Defining the Trajectory Motion with Constrained Rotation

The motion path for the component passing through the tank was previously defined in a CSV (comma separated variable) file. After importing this file for the trajectory motion, you position the geometry in such a way that the location of the first contact point in the real scenario—for example the first hanging point of the rack on the skid, matches the first path point in the CSV table. The starting orientation of the moving region is kept unless you define an extra rotation.

There is no physical contact between the region and the trajectory. After setting up the trajectory motion, a translation is calculated based on the trajectory and assigned to the region after each time step. In the paint dipping case, a superposed rotation must also be defined to follow the orientation of the curved skid. That is, you add a constrained rotation for the motion in addition to the translation. The complete transformation is then applied to the chassis region. The paint dipping motion is illustrated below:



  1. To define a trajectory motion:
    1. Right-click the Tools > Tables node and select New Table > File Table.
    2. In the pop-up dialog select Track.csv from the motion folder of the downloaded tutorial files and click Open.
    3. Right-click the Tools > Motions node and select New > Trajectory.


    4. Select the Trajectory > Table(x,y,z) node and set the following properties:
      Property Setting
      Table Track
      Table: Position X column0
      Table: Position Y column1
      Table: Position Z column2
      Speed Specification Velocity Function

      To set the speed with which the chassis moves along the trajectory, you create a user-defined field function. In this tutorial, you define a constant value:

    5. Right-click the Automation > Field Functions node and select New > Scalar.
    6. Rename the User Field Function 1 node to user_velocity.
    7. Select the user_velocity node and set the properties as follows:
      Property Setting
      Function Name user_velocity
      Dimensions Length/Time
      Definition 0.5
    8. Within the Tools > Motions > Trajectory node, select the Table(x,y,z) > Velocity Function node and set Scalar Function to user_velocity.
  2. To capture a certain part of a moving body in a post-processing scene, you create a coordinate system managed by the trajectory motion and apply this moving coordinate system in the View of the specific scenes.
    1. Right-click Tools > Coordinate Systems > Laboratory > Local Coordinate Systems and select New > Cartesian.
    2. In the Create Cartesian Coordinate System dialog, set the following properties:
      Property Value
      Origin [4.2, 0, 1]
      i Direction [-1,0,0]
      j Direction [0,-1,0]

      The origin of Cartesian 1 corresponds to the first point of the trajectory in the CSV file supplied.

    3. Click Create followed by Close.
    4. Select the Tools > Motions > Trajectory node and set Managed Coordinate System to Cartesian 1.
      NoteYou create a motion managed coordinate system for visualization. It is not required by any solver.
  3. To complete motion setup with constrained rotation:
    1. Right-click the Motions > Trajectory > Superposing Motions node and select Constrained Rotation.
    2. Select the Constrained Rotation node and set Horizontal Offset to 4.8m.

      This offset corresponds to the distance h in the illustration shown previously.

      You apply the constrained rotation of the trajectory motion to the overset region. The background region is stationary by default.

    3. Select the Regions > Overset > Physics Values > Motion Specification node and set Motion to Trajectory->Constrained Rotation.