Creating Bodies

You can create a body as a geometry reference in a mechanism, and use mechanical relations to simulate the mechanism motion.

This task shows you how to:

See Also
About Bodies

Create Rigid Bodies

You can create a rigid body either by associating it with an existing product, or by defining its position or properties manually.

  1. From the Mechanism section of the action bar, click Body .
  2. In the Body dialog box, select Rigid .

    Use this option to create a body with a specified mass and inertia.

  3. To convert an existing product into a body, select a geometry in the work area.
    • The position of the body corresponds to the position of the associated product.
    • The properties of the product appear in the corresponding fields of the dialog box.
  4. Optional: To dissociate the position of the body from the position of the geometry, use the Override options:
    1. Select Override geometry position.
    2. Define the position of the body.
    OptionDescription
    Free The position of the body can be modified.
    Fixed The position of the body cannot be modified.
  5. Optional: To modify the mass of the body, in the Mass section of the dialog box:
    1. Select the mass Override check box.
    2. Specify a value for the mass.

      Note: By default, the value is 1 kg.

  6. Optional: To modify the reference frame for the center of mass:
    1. Select the center of mass Override check box.
    2. Select a marker to use as the reference frame.

      • Body reference marker: marker created by default at the origin of the body.
      • Custom marker: existing marker from the tree, or new marker.

    3. Optional: If you selected Custom Marker, select an existing marker from the tree or click and select Create New to create a new marker.
      The Marker creation dialog box opens. For more information, see Creating Markers.
    4. Specify the position of the center of mass along the x,y and z-axis.
  7. Optional: To modify the inertia of the body:
    1. Select the inertia Override check box.
    2. Select one of the following markers as the reference frame:

      • Center of Mass
      • Body reference marker
      • Custom marker

    3. Optional: If you selected Custom Marker, select an existing marker from the tree or click and select Create New to create a new marker.
      The Marker creation dialog box opens. For more information, see Creating Markers.
    4. In the inertia matrix, specify values for each plane and direction.
  8. In the Position and Orientation section of the dialog box:
    1. Enter a position value for the element along the x, y, and z-axis.
    2. Select one of the following rotation sequences:

      • Extrinsic: Rotations that apply to an axis in the world coordinate system. The orientation follows the x, y, and finally the z-axis.
      • Euler: Three angles that describe the orientation of a rigid body with respect to a fixed coordinate system. The orientation follows the z, x', and finally the z"-axis.
      • Cardan: Rotation sequence from angular orientation data. The orientation follows the x, y', and finally the z"-axis.

    3. Specify a value for each orientation angle.

      Note: You can also use the Robot to modify the position and orientation of the marker. For more information, see About the Robot.

  9. Click .
    The body and its markers appear in the tree, under the Bodies node of the active product.

Create Rigid Massless Bodies

You can create a rigid massless body either by associating it with an existing product, or by defining its position or properties manually.

  1. From the Mechanism section of the action bar, click Body .
  2. In the Body dialog box, select Rigid Massless .

    Use this option to create a body with no specified mass and inertia. You can only edit the position and orientation of a rigid massless body.

  3. To convert an existing product into a body, select a geometry in the work area.
    • The position of the body corresponds to the position of the associated product.
    • The properties of the product appear in the corresponding fields of the dialog box.
  4. Optional: To dissociate the position of the body from the position of the geometry, use the Override options:
    1. Select Override geometry position.
    2. Define the position of the body.
    OptionDescription
    Free The position of the body can be modified.
    Fixed The position of the body cannot be modified.
  5. In the Position and Orientation section of the dialog box:
    1. Enter a position value for the element along the x, y, and z-axis.
    2. Select one of the following rotation sequences:

      • Extrinsic: Rotations that apply to an axis in the world coordinate system. The orientation follows the x, y, and finally the z-axis.
      • Euler: Three angles that describe the orientation of a rigid body with respect to a fixed coordinate system. The orientation follows the z, x', and finally the z"-axis.
      • Cardan: Rotation sequence from angular orientation data. The orientation follows the x, y', and finally the z"-axis.

    3. Specify a value for each orientation angle.

      Note: You can also use the Robot to modify the position and orientation of the marker. For more information, see About the Robot.

  6. Click .
    The body and its markers appear in the tree, under the Bodies node of the active product.

Edit Bodies

  1. In the tree, double-click a body.

    Tip: You can also click a body in the tree and select Edit Feature from the context toolbar.

    The Body dialog box opens.
  2. Edit the body parameters.
  3. Click .