| 摘要 |
PURPOSE: To provide a ground vehicle speed sensor by which the ground speed in the transverse direction of a vehicle can be detected with good accuracy even when an obstacle exists on the side part of the vehicle by a method wherein a Doppler shift frequency by the relative speed of the obstacle on the side part of the vehicle to the vehicle is removed from a received Doppler signal. CONSTITUTION: When a transmitted signal from a transmitter 10 is impinged on a road surface on the side part of a vehicle, a part of it is conducted diffused reflection so as to advance to the side of a receiver 16. At this time, a Doppler shift frequency fd in the transverse direction of the vehicle is superposed on a signal received by the receiver 16. When an obstacle 32 exists on the side part of the vehicle, the transmitted signal which has been reflected specularly by the road surface is reflected further by the obstacle 32 so as to advance to the receiver 16. A Doppler shift frequency fd1 according to the relative speed of the vehicle 30 to the obstacle 32 is superposed on the signal. On the other hand, the relative speed of the veicle 30 to the obstacle 32 is detected by the time differentiated value of the distance S, between the vehicle 30 and the obstacle 32, detected by a side-part distance sensor 28. On the basis of the relative speed, the Doppler shift frequency fd1 is operated so as to be removed from a Doppler signal. |
