Then, the pseudo tracking servo output signal is used to compute {HEAD ~ the speed} of {TAIL ~ the sledge motor} 
Then , the pseudo tracking servo output signal is used to compute { HEAD ~ the speed } of { TAIL ~ the sledge motor }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL