Compartmental network modelling is compared with the bond graph approach. Whilst both approaches build on the conservation principle, the compartmental network approach is on a slightly higher level and more compact. Also no analogies must be used, the concepts of physics are used directly in connection whilst system theoretical arguments define consistency and solvability, being roughly equivalent to causality in bond graphs.Keywords: modelling, mechanistic, first principle, Bond Graphs
ScopeThe author looks back to somewhere around 20 years of research in computer-aided modelling, which resulted in a methodological approach to modelling of physical-chemicalbiological systems implemented now in the third generation as a tool we call Modeller (Westerweele (2003)). The method builds on a compartmental network modelling approach and in the course of the last few years the question of the relation of this network approach with the bond graph approach has been raised a couple of times. Thus this paper is trying to illuminate some of the main differences. The views being reflected are personal and may not be shared by the bond graph specialist as both approaches are rather much building on macroscopic physics, meaning that the quantisation of matter and energy is not of relevance, but that it deals in general with a larger time scale and field theory applies in its full scope. It should be noted that modelling is here limited to defining a set of differential algebraic equations describing the behaviour of natural systems 1 .
Compartmental Network ModellingThe approach is based on splitting the relevant piece of the world into a set of communicating control volume. Thus we define a basic model topology as a mapping of the real world object into a network of primitive systems that can store EXTENSIVE CAPACITIES and CONNECTIONS, which can transfer extensive quantities. This topology we call the PHYSICAL TOPOLOGY, as it represents the physical containment of the process. This first step cannot be automated. * e-mail: Heinz.Preisig@chemeng.ntnu.no 1 The limitation to natural is not necessary, but the extension is also not of relevance to this discussion.