A DIFFERENT LOOK AT OUTPUT TRACKING - CONTROL OF A VTOL AIRCRAFT

In this paper we propose a scheme for output tracking of nonminimum ph ase Aat systems. The technique, which is applicable even in the minimu m phase case, uses an inverse trajectory for feedforward which is stab ilized by a state tracker built using the hat output. In contrast to a pproximate-linearization based control [Hauser, J., S. Sastry and G. M eyer (1992). Nonlinear control design for slightly nonminimum phase sy stems: application to v/stol aircraft. Automatica, 28, 665-679], which yields good performance in slightly nonminimum phase systems, our app roach applies equally well to slightly and strongly nonminimum phase s ystems. The proposed control scheme and the approximate-linearization based controller are applied to a Vertical Take Off and Landing (VTOL) aircraft example and the performances are compared.