Pubali Mitra, Chanchal Dey, and Rajani K. Mudi


Fuzzy PID controller; set-point weighting; dynamic set-pointweighting


Fuzzy controllers are now being increasingly used in process control applications but till today no benchmark rule is available for their tuning. Improper choice of the scaling factors (SFs) leads to unsatisfactory performance for controlling higher order and nonlinear processes. Dynamic set-point weighting (DSW) technique is an effective tool for conventional PID controllers towards achieving an overall improved performance during both set-point change and load variation phases similar to two degrees-of-freedom controller. Effectiveness of the DSW mechanism is utilized here for fuzzy PID controllers (FPID) so that an overall improved response can be achieved irrespective of the improper choice of their SFs. Moreover, DSW is also found to perform equally well with two dissimilar rule bases defined on two distinct fuzzy partitions. These two widely different rule bases are designed based on the sliding mode principle without having any prior knowledge about the process to be controlled. Performance enhancement of FPID with DSW for two widely different rule bases justifies the versatility of the reported scheme. Performance as well as stability robustness of the proposed work is also verified in the presence of measurement noise and uncertainty of the process parameter.

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