QGC shows incorrect heading after Onboard Magnetic Cal

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QGC shows incorrect heading after Onboard Magnetic Cal

Postby johandm_be » Sat Jun 14, 2014 4:01 pm

Hi,

In stalled a DIMU on my AQ board. The firmware is 7.0-EXPR r399 b1758.

I looked up my magnetic inclination (66d 21m) and declination (0d 32m).

I used the AQ tool to convert it to decimal degrees: -66.35 and 0.53 (I reversed the sign on inclination as described in the documentation). I entered these 2 numbers in the Misc. settings, Mounting & environment page. The IMU rotation I kept at zero, because my AQ is mounted with the front EDGE of the PCB forward. I stored the parameters to the permanent memory.

I then performed the Onboard Magnetic Calibration and the TARE calibration. In the QGC log it shows the cal is successful, but when I point the quad to the north, the "primary flight display" in QGC shows a heading of 310 degrees. That is 50 degrees off...

QGC log also shows the settings were saved correctly, however: if I cycle power to the quadcopter, then QGC shows the heading is 068 degrees after I cycled power???

I wonder what is going on?

Here is what the log tab shows in QGC:

(MAV 228) AQ FW ver: 7.0 - EXPR rev399 b1758, HW ver: 6 rev1
(MAV 228) SUCCESS: Executed CMD: 245
(MAV 228) Parameters saved to onboard EPROM.

-> this is when I updated the magnetic inclination & declination

(MAV 228) Calibration complete
(MAV 228) Disarmed
(MAV 228) DIMU: wrote calibration parameters to EEPROM

-> this is after magnetic cal + TARE + store (all with the sticks)

(MAV 228) Radio init
(MAV 228) GPS init
(MAV 228) Nav init
(MAV 228) Command interface init
(MAV 228) GCS: UNABLE TO DECODE MESSAGE NUMBER 23
(MAV 228) Motors init
(MAV 228) Control init
(MAV 228) Control task started
(MAV 228) GPS: trying new baud rate
(MAV 228) RTC set: 2014-06-14 14:50:24 UTC

-> this is after the power cycle.


So I think I have 2 problems:

1) after the calibration, it does not show a correct heading (310 degrees when facing north)
2) after a power cycle, it shows a different heading (068)

Am I doing something wrong? Or is there something wrong with my setup or one of my parts?

Thanks & kind regards,
Johan.
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby kinderkram » Sat Jun 14, 2014 4:33 pm

Hi Johan,

what are your values for ACC & Mag Magnitude after the calibration?
Did you perform the calibration indoors?

Norbert
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby chschmid » Sat Jun 14, 2014 4:33 pm

Hi Johan

The IMU rotation I kept at zero, because my AQ is mounted with the front EDGE of the PCB forward.


Here you find the orientation. http://autoquad.org/wiki/wiki/getting-started/configuring-autoquad-flightcontroller/

Maybe you can post a pict of your craft/AQ mounting.

Cheers
Christof
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby kinderkram » Sat Jun 14, 2014 5:02 pm

Oh yes - Johan was talking about the EDGE, not the CORNER.
So it should have -45deg offset.
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby johandm_be » Sat Jun 14, 2014 5:03 pm

Hi Norbert and Christof,

thanks for the quick replies!

I have included 2 pictures of the mounting, one is fully mounted but then the shield below the GPS covers the view of the AQ board. I included a 2nd picture where the GPS is removed to show the board. The front is indicated on the yellow label.

IMG_4251.JPG
IMG_4251.JPG (152.12 KiB) Viewed 6240 times

IMG_4252.JPG
IMG_4252.JPG (203.62 KiB) Viewed 6240 times


I did find one mistake in my setup: instead of setting "0.53 degrees", I had set 53 degrees for my declination (ouch!)
that has been corrected, and I redid the calibrations. Now it shows a heading of 017 when pointing to the magnetic north.

It's closer, but it is still quite off bearing in mind my declination of 0.53 degrees.

I did calibrate outdoors.
Right now, sitting level on the ground, it reads 9.7 for ACC magnitude and about 1.6 for MAG magnitude.

