{HEAD ~ A load force} feeds into {TAIL ~ a PID controller} programmed with preset proportional, differential and integral parameters 
{ HEAD ~ A load force } feeds into { TAIL ~ a PID controller } programmed with preset proportional , differential and integral parameters
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH