Modeling from Physical Principles

Abstract

Modeling and simulation are central to the design of control systems, since, for complex large-scale nonlinear industrial plants, there usually don't exist, or at least are not known, any suitable analytical design approaches. Simulation may often be the only resort short of building the physical plant itself and experimenting with the real system.

Another article in this handbook by Otter and Cellier entitled "Software for Modeling and Simulating Control Systems%quot; deals with a wide palette of issues relating to the simulation of control systems. This article, on the other hand, shall concentrate on issues relating to modeling the physical plant to be controlled.

Modeling physical systems seems to be a straightforward task. Since physical systems and experiments are often reproducible in a reliable fashion, since measurements from physical systems are frequently available in abundance and of high quality, since the meta-laws of physics are mostly well understood, it seems to be a particularly easy task to come up with accurate mathematical descriptions of most physical plants.

Yet, there are some typical pitfalls and frequent misconceptions about the modeling of physical systems, especially among control engineers. These shall be illustrated, and a sound methodological basis for modeling from physical principles shall then be created.


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