Process Control: Modeling, Design, and Simulation

4.4. Discrete-Time Autoregressive Models

Most of the models developed and used in this text are based on continuous time. In the most general case of fundamental models, these are nonlinear ordinary differential equations. State space models consist of sets of linear ordinary differential equations, where the states and inputs are in deviation variable form. Transfer functions are used to denote a linear relationship between inputs and outputs. All these previous models assume that the manipulated input and the measured output signals are continuously available.

In practice, manipulated input changes are made at discrete time intervals and measured outputs are available at discrete sample times. The physical inputs and outputs are continuous; ...