The VX function returns the x-component of the difference between the velocity vector of marker i and the velocity vector of marker j as computed in the coordinate system of marker k. All vector time derivatives are taken in the reference frame of marker l. Marker j defaults to the global coordinate system if it is not specified. Similarly, markers i and j default to the global coordinate system if they are not specified.
VX(i[,j][,k][,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 to default to the global coordinate system. |
| k | The marker in whose coordinate system the velocity vector is being expressed. Set k = 0, while still specifying l, if you want the results to be calculated along the x-axis of the global coordinate system. |
| l | The reference frame in which the first 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, VX is calculated as follows:
where:
is
the displacement of marker i in ground.
is
the displacement of marker j in ground.
is
the unit vector along the x-axis of marker k. FX=-10*VX(236,168,168,168)
This function defines a damper acting between Markers 236 and 168. The damping force components are proportional to the components of the velocity between Markers 236 and 168 as seen and measured by an observer at Marker 168.