An underactuated ℋ∞ control strategy for a quadrotor helicopter

In this paper a nonlinear robust control strategy designed for underactuated mechanical systems is proposed in order to solve the path tracking problem for a quadrotor unmanned aerial vehicle. An underactuated nonlinear ℋ
_∞
controller based on the six degrees of freedom dynamic model is designed to control the helicopter attitude and altitude in the inner-loop. The outer-loop control is performed using a model-based predictive controller (MPC) to track the reference trajectory. Simulations results in presence of aerodynamic forces and moments disturbances and parametric uncertainties are carried out to corroborate the effectiveness and the robustness of the strategy proposed.