On the unknown input observer design: A decoupling class approach

This paper deals with state estimation for linear discrete-time systems subject to unknown input. Although many papers have dealt with the problem of Unknown Input Observer design, state decoupling and reconstruction; the goal is to present a new method allowing to characterize a class of unknown inputs to which the estimation error is decoupled. This contribution considers two problems: exact decoupling and ℒ 2 -attenuation of the unknown input to the state estimation error.