Practical considerations of bond graph causality for physical systems with nonlinear geometry

When using bond graphs to model physical engineering systems that have parts that execute large angular motions, ones modeling decisions can often lead to derivative causality and algebraic problems. There are several ways to address this problem with the goal of ultimately deriving a set of first order state equations. For these highly nonlinear systems, analysis is out of the question and computer simulation is the only practical way to obtain a solution. It is shown here that ones choices of coordinates and causal assignments can lead to equation sets that have computational problems. Such issues are developed here and suggestions are made for choosing coordinates and causal assignments that lead to equation sets that compute efficiently.