2001 Volume 63 Issue 2 Pages 39-46
A high-resolution ultrasonic Doppler speed sensor was developed to improve the accuracy of speed measurement for autonomous driving systems. The prototype sensor consists of ultrasonic transducers of 200kHz and electronic circuits of a preamplifier, a tuned amplifier, a frequency multiplier and so on. The frequency of received signal from the ground was multiplied by 5 to improve the resolution and mixed with a reference signal of 950kHz. The reference signal was generated from the same oscillator as used for the transmission signal using a frequency synthesizer. The speed sensor was tested on five types of model ground surface using a linear actuator with a 4m distance of motion. The sensor could measure the speeds of both forward and reverse motions with relatively high accuracy, and could measure speeds of as low as 10mm/s.
