| 摘要 |
<p>PURPOSE:To enable the prevention of false measurement, by computing the radius of curvature of running of a vehicle body on the basis of a vehicle speed and a change rate with time of an angle formed by the direction of advance of the vehicle body and the direction of geomagnetism, and by limiting the range of a distance to be measured in accordance with the radius. CONSTITUTION:Outputs of a geomagnetic sensor 4 and a vehicle speed sensor 5 are given to a processing circuit 32, change rates with time of the intensity and direction of a magnetic field existing around the sensor 4 and a running speed are determined, the radius of curvature of a running track is determined on the basis of the values determined in the above, and based on the value of said radius, and a contact of a switch S is selected in accordance with a reference. A transmission wave W1 is emitted to a vehicle 7 going ahead and a reflected wave W2 is given to a mixer 24 and mixed with a part of the transmission signal wave. An output signal of the mixer 24 is given to an amplifier circuit 31, and thereby a wave of a frequency component being a difference between said two waves is extracted, amplified and given to the switch S. Then, by the contact selected by the processing circuit 32, any one of BPFs 33-35 being different in a band width from one another is selected. In other words, a measurable range of a distance in front is set to be larger as the radius of curvature increases.</p> |
