A frequency domain design of robust fuzzy PI controller for industrial processes

The Fuzzy Logic Controllers (FLCs) mark a considerable progress in controlling non-linear, time-varying and complex dynamic processes satisfying the high system performance demands. Since their emergence in the area of process control the FLCs design is constantly being improved laying it out on theoretical grounds and making it more general and simple. The present investigation aims at the development of an objective design and tuning procedure based on system robust stability and robust performance requirements. The process fuzzy PI controller comprises an input fuzzy unit and a classical position PI controller and has the system error as a Single Input (SI). A frequency domain design criterion for computing of the controller's scaling factors is derived combining Popov stability with robustness requirements using only a few estimated data about the plant. Simulation studies reveal equivalent closed-loop system performance to the more complex incremental PI SI FLC and internal model controller.