IMPLEMENTATION AND TUNING OF A FUZZY-PID CONTROL SYSTEM VIA FIELDBUS COMMUNICATION

Resumo

In research applications is very important to have a flexible automation structure for different plant conditions with a large flow of information. To satisfy real-time requirements a communication technique based in fieldbus network was used to interconnect devices in an intelligent distributed control system. Using this structure, an experimental tuning for fuzzy-PID controller based in scaling gains from a well-tuned conventional PID controller was studied in this work. Due to difficulties involving fuzzy controllers tuning (expert knowledge, adjustments in rules, membership functions and gains) it is recommended to develop a tuning procedure, which will greatly reduce the time of design. From the gains of a well-tuned conventional PID controller a hybrid velocity/position fuzzy-PID controller was designed. Experimental tests were carried out for level control in a tank system under different disturbances in set point values. Tuning performance of different conventional and fuzzy-PID structures were evaluated with respect to their functional behaviors (overshoot, rise time and ISE criterion). Results obtained showed that fuzzy controller structure has a great potential for application even when it is possible to implement a conventional PID controller. It is also observed that there is saturation of the manipulated variable for the conventional PID controller which does not occur in the fuzzy-PID controller.