EV3: which compass ?

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EV3: which compass ?

Postby HaWe » 10 Oct 2013, 12:40

hi,
for the EV3: which compass is to recomend? (least noise, least horizontal mounting requirements, highest accuracy)
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Re: EV3: which compass ?

Postby mattallen37 » 10 Oct 2013, 16:03

I don't think there are any compasses designed specifically for the EV3, so you're probably looking at the same options that are available for the NXT. If you want it to work in multiple orientations, you'll need a 3D compass, and another sensor (or sensors) to determine tilt (accelerometer, and maybe also gyro). It would require a fair bit of math to do what it sounds like you want to do. If I was trying to accomplish this, I would attempt it using the dCompass and dIMU.
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Re: EV3: which compass ?

Postby HaWe » 10 Oct 2013, 18:04

actually it would be adequate if the compass just referred to "local" magnetic north (i.e. by a more proper expression, compass north minus local deviation) and showed the heading to it jus like an airoplane compass or a nautic compass does, regardless of the vertical or inclined angle of the local magnetic field lines to the horizonal.
In other words, I would need only the local horizontal part of the magnetic field vector, regardless in which angle the compass is twisted, like as if mounted by a Gimbal (German: kardanische Aufhängung)
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Re: EV3: which compass ?

Postby HaWe » 12 Oct 2013, 08:05

so is there a compass available which has just very little sensor noise and which reliably refers to magnetic north even when it's not real horizontal, e.g., when a robot is climbing hills or the robot moves on an inclined plane?
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Re: EV3: which compass ?

Postby mattallen37 » 12 Oct 2013, 15:22

Not a pre-built solution that I know of, no. The only thing a magnetometer can measure is a magnetic field (or two or three, depending on the number of axis). If you combine a magnetometer with an accelerometer (which measures gravity), a gyroscopic sensor (which measures rate of rotation), and a proper filter, you could potentially get a pretty decent representation of the current heading.

Again, I do not know of any such ready-made systems that are available for the NXT or EV3.
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Re: EV3: which compass ?

Postby mightor » 14 Oct 2013, 05:08

I have not heard of such a device either. However, it is possible to combine the 3 magnetic fields readings from a Dexter Industries compass with that of the IMU. You'll have to do some math but it should work.

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Re: EV3: which compass ?

Postby HaWe » 18 Apr 2014, 08:19

now I just found such a 3rd party compass sensor for outdoors m+e robots and for aviation robots, feat. tilt compensation:
http://www.roboter-teile.de/Oxid/Naviga ... MPS10.html

http://www.roboter-teile.de/Oxid/out/media/cmps10.pdf

(now only nxt and ev3 NXC/C drivers are missing)
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