Stabilization of a VTOL aircraft-an L2 gain control approach

Considers the stabilization of a planar vertical take-off and landing (PVTOL) aircraft model. This model assumes that the aircraft is a rigid body with a set of moments and forces acting on it. More significantly, it includes the moment-to-force coupling and exhibits nonminimum phase characteristics. Consequently, it retains the essential properties relating to the stabilization of a real six-degree-of-freedom aircraft. In particular, the nonminimum phase response makes techniques like feedback linearization and sliding mode control, which require the zero-dynamics to be stable, inapplicable. In this study, the recently developed nonlinear L₂-gain (or nonlinear H^∞) control technique is used. It is noted that the theory does not explicitly address the zero-pole structure of the nonlinear system and hence appears more applicable for flight control problems