a control means including a CPU for controlling said wheel driving means in accordance with {HEAD ~ the outputs} of {TAIL ~ said sensor means} 
of
a control means including a CPU for controlling said wheel driving means in accordance with { HEAD ~ the outputs } of { TAIL ~ said sensor means }
OTH OTH OTH 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