Fault diagnosis viewed as a left invertibility problem

Dahhou

et al. 2021

Entropy

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.

Section: Introductionmentioning

confidence: 99%

Observer Based Multi-Level Fault Reconstruction for Interconnected Systems

Dahhou

et al. 2021

Entropy

“…The relevant literature on this topic has its roots on system inversion theory (Pinheiro and Araújo, 2013). There are several techniques available for fault reconstruction: sliding mode observers (Xu et al, 2012;Edwards et al, 2012;Martínez-Guerra et al, 2013), unknown input observers (Manaa et al, 2015;Blesa et al, 2014;Nagy-Kiss and Schutz, 2013;Zarei and Shokri, 2014), input reconstruction (Maksimov and Pandolfi, 2001;Yang et al, 2015;Szigeti et al, 2002;Schubert et al, 2012;Edelmayer et al, 2004). The key requirement is to completely decouple the faults from the effect of disturbances and also the input signals.…”

Section: Introductionmentioning

confidence: 99%

Root cause analysis of actuator fault based on invertibility of interconnected system

Cabassud

et al. 2017

IJMIC

This paper addresses the problem of root cause analysis (RCA) of actuator fault. By considering an actuator as an individual dynamic subsystem connected with process dynamic subsystem in cascade, an interconnected system is then constituted. The fault detection and diagnosis (FDD) algorithm is carried out in actuator subsystem and aims at identifying the root causes of actuator faults. According to real plant, outputs of the actuator subsystem are assumed inaccessible and are reconstructed by measurements of the global system, thus providing a means of monitoring and diagnosis of the plant at both local and global level. A condition of invertibility of the interconnected system is first developed to guarantee that faults occurring in the actuator subsystem will affect the measured output of the global system distinguishably. For that, a necessary and sufficient condition is proposed to ensure invertibility of the interconnected system. Effectiveness of the proposed approach is demonstrated on an intensified HEX reactor.

“…Another main aspect is inversion based FD I, which uses the system inverse to check whether the expected inputs are consistent with the measured outputs, such as [9]. System inversion is also used to estimate fault dynamics, popular techniques include sliding mode observer [10], differential-geometric [11] , unknown input observer in [12]. Since internai dynamics ofactuator is not accessible, the applications of these FDD methodologies mainly limit to the existence and the isolation of an actuator fault at a global level.…”

Section: Introductionmentioning

confidence: 99%

Fault diagnosis for HEX/reactor system via invertibility

2016 24th Mediterranean Conference on Control and Automation (MED)

Dahhou

et al. 2016

A fault diagnosis approach is developed for pneumatic valve used in intensified HEX/reactor system. The pneumatic valve is viewed as an actuator subsystem interconnected with process subsystem in series. A condition of invertibility of the cascade system bas been derived in [18], characterizing that effects of faults occurred in actuator subsystem are distinguishable by the global output uniquely. Using this idea, the fault diagnosis scheme proposed in this paper is based on local fault filtering, each subsystem is assigned to monitor one subsystem and provided a decision regarding its health. In particular, the connection point between the two subsystems is not accessible to measurements. An input estimator is then developed to estimate this unknown connection point only rely on the global system output. Different from [18], any information of the derivatives of the output vectors is not involved in the input estimation stage. For that, a high-gain second-order sliding mode observer is considered to exactly estimate the derivatives of the output vectors in a finite time. Numerical simulation examples are given to illustrate the effectiveness of the proposed methods.