Top-Down Modelling of Complex Systems by means of Word Bond Graphs

Abstract

Development of dynamic models for complex systems often does not exploit the hierarchical structure of the system design. Rather, equations describing physical effects of interest are set up, manipulated, and combined at an early stage of the modeling process. In contrary, by applying a structured bond graph approach to an electrohydraulic servo valve as an example of a complex multi energy domain system it is shown how word bond graphs, known since bond graphs were invented by Paynter but seldom used, account for the hierarchical structure of a system design in a natural way and allow for systematic top-down development of a consistent simulation model on a graphical basis. Formulation of dynamic system equations is the last step in this modeling procedure and can be easily carried out by inspection of the final bond graph. By this way a state space model was prepared for the servo valve, coded as a FORTRAN subroutine of a general ODEs solver, and the system simulated on a workstation.