Robust nonlinear motion control of a helicopter

We consider the problem of controlling the vertical motion of a nonlinear model of a helicopter to a reference signal, while stabilizing the lateral and horizontal position and maintaining a constant attitude. The reference to be tracked is given by a sum of a constant and a fixed number of sinusoidal signals, and it is assumed not to be available to the controller. This represents a possible situation in which the helicopter is required to synchronize its vertical motion with that of an oscillating platform, as the one given by a sea carrier subject to wave-induced oscillations. We design a nonlinear controller which combines results on nonlinear adaptive output regulations and robust stabilization of systems in feedforward form by means of saturated controls. Simulation results show the effectiveness of the method and its ability to cope with large uncertainties on the plant, the actuator model and the exogenous reference signal.