25-08-2011, 09:35 AM
Abstract
The paper describes the Fuzzy–PID cascade controller to control the level of horizontal tank that has diameter 300 mm and 480 mm long. Interface card module PCI-6024E in computer and Lab View software program is used for built the cascade controller. Structure of its where the inner loop is a PID controller for regulating flow rate of system and outer loop is a Fuzzy logic controller for control the level. The response time, steady state error, load disturbance, and control valve action of cascade are tested and compared with the simple controller. The experimental shows that at the same water level 50% set-point, the rising time to set-point of cascade controller is less than the simple controller about 1750 ms, and it has steady state error less than simple controller about ±1% . The load disturbance on the plant has no affect when using the cascade controller. The control valve action of the cascade controller has operation high frequency than the simple controller so the water level in horizontal tank is smoothly constant. Overshoot affect on cascade and simple controller has not occurred. the cascade controller that consist of the PID and the fuzzy logic control to improve the dynamic characteristic of the level control in horizontal tank. The performance of it will comparing with the simple loop or fuzzy logic controller. Keywords—Fuzzy PID, level control, horizontal tank.
I. INTRODUCTION
NOWADAYS, the various parameters in the process of industrial are controlled such as temperature, level, and etc. Some process needs to keep the liquid level in the horizontal tank such as oil, chemical liquid in its. The level control is a type of control method for common in process system. The level control system must be controlled by the proper controller. The objective of the controller in the level control is to maintain a level set point at a given value and be able to accept new set point values dynamically. The conventional proportional-integral-derivative (PID) is commonly utilized in controlling the level, but the parameter of those controllers must be turned by tuning method either in time response of frequency response to meet their required Manuscript received November 30, 2006. The research has been supported in part by Faculty of Engineering, Pathumwan Institute of Technology, Bangkok 10330, Thailand and Research Center for Communications and Information Technology, King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand. Satean Tunyasrirut is with Asst. Prof at Pathumwan Institute of Technology, Thailand. His research interests include modern control, intelligent control, Power Electronics, Electrical Machine, and Drives (email: satean2000[at]gmail.com). Santi Wangnippranto is with Asst. Prof. at Department of Electrical Engineering, Faculty of Engineering, Pathumwan Institute of Technology, Bangkok 10330, Thailand. His research interests include sensor technology, control system, enhance heat transfer, and energy conversion. (e-mail:nipparnto[at]gmail.com). performances [1,2]. On the other hand, the fuzzy controller is also popularly implemented in many practical industrial automation applications.
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