Fuzzy Self-tuning of Conventional PID Controller for High-Order Processes
We propose an improved auto-tuning Ziegler-Nichols PID (ZNPID) controller. The proposed controller is a Fuzzy self-tuning ZNPID controller (FST-ZNPID). Conventional Ziegler-Nichols tuned PI and PID controllers provide poor performance for non-linear and high-order systems. In FST-ZNPID enhanced performance is obtained by continuous modification of the proportional constant depending on the process trend. In the proposed FST-ZNPIDC an online auto-tuning factor ‘α’ is incorporated, which is derived by firing 25 fuzzy rules defined on the process error and change of error. Performance of the proposed controller (FST-ZNPID) is tested and compared with other reported works for high-order linear and non-linear dead time systems under both set point change and load disturbance. The developed controller is found to be robust with considerable changes in the process dead time.
KeywordsPID controller Ziegler-Nichols tuning Auto-tuning Self-tuning fuzzy controller
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