Thanks and kind regards,
Johan.
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby kinderkram » Sat Jun 14, 2014 5:14 pm

Your Magnitudes are too low. It should be 9.8 for ACC and 2.0 for MAG - especially the mag is way off.

How long did it take to finish the onboard mag calibration?

Norbert
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby johandm_be » Sat Jun 14, 2014 5:31 pm

Hi Norbert,

I did not time it but it was in between one and more minutes. It may be due to the fact that I get really confused on what it is I should do: I rotate the craft over every axis I can image and then I am typically left with the blue LED blinking and I then try whatever I can come up with until the green LED goes to the normal blinking. I wish there was a demo video that shows every orientation you need to hold the craft and rotate, because I wonder if I am systematically missing one axis in my procedure ?

I redid the full calibration again and this time I get a heading of 340 when pointing to magnetic north and 9.7 for ACC and 1.7 for MAG.

Thanks and kind regards,
Johan.
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Location: Belgium

Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby johandm_be » Mon Jun 16, 2014 4:39 pm

Hi,

I am still struggling big time with this. I have redone the MAG calibration numerous times, and I always get inconsistent readings of the heading in the primary flight display.

In fact, I even noticed several times that if I just power cycle the AQ without moving the quad at all, I get a completely different heading number when it comes back online in QGC. I really wonder what is up with that?

When calibrating, I always make sure that I see this in the QGC log to ensure I did all the steps and the calibration parameters were saved:

...
(MAV 228) Starting MAG calibration mode.
(MAV 228) Calibration complete
(MAV 228) Disarmed
(MAV 228) Level calibration complete.
(MAV 228) config: Parameters saved to flash memory.
(MAV 228) DIMU: wrote calibration parameters to EEPROM
...


Still, one time while the craft is pointed to the magnetic north (and I verified that with 2 independent compasses) it may read 017. I then disconnect and reconnect the quad's battery, when AQ comes online again, my heading was showing 025.

Usually it shows 025 or 026 when pointing to the magnetic north. One time (after I was moving it around a bit) it showed 003. I unplugged and replugged its battery and made sure I did not bump the craft doing so. When it came online again, it was showing 026.


When I bought this DIMU, I actually ordered a pair (because I do have 2 AQ's; the one I am using now is a brand new one that I ordered together with the DIMU's). I tried plugging in that other DIMU on this same AQ, and that DIMU is not recognized by AQ at all! When I power it on with that DIMU inserted I just get one red LED on the AQ and nothing else happens. I conclude from that this 2nd DIMU is definately a bad unit.

I still don't know what to think about the first DIMU. I can not get it to show a correct heading after MAG calibration and occasionally it also shows inconsistent headings between power cycles...

Any help or advice would greatly be appreciated.

Thanks and kind regards,
Johan.
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Location: Belgium

Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby SuperSharpShooter » Mon Jun 16, 2014 11:27 pm

The AQ on my hexa is behaving in the same way. For example when it's pointed at a heading of 320 deg, I have watched the indicated heading on the HUD go from 140 deg at startup, up to 230 so far, and it climbs a degree continuously every 1.5 sec. It eventually settled on 280.

I've done the live mag calibration twice and checked that my inclination & declination are set correctly (they're the same as on my other AQ which works perfectly and indicates heading correctly).

I have two batteries mounted on a plate above the AQ board, but I was under the impression that the mags aren't used to maintain the heading in flight any more, so that should be ok?

When I did my mag calibration, both batteries were in place, and I unplugged my gimbal, and taped it so that it couldn't move when I rotated the copter.

I'm quite keen to get this issue sorted too, the hexa flies very sideways when position hold is entered, but straightens itself out after a minute.
-Glenn
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Re: QGC shows incorrect heading after Onboard Magnetic Cal

Postby johandm_be » Mon Jun 16, 2014 11:53 pm

Hi Glenn,

Thank you for this input. It is good to know that the problem I am seeing is not an isolated case.

I was not comfortable taking it out to fly with this problem - after reading your feedback I feel slightly less worried about that.

Kind regards,
Johan.
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