Chemical processes are nonlinear and have been controlled using linear mode
ls. However, controllers based on linear models do not perform well for hig
hly nonlinear situations. Several methods have been proposed to deal with t
he nonlinearity. Most of these methods are based on fundamental models, in
the form of differential equations, that are difficult to obtain for indust
rial processes. In this paper, a procedure for handling the nonlinearity of
industrial processes is presented which is based upon step response models
that are easier to obtain. The step response models are obtained for a few
sub-regions of the operating region experimentally and the models for othe
r sub-regions are determined through interpolation. The approach is tested
on example problems from the literature through simulations. The results sh
ow that a significant improvement in the control performance can be achieve
d in this manner.