Documents disponibles écrits par cet auteur

Root cause analysis of linear closed-loop oscillatory chemical process systems / S. Babji in Industrial & engineering chemistry research, Vol. 51 N° 42 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 42 (Octobre 2012) . - pp. 13712–13731 Titre : Root cause analysis of linear closed-loop oscillatory chemical process systems Type de document : texte imprimé Auteurs : S. Babji, Auteur ; U. Nallasivam, Auteur ; R. Rengaswamy, Auteur Année de publication : 2012 Article en page(s) : pp. 13712–13731 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Oscillations Résumé : In a single-input single-output (SISO) closed-loop system, under constant or nonoscillatory set-point, oscillations in the output can occur mainly because of one or a combination of the following reasons: (i) presence of stiction in control valve, (ii) marginally stable control loops (because of aggressively tuned controller/changes in process time constant/gain/time delays or a combination of them), and (iii) disturbances external to the loop. The presence of these oscillations can propagate plant-wide and force plants to deviate from optimal operating conditions. Therefore, it is essential to develop techniques that can diagnose the source of oscillations in control loops. Several data-driven methods have been developed to address the diagnosis problem by focusing on only one of the causes for oscillations. In the current study, an off-line data driven approach is developed to identify the root cause for oscillations in control loops using the routine plant operating data. Unlike the existing techniques, this approach identifies and distinguishes between the three major causes for oscillations in linear closed loop systems. The proposed methodology combines both parametric (Hammerstein-based approach) and nonparametric (Hilbert–Huang spectrum) schemes for performing oscillation diagnosis. Simulation and industrial case studies that demonstrate the utility and limitations of the proposed method for root cause diagnosis in closed loop systems are discussed. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2024323 [article] Root cause analysis of linear closed-loop oscillatory chemical process systems [texte imprimé] / S. Babji, Auteur ; U. Nallasivam, Auteur ; R. Rengaswamy, Auteur . - 2012 . - pp. 13712–13731. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 42 (Octobre 2012) . - pp. 13712–13731 Mots-clés : Oscillations Résumé : In a single-input single-output (SISO) closed-loop system, under constant or nonoscillatory set-point, oscillations in the output can occur mainly because of one or a combination of the following reasons: (i) presence of stiction in control valve, (ii) marginally stable control loops (because of aggressively tuned controller/changes in process time constant/gain/time delays or a combination of them), and (iii) disturbances external to the loop. The presence of these oscillations can propagate plant-wide and force plants to deviate from optimal operating conditions. Therefore, it is essential to develop techniques that can diagnose the source of oscillations in control loops. Several data-driven methods have been developed to address the diagnosis problem by focusing on only one of the causes for oscillations. In the current study, an off-line data driven approach is developed to identify the root cause for oscillations in control loops using the routine plant operating data. Unlike the existing techniques, this approach identifies and distinguishes between the three major causes for oscillations in linear closed loop systems. The proposed methodology combines both parametric (Hammerstein-based approach) and nonparametric (Hilbert–Huang spectrum) schemes for performing oscillation diagnosis. Simulation and industrial case studies that demonstrate the utility and limitations of the proposed method for root cause diagnosis in closed loop systems are discussed. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie2024323