Autonomous Helicopter Landing

We consider the problem of controlling the vertical motion of a nonlinear model of a helicopter during landing, while stabilizing the lateral and longitudinal position and maintaining a constant attitude. The dynamics of the helicopter main and tail rotors are often neglected to simplify the control design, but this reduction has the disadvantage of an unreal choice of the control inputs. We have solved this contradiction by choosing the main controller required for performing the secure landing by neglecting the complex rotors dynamics, and then we have included these important dynamics in a closed loop model having real controls determined from an auxiliary controller. Simulation results show the effectiveness of the method to cope with uncertainties on the plant and actuator model. We apply a nonlinear controller which combines recent results on nonlinear adaptive output regulation and robust stabilization of systems in feed forward form by means of saturated controls. The added dynamics required the design of an auxiliary controller to force the states of the main and tail rotors systems to follow their reference values determined from the main controller.