  This note studies the robust output feedback stabilization problem of a class
of multi-input multi-output invertible nonlinear systems, for which an "ideal"
state feedback based on feedback linearization can be designed under certain
mild assumptions. By systematically designing a set of extended low-power
high-gain observers, we show that this "ideal" linearizing feedback law can be
approximately estimated, which provides a robust output feedback stabilizer
such that the origin of the resulting closed-loop system is semiglobally
asymptotically stable.
