Point to Surface (PTSF)

A point to surface joint constrains a fixed point on a body to slide along a surface. The point to surface joint provides five degrees of freedom: three rotational at the instantaneous point of contact and two translational DOF.

In order to completely specify a point to surface Joint, the following entities must be created first:
  • A 3D surface entity (created using the Surfaces panel ).
  • A marker that belongs to Body 2 of the joint and is 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 Project Browser or in the modeling window.
    The Advanced Joint panel is automatically displayed.
  2. From the Connectivity tab, click Body 1 and pick a body from the modeling window, or double-click Body 1 to open the Model Tree (from which the desired body can be selected).
  3. Click the Point collector and select the point of the PTSF joint from the modeling window (or pick the point from the Model Tree).
  4. Click the Surface collector and select the predefined surface for the joint from the modeling window (or pick the point from the Model Tree).
  5. Click the Ref Marker collector and select the surface reference marker that belongs to Body 2 from the modeling window or the Model Tree.
  6. Click the Initial Conditions tab.
  7. Activate the User Initial Condition Marker check box and select the desired marker using the Marker collector.
    The default initial condition marker for the joint is the reference marker that is specified in the Connectivity tab.
  8. Activate the Use XYZ check box and enter in the initial position values into the X, Y, and Z fields to specify an initial position for the point.
    Note: These values will supersede those specified by the Point collector in the Connectivity tab.
Tip: If initial conditions are known, it is better to specify them while defining the joint as this will help reduce chances of error in results. If the initial conditions are not specified, MotionView will calculate the point on the surface that is nearest to the point specified for the joint in the Connectivity tab.