High-gain robust control

We consider linear time-invariant SISO systems with parametric or non-parametric uncertainty in the transfer function. It is assumed that the system is robustly minimum-phase; we obtain necessary and sufficient conditions for the system to be robustly stabilisable by a high-gain controller and explicitly calculate the gain margin for interval systems. Thus, such systems need neither identification nor adaptation to be robustly stabilised and to attenuate disturbances. The case of unmodelled dynamics is more sophisticated; some models admit high-gain stabilisation while others do not.