Most chemical processes are nonlinear in nature. When large set point
changes or load disturbances occur frequently, nonlinear control syste
ms are required. Instead of using the differential geometric method or
nonlinear model predictive method, simple gain scheduling may be suff
icient for many nonlinear single input-single output (SISO) processes.
To design such simple control systems systematically, a nonlinear fir
st-order plus time delay model is proposed for model-based control. A
logarithmic transformation which is very useful for control of high pu
rity distillation columns is shown to be effective in general. Several
chemical process examples are also given. Copyright (C) 1996 Elsevier
Science Ltd