Modelica Simulation of Pendulums and Crane Crab: PyMbs vs. OpenModelica

Abstract

Modelica has become an approved and comfortable tool for modeling. Modelica is a textual and graphical modelling environment with many application libraries. Modelica compilers are generating an implicit state space model (DAE model), which can be handled by simulation environments. This contribution presents a comparison between the two open software simulation environments PyMbs and OpenModelica for multibody systems using three case studies, a pendulum, a double pendulum, and a simplified version of a controlled crane crab. After description of the directly derived mathematical models and the setup of a model-specific error analysis for comparison purposes, implementations within PyMbs and OpenModelica are discussed. The final part consists of the numerical comparison of the results between the two simulation environments. Generally, not only deviations caused by the DAE algorithms can be observed, but also deviations caused by different DAE models generated by the Modelica compilers and caused by the stability of the systems.