About Generating a Modelica Representation of a Mechanism of a Physical Product

You can generate a Modelica representation of a mechanism of a physical product. This is done by building a Dymola behavior (model) in Modelica using the kinematic description of the mechanism in the physical product. This allows for integrating Modelica features with mechanical system design.

This page discusses:

See Also
Generating a Modelica Model from a Kinematic Mechanism

General Information

The command Generate from Kinematic enables you to generate a Modelica behavior (model) of a selected mechanism of a physical product. The Modelica code is automatically generated, and can then be simulated as-is, or further extended with other Modelica components.

You can also use an Engineering Knowledge Language (EKL) scripting method to generate the Modelica behavior.

Data converted from the mechanism are:

  • Parts, including mass and inertia, and optionally VRML 3D representations.
    Note: VRML 3D representations can only be handled by the command, not the EKL scripting method.
  • Supported mechanical joints.
  • Mechanism commands, including mechanical motors attached to such commands.
  • Published axis system, when publication is directly under the same product as the mechanism.
  • Acceleration of gravity.
Other data is not used for model generation.

Overview of Generated Modelica Representation

As a result of the Modelica model generation, a number of classes are created under the selected target package:

  • A locked base class containing the generated model. This class is inserted in the class InternalGenerated.
  • An extended class from the generated model class, where you can add your modifications, for example, extend the model or replace components.

Structure of the Generated Model

The selected mechanism includes mechanical constraints, from which the parts are retrieved. The components in the generated Modelica representation are corresponding to sets of identified parts. Parts included in the root product but not involved in the mechanism are ignored.

In the generated model, all components are replaceable, except the "world" component. This component is by default added if the initial physical model does not contain any published axes. However, if you generate the Modelica model using the command, you can select to always generate a "world" component and have it connected to the fixed parts, even if the physical model contains published axes.

Naming Rules

The name of the components (bodies, joints) is generated from the instance name in the physical product model. The description of the components is the occurrence path from the physical product model. To comply to Modelica name rules, special characters in names are replaced, and prefixes may be included to ensure unique entities.

Generated Diagram Layer and 3D Representation

The diagram layer is generated from the topology of the mechanism. The 3D body components have picture representation from 3D screen shots of the 3D shapes.

Optionally, when generating the Modelica representation with a command, the generated model can include a 3D representation of the shape, in VRML format as resource of the generated model. In this mode, the VRML visualization is used for animation instead of the physical model itself. This can be useful if you want to export the model to another tool, for example, Dymola.

If you select not to generate a VRML representation, the generated model includes links to the initial 3D physical model, so it can be animated from the results.

The pictures are stored as resources of the generated Modelica model.

Generated Icon Layer

The icon layer of the generated Modelica model has a different extent value from the diagram layer. A screenshot of the physical product containing the originating mechanism is used for the image of the icon layer.

Model Documentation

The generated base model includes an annotation with some information about the origin model. That information is available from the documentation editor.

Parts Customization

Customization of the Orientation of the Part Frame Connectors

By default, the axis system of the frames of the part components in the generated Modelica model corresponds to the local axis system of the corresponding physical product.

To specify the customized axis system for the frame of that part component, a publication named ModelicaAxisSystem must be created in the reference of the corresponding product.

Customization of Color Animation of Physical 3D Parts

In the class CATIAMultiBody.Parts.BodyShapeWithFrame, you can specify the parameter UseModelicaColor to true to display input connectors for color handling. The default value of the parameter is false. One Boolean input connector is used to switch the color animation on or off, while an array connector of four Reals is used to specify the color of the shape with RGBT coding (red, green, blue, transparency). The Real values must be in the range of 0–255.

Handling Replaceable Components

The generated Modelica components are all replaceable. You can replace a component with a more specialized version, for example, replacing a rigid body with a flexible body.

To do so, you must create a dedicated Modelica class extending CATIAMultiBody.Interfaces.PartialArrayofFrames. The frame_a array can then be connected to the relevant internal geometry of the specialized class.

Tip: If you replace a joint of another type with a cut joint, you must also recompute the cut joint configuration. This may also be required in other cases. See Recomputing the Cut Joint Configuration.

If you specify the hidePhysicalPart parameter to true, the corresponding 3D physical shape is hidden when the 3D animation is displayed.

Links and Relations from the Kinematic Model to its Modelica Representation

You can see the relationships between the generated Modelica representation and the original Kinematic model using the command Links and Relations from the Dymola Behavior Modeling app. For more information about this command, see Mechanical Systems Design User´s Guide: Links and Relations.

Note: The links are not bidirectional. You cannot see these links from the Mechanical Systems Design app.

Updating a Modelica Model Corresponding to a Modified Mechanism

When the physical data involved in a mechanism generating a Modelica model is modified, you can update the corresponding generated model using any of the following commands:

  • The model generation command Generate from Kinematic
  • The dedicated update command Update Current Model from Physical Model
  • Any of the generic PLM update commands Update or Update Assistant
    Note: There are conditions for using any generic PLM update command.
For more information, see Updating, from the Physical or Logical Model, a Generated Modelica Model of a Kinematic Mechanism or an Engineering Model.

Detecting and Handling Physical Clashes

You can detect and handle clashes in simulations of Modelica models generated from physical mechanisms. If a clash occurs, clashing objects are highlighted, and the simulation can be stopped. For more information, see Detecting and Handling Physical Clashes.

Licenses

To be able to generate a Modelica representation of a mechanism of a physical product, you must also have the Mechanical Systems Design app.