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Closed - loop identification of second - order plus time delay (SOPTD) model of multivariable systems by optimization method / C. Rajapandiyan in Industrial & engineering chemistry research, Vol. 51 N° 28 (Juillet 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 28 (Juillet 2012) . - pp. 9620-9633 Titre : Closed - loop identification of second - order plus time delay (SOPTD) model of multivariable systems by optimization method Type de document : texte imprimé Auteurs : C. Rajapandiyan, Auteur ; M. Chidambaram, Auteur Année de publication : 2012 Article en page(s) : pp. 9620-9633 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Optimization  Multivariable  system  Modeling  Second  order  Closed  loop Résumé : The closed-loop identification of second-order plus time delay (SOPTD) transfer function models of multivariable systems is presented based on optimization method using the combined step-up and step-down responses. The need for combined step up and step down changes in the set point is brought out for the convergence of the model parameters. A standard nonlinear least-squares optimization method is used to obtain the parameters of the SOPTD model transfer function matrix by minimizing the sum of squared errors between the closed-loop responses of the model and the actual process responses. A simple method is proposed to obtain the initial guess values of SOPTD transfer function model parameters from the main and interaction responses of the actual process. This method was applied to two-input two-output (TITO) second-order plus time delay (SOPTD), higher order and 3 × 3 SOPTD transfer function models of multivariable systems. The proposed method considerably reduces the computational time for the optimization for 2 × 2 SOPTD model systems (11 min and 11 s) when compared with the genetic algorithm (GA) method reported by Viswanathan et al. (Ind. Eng. Chem. Res. 2001, 40, 2818-2826). ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26163299 [article] Closed - loop identification of second - order plus time delay (SOPTD) model of multivariable systems by optimization method [texte imprimé] / C. Rajapandiyan, Auteur ; M. Chidambaram, Auteur . - 2012 . - pp. 9620-9633. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 28 (Juillet 2012) . - pp. 9620-9633 Mots-clés : Optimization  Multivariable  system  Modeling  Second  order  Closed  loop Résumé : The closed-loop identification of second-order plus time delay (SOPTD) transfer function models of multivariable systems is presented based on optimization method using the combined step-up and step-down responses. The need for combined step up and step down changes in the set point is brought out for the convergence of the model parameters. A standard nonlinear least-squares optimization method is used to obtain the parameters of the SOPTD model transfer function matrix by minimizing the sum of squared errors between the closed-loop responses of the model and the actual process responses. A simple method is proposed to obtain the initial guess values of SOPTD transfer function model parameters from the main and interaction responses of the actual process. This method was applied to two-input two-output (TITO) second-order plus time delay (SOPTD), higher order and 3 × 3 SOPTD transfer function models of multivariable systems. The proposed method considerably reduces the computational time for the optimization for 2 × 2 SOPTD model systems (11 min and 11 s) when compared with the genetic algorithm (GA) method reported by Viswanathan et al. (Ind. Eng. Chem. Res. 2001, 40, 2818-2826). ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26163299

Controller design for MIMO processes based on simple decoupled equivalent transfer functions and simplified decoupler / C. Rajapandiyan in Industrial & engineering chemistry research, Vol. 51 N° 38 (Septembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 38 (Septembre 2012) . - pp. 12398-12410 Titre : Controller design for MIMO processes based on simple decoupled equivalent transfer functions and simplified decoupler Type de document : texte imprimé Auteurs : C. Rajapandiyan, Auteur ; M. Chidambaram, Auteur Année de publication : 2012 Article en page(s) : pp. 12398-12410 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Transfer  function  Design Résumé : A method for the independent design of proportional-integral/proportional-integral derivative (PI/PID) controllers is proposed based on the equivalent transfer function (ETF) model of the individual loops and the simplified decoupler matrix. It is shown that the conventional effective open-loop transfer function (EOTF, derived from the dynamic relative gain array (DRGA)) is equivalent to the ETF (derived from the relative normalized gain array (RNGA) and relative average residence time array (RARTA)). This relation is used to approximate the decoupled process models as ETF models. The simplified decoupler is shown to decompose the multiloop systems into independent loops (multi-single loop systems) with the ETFs as the resulting decoupled process model The concept of the ETF (perfect control approximation) is validated by introducing the decoupler. Based on the corresponding ETFs, the decentralized PI controllers are designed using the simplified internal model control (SIMC) method. Three simulation examples of multi-input multi-output (MIMO) process models are considered to demonstrate the simplicity and effectiveness of the proposed method. The performance of the proposed control system is compared with the ideal, normalized, inverted decoupling, and centralized control systems. