Robust LQR attitude control of a 3-DOF laboratory helicopter for aggressive maneuvers

Robust attitude control problem for a three-degree-of-freedom (3-DOF) laboratory helicopter is investigated. The helicopter dynamics involves nonlinearity, uncertainties, and strong interaxis coupling. A robust controller is proposed with three parts: a nominal feedforward controller, a nominal linear quadratic regulation (LQR) controller, and a robust compensator. The LQR controller is applied to deal with a nominal linear error system derived by the feedforward control strategy and linearized approximation, while the robust compensator is designed to restrain the effects of uncertainties, nonlinear properties, and external disturbances. It is shown that the attitude tracking error of the closed-loop system can be guaranteed to converge to any given small neighborhood of the origin in a finite time. Experimental results on the 3-DOF laboratory helicopter demonstrate the effectiveness of the proposed control strategy.