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Real-time implementation of a robust hierarchical controller for a laboratory helicopter

In this paper, robust control problem is addressed for a three degree-of-freedom (3-DOF) laboratory helicopter. This helicopter system has three angles: the elevation, pitch, and travel angles and is a nonlinear multiple-input multiple-output (MIMO) uncertain system. The proposed controller is a robust hierarchical controller, which consists of a position controller and an attitude controller. The desired reference of the pitch angle is generated by the position controller based on the tracking error of the travel angle. Reference tracking of the pitch and elevation angles is achieved by the attitude controller. The tracking errors of the three angles are proven to converge ultimately into the given neighborhoods of the origin. Experimental results are also given to demonstrate the effectiveness of the proposed control strategy.