Artificial Horizon is acting strange

[jimmaplesong]

Hey paede, I think it's working correctly too. I don't think you'll find any other AHI that behaves any better.

The reason its moving is because the plane _is_ moving. The AHI is overreacting because the plane is pointing straight up. When you're pointing straight up, even a few degrees of movement can have you pointing from north to south. I used to work on magnetic tracking systems in aerospace, and the problem is sometimes called 'gimbal lock.' The math represents the 3d orientation read from the accelerometers as Euler ( Oiler) angles, Azimuth, Elevation and Roll. When the plane is pointing up, your elevation reaches 90 degrees, and now your azimuth degree of freedom and your roll degree of freedom are nearly parallel. So any tiny change in orientation shows up as a change in roll in the AHI.

Even if the math in the AHI is done with quaternions, which represent orientation with four numbers, which are a hypercomplex number... you don't have any problems with math around the elevation approaches 90 orientation... the visual representation still just extracts the roll...

The day that I see a good AHI, that really follows the horizon as the horizon is represented in the camera (it would have to be configurable.) and you don't see the horizon in the OSD when you don't see it in the camera... then I'll buy one. I've only seen one OSD in a FPV ground recording ever that wouldn't just be a maddening distraction for me. (Of course my opinion will change next time I'm in fog... and I'll be thrilled to have any cue to keep me upright!)

[jimmaplesong]

What do you think Eagletree? Can you just hide the AHI when elevation is over 50 degrees?

[GregSilver]

The ahi drifts. It's not working correctly. It corrects itself after a few seconds. It's most noticble at landing.

[paede]

The ahi drifts. It's not working correctly. It corrects itself after a few seconds. It's most noticble at landing.

That is what I think is not good. But mabe the ahi is not fast enough ...
... I have changed the postition of the guardian and will report how it works now ...

thanks for your ansers
paede

[scallopking]

...

[paede]

I don't use guardian anymore, since I have a EZUHF. I also changed the wiring to steer the servo and motor directly from the ez-receiver.
Because I have RSSI now I feel much more confident and do not need a RTH-System anymore.

[Zeeflyboy]

Not an issue for your now, but here's my take...

The problem is that you are expecting the AHI to stay on the horizon. The AHI isn't actually calibrated to the horizon, it's calibrated to whatever datum you set as "level flight". As you pitch up or down, the flight path vector (okay, not a really vector, but it looks like one - the airplane symbol in the middle) shows deflection away from this level datum. This is not necessarily in a linear relationship with the actual horizon you see on the video.

That explains why sometimes when pitching down the AHI appears above the horizon and when pitching up it appears below the actual horizon. Really you need to imagine markings of degrees between the vector and the ahi showing degrees of aircraft pitch (like a real ahi), because this is what it's actually telling you. It is not telling you where the actual horizon is...

Hope that made some sense