Semiglobal stabilization of a class of nonlinear systems using output feedback

The stabilization of a class of multivariable nonlinear systems, about an equilibrium point at the origin, using output feedback is considered. Emphasis is placed on a class of systems that can be transformed into a global normal form with no zero dynamics. Semiglobal stabilization means that for every compact set of initial conditions, it is possible to design an output feedback controller that stabilizes the origin and includes the given compact set in the region of attraction. The system equations are allowed to depend on constant unknown parameters that do not change the vector relative degree of the system. The controller is robust with respect to these parameters. Global Lipschitz conditions are not required