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Topic: Accelerometer to track relative position in space (Read 49 times) previous topic - next topic

magnomp

Would it be possible to use an accelerometer to determine an objects position (milimetrically precise) in space, relative to a know point?

The reference point would be just a few meters away from the device

I mean, would it be that precise?
If I move the device, say, 1mm to the left, would it detect?

jremington

Not possible using commercial grade accelerometers. They are too noisy and inaccurate. For more details, see this technical note: http://www.chrobotics.com/library/accel-position-velocity

JohnLincoln

An accelerometer gives an output proportional to acceleration.  By performing the mathematical operation of integration on the output you can determine velocity.  By integrating a second time you can determine distance moved.

You can use use an op-amp circuit to do a double integration of the accelerometers output, but due to imperfections in all op-amps, the integrating capacitors will charge up or down due to leakage currents.

This gives a drift in position, which is quite significant, even if you use the highest quality components.

However if you have some type of vehicle that gets launched, (e.g. a rocket, or a drag car) at a known time, and keep the integrating capacitors shorted out until the moment of launch, you can obtain good results over a period of a few seconds.

johnwasser

An accelerometer can't tell the difference between sitting upright on the surface and upside-down in the air accelerating toward the earth at 2 g's.  To get a position you will need to know the orientation of the accelerometer relative to the local gravity vector and the exact magnitude of the gravity vector so you can null it out.  Otherwise your calculations are going to be showing your accelerometer accelerating toward the center of the earth at 1 g.
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