| 摘要 |
PURPOSE: To accurately obtain a vehicle speed by removing the influence of water splash caused by a flooded road surface. CONSTITUTION: The on-vehicle vehicle speed measuring apparatus comprises a receiving state discriminator having a water splash detector 30 for sending ultrasonic signals intermittently at a predetermined elevational gradient to a road surface and discriminating whether the signal of a reflected wave input to an intermittent transceiver 1 for receiving the reflected wave includes the reflected wave from water splash or not and an envelope detector 10, a level comparator 11 and a gate circuit 31, and a received signal switching unit 15 for switching the transceiver 1 to a continuous transceiver 2 when a receiving state discriminator discriminates that the signal of the reflected wave input to the transceiver 1 includes the reflected wave from the splash. The vehicle speed is calculated by a vehicle speed calculator having a frequency measuring unit 33 and a calculator 34 for calculating the speed of the vehicle to the road surface by measuring the frequencies of the output signals from the transceivers 1, 2. |
