Fuzzy and sliding mode control of a pH neutralization system

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Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2002

Thesis Language: English

Student: ÜSTER AKBAY

Co-Supervisor: CANAN ÖZGEN, MEHMET KEMAL LEBLEBİCİOĞLU

Abstract:

ABSTRACT FUZZY AND SLIDING MODE CONTROL OF A PH NEUTRALIZATION SYSTEM Akbay, Üster M.S., Department of Chemical Engineering Supervisor: Prof. Dr. Canan Özgen Co-Supervisor: Prof. Dr. Kemal Leblebicioğlu December 2002, 8 1 pages Control of the pH neutralization process is very important in wastewater treatments and in biochemical processes. The control of pH in neutralization operations is very challenging and difficult because of the nonlinear S shaped titration curve. In this study, a laboratory scale pH neutralization system has been constructed for observing the performance of some designed intelligent control techniques such as; sliding mode control, SMC, extended sliding mode control, E- SMC, and fuzzy-sliding mode control, F-SMC. In order to achieve effectiveness and high control performance in neutralization operations, the existence of a good process model is extremely important. Thus, a first order state-space model iiipreviously developed in another study is used for strong acid-strong base system and weak acid-strong base system. The model parameters are obtained experimentally in a CSTR. In an actual waste water treatment system, the model of the process can vary in time. This is due to the changes in the concentration and the type of acid in the chemical process effluent stream. To be able to perform a satisfactory control, online identification to specify changes in the effluent is important. Therefore, the second experimental setup is constructed with two reactors; One of the reactors is the main reactor and the other one is a small identification reactor which is located before the main reactor. The performances of the designed controllers are checked with experiments for set point tracking and for disturbance rejection. All the designed controllers are found to be satisfactory in set point tracking and disturbance rejection experiments. However the change in manipulated variable (flowrate) can not be acceptable in pure SMC. In general, there is no stability problems with designed controllers used. E- SMC is better in performance with the least integral derivative error (IAE) score compared to pure SMC and F-SMC, whereas the smallest response time is obtained in pure SMC. Keywords: pH Control, Sliding Mode Control, Fuzzy Logic Control, Online identification. 1V _- t.c YuKsixoeRfrmf samaw POldlMANTASYON MERKEZİ