| 1. |
- Engelson, Vadim
(författare)
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3D graphics and Modelica : an integrated approach
- 2000
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Ingår i: Linköping Electronic Articles in Computer and Information Science. - : Linköping University Electronic Press. - 1401-9841. ; 5:9
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Tidskriftsartikel (refereegranskat)abstract
- The Modelica standard library and available Modelica tools contain some facilities for specification of 3D geometry and 3D graphics. Geometry and graphics is associated with physical objects included in simulated Modelica models. However, important graphics properties are missing from this model. In particular, physical objects cannot change their shape (geometry) and rendering features (graphics) dynamically. The physics of simulation, is often not affected by geometry of physical objects. For instance, a body is often approximated by its center of mass under certain conditions. Either simple predefined shapes or specifications of geometry via external files are used. The last facility leads to separation between the model and the corresponding graphics and geometry. Our proposal is to integrate 3D geometric and graphical features with Modelica models of physical objects. The 3D graphics information is specified explicitly via annotations containing certain graphics primitives or using instances from a specially designed geometry class library. The motivation, syntax and implementation outline for this approach are discussed in this report.
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| 2. |
- Engelson, Vadim
(författare)
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Integration of collision detection with the multibody system library in Modelica
- 2000
-
Ingår i: Linköping Electronic Articles in Computer and Information Science. - : Linköping University Electronic Press. - 1401-9841. ; 5:10
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Tidskriftsartikel (refereegranskat)abstract
- Collision detection and response is one of the most difficult areas in simulation of multibody systems. Two known approaches, the impulse-based method and the force-based (penalty) method, can be applied for multibody simulation in Modelica. The impulse-based method requires instantaneous modification of some variables, but such modification is not always possible in Modelica. The force-based method leads to stiff ODE, which can be handled by solvers used with Modelica. We suggest a new way to express the penalty coefficients. The force-based method, however, requires computation of penetration depth which is time-consuming.We also suggest a method that combines the distance between bodies and the penetration depth into a single quantity used for force computation.Calling external functions is a preferable method integrate collision detection algorithms with practical physical models, since body geometry is stored externally. We describe an interface with collision detection tool SOLID.
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| 3. |
- Engelson, Vadim
(författare)
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ObjectMath inheritance and composition diagram editor
- 2000
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Ingår i: Linköping Electronic Articles in Computer and Information Science. - Linköping : Linköpings Universitet. - 1401-9841. ; 5:6
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Tidskriftsartikel (refereegranskat)abstract
- ObjectMath is a new object-oriented modeling language for scientific computing. The major innovation of this language is the introduction of object-oriented structure into a computer algebra language making it possible to group equations and formulae into classes. ObjectMath contains three object-oriented structuring constructs (class, instance and part) providing classes, single and multiple inheritance and composition of parts. Typical models in ObjectMath include between 10 and 30 such constructs. Inheritance and composition relationships are established between them. The problem is how to inspect, browse, and modify these relations in a convenient way. Our solution to this problem is using a graphical two-dimensional diagram editor connected to a text editor. An integrated programming environment for ObjectMath includes this editor. The report describes how object-oriented constructs of ObjectMath are mapped to their graphical representation. The ObjectMath syntax rules are mapped to diagram editor operations so that only syntactically correct models can be created.
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| 4. |
- Engelson, Vadim
(författare)
-
Simulation and visualization of autonomous helicopter and service robots
- 2000
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Ingår i: Linköping Electronic Articles in Computer and Information Science. - : Linköping University Electronic Press. - 1401-9841. ; 5:8
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Tidskriftsartikel (refereegranskat)abstract
- To decrease the costs and the time it takes to develop and test new products, computer simulations are very helpful. Product models can be simulated, and their behavior can be examined. This applies not only to hardware, but even to software products that are composed of several components, so that their cooperative behaviour is simulated in a virtual environment. Some components of this environment can later be replaced by physical, real world devices. Some other components can be just prototypes, which are later replaced by more complex and realistic software components. In any case the idea is to construct a model and simulate both software and hardware before the actual production starts. In the WITAS project there is a need to develop a system which contains helicopters, robots and various control software and hardware. In particular there is a need to simulate the dynamic behavior of an autonomous aircraft within a virtual environment. There is a need to simulate a service environment, where robots can interact with the landed helicopter.In this report a study of object-oriented modeling of mechanical systems using Modelica is presented with applications to autonomous helicopters and robots. Mechanical features of an autonomous helicopter have been modeled in order to verify the control system. As the result the control system has been tested and tuned. However, the flight still is not stable in the cases when flight mission directions change too often.A robot which is able to grab, move, and release objects using automatic or manual control have been modeled. The problem of inverse geometry (and inverse kinematics) can be solved for robots using our approach. The robot models can be controlled interactively.The geometry and dynamic structure of these systems has been designed in CAD tools and later integrated with control systems for steering these devices. The simulation has been performed in Modelica.
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| 5. |
- Engelson, Vadim
(författare)
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Tools for design, interactive simulation and visualization for dynamic analysis of mechanical models
- 2000
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Ingår i: Linköping Electronic Articles in Computer and Information Science. - : Linköping University Electronic Press. - 1401-9841. ; 5:7
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Tidskriftsartikel (refereegranskat)abstract
- The complexity of mechanical and multi-domain simulation models is rapidly increasing. Therefore new methods and standards are needed for model design. A new language, Modelica, has been proposed by an international design committee as a standard, object-oriented, equation-based language suitable for description of the dynamics of systems containing mechanical, electrical, chemical and other types of components. However, it is complicated to describe system models in textual form, whereas CAD systems are convenient tools for this purpose. Therefore we have designed an environment that supports the translation from CAD models to standard Modelica representation. This representation is then used for simulation and visualization. Assembly information is extracted from CAD models, from which a Modelica model is generated. By solving equations expressed in Modelica, the system is simulated. We have designed several interactive 3D visualization tools which display expected and actual model behavior, as well as additional graphical elements for the purpose of engineering visualization. We applied this environment for robot movement and helicopter flight simulation.
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| 6. |
- Larsson, Staffan, 1969, et al.
(författare)
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Information states and dialogue move engines
- 1999
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Ingår i: Linköping Electronic Articles in Computer and Information Science. - 1401-9841. ; 4:23
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Tidskriftsartikel (refereegranskat)abstract
- We explore the notion of information state in relation to dialogue systems, and in particular to the part of a dialogue system we call the dialogue move engine. We use a framework for experimenting with information states and dialogue move engines, which is being implemented in the form of TRINDIKIT, a toolkit for building dialogue move engines and dialogue systems. We also show how an experimental dialogue system (GoDiS) currently being developed in Göteborg within the framework can be provided with rules to handle accommodation of questions and plans in dialogue.
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