Modeling of Complex Systems

The role of modeling is becoming increasingly important in design and operation of complex natural and man-made systems. Models are also appearing as components of control systems because of the increased use of model based control strategies such as Kalman filters and model predictive control. Mechanized tools are necessary to fully exploit modeling. The development of modeling is therefore closely associated with the development of computational tools for simulation. There has been a very dynamic development from the beginning in the 1920s. At that time, the technology was available only at a handful of university groups who had access to mechanical differential analyzers. Today modeling and simulation are available at low cost on the desk of everyone who needs it. This paper presents a perspective on modeling of complex systems leading up to the recent development of Modelica, which draws on object oriented methodology in computer science, differential algebraic equations in numerical mathematics and control theory.