Design and implementation of fuzzy logic controllers for a heat exchanger in a water-for-injection system

Although many industrial applications of fuzzy logic control have been reported, few of them start with an existing industrial process under conventional PID control implemented with programmable logic controllers (PLCs). This article aims to illustrate to practicing engineers and academic researchers the usefulness of fuzzy logic control through the design and implementation of an industrial heat exchanger in a water-for-injection (WFI) system. After a basic FLC was designed and tested, this article shows how its rule base evolved to achieve superior system performance by utilizing additional low-cost sensing information in the process and its environment. A method for the implementation of FLCs into the existing PLC is also reported. The system performance of the five designed FLC rule bases is compared with that of the original PID controller. This article concludes that better performance can be achieved by using the fuzzy logic control technology. It reports the authors' experience in FLC design and implementation. Finally, this article discusses some blocking problems in widespread industrial applications of FLCs and the possible solutions to them.