Hierarchical Control System with Fuzzy Supervisory System and PID Controller and Application to Large-Scale Hydrogen Gas Purity Control
Tetsuji Tani*, Takahiro Kobayashi* and Sadaaki Miyamoto**
*Manufacturing Department, Idemitsu Kosan Co., Ltd.
2-1 Anesaki-Kaigan, Ichihara, Chiba 299-0192, Japan
**Institute of Information Sciences and Electronics, University of Tsukuba 1-1-1 Tennoudai, Tsukuba-shi, Ibaraki 305-8573, Japan
We present hierarchical control that combines conventional PID controllers and their supervisory fuzzy control designed based on human knowledge. Hierarchical control consists of 2 control function blocks, where we use (1) a statistical model using multiregression with an updating factor for the function block to estimate parameters of plant operations and (2) fuzzy logic for the control function block to compensate for operating conditions. Hierarchical control has been applied to hydrogen gas purity control in large-scale petroleum-refining plants. It has been verified that this control shows better performance than conventional human supervisory control and (1) reduces operator interaction, (2) cuts energy consumption, and (3) lowers CO2 generation.