QGC shows incorrect heading after Onboard Magnetic Cal

[johandm_be]

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.

[kinderkram]

Hi Johan,

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

Norbert

[chschmid]

[kinderkram]

Oh yes - Johan was talking about the EDGE, not the CORNER.
So it should have -45deg offset.

[johandm_be]

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 (152.12 KiB) Viewed 22126 times

IMG_4252.JPG (203.62 KiB) Viewed 22126 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.

[kinderkram]

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

[johandm_be]

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.

[johandm_be]

[SuperSharpShooter]

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.

[johandm_be]

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.