Design of fuzzy fractional-order PI+ PD controller

This paper presents the design of a fuzzy fractional-order Proportional Integral plus Proportional Derivative controller in a two stage control structures where fractional-order terms were considered. Due to some weaknesses discovered in both PID and fuzzy controllers, this design was proposed. Basically, fuzzy system was implemented to tune the fractional-order of PI while fractional-order PD was fixed. The proposed controller was compared against conventional PID controller, fuzzy PID and fuzzy PI+PD controller. All results were presented from simulation studies applied to a steam temperature process which inherit slow dynamics and non-linear properties. Based on the results, the significance of fractional-order controller was evidently shown where the proposed controller had improved the response in terms of speed and control output efficiency.