Bond graph method assumes that mechatronic systems consist of basic components, which are connected. The theory comes up with two types of connection abstractions: (i) 0-junctions modeling the equal effort and sum of oriented flows equal to zero, and (ii) 1-junctions modeling the equal flow and sum of oriented efforts equal to zero.

Gawthrop, P. J., Bevan, G. P.: Bond-Graph Modeling. IEEE Control Systems Magazine, April 2007 [-]