A methodology for the design of robust stable controllers for non-linear pr
ocesses is proposed. The non-linear process is initially identified in the
form of a non-linear ARMA polynomial. This model is then transformed into a
non-linear state affine model which is especially convenient for robustnes
s analysis and design. The model uncertainty is calculated from the non-lin
ear terms of the non-linear state affine model. The uncertainty elements ar
e shown to be a function of the input only and this facilitates the calcula
tion of the uncertainty bounds. The technique is illustrated through a CSTR
(continuously stirred tank reactor) control problem.