Abstract

Multivariable control systems suffer very much from unwanted interactions among control loops. Change in setpoint of one variable may cause other variables to deviate from their respective steady states because of couplings between unpaired variables. Due to unreliability problems, conventional decouplers are not appropriate for higher order processes. This paper proposes Partial Least Squares (PLS), multivariate statistical process control technique (MVSPC), based decoupling strategy to attain satisfactory performance and consistent product quality in spite of disturbances. The proposed scheme was applied on conventional and heat integrated distillation processes. The results have shown the reliability and robustness of Partial Least Squares based decouplers over conventional decouplers.

References

• H. B. Edgar, "On a New Measure of Interaction for Multivariable Process Control", IEEE T. Automat. Contr, Vol. 11 (1), (January, 1966), pp: 133-134.
• J-P. Gagnepaln, D. E. Seborg, "Analysis of Process Interactions with Applications to Multiloop Control System Design", Ind. Eng. Chem. Process Des. Dev. , Vol. 21, (1982), pp: 5-11.
• W. L. Luyben, "Distillation decoupling", AIChE J. , Vol. 16 (2), (1970), pp: 198-203.
• K. V. T. Waller, "Decoupling in distillation", AIChE J. , Vol. 20 (3), (1974), pp: 592-594.
• T. J. McAvoy, "Steady-State Decoupling of Distillation Columns", Ind. Eng. Chem. Fundam. , Vol. 18 (3), (1979), pp: 269-273.
• K. Weischedel, T. J. McAvoy, "Feasibility of decoupling in conventionally controlled distillation columns", Ind. Eng. Chem. Fundam. , Vol. 19 (4), (1980),pp: 379-384.
• Y. Arkun, B. Manouslouthakis, A. Palazoglu, "Robustness analysis of process control systems. A case study of decoupling control in distillation", Ind. Eng. Chem. Process Des. Dev. , Vol. 23 (1), (1984), pp: 93-101.
• D. E. Seborg, T. F. Edgar, D. A. Mellichamp, "Process Dynamics & Control", John Wiley & Sons, New York, 1989.
• H. L. Wade, "Inverted decoupling: a neglected technique", ISA T. , Vol. 36 (1), (1997), pp: 3-10.
• E. Gagnon, A. Pomerleau, A. Desbiens, "Simplified, ideal or inverted decoupling?", ISA T. , Vol. 37, (1998),pp: 265-276.
• S-J. Shiu, S-H. Hwang, "Sequential Design Method for Multivariable Decoupling and Multiloop PID Controllers", Ind. Eng. Chem. Res. , Vol. 37, (1998), pp: 107-119.
• O. B. Gjosaeter, B. A. Foss, "On the use of diagonal control Vs Decoupling for ill-conditioned process", Automatica, Vol. 33 (3), (March 1997), pp. 427-432.
• I-L. Chien, W-H. Chen, T-S. Chang, "Operation and decoupling control of a heterogeneous azeotropic distillation column", Comput. Chem. Eng. , Vol. 24, (2000), pp: 893-899.
• T. Chai, L. Zhai, H. Yue, "Multiple models and neural networks based decoupling control of ball mill coal-pulverizing systems", J. Process Contr. , Vol. 21, (2011), pp: 351–366.
• H. Wold, "Estimation of principal components and related models by iterative least squares", In MultiVariate Analysis II; Krishnaiah, P. R. , Ed. ; Academic Press, New York, (1966), pp 391-420.
• P. Geladi, B. R. Kowalski, "Partial least-squares regression: A tutorial," Anal. Chim. Acta, Vol. 185, (1986), pp: 1-17.
• S. J. Qin, T. J. McAvoy, "Nonlinear PLS modeling using neural network," Comput. Chem. Eng. , Vol. 16 (4), (1992), pp: 379-391.
• S. J. Qin, "A statistical perspective of neural networks for process modelling and control," In Proceedings of the 1993 Internation Symposium on Intelligent Control, Chicago, IL, (1993), pp: 559-604.
• D. J. H. Wilson, G. W. Irwin, G. Lightbody, "Nonlinear PLS using radial basis functions," Trans. Inst. Meas. Control, Vol. 19(4), (1997), pp: 211-220.
• T. R. Holcomb, M. Morari, "PLS/neural networks," Comput. Chem. Eng. , Vol. 16 (4), (1992), pp: 393-411.
• E. C. Malthouse, A. C. Tamhane, R. S. H. Mah, "Nonlinear partial least squares," Comput. Chem. Eng. , Vol. 21 (8), (1997), pp: 875-890.
• S. J. Zhao, J. Zhang, Y. M. Xu, Z. H. Xiong, "Nonlinear projection to latent structures method and its applications", Ind. Eng. Chem. Res. , Vol. 45, (2006), pp: 3843-3852.
• D. S. Lee, M. W. Lee, S. H. Woo, Y. Kim, J. M. Park, "Nonlinear dynamic partial least squares modeling of a full-scale biological wastewater treatment plant," Process Biochem. , Vol. 41, (2006), pp: 2050-2057.
• M. H. Kaspar, W. H. Ray, "Dynamic modeling for process control", Chem. Eng. Sci. , Vol. 48(20), (1993), pp: 3447-3467.
• S. Lakshminarayanan, L. Sirish, K. Nandakumar, "Modeling and control of multivariable processes: The dynamic projection to latent structures approach," AIChE J. , Vol. 43, (September 1997), pp: 2307-2323.
• S. K. Damarla, M. Kundu. "Identification and Control of Distillation Process using Partial Least Squares based Artificial Neural Network". IJCA, Vol. 29(7), (September 2011), pp: 29-35,
• S. K. Damarla, M. kundu, "Design of Multivariable Neural Controllers Using A Classical Approach", IJCEA, Vol. 1 (2), (2010), pp: 165-172
• R. K. Wood, M. W. Berry, "Terminal Composition Control of a Binary Distillation Column," Chem. Eng. Sci. , Vol. 29, (1973), pp: 1707-1717
• T-P. Chiang, W. L. Luyben, "Comparison of the Dynamic Performances of Three Heat-Integrated Distillation Configurations", Ind. Eng. Chem. Res. , Vol. 27, (1988), pp: 99-10