The VR function calculates the radial (separation) velocity of marker i with respect to marker j. The vector time derivative is taken in the reference frame of marker l. Markers j and l default to the global coordinate system if they are not specified.
VR(i[,j][,l])
| i | The marker whose velocity is being measured. |
| j | The marker with respect to which the velocity is being measured. Set j = 0, while still specifying l, if you want j default to the global coordinate system. |
| l | The reference frame in which the time derivative of the displacement vector is taken. Set l = 0 or omit the argument if you want the time derivatives to be taken in the ground coordinate system (GCS). |
Mathematically, VR is calculated by projecting the velocity vector on a unit vector along the line of sight between i and j, as follows:
where:
is
the displacement of marker i with respect to the global origin.
is
the displacement of marker j
with respect to the global originAs markers i and j separate from each other, VR is positive. VR is negative when markers i and j approach each other.
-10*VR(467,764)
This function implements a translational damper with a damping constant of 10.