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Fault detection for the Benfield process using a closed-loop subspace re-identification approach
Dissertation (MEng)--University of Pretoria, 2008.
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University of Pretoria
2013
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| _version_ | 1867613688879382528 |
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| access_status_str | Open Access |
| author2 | Camisani-Calzolari, Ferdinando Roux |
| author_browse | Camisani-Calzolari, Ferdinando Roux |
| author_facet | Camisani-Calzolari, Ferdinando Roux |
| collection | Thesis |
| dc_rights_str_mv | © 2008, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MEng)--University of Pretoria, 2008. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/29844 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:40:07.894Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/29844 Fault detection for the Benfield process using a closed-loop subspace re-identification approach Camisani-Calzolari, Ferdinando Roux philip.maree@gmail.com Maree, Johannes Philippus Guaranteed stability Shift invariant Extended observability matrix Subspace identification Extended kalman filter Rmpct Benfield Closed-loop identification Fault detection Lq decomposition Black box UCTD Dissertation (MEng)--University of Pretoria, 2008. Closed-loop system identification and fault detection and isolation are the two fundamental building blocks of process monitoring. Efficient and accurate process monitoring increases plant availability and utilisation. This dissertation investigates a subspace system identification and fault detection methodology for the Benfield process, used by Sasol, Synfuels in Secunda, South Africa, to remove CO2 from CO2-rich tail gas. Subspace identification methods originated between system theory, geometry and numerical linear algebra which makes it a computationally efficient tool to estimate system parameters. Subspace identification methods are classified as Black-Box identification techniques, where it does not rely on a-priori process information and estimates the process model structure and order automatically. Typical subspace identification algorithms use non-parsimonious model formulation, with extra terms in the model that appear to be non-causal (stochastic noise components). These extra terms are included to conveniently perform subspace projection, but are the cause for inflated variance in the estimates, and partially responsible for the loss of closed-loop identifiably. The subspace identification methodology proposed in this dissertation incorporates two successive LQ decompositions to remove stochastic components and obtain state-space models of the plant respectively. The stability of the identified plant is further guaranteed by using the shift invariant property of the extended observability matrix by appending the shifted extended observability matrix by a block of zeros. It is shown that the spectral radius of the identified system matrices all lies within a unit boundary, when the system matrices are derived from the newly appended extended observability matrix. The proposed subspace identification methodology is validated and verified by re-identifying the Benfield process operating in closed-loop, with an RMPCT controller, using measured closed-loop process data. Models that have been identified from data measured from the Benfield process operating in closed-loop with an RMPCT controller produced validation data fits of 65% and higher. From residual analysis results, it was concluded that the proposed subspace identification method produce models that are accurate in predicting future outputs and represent a wide variety of process inputs. A parametric fault detection methodology is proposed that monitors the estimated system parameters as identified from the subspace identification methodology. The fault detection methodology is based on the monitoring of parameter discrepancies, where sporadic parameter deviations will be detected as faults. Extended Kalman filter theory is implemented to estimate system parameters, instead of system states, as new process data becomes readily available. The extended Kalman filter needs accurate initial parameter estimates and is thus periodically updated by the subspace identification methodology, as a new set of more accurate parameters have been identified. The proposed fault detection methodology is validated and verified by monitoring process behaviour of the Benfield process. Faults that were monitored for, and detected include foaming, flooding and sensor faults. Initial process parameters as identified from the subspace method can be tracked efficiently by using an extended Kalman filter. This enables the fault detection methodology to identify process parameter deviations, with a process parameter deviation sensitivity of 2% or higher. This means that a 2% parameter deviation will be detected which greatly enhances the fault detection efficiency and sensitivity. Electrical, Electronic and Computer Engineering unrestricted 2013-09-07T16:53:52Z 2009-12-09 2013-09-07T16:53:52Z 2009-09-02 2008 2009-11-26 Dissertation Maree, JP 2008, Fault detection for the Benfield process using a closed-loop subspace re-identification approach, MEng dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/29844 > E1473/ag http://hdl.handle.net/2263/29844 http://upetd.up.ac.za/thesis/available/etd-11262009-224053/ © 2008, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Guaranteed stability Shift invariant Extended observability matrix Subspace identification Extended kalman filter Rmpct Benfield Closed-loop identification Fault detection Lq decomposition Black box UCTD Fault detection for the Benfield process using a closed-loop subspace re-identification approach |
| title | Fault detection for the Benfield process using a closed-loop subspace re-identification approach |
| title_full | Fault detection for the Benfield process using a closed-loop subspace re-identification approach |
| title_fullStr | Fault detection for the Benfield process using a closed-loop subspace re-identification approach |
| title_full_unstemmed | Fault detection for the Benfield process using a closed-loop subspace re-identification approach |
| title_short | Fault detection for the Benfield process using a closed-loop subspace re-identification approach |
| title_sort | fault detection for the benfield process using a closed loop subspace re identification approach |
| topic | Guaranteed stability Shift invariant Extended observability matrix Subspace identification Extended kalman filter Rmpct Benfield Closed-loop identification Fault detection Lq decomposition Black box UCTD |
| url | http://hdl.handle.net/2263/29844 http://upetd.up.ac.za/thesis/available/etd-11262009-224053/ |