Fuzzy logic process controller

The application of a hierarchical structure for the design of a fuzzy logic process controller is described. With this hierarchical structure, the number of rules constituting a fuzzy controller will increase linearly and not exponentially with the number of system variables. An example in which the hierarchical fuzzy control method is used to control the feedwater flow of the steam generator of a power plant is described. The effectiveness of the fuzzy controller is studied through simulation for several disturbances. The results show that the fuzzy controller yields better performance than a proportional, integral, and derivative (PID) controller in terms of less risetime and less overshoot for feedwater flow and maintenance of drum level at the desired value