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Modeling And Control Of Nonlinear Process Using Robust And Soft Controllers.

M.Sridevi, P.Madhavasarma, P. veeraragavan.

Level control in a hemispherical tank is a challenging task in process industries due to nonlinear variation of level with height. The need for an accurate and appropriate online or off line model to control such nonlinear process is on huge demand to avoid process complications in practical applications such as oil refineries, dye industries etc. In this work, a hemispherical tank of 40 liter capacity was subjected to dynamic analysis and level measurement was done using an on-line Honeywell capacitance sensor. Modeling was performed using first principle of mathematics, open loop analysis and Skogestad technique. The various models were validated using standard performance indices and it was observed that Skogestad model performed better with minimum model error. Real time level control was implemented using various robust, adaptive and intelligent controllers such as Smith, IMC and NMPC. The performance of the controllers was evaluated using time domain specifications. Error analysis was also performed and it was observed that NMPC and IMC controller outperformed the other controllers.