This paper presents a new approach in Modelica that allows a modeler to separate a model into different partitions for which individual solvers can be assigned. In effect; this allows to use multi-rate and multi-method time integration schemes that can contribute to improve the efficiency of a (real-time) simulation.
The first part of the paper discusses basic consideration relating to modular (real-)time integration. Afterwards; the implementation of a convenient Modelica library for the partitioning of physical models is briefly described. Finally; the presented library is used to partition a detailed six degree of freedom robot model for modular simulation. The simulation performance of that partitioned model is compared to the simulation performance achieved by using â€śconventionalâ€ť global solvers.
Keywords: Multi-rate / multi-method time integration; simulation; clocked discretized continuous-time partitions.
Proceedings of the 10th International Modelica Conference; March 10-12; 2014; Lund; Sweden
 Dennis S. Bernstein. The treatment of inputs in real-time digital simulation. SIMULATION, 33(2):65â€“68, 1979.
 Martin Busch. Zur effizienten Kopplung von Simulationsprogrammen. PhD thesis, UniversitĂ¤t Kassel, 2012.
 Francois Cellier and Ernesto Kofman. Continuous System Simulation. Springer Science + Business Media, Inc., 2006.
 Hilding. Elmqvist, Sven Erik Mattsson, and Hans Olsson. New Methods for Hardware-in-the-Loop-Simulation of Stiff Models. In Martin Otter, Hilding Elmqvist, and Peter Fritzson, editors, 2nd Int. Modelica Conference, Oberpfaffenhofen, Germany, March 18â€“19 2002.
 Hilding Elmqvist, Martin Otter, and FranĂ§oise E. Cellier. Inline Integration: A New Mixed Symbolic/Numeric Approach for Solving Differential-Algebraic Equation Systems. In European Simulation Multiconference, 1995.
 R. KĂĽbler and W. Schiehlen. Modular simulation in multibody system dynamics. Multibody System Dynamics, 4(2-3):107â€“127, 2000.
 Jim Ledin. Simulation Engineering. CMP Books, Lawrence, Kansas 66046, first edition, 2001.
 Modelica Association. Modelicaâ€”A Unified Object-Oriented Language for Systems Modeling v3.3. Standard Specification, May 2012. available at http://www.modelica.org/.
 Stefan Nowack and Georg Feil. Reduction of time delays in Runge-Kutta integration methods. SIMULATION, 48(1):24â€“27, 1987.
 Martin Otter, Bernhard Thiele, and Hilding Elmqvist. A Library for Synchronous Control Systems in Modelica. In Martin Otter and Dirk Zimmer, editors, 9th Int. Modelica Conference, Munich, Germany, September 2012.
 Anton Schiela and Hans Olsson. Mixed-mode Integration for Real-time Simulation. In Modelica Workshop 2000 Proceedings, pages 69â€“75, Lund, Sweden, 2000.
 Tom Schierz and Martin Arnold. Stabilized overlapping modular time integration of coupled differential-algebraic equations. Applied Numerical Mathematics, 62(10):1491 â€“ 1502, 2012.