Prescribed-Time Unknown Input Observer Design for Linear Systems With Commensurate Delays

This letter investigates the problem of prescribed-time observer design for a class of linear time-delay systems with commensurate delays and unknown inputs. Based on ring theory and the periodic delayed feedback approach, Luenberger-like observers are designed such that the estimation error converges to zero within a prescribed time. As a by-product, it is demonstrated how a previously proposed generalized coordinate transformation allows to extend the scope of periodic delayed output feedback, originally developed for systems with input-output delay, to a class of systems with state-delays.