The Dynasim Derivative

August 1, 1995

Dymola in Industry

The forth year of operation is now starting for Dynasim. More and more customers are utilizing the power of object-oriented modeling in Dymola. We are very satisfied with the increasing interest from industry in the methodology. The experiences within three companies are reported below. In November 1994 we started to ship a new series of products: Dymodraw for graphical modeling, Dymosim for simulation and Dymoview for animation and plotting. Dynasim thus delivers a complete modeling and simulation environment which we call Dynamic Modeling Laboratory (Dymola).

Power Plant Simulation

BENIMA are engineering consultants in the field of industrial automation. We started using the DYMOLA package for modeling and simulation in the late autumn 1994. Since then we are using it in two major projects at Ringhals nuclear power plant. The projects are reengineering and exchange of control equipment for

The feedwater control system
The reactor control system in one of the blocks.

The rather complex hydraulic network systems are handled very neatly in DYMOLA. The tearing function to reduce the dimension of the resulting systems of equations, the efficient handling of events and instantaneous equations, DYMODRAW to administrate the libraries and complex models and, further, the efficient numerics for stiff systems in DYMOSIM has been particularly useful. The symbolic equation solver made the modeling task much easier than in a conventional simulation environment implementing the thermo-hydraulic model of the reactor.

BENIMA has customers in almost all industrial branches and DYMOLA's object oriented language makes it very easy to collect models in libraries for efficient reuse. The possibility to translate models from BENIMA's DYMOLA representation to a customers favorite simulation environment, does not make the package less attractive. BENIMA is so far very satisfied with the DYMOLA package and looks forward to the future development.

Pontus Ryd
BENIMA AB, Box 283
Mölndal, Sweden

Realtime Robot Control

DLR has successfully finished a cooperation with Germany's largest robot manufacturer, KUKA. As a result the new KUKA control software RC30/51 contains
an optimization module from DLR which minimizes the travel time during the robot movement online, taking into account the performance restrictions of the robot, such as maximum motor torques. The heart of the realtime optimization code is based on the mechanical equations of the robot. Due to the severe time restrictions, the efficiency of the robot equations is crucial. For providing these equations, three commercial symbolic multibody packages have been compared with Dymola and its Dymola-library mbs.lib. Since the Dymola generated code was about 10-50 % faster than the code of the other examined packages, Dymola was selected as the code generator.

Martin Otter
DLR Oberpfaffenhofen

Dymola at ABB Industrial Systems

ABB Industrial Systems works, among other things, with drive systems for industrial applications like rolling mills, cranes, mining hoists etc. The systems under consideration contain the electrical distribution net, rectifiers, electrical machines and mechanical systems. We have for a long time been looking for a simulation tool that enables us to build a model library for our most common applications. We want to be able to quickly change, for example, the net topology to test different modes of operations. This has not been possible with traditional modeling tools since one has to develop the model equations for each topology.

One of our Dymola models is a brush-less field exciter to a synchronous machine. A part of the machine is built as an induction motor with open rotor windings. The stator is fed via a net switch with two anti-parallel thyristors in each phase. The rotor is connected to a rotating diode rectifier. The model is stiff and there are many switching events. Pspice was not able to simulate it. Dymola and Dymosim did not have any problems.

Object-oriented modelling is a requirement for a modern simulation program as we need to reuse our models. We hope there will be more extensive libraries available soon. Efficient event handling is also necessary within power electronics. Dymola meets these requirements.

Johann Galic
ABB Industrial Systems
Västerås, Sweden