Variable Structure System Simulation via Predefined Acausal Components

Abstract

This article outlines a new approach of the experimental open-source modeling and simulation system Modia to simulate systems where the number of variables and equations can be changed after compilation and also during simulation, without having to re-generate and rec-ompile the code. Details are given for heat transfer in an insulated rod, where the discretisation of the rod is completely hidden from the symbolic engine. It is discussed how this approach could also be used in a future version of Modelica and/or FMI. Furthermore, this feature is also used in various variants to speed up collision handling in 3D mechanical systems. For example, by rigidly fixing an object after it has been gripped, with or without calculating the elastic response, and thereby dynamically changing the number of degrees of freedom.