Fuzzy Rule-Based Set Point Weighting for PID Controller

Abstract

PID controllers are still very popular in process industries due to their simple design and easy tuning. Model-free tuning relations are relatively preferred compared to model-based tuning relations as identification of the true model for industrial processes is not an easy task. Ziegler-Nichols (ZN) setting is one of the most widely accepted model-free tuning guidelines. However, for higher-order processes, it provides undesired oscillations during set point change and load variation. Fixed set point weighting (FSPW) and variable set point weighting (VSPW) techniques are reported to restrict the oscillations during set point tracking only. Recently, reported dynamic set point weighting (DSPW) is capable to provide an overall improvement during set point change as well as load varying conditions. But to achieve further performance enhancement of a PID controller, a simple fuzzy rule-based set point weighting (FRSPW) technique is reported here for under-damped second-order processes. Superiority of the proposed FRSPW-based PID controller is established through quantitative estimation of various performance indices and, moreover, its adequate robustness is also observed in presence of considerable perturbation of process parameters.