Discrete-Time Nonlinear Feedback Control of Multivariable Processes

Discrete-time nonlinear feedback control laws are derived for multivariable nonlinear processes, whose “delay-free” parts are minimum phase. These include mixed errorand state-feedback, error-feedback, and mixed errorand output-feedback laws, which can induce linear input output closed-loop response. This study is carried out within the framework of the discrete-time globally linearizing control. The broader class of nonlinear processes, in which controlled outputs as well as some other process variables are measured, are also considered. A mixed errorand output-feedback control law is derived for this class of processes. The conditions under which the mixed errorand output-feedback can be applied to a process operating at or around an open-loop unstable equilibrium point are determined. The application and performance of the derived control laws are illustrated by the numerical simulation of a chemical reactor.