In a preferred embodiment, {HEAD ~ the frame} emulates {TAIL ~ a workpiece cassette} and the distance sensors provide a numerical output of the distance to the workpiece 
emulates
In a preferred embodiment , { HEAD ~ the frame } emulates { TAIL ~ a workpiece cassette } and the distance sensors provide a numerical output of the distance to the workpiece
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH