POSITION DETECTION SENSOR FOR AUTOMATIC TRAVELING DEVICE

PROBLEM TO BE SOLVED: To accurately control the travel of a vehicle while keeping high position detection precision at all times by composing a mark of a metallic material which is nonmagnetic and has high conductivity, exciting an electromagnetic induction type sensor with two different kinds of frequency signal, and processing two kinds of frequency signal outputted by the electromagnetic induction type sensor as specified and calculating the quantity of the deviation of the electromagnetic induction type sensor from the mark. SOLUTION: The mark 23 is made of the beltlike metallic material, such as aluminum and copper, which is nonmagnetic and has high conductivity. The position detection sensor 24 has differential type constitution of two coils 24a and 24b excited with two different frequency signals and their outputs are sent out to a signal converting amplifier 25 and sent to a signal arithmetic unit 26. The signal arithmetic unit 26 processes the two frequency signals according to preset arithmetic initialization to remarkably reduce the influence of the approach of magnetic metal 27 to the mark 23 even in such a case and calculate the value accurately corresponding to the quantity of the shift of the position detection sensor 24 from the mark 23, thereby allowing the vehicle 21 to travel along the mark 23.