A new methodology for designing a fuzzy logic controller and PI, PD blending mechanism

In this study, a hybrid and intelligent structure that blends the "Pi-type" and "PD-type" output portions of a new fuzzy logic controller is presented. The new fuzzy logic controller consists of two rule-base blocks and a logical switch in between and its rule-base is formed using new meta-rules. The rule-base blocks admit two inputs one of which is newly devised and called "normalized acceleration" and the other one is the classical "error". The newly devised input gives a relative value about the "fastness" or "slowness" of the system response and provides an easy and straightforward way of forming the rule-base. The new hybrid controller structure is formed in such a way that it intelligently blends PI and PD portions of the fuzzy logic controller through a new empirical relation or a rule-base. Both the empirical relation and the rule-base use the same inputs of the new fuzzy logic controller. The robustness and effectiveness of the new fuzzy logic controller with/without the blending mechanism are illustrated through simulations done on a second-order system with varying parameters. Furthermore, the results of the new hybrid fuzzy PID controller is compared with the results obtained using both the conventional fuzzy PID controller and another hybrid method which is an augmented version of fuzzy PI controller with a resetting factor.