Creating a Sketched-Law Excitation

You can use a sketched-law excitation to drive a command in your mechanism according to a design table or a formula. To do so, for each time step of the kinematics simulation, associate a spline or a curve and a reference axis to the command.

Before you begin:
  • Open a kinematics simulation referencing a mechanism in the Mechanical Systems Experience app. app.
  • Design a spline or curve in the Sketcher app
  • Create a sketch, or sketch-based law in the Generative Shape Design app.
See Also
About Interpolation of Time Increments
Creating a Kinematics Scenario
  1. From the Scenario section of the action bar, click Sketched-Law Excitation .

    The Sketched-Law Excitation dialog box appears.

  2. To define the sketched-law excitation:
    1. Under the mechanism representation node in the tree, select the kinematics command to drive with this excitation.

      The name of the selected command appears in the Piloted command box

    2. Under the part representation node, select either a Generative Shape Design sketch-based law or a sketch defining the excitation profile.

      The name of the sketch-based law or sketch appears in the Sketched-law/Sketch box. In this case, the command generates the corresponding law and adds it to the part including the initial sketch.

    3. Under the Scenario node, select a scenario to attach the excitation to it.

      If no scenario exists, the Referenced scenario option is grayed out, and you can select the Time-scale option.

      When a scenario exists, the option is selected by default, and the excitation is time-scaled according to the duration of the selected scenario. You can also enter a specific Time-scale value.

    Important:
    • If the sketch-based law is not a proper mathematical function (for example, if the curve has undetermined points), then the output excitation may be truncated, discontinued or in a stepped-shape curve.
    • The sketch selected as input data must have been drawn on the standard XY plan.
  3. Click OK.

    Note: The Sketched-Law Excitation command only creates new sketched-law excitations. You cannot use it to modify an existing sketched-law excitation. To do so, use the Formula Editor.

    The excitation law appears under the scenario node.

    By default, the name is "Law Excitation.xx", where "xx" is the number of existing law excitations plus one.

    The command validation adds information to the resource table and generates a knowledge formula. When a resource table is created, it is completed by a new law resource referencing the selected sketched-law. It is named "ExcitationName_LawResource", where "ExcitationName" is the name you have chosen for their new law excitation.

    A new knowledge formula based on this resource is then generated and selected as the definition of the new law excitation.

    When the Sketched-Law Excitation command is validated, the excitation is created and appears in the excitation list. If you have chosen the Referenced Scenario option, the excitation also appears in the excitation list of the scenario.

  4. To define the sketched-law excitation, do one of the following:
    • Right-click the law excitation and select Definition.
    • Double-click the law excitation.
    • Under the Relations node in the tree, click the scenario formula.

    The Law Excitation dialog box opens, displaying the name of the excitation, the number of commands selected in the tree, and the length of the formula.

  5. To visualize the new knowledge formula generated as the new definition of the law excitation, click or double-click the scenario.
    1. Click Preview to run the PLM Update.
    2. Click to run the kinematics scenario.
      The element moves along the curve, sketch or GSD law.
    The Kinematics scenario dialog box opens.

    Depending on the Referenced scenario or Time-scale you selected, the Length formula (start/end time) appears in the Excitation Length box of the Formula Editor:

    Selection Description Formula
    Referenced scenario The sketched-law excitation is attached to a specific scenario Excitations\ExcitationName\[Length/Angle] = (AccessResource("ExcitationName_LawResource", "Law"):Law).Evaluate(`Excitations\ ExcitationName \Time`/((`ScenarioName\End time`-`ScenarioName\Start time`)/1s))*1[mm/deg]
    Time-scale A time-scale factor is specified Excitations\ExcitationName\[Length/Angle] = (AccessResource("ExcitationName_LawResource", "Law"):Law).Evaluate(`Excitations\ ExcitationName \Time`/TimeScaleFactor)*1[mm/deg]

    You can edit the length directly in this window. The new sketched-law excitation becomes a usual law excitation and must be considered as such.

  6. To define the excitation using a formula, right-click the Length formula or Angle formula box, and select Formula > Edit.For more information, see About Writing Formulas for Law Excitations.
  7. To define the excitation using a design table, from the Tools section of the action bar, click Design Table .
    The design table appears in the Length formula or Angle formula box.
    Note: To edit the design table, click .

    For more information, see About Using Design Tables for Law Excitations.

  8. Once the appropriate excitation is defined, click OK to save the kinematics excitation.