ABSTRACT
System modeling has evolved along different paths within different disciplines. For mechanical systems, traditional training teaches us to rely on Newton’s equations of motion to model system behavior, while for electrical circuits, Kirchoff’s laws determine the basic system behavior. For hydraulic systems sometimes the electric circuit analogy is used as well. The different disciplines that we mention here, such as mechanical, electrical, hydraulic, and so forth, are artifi cial divisions we have used for many ages to study system behavior. These artifi cial divisions were formed a long time ago to handle information as well as for the purposes of keeping education and training manageable. Real-world systems often contain components from many different domains interacting with each other. Although the analysis techniques developed by experts in various disciplines have been different, the inherent behavior of systems is essentially the same. The under lying governing law is the same, that is, conservation of energy (or power). Leibnitz alluded to this concept (Mukherjee and Karmakar, 2000) when he stated, “The forces are of two kinds, namely dead and live. The dead force depends on position and/or confi guration, and the live force is proportional to the square of velocity. The sum of the two forces in the universe remains constant.” If the word force is replaced by the word energy, Leibnitz was actually stating the conservation of energy principle. Even though the immediate successors of Leibnitz and Newton found that the problems of mechanics are more easily solved using the energy approach, the Newtonian approach of using actions and reactions became more popular. Part of the reason may be because the concept proposed by Leibnitz and its usefulness was unclear as many other areas of the physical sciences (such as electricity and magnetism) were not yet developed at that time.
