Multivariable gain-scheduled fuzzy logic control of a fluidized catalytic cracker unit

The fluidized catalytic cracker unit (FCCU) process provides an involved, c oupled and nonlinear multivariable control problem. A systematically constr ucted chain of gain-scheduled fuzzy logic controllers (GS-FLCs) is used wit h some generalisable modifications. A single fixed 'full' fuzzy rule-base i s sufficient to sustain performance for each control channel. The key FLC m odification is the use of a sigmoidal gain-schedule (SGS) that is the signi ficantly parameter-reduced equivalent of a flexible fuzzy input/output vari able. The SGS simultaneously has a crisp and intuitive gain-like format, an d together these permit relatively simple heuristic tuning for the GS-FLC. This nonlinear GS-FLC structure permits the use of a very simple static lin ear decoupler (SLD). The general multivariable GS-FLC/SLD construct demonst rates very good controller performance, covering servo/regulatory and robus tness tests. (C) 2000 Elsevier Science Ltd. All rights reserved.