Research article

Exergetic Port-Hamiltonian Systems for Multibody Dynamics

Markus Lohmayer, Giuseppe Capobianco, Sigrid Leyendecker

Multibody System Dynamics, 2024

Multibody dynamics simulation plays an important role in various fields, including mechanical engineering, robotics, and biomechanics. Setting up computational models however becomes increasingly challenging as systems grow in size and complexity. Especially the consistent combination of models across different physical domains still requires significant effort. This motivates the study of formal languages that enable a compositional approach to modeling multiphysical systems with basic guarantees. The article shows how multibody systems, or more precisely assemblies of rigid bodies connected by lower kinematic pairs, can be described as Exergetic Port-Hamiltonian Systems (EPHS). The EPHS modeling language features a straightforward graphical syntax for expressing the energy-based interconnection of hierarchically nested subsystems. This reduces cognitive load and facilitates clearer communication among experts, non-experts and computational tools. Hierarchical nesting of systems enables abstraction of lower-level details and it promotes the reuse of models at different levels of complexity. At the lowest level, there are three basic kinds of systems, representing energy storage and reversible/irreversible energy exchange. The structured approach guarantees fundamental properties of macroscopic systems, such as conservation of energy and non-negative entropy production. In combination with the compositional syntax, this makes building and modifying models simpler and less error-prone.