Title: Bicausal Bond Graphs
Author: P.J. Gawthrop
Keywords: Bond graphs; causality; system inversion; parameter estimation
Abstract:
Conventional bond graph theory is predicated on the notion that a bond
has a single causal stroke: an effort imposed at one end implies a flow
imposed at the other. This notion is implied by components having  a
known constitutive relationship.

This paper discusses bond graphs with two causal strokes - Bicausal
bond-graphs. These can, for example, handle systems with unknown
parameters.  This paper addresses issues arising from the general idea
of inverse systems - physical systems with a non-standard input-output
pattern; in particular: dynamic inverses, parameter estimation and
state estimation.