Surface to Surface (SFSF)

The surface to surface constraint consists of a surface on one body rolling and sliding on the surface of a second body. Each of the surfaces are required to have a unique contact point. The surface to surface joint constrains the two surfaces as follows: the surfaces have exactly one contact point, and the normal at the contact point for each is anti-parallel.

In order to completely specify a surface to surface joint, the following entities must be created first:
  • Two reference surface entities (created using the Surfaces panel ).
  • Two markers that belong to Body 1 and Body 2 of the joint and are located appropriately so that the surface entity can be meaningfully described as belonging to the coordinate system of the reference marker.

  1. If the Advanced Joint panel is not currently displayed, select the desired advanced joint by clicking on it in the Model Browser or in the modeling window.
    The Advanced Joint panel is automatically displayed.
  2. From the Connectivity tab, click the Surface 1 collector and select the surface that belongs to Body 1 from the modeling window, or double-click the collector to open the Model Tree (from which the desired surface can be selected).
  3. Similarly, click the Surface 2 collector and select the surface that belongs to Body 2 from the modeling window or the Model Tree.
  4. Click the Ref Marker 1 collector and select the reference marker that belongs to Body 1.
  5. In the same manner, click the Ref Marker 2 collector and select the reference marker that belongs to Body 2.
    The Body 1 and Body 2 fields are automatically populated with the appropriate body labels.
  6. Click the Initial Conditions tab.
  7. Select the User Initial Condition Marker check boxes and select the desired markers using the Marker collectors.
    The default initial condition markers for the surfaces are the reference markers that are specified in the Connectivity tab.
  8. Select the Use XYZ check boxes and enter the initial position values into the X, Y, and Z fields to specify an initial position for each surface.
    Note: In the absence of user input, MotionView will measure the distance between all the points on the surfaces and pick two points, one on each surface, that are close to each other.
Tip: If the values for the initial contact point are known for the SFSF joint, then it is recommended that they are specified while defining the joint.