Extension and application of an algorithm for systematic identification of weak coupling and partitions in dynamic system models

Abstract

This paper reviews and extends a technique to detect weak coupling (one-way coupling or complete decoupling) among elements of a dynamic system model, and to partition and reduce models in which weak coupling is found. The ability to partition a model increases the potential for physical-domain model reduction, and allows parallel simulation of smaller individual submodels that can reduce computation time. Negligible constraint equation terms are identified and eliminated in a bond graph by converting inactive power bonds to modulated sources. If separate bond graphs result, between which all modulating signals move from a "driving" subgraph to a "driven" one, then one-way coupling exists in the model and it can be separated into driving and driven partitions. Information flow between the subgraphs is one-way. In this paper the algorithm is extended to models in which two-way information flow from modulating signals precludes complete partitioning. It is shown for several classes of modulating signals that, under certain conditions the signal is "weak" and therefore can be eliminated. Removal of weak signals allows partitioning of the longitudinal and pitch dynamics of a medium-duty truck model. The intensity of dynamic coupling and the potential for model reduction are shown to depend on the magnitude of system parameters and the severity of inputs such as road roughness. © 2007 Elsevier B.V. All rights reserved.