This paper proposes a new bond-graph method for modelling pneumatic systems, which have compressible fluid flow and thermal fields. In constructing bond-graph models for such systems, fluid and thermal power bonds have been employed. Furthermore, multi-port C and multi-port R elements have been used. Therefore, the resulting bond-graph models become complicated, and it is difficult to understand how energy flows branch off or join together. From these viewpoints, a new bond-graph method for modelling such systems is proposed in the present study by introducing a new concept of effort and flow applied to both compressible fluid-flow and thermal fields. In this bond-graph method, the product of effort and flow is power, which means that the true bond-graph is employed. Furthermore, 1-port C and 1- port R elements are used for modelling. Therefore, the energy flows can be easily understood from the resulting bondgraph. A simulation example is shown to confirm the usefulness of the proposed bond-graph method.

Keywords: pneumatics, compressible fluid-flow field, thermal field, bond-graph method, simulation