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Can any one of IMUs measure velocity?
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Can any one of IMUs measure velocity?

by eikish on Mon May 18, 2020 5:26 pm

Can't find any reliable info on measuring velocity (like in a straight line, not spin velocity) with Adafruit IMU boards. I know accelerometers alone are not great to measure velocity because you would need to pull the acceleration info often (assuming you start with velocity=0) and calculate V continuously with the compounding error rate.

I want to strap an IMU on the back of another sensor to "label" the velocity along with the other sensors data together with timestamps. I'll be moving/shaking the package manually or with some contraption back and forth along a mostly linear path while facing the same direction and I'm missing the velocity in the direction the package is moving (starting from 0).

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Re: Can any one of IMUs measure velocity?

by adafruit_support_bill on Mon May 18, 2020 5:55 pm

I don't know of any hobbyist grade IMUs that will calculate velocity for you. You generally need to integrate the acceleration over time in order to get velocity.

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Re: Can any one of IMUs measure velocity?

by jps2000 on Tue May 19, 2020 1:06 am

First of all you need to replace the word measure by estimate :-)

Integrating linear acceleration does the job but integration over time cumulates offset errors quickly.
You need to take linacc because you have to cancel out gravity. Also high pass filtering ( differentiation) may do this. The latter is only approipriate for "fast" movements.

In case of planar and horizontal movements you may just ignore the z (vertical) component.
Having sinusoidal movements you can calculate velocity from the peak acc value in case the frequency and amplitude is known.

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Re: Can any one of IMUs measure velocity?

by bludin on Tue Jun 02, 2020 3:28 am

Velocity is always relative to something. If you have a reference, you may use a sensor to measure the distance (e.g. via ToF, VL6180X) and calculate the velocity from that.

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Please be positive and constructive with your questions and comments.