A Novel Design of Unknown Input Observer for Fault Diagnosis in Non-minimum Phase Systems

Abstract

Fault diagnosis has become a significant issue due to rising demands for reliability as well as higher system performance and product quality. There are various approaches for the goal of fault detection and isolation among which we focus on the unknown input observer since observer-based schemes have been successfully adopted in a variety of application fields. This paper presents a novel design of Unknown Input Observer (UIO) for fault detection and isolation which can be applied to non-minimum phase systems. Unlike many previous UIO methods developed in the literature, the proposed scheme can carry out real-time reconstruction of unknown input in the presence of unstable invariant zero (with respect to the relation between the output and the unknown input). We extend the system by augmenting low pass filter(s) in the input(s)-output(s) path to tackle the non-minimum phase problem and generate robust residuals. Finally, the effectiveness of the proposed design method is confirmed through demonstrating a simulation-base example.