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