Physical System Modeling with Modelica

Abstract Models are useful for design of control systems and they are also an integral part of high performance controllers. Although modeling is an important aspect of most engineering activities, the control engineer faces special problems because he has to deal with strongly heterogeneous systems which have mechanical, electrical, and chemical parts. This paper describes a general approach that can be applied to a wide range of systems. Basic models are designed with a maximum range of validity, symbolic manipulation is used by the translator in order to simplify the model for the chosen use. Modeling is based on constraijnts and object orientation and leads naturally to behavioral systems. The approach is illustrated in this paper with modeling two-phase flow in a refrigeration cycle.