Inav: Problem with horizon drift.

[marbalon]

My friend use iNav 1.7.1 in a 3.5M glider. When he make a circles in thermals he get a huge drift in angles.

Situation is always the same. When he hold roll for a long time IMU roll angle calculation have gets huge drift and think that it is leveled....

The best if you see that movie:
OSD time:
23:00 - 24:08 - circles with roll stick
24:09 - 24:39 - circles without roll input, IMU "think" that plane is leveled
24:40 - roll stick in opposite side and big horizon error

https://www.youtube.com/watch?v=e3H8lEJbgv4

Like you see on the video this is without motor so it is not because of motor noisy... The same situation is for pitch, sometimes he hold Pitch down a little when make a circles and when release model stayed pitch up.

Is there any parameters to tune to avoid this situation ? Filters, ACC weight in calculations ?

Sensor is MPU6000 over SPI.

Any suggestions?

[oleost]

Share blackbox log and cli dump

[wiesiekkr]

Below you will find the cli dump, while the video will be tomorrow :)
dump1.7.1.txt

[Redshifft]

From description it's radio drift or FC sensor drift or I term pumping up - With a little imagination you could test this on the bench quite easily, also test it in passthrough

[wiesiekkr]

I flew between trees in acro mode and pass and everything was fine :)
This is not a drift radio signal

[rb1205]

I recently (after version 1.7) had this issue myself. I partially fixed it by doing a new accelerometer calibration as explained in the wiki. I verified in the CLI that the relevant parameters changed by a noticeable margin, and a second calibration confirmed them with a good approximation. I say partially because I keep on experiencing some drift that I didn't notice before, but given that the issue (and the firmware upgrade) arised after a crash I'm not sure if it's due to software or hardware issues.

Did your friend experience a crash previous to the issue? Does anyone know if a MEMS accelerometer can change its characteristics (but keep working) following a moderate shock?

[digitalentity]

We certainly have issues with accelerometers on our boards. Their characteristics change with temperature and we don't compensate for it. I've also seen accelerometers killed by moderate crashes.

[wiesiekkr]

In my case, it is not drifting due to temperature. I never had this model of any accident that could affect my work ACC
Shortcut of my settings:
set acc_hardware = MPU6000
set acc_lpf_hz = 15
set acczero_x = 114
set acczero_y = 23
set acczero_z = -286
set accgain_x = 4063
set accgain_y = 4082
set accgain_z = 4062

[digitalentity]

@wiesiekkr Ok, this might be something https://github.com/iNavFlight/inav/pull/1481 is going to fix. It was not tested yet, so caution is advised.

[wiesiekkr]

Promised log file:
https://drive.google.com/file/d/0B3GW08HpYYLJek1qTnJrUk52Tm8/view?usp=sharing

[oleost]

@DigitalEntity had a chance to look at log?

[digitalentity]

@oleost @wiesiekkr looks like the problem that is unsolvable without additional external reference (like GPS). In a proper balanced turn accelerometer reads 1G, but in a wrong direction. Basically, plane indeed thinks it's flying level, while it's in a balanced turn.

I'm going to further develop and test #1481 once I get home

[Dronek]

Situation is always the same. When he hold roll for a long time IMU roll angle calculation have gets huge drift and think that it is leveled....

I can confirm this drift on my wing as well. It's enough to do a constant roll turn for a few seconds to get a slanted AHI in the OSD in leveled flight. Turning the other direction for a few seconds gets AHI back to level. Meanwhile I calibrated the ACC several times with quite similar results in terms of values.

Also, I don't remember having this issue with 1.6.x versions on identical hardware.

Will try to reproduce this behavior in a bench test.

[digitalentity]

I'm moving this issue to 1.9. The problem related to OSD updates is fixed, the problem with making longish banked turns remains, but it will have to wait a bit.

[wiesiekkr]

Hello,
something going on in the topic?
When I flying a glider it is really very annoying :(
Below is a movie from the flight.
INAV 2.2.0

BR
Wiesiek

http://youtu.be/nRl5xqnDpMQ

Edit
in attachment my diff file
drewniak 2.2.0 .txt

[marbalon]

Btw. Wiesiekkr recalibrated ACC, and still have a problem. It is quite danger because when you got failsafe when IMU goes creazy you have big chance to see your plain will make something not expectect...

[lgojniczek]

I have the same issue as @wiesiekkr has, and it is very annoying too. My horizon drifts in pitch axis after 2 or more circles.

[wiesiekkr]

Hello, Horizon Drift Fixed - probably :)
I did only two flights, but everything looks promising.
I entered the suggested value in cli : imu_acc_ignore_rate = 10
Below I'm sending you a link to the movie

https://www.youtube.com/watch?v=xfZFMtaLGnA&feature=youtu.be

BR
Wiesiek

[digitalentity]

Thanks for sharing your experience!
This was not a "fix", rather a "workaround", but at least it's something that works.

I'll close this issue now.