SLIDING MODE CONTROL OF LINEAR-SYSTEMS WITH MISMATCHED UNCERTAINTIES

It is well-known that sliding mode control is robust to matched uncert ainties that lie in the range space of the input matrix. However many systems are affected by mismatched uncertainties and yet do not enjoy the matching conditions. It is the purpose of this paper to present a new dynamical approach of sliding variable formulation which, when the system is in sliding mode, can explicitly deal with mismatched uncert ainties. Our first step is to treat certain states as inputs to a redu ced-order system and use adaptive techniques to design fictitious cont rollers for these inputs, which can then tackle the mismatched uncerta inties. The second step is to use sliding control to realize the adapt ive fictitious controllers. The design is systematic, modular and intu itively simple.