I wanted to start a conversation around the roll and pitch of Arducopter drifting as you fly.


The reason is I just assembled new hardware and problems that weren't there before have now shown up in a bad way. Flying indoors in a 5ft space I was able to get up to 30° error in roll and around 10-15° in pitch. I was able to control it and it flew perfectly level the whole time, I just had to hold the stick into the corner of the radio. Lading and waiting corrects the issue.


What could cause this. I had been flying an older version of the IMU this whole time. This version has an analogue filter for the gyros where the new hardware has it as an option. You must solder the pads around the gyros to enable them. I was also flying with two slightly tweaked motors giving off a lot of vibration. This could affect the accels. 


My question is: If you have a problem like this, what is the vibration level on your copter, and do you have the filter pads soldered? 


And notice I didn't say "loss of control" or "it didn't fly stable". I had control, and it flew perfectly. It just lost it's reference to the ground and I had to compensate with the stick. Had it been worse than 45° I would have lost control. 

There are three pairs of pads, each with a white outline. (look for GYRO-XY near the relay).

Jani Solders his to enable the filter. I have never flown this board until now. I will solder them to test the filters this week.


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maiden flight today with hexa+ using 23 code on a foxtrap imu. I had none of the pitch/roll drift, just hovering in perfectly calm conditions in stabilise. I did have to hold in some right and forward, so I have a level issue even though it was leveled with a cheap bubble level or an expensive German spirit level. Have always had this level issue even as a completly different quad frame running pirates 527. At least with the old configurator I could tweak the offsets.


I did have the slow yaw oscillations mention above by Robert until I reduced stab yaw P to 0.3.  Left yaw was more responsive than right, but if the stick was held for longer than say half a second , it would not stop without a stab of right yaw. This was quite repeatable and only on left yaw. If it helps, I'll do a short log flight to demonstrate tomorrow

As I mentioned before. If there is just a slight defect in a arm or a engine mount so a engine is not perfectly allignedupwards, it's not possible for the quad/hexa to hover steady. It will drift! This is why using trim should be "allowed".
I agree. As a heli person I prefer trim to autotrim. My frame is new and perfectly true. When I was flying pirates code there was even a difference in trim between stab and acro.

Can Chris or Jason explain why TX trim has to be a no-no. How does the APM code know the neutral position for each channel, as setup only ever asks for the endpoints?

Assuming it does record the neutral position at some point during setup, presumably it must allow one or two counts either side of this to allow for natural error/drift. Why can't this range be increased to allow for trim input to still be detected as 'neutral' ?




will read the offset from your rc equipment.

and that is a constant offset when using the tx trim.

the upper procedure trim_accel will go nuts until your your copter tries to land belly up.

the goal is having a fully leveled copter without tx trim and no hands moving the sticks.


that soldering excercise delivers great results.

the copter is stable when jumping in the air.

have not flown to much - but the stability is back.


i reduced the i term for yaw - that gave nice results with no overshooting.

I just programmed my eurgles ch7. So from the rx I should connect ch7 to the seventh input on the APM?


I just flew a bit. No wind at all ;-) Changed the code and did a new upload.

Tried to keep the quad stable and engage ch7. Nothing really happens. Put it back.

Then trimmed the TX and engaged ch7. Quad tended to drift in different directions.

What I am doing wrong?


I'm attaching two logs, one from before I soldered the pads with stick drift, etc. The other is from this evening, after the soldered gyro pads - and a bit of PID tweaking. I made a very minor change to stab D, increasing just one point and it had a significant effect on stability - much more stable. It was immediately obvious in how the quad handled, much less sensitive and stable. In loiter it is a bit quieter as well, sonar hold working fine, but baro hold still not working at all.


This evening's flights were very stable and no stick drift. On the last flight I hovered in loiter for eight minutes, then took it back to stabilize and flew it around manually, after another 3 minutes of flying around, I tried to hold a stable hover - no problem with just a little bit of right aileron needed to keep it steady - no wind, maybe half a knot occasionally. It really seems very stable now.


Only changes were the gyro pad soldering, motor re-alignment and PID changes described above.


If I change Loiter setting from 1 to 0 will it hold tighter position?


hey jim, thanks for your active responses! it really does inspire me to keep at it after my hugh flipover crash last week which i think was due to a combination of things mentioned here. would you be able to tell me on how to motor align?
Paul, I use a small level on the motor booms to make sure the booms are level, the motors are quite firmly attached to the booms, so I just give the boom a careful twist to get them all level.

sounds easy enough. thanks!


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