The Dynasim Derivative

May 15, 1994

Development at Dynasim

This is the second newsletter from Dynasim. We would like to report on the latest developments and other activities concerning Dynasim products. Dynasim now offers several new products in addition to Dymola: Dymosim is a powerful simulator. Dymoview is used to visualize simulation results by 3D animation. Dymodraw - the latest development - is an object diagram editor allowing model definition by drawing a diagram containing submodels and connections.

Dymola has been enhanced considerably. Tearing of systems of equations is available as described in a paper by Elmqvist and Otter entitled "Methods for Tearing Systems of Equations in Object-Oriented Modeling" presented at the ESM'94 (European Simulation Multi-Conference), Barcelona, June 1994. It is a very powerful feature which has made it possible to develop libraries for multi-body systems with closed kinematic loops. A graphical user interface (GUI) is now available for Dymola. Both PC/Windows and Unix/Motif versions are now beta-tested.

Last year, discrete event features were included in Dymola. It has, for example, been used for modeling power electronic systems , i.e. systems containing diodes, thyristors, etc. Users have reported that simulation was 20 times faster compared to using SPICE.

Dymola is used to teach modeling at many universities. Prof. Francois Cellier reports on his experiences at University of Arizona in the March issue of Eurosim - Simulation News Europe.

Ph.D. thesis

Dr Martin Otter at DLR (German Aerospace Research Establishment) has received a Ph.D. with a thesis entitled "Objektorientierte Modellierung mechatronischer Systeme am Beispiel geregelter Roboter", in English: "Object-oriented modeling of mechatronic systems such as controlled robots". Dr Otter utilizes Dymola and has developed very powerful and efficient Dymola libraries for multi-body systems. These libraries have, for example, been used for trajectory optimization in robotics. The powerful symbolic facilities of Dymola, together with the possibility to model variable structure systems, made the optimizations run 100 times faster compared to using other tools. The reason is that constraints in state variables are not maintained by the optimizer but are handled via variable structure models.

Dymola has also generated code for real-time simulation of robots, where other special purpose MBS programs failed to meet the speed requirements.

Dymosim - a new simulator

Dymosim is a powerful simulation program for solving ordinary differential equations (ODE) and differential-algebraic equations (DAE). It has a variety of proven numerical integration methods: one-step, multi-step and extrapolation methods. There are methods suitable for stiff dynamical systems and also methods that handle time- and state events.

Dymoview - 3D visualization

Dymoview is used to visualize dynamic behaviour. Plots of the time response of variables are often hard to interpret. A more realistic graphical view and animation is needed. Dymoview supports a 2- or 3-dimensional model-view built up by graphical objects such as polylines, polygons, boxes, spheres and cylinders, rendered with shading and hidden surfaces removed. To allow animation on low cost hardware, a wire-frame representation is used since smooth motion is then most important.

Dymodraw - object diagram editor

Dymodraw is an object diagram editor for Dymola. It allows creation and editing of model classes. Structural properties, such as submodels and connections are edited graphically. Equations and declarations are edited with a built-in text editor. A model class can be annotated with graphics. The object diagram editor is suitable for modeling of various kinds of physical objects. It is much more powerful than block diagram editors since composite non-causal connections are supported.

Exhibitions

Dymola was exhibited at ESS'93 (European Simulation Symposium) in Delft, The Netherlands in October 1993. At the CACSD'94 (Computer Aided Control System Design), Tucson, Arizona in March 1994, Dymosim and Dymoview were launched and gained a lot of interest. At ESM'94 (European Simulation Multi-Conference), Barcelona, June 1994, the object diagram editor, Dymodraw, is launched. We are proud to present Dymodraw since it is an essential part of the complete object-oriented modeling and simulation environment available from Dynasim.