Robust PI observer design for linear time-delay systems

A method for H_infin proportional-integral (PI) observer design for linear time-delay systems is proposed in this paper. The design method involves attenuating of the disturbance to a pre-specified level while estimating the states of the delay system. The PI observer design requires solving certain algebraic Riccati equation. Although the PI observer for time delay system is used for disturbance attenuation in this paper, it has the advantage of using it in estimating the disturbance or fault as well as other scenarios in robust control applications. The main result of the paper is the derivation of PI observer for system with one delay; however, its generalization for two delays is also outlined. Illustrative examples are included to support the theoretical results.