ULTRASONIC VEHICLE SENSOR AND VEHICLE SPEED MEASURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a ultrasonic vehicle sensor allowing accurate measurement of a sonic velocity in a propagation space for ultrasonic waves and the use of the measurement result for finding a vehicle speed with high precision. SOLUTION: The ultrasonic vehicle sensor comprises speed measurement ultrasonic heads 53, 54 for transmitting ultrasonic waves at an angle to downward to permit the measurement of the speed of a traveling vehicle using Doppler effect and existence detection ultrasonic heads 55, 56 for transmitting the ultrasonic waves right downward to permit the identification of the vehicle traveling right thereunder. A sonic velocity is found from a time for receiving the road surface reflected waves of signals transmitted from the existence detection ultrasonic heads and the sonic velocity is used in calculating the vehicle speed from the reception frequency of the signals received by the speed measurement ultrasonic heads. The sonic velocity in a space where the ultrasonic waves are actually propagated is actually measured and the actual measurement value is used in computing the vehicle speed, therefore producing an increase in measurement precision of the vehicle speed.