A NEW APPROACH OF CASCADE CONTROL BASED ON FUZZY LOGIC YOHN GARCIA Escuela de Ingeniería Química Universidad de Los Andes Núcleo la Hechicera. Mérida 5101 VENEZUELA yohn@ula.ve OSCAR CAMACHO Escuela de Ingeniería Eléctrica Universidad de Los Andes Núcleo La Hechicera. Mérida 5101 VENEZUELA ocamacho@ula.ve MARCO SAN JUAN Departamento de Ingeniería Mecánica, Universidad del Norte, Barranquilla, Colombia msanjuan@uninorte.edu.co EDINZO IGLESIAS Escuela de Ingeniería Química Universidad de Los Andes Núcleo La Hechicera. Mérida 5101 VENEZUELA iedinzo@ula.ve CARLOS SMITH Chemical Engineering Department University of South Florida, Tampa, FL 33620, USA csmith@eng.usf.edu Abstract: This paper proposes the design of a cascade control using fuzzy logic. A new set of fuzzy logic rules are added to a conventional Fuzzy Logic Controller (FLC) to build the Fuzzy Controller with Intermediate Variable (FCIV). The proposed controller is tested in the control of a nonlinear chemical process, and its performance is compared to other controllers. Keywords: Fuzzy logic control, Process control; Cascade control 1 Introduction The well-known PID controllers are still the most adopted in the process industries. However, real systems often have nonlinearities and contain high- order dynamics and dead time, all of which diminish the performance of these controllers. Fuzzy logic is a technique that uses language and reasoning principles similar to the way in which humans solve problems [1]. This technique provides means to deal with nonlinear functions, and flexibility and simplicity that makes it suitable for many industrial applications [2, 3, 4]. In the process control field the boom started in 1974 when Mandani controlled a steam engine using fuzzy logic [5]. In recent years, the technique has been applied successfully in the area of nonlinear process control [6, 7]. Feedback Control (FC) is the simplest form of automatic process control. However in many processes with slow dynamics and with too many upsets, the control performance provided by feedback control often becomes unacceptable. It is necessary in these cases to use other strategies to provide the required performance. Cascade control is a strategy that improves, in some applications significantly, the performance provided by conventional feedback control. Recently, some works have been developed applying fuzzy logic into cascade control strategies to Proceedings of the 9th WSEAS International Conference on Automatic Control, Modeling & Simulation, Istanbul, Turkey, May 27-29, 2007 36