Robust output-feedback attitude control of a three-degree-of-freedom helicopter via sliding-mode observation technique

A robust output-feedback attitude controller for three-degree-of-freedom laboratory helicopter is proposed in this study. The laboratory helicopter has three rotational degree-of-freedom and preserves essential control challenges in the attitude control of actual helicopter. An output injection sliding-mode observer is developed to estimate the angular velocities and the external disturbances in finite time. The estimations are used to construct a robust LQR controller that requires angular position measurements only and compensates the external disturbances. The finite time asymptotic convergence of the observed states and disturbances to the actual values is proved and the results are verified numerically through simulation.