Hey all –
I'm on my 3rd build with APM 2.6, about a few hundred flights under my belt. So far it's been a dream platform to work on. Done around anything and looking to enter pixhawk this summer.
With my latest build I'm going crazy with a new bug I can't figure out. Also left note on ardupilot forum, but waiting for my post to show and it seems there is more activity here to bug problems.
When I enter alt. hold, the copter rapidly decreases throttle and wants to drop to the ground. Goes from 50% throttle to 10% immediately. Loiter does so as well.
Only setup my usual PIDs, didn't change anything else. (Throttle Mid is around 45%, thats about it.)
I've performed all calibrations, run a good compassmot, reloaded firmware and started from scratch as well. Attached my logs below. Didn't include INT yet, but will run a test to see what vibrations are doing. Don't think I have much.
Running a 500mm quad with 620kv motors, 4s, dragonlink, tarot2d and some fpv gear.
A couple logs from today are attached. Is there anything obvious I'm missing?
Really need help. Thanks so much.
Replies
As jg already ask, is your baro protected against light?
I did a test where i powered up the APM in shadow and faced it than in the direct sunlight. I got a alt reading of 140m, in shadow it was than again 0m!
Honestly I think it was just in need for a hard reset. Sometimes you have to turn things off and on :)
Flies like a diamond now.
Thanks for the help guys.
Things that have led to the same issue in the past on my quads with apm are, not placing the throttle in the center of the stick travel while in ALT or Loiter, light hitting the barometer, and air hitting the barometer. High z vibes can also cause the same issue.
Thanks jg. I've done a few apm builds – not sure why this happened. It's very balanced, the apm is protected and above the props, and there are no vibrations.
I reset the board, calibrated, setup my PIDs and it is solid as a rock. Loiters within 2 feet, alt hold within 2 feet.
Not sure what the gremlin was. : /
Is the throttle in the mid position when doing the Alt Hold? If it is below the mid position, it will surely decrease the altitude.
Wasn't like that. Was almost 0% throttle. It fell out of the sky. After a couple trials, I had it shoot up at 100% throttle.
All of which I had to recover with stability.
Once I reset the board and recalibrated, the throttle acted like it normally does when properly tuned.
Would love to know why. Until then, chalk it up to a gremlin.
Does it fly ok when its cloudy? I had one that on a cloudy day would hold alt ok. But sunny days not. Even if the APM is in a case, it needs black tape over that area on the case, or the foam over the barometer inside the case. It makes a huge difference. Even if your APM is not in the prop wash, there can still be air movement that makes it to the barometer. It does not take much to make it sense incorrectly. The pressure change over a few feet of altitude is very very small.
no help?
A very short test I ran with IMU logs on, attached here – I have my apm on an anti-vibration mount.
Dying to know why she keeps dropping out of the sky. I've done almost an exact similar build, and she flies like a diamond. Not sure what I'm doing wrong. Thanks for the help guys.
2014-06-09 00-24-16_52.log
My tuning:
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