An improved delay and state observer for SISO LTI systems with known delay lower bound

Abstract

It is known that the presence of delays hinders the performance achievable by a feedback control system, and it can even lead to closed-loop instability if not considered during the design. For this reason, predictors are often included in the loop, although they typically require the knowledge of the exact value of the delay, which in some applications is hard to obtain in practice. This paper presents a method to design an observer that simultaneously estimates the unknown state and the time-varying input delay of a plant based on an available model and the measurements coming from the sensors. In particular, the main contribution of this paper is to show that by accounting for a known lower bound of the input delay, it is possible to improve the observer’s performance when compared to state-of-the-art approaches encountered in the literature. Simulations are used to illustrate the efficiency of the proposed design method.