover as well as vertically take-off/landing of an unmanned autonomous helicopter in the presence of external wind gusts. A heave motion model of a small helicopter is considered to derive the proposed controller for the purposes of capturing dynamic variations of thrust due to the external disturbances. A recursive (backstepping) design procedure is used to design the robust controller for vertical dynamics based on Lyapunov approach. To show the effectiveness of the proposed control method and its ability to cope with the external uncertainties in the vertical dynamics, results are compared with a classical PD controller. Comparative studies demonstrate that the proposed robust backstepping control method greatly enhance the performance over the classical PD controller and it is applied to RUAV hovering condition as well as vertical take-off/landing.