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Calculate Earth Referenced Acceletation with BNO055
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Re: Calculate Earth Referenced Acceletation with BNO055

by dkelly on Sun Jul 23, 2017 10:39 pm

gammaburst,

I'm trying out your "earth referenced acceleration" sketch tonight. Looks like it's running great. What do you mean when you say "excludes sensor tilt" (line 36)? Does it mean that if you're not in the X-Y plane that this approach doesn't work, or is less accurate?

I'm guessing, from your code that your XYZ accel output is in the NED reference frame. Earth reference frame, at least to me, could mean a number of things (ECI, ECEF, ENU, NED), so I want to make sure I'm really clear on what you're doing!

Thx!

dkelly
 
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Re: Calculate Earth Referenced Acceletation with BNO055

by gammaburst on Mon Jul 24, 2017 2:57 am

I'm not sure which sketch you're referring to. I have several similar sketches with confusingly different axes arrangements for different purposes. If the sketch is based upon the bunny sketch, then its axes are inconsistent and not defined anywhere that I've found.

My comment "compute earth-referenced acceleration (excludes sensor tilt)" is trying to say that the calculated acceleration vector tells you the acceleration relative to earth frame, and is therefore unaffected by sensor orientation. For example, if you shake the sensor east-west, then you should see activity on only one of the XYZ components, no matter which way the sensor is oriented.

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Re: Calculate Earth Referenced Acceletation with BNO055

by dkelly on Mon Jul 24, 2017 7:49 am

Hi gammaburst,
It was the post from Mar 24th....
Thx again! DK

Re: Calculate Earth Referenced Acceletation with BNO055
by gammaburst on Fri Mar 24, 2017 3:16 am
Hi bugratufan,
That looks like a code snippet from one of my examples.
To transform the BNO's sensor-referenced linear acceleration to an earth-referenced linear acceleration, rotate the BNO's linear acceleration by the conjugate of the BNO's normalized quaternion. That's what my code snippet should do.

dkelly
 
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Re: Calculate Earth Referenced Acceletation with BNO055

by gammaburst on Mon Jul 24, 2017 11:29 am

I see, it's this message and sketch: viewtopic.php?f=45&t=114125#p570484
That code is based upon the bunny sketch, so the axes definitions should match the Adafruit library. I forget which way they point, perhaps ENU.

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Re: Calculate Earth Referenced Acceletation with BNO055

by dkelly on Mon Jul 24, 2017 11:39 am

Thx gammaburst. I'm going to do a run with my Kalman filter that uses GPS measurements, now aided with accelerometer data, and I'm guessing (hoping) it'll be be obvious if it's ENU or NED once I process some data. Thx!

dkelly
 
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Re: Calculate Earth Referenced Acceletation with BNO055

by hichamaziz on Tue Jul 25, 2017 10:31 am

thank you for thread

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