Creating Initial Conditions

You can define initial positions for a marker or joint to modify their position or velocity at the start of a simulation. For each direction of the motion element, you can specify position, velocity, or position and velocity conditions.

Note: The generated motion is submitted to friction, which results in a progressive loss of speed. To apply a constant initial speed to a joint, for example, use a joint driver. For more information, see Creating Joint Drivers.

This task shows you how to:

 

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Create Initial Conditions for Markers

You can define the relative position and orientation of a marker according to the position and orientation of another marker.

  1. From the Mechanism section of the action bar, click Initial Conditions .
  2. Select For Marker .
    • The options displayed in the dialog box adapt to the selected motion element.
    • The For Marker element appears under the Initial Condition node of the active mechanism.
  3. Click the Marker field and, in the tree, select a marker.

    Note: Markers are available under the Bodies node of the mechanism.

  4. Click the Relative to marker field and, in the tree, select a marker.
  5. Click the Coordinates with respect to marker field and, in the tree, select a marker.
  6. Select one of the following conditions to create for the marker:
    OptionDescription
    Translation Translates the marker.
    Rotation Rotates the marker.
    Translation and rotation Translates and rotates the marker.
  7. If you select Translation:
    1. For each translation axis, select one of the following conditions:

      • None
      • Position
      • Velocity
      • Position and velocity

    2. According to the selected condition, enter a value for the position and the velocity.

      Express positions in mm, and velocities in m/s.

  8. If you select Rotation:
    1. For each rotation axis, select a Position or Position and velocity condition to create.
    2. According to the selected condition, enter a value for the position and the velocity.

      Express positions in deg, and velocities in turn/mn.

  9. If you select Translation and rotation:
    1. For each translation axis, select one of the following conditions:

      • None
      • Position
      • Velocity
      • Position and velocity

    2. According to the selected condition, enter a value for the position and the velocity.

      Express positions in mm, and velocities in m/s.

    3. For each rotation axis, select a Position or Position and velocity condition to create.
    4. According to the selected condition, enter a value for the position and the velocity.

      Express positions in deg, and velocities in turn/mn.

  10. Click .

Create Initial Conditions for Joints

You can define the relative position and velocity of a joint according to the position and velocity of another joint.

  1. From the Mechanism section of the action bar, click Initial Conditions .
  2. Select For Joint .
    • The options displayed in the dialog box adapt to the selected motion element.
    • The For Joint element appears under the Initial Condition node of the active mechanism.
  3. Click the Joint field and, in the tree, select a joint including at least one degree of freedom.

    Note: Joints are available under the Joints node of the mechanism.

    Condition options appear for each translation and rotation degree of freedom of the joint.
  4. For each rotation or translation degree of freedom, select one of the following conditions:
    • None
    • Position
    • Velocity
    • Position and velocity
  5. According to the selected condition, enter a value for the position and the velocity.

    For translation degrees of freedom, express positions in mm, and velocities in m/s. For rotation degrees of freedom, express positions in deg, and velocities in turn/mn.

  6. Click .