HM-3670: Position a Dummy Using Limiting Constraints

In this tutorial, you will learn how to position the H-point of the dummy on a seat cushion.

This helps to reduce design and remeshing of the seat based on the pre-stress analysis. To do this exercise you will be using a limiting constraint and freehand morphing.

This exercise uses the dummy.hm file, which can be found in the hm.zip file. Copy the file(s) from this directory to your working directory.


Figure 1.

Open the Model File

In this step, you will open the model file, dummy.hm.

  1. Open the model file, dummy.hm.
  2. Review the model.

Create Constraints

In this step, you will create constraints.

  1. From the menu bar, select Morphing > Create > Morph Constraints.
  2. Set name= to const1.
  3. Set type of constraint to on elements.
  4. Set the option under nodes to bounded.
  5. Set project along: to N1,N2 along negative z (choose from side of cushion).


    Figure 2.
  6. Set distance= to 2. This will ensure that there is a distance of units between the dummy and the seat after the morphing is complete.
  7. Use nodes >> by collector and select cushion.
  8. Click select.
  9. Use elems >> by collector and select dummy.
  10. Click select.
  11. Click create.
    Constraints with a diamond shape are created.


    Figure 3.

Morph the Part

In this step, you will morph the part.

  1. Right-click MorphingConstraint in the Model Browser and select Hide.
  2. From the menu bar, select Morphing > Free Hands and select the move nodes subpanel.
  3. Switch the moving method to translate.
  4. For moving nodes, use nodes >> by collector and select cushion.
  5. Click select.
  6. For fixed nodes, use nodes >> by collector and select dummy.
  7. Click select.
  8. For affected elements, use elems >> by collector and select cushion.
  9. Click select.
  10. For the translate magnitude, set the following:
    • X = 0
    • Y = 0
    • Z = 80
  11. Click morph.
    The top surface of the cushion has conformed to the shape of the dummy. The distance between the dummy and the seat-cushion is 2 mm. Using limiting constraints, you are able to move a mesh such that it moves an adjoining mesh along with it, thus preventing penetration between the two of them.


    Figure 4.