I am curious as to how the ultrasonic sensor calculates relative velocity and distance to an object. What methods does it use? Triangulation or trilateration? Doppler effect? How can I model this sensor in Simulink? I know I may need a time delay for the time for the machine to process but how is that determined?
1 Answer
I presume it would use delay to determine the distance and frequency shifting due to the doppler effect to determine speed. The real question is what sort of signal are they using. Different signals will have different performance characteristics when it comes to extracting propagation delay and doppler shift information. For example, a short tone of a single frequency works well for measuring the doppler shift, but not so well for determining the delay. A chirped (frequency swept) pulse works better for determining delay, but doesn't work well for measuring doppler shift. A randomly modulated pulse works well for both, but requires more signal processing to detect. I would imagine they're probably using some form of digital modulation (amplitude or phase most likely) with a pseudorandom sequence and then using some digital signal processing to extract the information.
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\$\begingroup\$ So if you had to model this sensor would it be safe to say all you need is a time delay block and a gain block calculating distance? \$\endgroup\$– adamSep 16, 2016 at 1:31
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\$\begingroup\$ Maybe? I have never used simulink before. \$\endgroup\$ Sep 16, 2016 at 1:32
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\$\begingroup\$ Would you say these sensors take into account the weather conditions as well? Since weather effects how signals move through the air. \$\endgroup\$– adamSep 16, 2016 at 1:34
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\$\begingroup\$ They would probably have to to some extent. The speed of sound in air is dependent on temperature, pressure, and humidity, so there may be additional sensors for compensation. \$\endgroup\$ Sep 16, 2016 at 1:37
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\$\begingroup\$ If you wanted to get an estimate however would it be okay to neglect weather conditions? \$\endgroup\$– adamSep 16, 2016 at 1:42