Official URL: webcat.warwick.ac.united kingdom/record=b1345915

Abstract

Within the chemical industry, the charge of pH is really a well-known problem that presents
difficulties because of the large variations in the process dynamics and also the static nonlinearity
between pH and concentration. pH control requires the use of advanced control
techniques for example straight line or nonlinear adaptive control methods. Regrettably, adaptive
controllers depend on the mathematical type of the procedure being controlled, the parameters
being determined or modified instantly. Due to its characteristics, the pH control
process is very hard to model precisely.
Fuzzy logic, which comes from Zadeh’s theory of fuzzy sets and algorithms,
offers an effective way of recording the approximate, inexact nature from the physical
world. You can use it to transform a linguistic control strategy according to expert understanding,
into a computerized control technique to control a method even without the a precise
mathematical model. The job described within this thesis sets to investigate
appropriateness of fuzzy approaches for the charge of pH inside a continuous flow titration
process.
Initially, an easy fuzzy development system was created and accustomed to provide an
experimental fuzzy control program. An in depth study ended up being performed around the
relationship between fuzzy decision table scaling factors and also the control constants of the
digital PI controller. Equation produced from this research were then confirmed
experimentally utilizing an analogue simulation of the first order plant. Because of this
work a manuscript approach to tuning a fuzzy controller by modifying its scaling factors, was

derived. This method ended up being used through out the job described within this
thesis.
The findings from the simulation studies were confirmed by a comprehensive number of
experiments utilizing a pH process pilot plant. The performance from the tunable fuzzy
controller was in contrast to what conventional PI controller as a result of step
alternation in the set-point, at numerous pH levels. The outcomes demonstrated not just that the
fuzzy controller might be easily adjusted to provided an array of operating characteristics, but additionally the fuzzy controller was far better at controlling
the highly non-straight line pH process, than the usual conventional digital PI controller. The fuzzy
controller achieved a shorter settling time, created less over-shoot, and it was less
impacted by contamination compared to digital PI controller.
Probably the most important characteristics from the tunable fuzzy controller is its ability
to apply a multitude of control mechanisms by simply modifying a couple of
control variables. Thus the controller can be created some thing inside a manner much like that
of the conventional PI controller, or with various parameter values, can imitate other
types of controller. One particular mode of operation uses sliding mode control, using the
fuzzy decision table primary diagonal getting used because the variable structure system (VSS)
switching line. A theoretical explanation of the behavior, and it is boundary conditions,
receive inside the text.
As the work described in this particular thesis has focused on using fuzzy

approaches to the charge of continuous flow pH plants, the versatility from the fuzzy
control strategy described here, allow it to be of great interest in other locations. Chances are it will be
particularly helpful in situations where high levels of non-linearity make more
conventional control methods ineffective.

Thesis or Dissertation (PhD)

• E. Iglesias a
• Y. Garca a
• M. Sanjuan b
• O. Camacho a
• C. Cruz c,.

• a Escuela de Ingeniera Qumica, Universidad de los Andes, Mrida, Venezuela
• b Departamento de Ingeniera Mecnica, Universidad del Norte, Barranquilla, Colombia
• c Chemical Engineering Department, College of Florida, Tampa, FL, USA

Received 6 2006. Recognized 6 April 2006. Available on the web 8 Feb 2007.

Abstract

A brand new controller with different mixture of Sliding Mode Control and Fuzzy Logic is suggested. The traditional sliding surface is modified using some fuzzy rules. This mixture confers controller sturdiness and versatility. A neutralization process along with a mixing process are utilized to compare the performance from the new controller to what conventional sliding mode controller along with a PID controller.

Keywords

• Fuzzy surface
• Sliding mode control
• Chemical processes
• Nonlinear process

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Vitae

Edinzo Jess Iglesias Snchez, Ph.D. is definitely an Affiliate Professor within the Chemical Engineering Department in the College of Los Andes (ULA), Venezuela since 1993. He received his B.S. (1993) and the M.Sc. (1998) in Chemical Engineering at ULA, and the doctorate degree (2006) in Chemical Engineering in the College of Florida (USF). His research interests include intelligent control, fuzzy logic applications and automation in Chemical Engineering.

Yohn Garca, Ph.D. received his bachelor in Chemical Engineering (1993) and the Master of Science in Chemical Engineering (1997) at Universidad de Los Andes, Venezuela. He graduated in 1997 having a Thesis in Distribution of Nonionic Surfactants in Emulsions. In 1998 he cooperated with Pequiven (Petroqumica de Venezuela) within the automatic process control area. Yohn Garcia received his doctorate degree in Chemical Engineering in the year 2006 having a dissertation entitled Fuzzy Logic in Process Control.

Marco E. Sanjuan, Ph.D. is definitely an Assistant Professor at Universidad del Norte, Colombia, where also, he may be the Director from the Robotics and Automation Laboratory. Dr. Sanjuan earned his B.S. in Mechanical Engineering (1995) from Universidad del Norte, Colombia, and the Master of Science (1999) and Physician of Philosophy (2002) in Engineering Science at College of Florida. Professor Sanjuan is Consultant and Instructor in Automatic Control for that Colombian Oil Company (Ecopetrol). His research interests include Intelligent Control, Industrial Automation, and Smart Data Acquisition Systems.

Oscar Camacho, Ph.D. received the Electrical Engineering and M.S. in charge Engineering levels from Universidad de Los Andes (ULA), Mrida, Venezuela, back in 1984 and 1992, correspondingly, and also the M.E. and Ph.D in Chemical Engineering at College of Florida (USF), Tampa, Florida, in 1994 and 1996, correspondingly. He’s held teaching and research positions at ULA, PDVSA, and USF. His current research interest includes sliding mode control, deadtime compensation, and fault recognition systems. He’s the writer in excess of 60 publications in journals and conference proceedings.

Carlos A. Cruz, Ph.D.. received his B.Sc. in Chemical Engineering from College of Florida, and the M.Sc. and Ph.D. in Chemical Engineering from Louisiana Condition College. He’s the writer of Continuous Automated Process Control (2002), and co-author of Concepts and exercise of Automated Process Control (1984, 1997). Dr. Cruz is really a Full Professor within the College of Engineering at College of Florida. Dr. Cruz continues to be instructor of Automatic Control for businesses for example Union Carbide, DAO Chemical, and Procter and Gamble.

Corresponding address: 4202 E. Fowler Avenue, ENB 118, Tampa, FL 33620-5350, USA. Tel. +1 813 974 5859 fax: +1 813 974 3651.

2007 Printed by Elsevier Limited.

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