{HEAD ~ a power supply unit} including {TAIL ~ a rechargeable battery} and a voltage regulator circuit for regulating and outputting a voltage of said battery for supplying power supply voltage to said sensor means, said wheel driving means, and said control means and 
including
{ HEAD ~ a power supply unit } including { TAIL ~ a rechargeable battery } and a voltage regulator circuit for regulating and outputting a voltage of said battery for supplying power supply voltage to said sensor means , said wheel driving means , and said control means and
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