.BondLib.UsersGuide.Overview.Connectors

d assumes a value of -1 at the connector, from which the bond emanates, and a value of +1 at the connector, where it ends.

All bond graph variables are declared as potential variables, i.e., rather than making use of the flow variables of Modelica, the bond graph library encodes the direction of flow explicitly using the d variable.

The bond graph connector is a grey dot. Its definition is given as follows:

The corresponding bond model has been encoded as:

It passes the physical variables along, like an electrical wire, and it defines the directional variable, d, at the two ends.

In the bond graph methodology, there are two types of nodes, called junctions, the 0-junction, which corresponds to a regular Modelica node, and the 1-junction, which offers the dual functionality.

The flows into a 0-junction add up to zero, whereas the efforts around a 0-junction are the same. Correspondingly, the efforts into a 1-junction add up to zero, whereas the flows around it are the same. This, by the way, is the reason, why the bond graph library doesn't make use of the Modelica flow variables, since Modelica offers only one type of nodes.

For example, the 1-junction with three bond connectors is defined as:

It inherits the effort and flow vectors from the (partial) ThreePortOne interface model:

which makes use of the directional d variables to decide on the sign in summing the efforts (or flows) into the junction.