Multi-domain Modeling and Simulation

One starting point for the analysis and design of a control system is the block diagram representation of a plant. Since it is nontrivial to convert a physical model of a plant into a blockk diagram, this can be performed manually only for small models. Based on reseach from the last 40 years, more andmore mature tools are available to achieve this transformation fully automatically. As a result, multi-domain plants, for example, systems with electrical, mechanical, thermal, and fluid parts, can be modled in a unified way and can be used directly as input-output blocks for control system design. An overview of the basic principles of this approach is given, and it is shown how to utilize nonlinear, multidomain plant models directly in a controller. Finally, the low-level "Functional Mockup Interface" standard is sketched to exchang multi-domain models between many different modeling and simulation environments

Objektorientierte Modellierung mit Modelica zur Echtzeitsimulation und Optimierung von Antriebssträngen

In diesem Beitrag werden Methoden und Werkzeuge zur Automatischen Applikation elektronischer Getriebesteuergeräte und deren Integration beschrieben. Am Beispiel eines mit der Sprache Modelica modellierten und in Echtzeit simulierten Sechsgang-Automatikgetriebes wird gezeigt, wie die Parameter eines exemplarischen Getriebesteuergerätes mittels numerischer Optimierung verbessert werden können

Signal Tables: An Extensible Exchange Format for Simulation Data

This article introduces Signal Tables as a format to exchange data associated with simulations based on dictionaries and multi-dimensional arrays. Typically, simulation results, as well as model parameters, reference signals, table-based input signals, measurement data, look-up tables, etc., can be represented by a Signal Table. Applications can extend the format to add additional data and metadata/attributes, for example, as needed for a credible simulation process. The format follows a logical view based on a few data structures that can be directly mapped to data structures available in programming languages such as Julia, Python, and Matlab. These data structures can be conveniently used for pre- and post-processing in these languages. A Signal Table can be stored on file by mapping the logical view to available textual or binary persistent file formats, for example, JSON, HDF5, BSON, and MessagePack. A subset of a Signal Table can be imported in traditional tables, for example, in Excel, CSV, pandas, or DataFrames.jl, by flattening multi-dimensional arrays and not storing parameters. The format has been developed and evaluated with the Open Source Julia packages SignalTables.jl and Modia.jl

StateGraph-A Modelica Library for Hierarchical State Machines

The new library Modelica.StateGraph is a freeModelica package providing components to modeldiscrete event and reactive systems in a convenientway. It has a similar modeling power as Statecharts,but avoids some deficiencies of Statecharts by usingelements of JGrafchart and by using Modelica as an“action” language. An overview of the StateGraphlibrary is given, the available components and anapplication example. The implementation of thelibrary in Modelica is sketched, especially theneeded extension to Modelica that will be availablein release 2.2 of the Modelica language

Modia3D: Modeling and Simulation of 3D-Systems in Julia

Modia3D is an experimental Julia package to model and simulate 3D mechanical systems. Ideas from modern game engines are used to achieve a highly flexible setup and features of multi-body algorithms are used to get a rigid mathematical formulation and support, for example, of closed kinematic loops. Collision handling is performed on convex geometries with elastic response calculation. A Modia3D model is solved with a variable-step solver. This is important to combine Modia3D with the equation-based modeling system Modia in the future

Variable Structure System Simulation via Predefined Acausal Components

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 re-compile 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

Modelling and Simulation of Physical Systems with Dynamically Changing Degrees of Freedom

A new approach is introduced to model and simulate equation-based systems where variables can appear and disappear during simulation without re-generation and re-compilation of code when the numbers of equations and states change during events. The method is presented in a generic, mathematical way and can be in principle applied to all types of declarative, equation-based modelling languages, such as Modelica. A concrete implementation is given for the Julia-based experimental modelling language Modia, which is similar to Modelica. However, Modia features far simpler semantics based on hierarchical collections of name/value pairs and has the ability to support domain-specific algorithms, especially for multibody systems with collision handling. The new method is demonstrated with heat-transfer in a rod, separation of stages of a rocket and gripping operations of a robot

Object Oriented Modeling of Hybrid Systems

ABSTRACT A new methodology for the object oriented description of models consisting of a mixture of continuous and discrete components is presented. The object oriented paradigm enables the user to describe such models in a modular fashion that permits the reuse of these models independently of the environment in which they are to be embedded. The paper explains the basic mechanisms needed for object oriented modeling of hybrid systems by means of language constructs available in the object oriented modeling language Dymola. It then addresses more advanced concepts such a s v ariable structure models containing e.g. ideal electrical switches, ideal diodes and dry friction