Nonlinear robust attitude tracking control of an underactuated 3 degree-of-freedom helicopter

This paper proposes a new asymptotic attitude tracking controller for an underactuated three degree-of-freedom laboratory helicopter system. The nonlinear robust control law is developed through a modified inner-outer loop approach, and is free of chattering. The controller requires very limited knowledge of the system dynamic model while achieving good robustness with respect to system parametric uncertainties. A Lyapunov based stability analysis shows that the proposed algorithms can ensure asymptotic tracking of the helicopter´s elevation and travel angles, while keeping the stability of the closed loop system. Numerical simulation results demonstrate that the controller has good tracking performance, and requires few model knowledge.