ABSTRACT
A naive trial-and-error approach to the design of a control system might consist of constructing a controller,
installing it into the system to be controlled, performing tests, and then modifying the controller until
satisfactory performance is achieved. This approach could be dangerous and uneconomical, if not impossible.
A more rational approach to control system design uses mathematical models. A model is a mathematical
description of system behavior, as influenced by input variables or initial conditions. The model is a stand-in
for the actual system during the control system design stage. It is used to predict performance; to carry out
stability, sensitivity, and trade-off studies; and answer various ‘‘what-if ’’ questions in a safe and efficient
manner. Of course, the validation of the model, and all conclusions derived from it, must ultimately be based
upon test results with the physical hardware.
