New Results on the Design of Non-Linear Controllers for Non-Linear Process Systems

Departing from the traditional approach of local linearization followed by linear controller design for the thus "linearized" system, it is shown in this paper how transformations may be found which transform the non-linear system into one that is exactly linear. The new approach is based on the hypothesis that a system which is non-linear in its original variables is linear in some transformation of these original variables. Constructive methods for finding the appropriate transformations are presented. The design of a controller for the linear transformed system may then be carried out with a great deal of facility (the resulting controller will of course be non-linear when recast in terms of the original system variables). The specific problem of level control in process flow systems having various geometric configurations is used to illustrate the transparency of this approach. An example simulation is used to demonstrate the design and performance of these controllers.