Ultrasonic Doppler Sensor for Measuring Vehicle Speed in Forward and Reverse Motions Including Low Speed Motions
نویسنده
چکیده
A signal processing method was developed to improve the resolution and accuracy of ultrasonic Doppler ground speed sensors particularly in low speed ranges. Prototype sensors were made and tested. The sensor consists of ultrasonic transducers of 200 kHz and electronic circuits for signal processing. The frequency of received signal from the ground was multiplied by 5 to increase the resolution and mixed with a reference signal of 950 kHz generated from the same oscillator as used for the transmission signal. The sensor outputs a beat frequency signal, the frequency of which changes from the neutral output of 50 kHz in proportion to the travel speed. Performance tests were conducted on model ground surfaces using a linear actuator and on field surfaces using a tractor. The prototype sensors could measure the speeds of both forward and reverse motions, including low speed motions, with high accuracy.
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