Discrete-time dynamic feedback linearization of a VTOL using observed states

This paper addresses the trajectory tracking problem for a remotely controlled quadrotor vertical take off and landing aircraft (VTOL), under the restriction that only the inertial coordinates are available for measurement. The problem is solved in two steps: first, a discretetime local exponential observer is designed which allows estimating the roll and pitching angles as well as all the velocities of the VTOL; Second, a discrete-time dynamic linearizing controller is proposed and the VTOL actual states variables are replaced by their corresponding estimates. It is shown that a kind of separation principle holds, in the sense that exponential convergence to the prescribed trajectory is preserved. Real-time experiments show that the proposed observercontroller scheme exhibits good performance.