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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?

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  • \$\begingroup\$ Time (delay) of echo is proportional to distance. The derivative of distance is speed. \$\endgroup\$ – Bort Sep 15 '16 at 23:33
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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\$ – adam Sep 16 '16 at 1:31
  • \$\begingroup\$ Maybe? I have never used simulink before. \$\endgroup\$ – alex.forencich Sep 16 '16 at 1:32
  • \$\begingroup\$ Would you say these sensors take into account the weather conditions as well? Since weather effects how signals move through the air. \$\endgroup\$ – adam Sep 16 '16 at 1:34
  • \$\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\$ – alex.forencich Sep 16 '16 at 1:37
  • \$\begingroup\$ If you wanted to get an estimate however would it be okay to neglect weather conditions? \$\endgroup\$ – adam Sep 16 '16 at 1:42

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