抄録
A new speedometer of vehicle using induction magnetometer has been designed and evaluated, while the wheels of vehicle were magnetized through natural geomagnetic field and by some artificial magnetic field as well. As a magnetized wheel rotated during a movement of a vehicle, periodic magnetic patterns are propagated and then detected by an induction magnetometer or a sensor which is placed nearby the wheel. The high-frequency components, which may cause aliasing, are eliminated using an anti-aliasing filter (Low Pass Filter; cutoff=40Hz). The desired Low-frequency components of the induced electric signals are proceeded and converted into digital data by ADC (Analog to Digital Converter; 10bit) that includes RISC (Reduced Instruction Set Computer). Primary parameters, such as a diameter(r) of a vehicle’s tire and estimated time period T of a rotated tire, should be set to determine the speed of the vehicle from the following equation V=2πr/T. The characteristics of the new speedometer have been evaluated with a conventional speedometer. We expect that our proposed sensor is very proper for speed control or measurement of automatic vehicles for ITS(Intelligent Transport System).
