ABSTRACT

This chapter discusses two applications of nonlinear control to polymerization reactors. The first is the application of a nonlinear regulator to a continuous solution polymerization reactor. In the second application, a nonlinear model-predictive control algorithm is applied to a semibatch solution polymerization reactor. Nonlinearities are invariably present to some extent in industrial systems. If a mathematical model of the nonlinear plant can be developed, then a nonlinear internal model control approach may be appropriate. The foregoing step-by-step procedure results in a controller that is based on the exact nonlinear inverse. Almost all chemical process systems are nonlinear. Some are only slightly nonlinear, and so can be analysed and controlled effectively with linear techniques. The nonlinear reference controller provides zero offset on setpoint change, even without explicit integral action. Most model-predictive control techniques, including dynamic matrix control, are based on linear models and are thus not very well suited for the control of nonlinear systems.