non-linear robust control scheme

In this paper, a free model robust control is designed to track the position of three degrees of freedom (3-DOF) helicopter model in the presence of a variety of external uncertainties and disturbances. In this work, the adaptive time-delay control eliminates non-linear dynamics of helicopter, uncertainties, and external disturbances by generating a time-delay signal. The purpose of applying the adaptive law in the time-delay control is to online, automated and appropriate adjustment the gains in order to increase the speed of convergence and efficiency in the tracking operation in the presence of fluctuation tolerance. On the other hand, a sliding mode controller is used in the control structure to achieve robust performance against the time-delay estimation (TDE) error due to use of the time-delay signal. The uniformly ultimately bounded (UUB) stability of the closed-loop system has also been proved using Lyapunov stability theory. Finally, the effectiveness of the designed control approach is demonstrated using simulations on a 3-DOF helicopter in the presence of perturbations and uncertainties.