Curve to Curve (CVCV)

The curve to curve constraint consists of a 3D curve fixed on one body rolling and sliding on a 3D curve fixed on a second body. The curves are required to have a unique point of contact and a common tangent at that point of contact. The curve-to-curve constraint is useful for modeling cams where the point of contact between two parts changes during the motion of the system. The curves always maintain contact, however, even when the physics of the model might dictate that one curve lift off the other.

In order to completely specify a CVDV Joint, the following entities must first be created:
  • Two 2D reference curve entities or one 3D entity created using the Curves panel.
  • Two markers that belong to Body 1 and Body 2 of the joint and are located appropriately so that the curves entity can be meaningfully described as belonging to the coordinate system of the reference markers.

  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 Curve 1 collector and select the curve that belongs to Body 1 from the modeling window, or double-click Curve 1 to open the Model Tree (from which the desired curve can be selected).
  3. In the same way, pick the curve for Curve 2 that belongs to Body 2.
  4. Click the Ref Marker 1 collector and select the reference marker that belongs to Body 1 from the modeling window, or double-click Ref Marker 1 to open the Model Tree (from which the desired marker can be selected).
  5. In the same way, pick the reference marker for Ref Marker 2 that belongs to Body 2.
    The fields of Body 1 and Body 2 will automatically populate with the appropriate body labels.
  6. Click the Initial Conditions tab.
  7. Select the User Initial Condition Marker check box and select the desired marker using the Marker collector.
    By default, this marker is the curve reference marker that belongs to Body 1 and Body 2 respectively.
  8. Select the Use XYZ check boxes and enter the initial position values into the X, Y, and Z fields to specify the two contact points.
    Note: If user-defined contact points are not provided, MotionView will measure the distance between all the points on the curves and pick two points (one for each curve) that are close to each other.
  9. Select the Use velocity check boxes and enter in values to set the initial contact velocities for Curve 1 and Curve 2.
    This velocity is as measured by an observer located at Ref Markers of each curve.
    Tip: If the values for the initial contact point and initial contact velocity are known for the CVCV joint, then it is recommended that they are specified while defining the joint.