Abstract

An analysis is made of the conditions under which non-linear state regulators possess infinite gain margins. It is shown that stability with respect to unbounded feedback gains can sometimes be disrupted by small external disturbances, an effect that is quite distinct from the well-known high-gain instability of linear and non-linear feedback systems. The definition of a stable infinite gain margin is thus motivated and Lyapunov's direct method is used to identify a class of systems that possess such a gain margin.