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26399691 [article] Controller design for MIMO processes based on simple decoupled equivalent transfer functions and simplified decoupler [texte imprimé] / C. Rajapandiyan, Auteur ; M. Chidambaram, Auteur . - 2012 . - pp. 12398-12410. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 38 (Septembre 2012) . - pp. 12398-12410 Mots-clés : Transfer  function  Design Résumé : A method for the independent design of proportional-integral/proportional-integral derivative (PI/PID) controllers is proposed based on the equivalent transfer function (ETF) model of the individual loops and the simplified decoupler matrix. It is shown that the conventional effective open-loop transfer function (EOTF, derived from the dynamic relative gain array (DRGA)) is equivalent to the ETF (derived from the relative normalized gain array (RNGA) and relative average residence time array (RARTA)). This relation is used to approximate the decoupled process models as ETF models. The simplified decoupler is shown to decompose the multiloop systems into independent loops (multi-single loop systems) with the ETFs as the resulting decoupled process model The concept of the ETF (perfect control approximation) is validated by introducing the decoupler. Based on the corresponding ETFs, the decentralized PI controllers are designed using the simplified internal model control (SIMC) method. Three simulation examples of multi-input multi-output (MIMO) process models are considered to demonstrate the simplicity and effectiveness of the proposed method. The performance of the proposed control system is compared with the ideal, normalized, inverted decoupling, and centralized control systems. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26399691

Enhanced control of unstable cascade processes with time delays using a modified smith predictor / S. Uma in Industrial & engineering chemistry research, Vol. 48 N° 6 (Mars 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 6 (Mars 2009) . - pp. 3098–3111 Titre : Enhanced control of unstable cascade processes with time delays using a modified smith predictor Type de document : texte imprimé Auteurs : S. Uma, Auteur ; M. Chidambaram, Auteur ; A. Seshagiri Rao, Auteur Année de publication : 2009 Article en page(s) : pp. 3098–3111 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Cascade  controller  Smith  predictor  structure  Unstable  cascade  Direct  synthesis  method  Internal  model  control Résumé : This paper presents a simple cascade controller in the enhanced modified Smith predictor structure for control of open loop unstable cascade processes with/without zero. The proposed structure consists of two control loops, a secondary inner loop and a primary outer loop. The method has totally three controllers of which the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is designed using the internal model control (IMC) technique. The primary loop set point tracking and disturbance rejection controllers are designed using the direct synthesis method. The primary set point tracking controller is designed as a proportional, integral, and derivative (PID) controller with lag filter and the primary disturbance rejection controller is designed as a PID with lead−lag filter. Simulation studies have been carried out on various cascade unstable processes with/without zero. The present method gives significant disturbance rejection both in the inner and outer loops. Also, the proposed method shows significant improvement when compared to the recently reported methods in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801590e [article] Enhanced control of unstable cascade processes with time delays using a modified smith predictor [texte imprimé] / S. Uma, Auteur ; M. Chidambaram, Auteur ; A. Seshagiri Rao, Auteur . - 2009 . - pp. 3098–3111. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 6 (Mars 2009) . - pp. 3098–3111 Mots-clés : Cascade  controller  Smith  predictor  structure  Unstable  cascade  Direct  synthesis  method  Internal  model  control Résumé : This paper presents a simple cascade controller in the enhanced modified Smith predictor structure for control of open loop unstable cascade processes with/without zero. The proposed structure consists of two control loops, a secondary inner loop and a primary outer loop. The method has totally three controllers of which the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is designed using the internal model control (IMC) technique. The primary loop set point tracking and disturbance rejection controllers are designed using the direct synthesis method. The primary set point tracking controller is designed as a proportional, integral, and derivative (PID) controller with lag filter and the primary disturbance rejection controller is designed as a PID with lead−lag filter. Simulation studies have been carried out on various cascade unstable processes with/without zero. The present method gives significant disturbance rejection both in the inner and outer loops. Also, the proposed method shows significant improvement when compared to the recently reported methods in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801590e