Observer Based Multi-Level Fault Reconstruction for Interconnected Systems.

Qinmu Wu,Mei Zhang,Zetao Li,Boutaïeb Dahhou

doi:10.3390/e23091102

Abstract

The problem of local fault (unknown input) reconstruction for interconnected systems is addressed in this paper. This contribution consists of a geometric method which solves the fault reconstruction (FR) problem via observer based and a differential algebraic concept. The fault diagnosis (FD) problem is tackled using the concept of the differential transcendence degree of a differential field extension and the algebraic observability. The goal is to examine whether the fault occurring in the low-level subsystem can be reconstructed correctly by the output at the high-level subsystem under given initial states. By introducing the fault as an additional state of the low subsystem, an observer based approached is proposed to estimate this new state. Particularly, the output of the lower subsystem is assumed unknown, and is considered as auxiliary outputs. Then, the auxiliary outputs are estimated by a sliding mode observer which is generated by using global outputs and inverse techniques. After this, the estimated auxiliary outputs are employed as virtual sensors of the system to generate a reduced-order observer, which is caplable of estimating the fault variable asymptotically. Thus, the purpose of multi-level fault reconstruction is achieved. Numerical simulations on an intensified heat exchanger are presented to illustrate the effectiveness of the proposed approach.

Highlights

IntroductionIncreasing developments in modern technologies have led to a high complexity of control systems
Addresses the multi-level fault input rec Dynamics of the unknown inputs are shown in Figures 13 and 14
By introducing the local faul values are denoted by the black solid lines, and the dash lines represent the reconstructed tionalFrom stateFigures and auxiliary outputs of the low subsystem, thefollows extended sta values

Summary

Introduction

Increasing developments in modern technologies have led to a high complexity of control systems. Either due to physical or analytical purpose, modern control systems are frequently tackled as interconnected systems. Potential faults in interconnected systems have become inevitable and increasingly complex since faults of the interconnected system can be represented at either the local subsystem level, or at the global system level with the whole system in view, considering faults such as unknown external disturbance, or parameter variations. The fault can usually be regarded as an unknown input to the system. The problem of reconstructing the inaccessible inputs from the available measurements is motivated and has attracted remarkable interest in the last decades. Reconstruction of unknown or inaccessible inputs from noise or indirect measures is very common in many real industrial situations

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Methods

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Conclusion