Type-II Fuzzy Logic Controller for Temperature control of a Double pipe heat exchanger system

The transfer of heat to and from process fluids is a necessary part of most of the process control applications. So the Heat Exchangers (HEs) are used widely and regularly in the process and allied industries and are very essential during design and operation. The most widely used type of heat exchangers are double pipe heat exchangers and shell-and-tube heat exchangers. Fuzzy Logic Controllers (FLC) have become popular in process control applications due to their capabilities of handling linearity and nonlinearity in process control systems. The common type of FLC´s that have been preferred so far is Type-I FLC´s. However, Type-1 FLC´s cannot completely handle high levels of linguistic and numerical uncertainties [14], because Type-1 FLC´s use precise Type-1 fuzzy sets and membership functions. The membership functions of Type-1 systems do not account for certain set of environmental and operating situations[15]. This can cause poor performance of FLC and it can result in poor control and inefficiency. Type-II FLC can model and handle the linguistic and numerical uncertainties associated with the inputs and outputs of the system [14, 15]. The extra degrees of freedom provided by the FOU (footprint of uncertainty) enables a Type-II FLC to produce outputs that cannot be achieved by the Type-1 FLC´s with the same number of membership functions [14-19]. Here in this paper a comparative study of Temperature control of Double pipe heat exchanger system using Type-II Fuzzy Logic Controller and the PI controller tuned using Genetic algorithm is presented. A Type-II Fuzzy Logic Controller is designed using velocity function derived from the differential equations representing the output of a PI controller. Simulations are performed using a fifth order mathematical model of Double Pipe heat exchanger system[13]. The least value of Integral Time Weighted Absolute Error (ITAE) decides the best controller for Double Pipe heat exchanger System.