Level automatically adjusting in flight...

I have an odd problem that just baffles me to no end.... I know this is not in the exact correct place, but I have a slight bit of pressure to get the quadcopter to tune-able conditions. I'm in a group working with autonomous vehicles as a project in college, and we changed frames from the older Jdrones frame to a hobbyking SK450, which is really bringing out some odd problems that the larger frames covered up. We have an arducopter APM 1.4, 850KV jdrones motors, 3S 2650 mha lipos, 3DR radio, magnometer, GPS, and a Turnigy 9x. First, we had some major vibration and balance problems, but with 9 years of rc airplane and heli experience, nothing too hard to take care of. Upon takeoff, the quadcopter would tip hard and fast back and too the right. After balancing, the flight characteristics were significantly better. However, we still had problems with back and to the right, but it was different. It was more of an exponential thing, and the quad would start stable, almost perfectly, then gradually move back and to the right, and requires full forward-left control after a while to keep level.

So, I went through the list. I tried leveling, calibrated the ESC's, re-balanced the props, checked the level of the motors, checked the motors for bent shafts, tested every esc and motor individually, checked all the joints, reloaded the firmware, changed version of the firmware, checked the parameters, checked them again, and nothing seems to make sense. Yesterday, I found something out that makes perfect sense and no sense at the same time. I leveled the quad in the mission planner, and flew, and the same behavior still existed, so I landed. I looked at the HUD, and on the same floor, same exact spot, the HUD read 15 degrees down and 15 degrees left. And, after a few seconds, the HUD returned to looking perfectly level. It happens, flying or not, I can manually tilt the quad, to the same effect. This problem seems to persist across all firmware from 2.6 - 2.8.1, so my question is, why does this happen, and how do I fix it? Any help appreciated, this one has me at a real loss.

I set the quad down on the floor, run level from the mission planner, wait for it to finish, everything shows perfectly level, so I arm, then take off. I get about 4-5 seconds of perfectly stabilized flight, until it starts slowly pitching back and to the right. Correcting for this only adds to the problem, until I'm using almost full correction on the sticks. When I land, it shows the offset. It does re-level by itself once I set it down, more of a it gradual and slow return to level over 4-5 seconds. The HUD just kind of slowly returns to level, like with pre-programmed precision, no snapping, just a perfectly smooth return to level. I can also get this effect just by manually tilting the quad and holding it there for about 8-10 seconds, and again, the instant I set it back down, it's 15 degrees off forward and left, and starts to return back to level over 4-5 seconds again.

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Søren Kuula December 4, 2012 at 1:50pm

Hi,

I have not read all of the topic, so forgive me if I suggest something already tried:

I also had an APM1 with serious IMU problems. I suspected hardware damage.

I found the AP_InertialSensor library, there is a .pde / .ino in examples called MPU6000. It does however support Oilpan, by changing a few defines.

I found a sensor input not working.. reflowing it did it for me.

Regards

Soren
Austin Suhler December 4, 2012 at 11:40am

Didn't even get to flying, already had an immediate problem. Tilted the quadcopter on the ground up, then back to level, and then down, and back to level.... and the results are immediate and way too noticeable. I've been doing some soldering around (1-2 feet from) the board, and I know some people have had problems with the boards being dirty and getting false readings..... could this be the case? Here's the log, it's pretty obvious what's wrong right off the bat. Also, above the timestamp on the HUD, what does that percentage mean? I'm not quite sure why it seems to increase.... it's always been at 100% before.

2012-12-04 14-33-20.tlog
Phil Cramer December 4, 2012 at 11:22am

Long shot. Check right rear motor temp and see if it's running hot. It might have a problem. Again, long shot guess.
Christopher Cooper December 2, 2012 at 2:18pm

Just a thought, do you have automatic trim enabled and assigned to channel 7?

The way I see it, if this were the case and channel 7 was always "high" this could lead to what you've described.

See here for auto trim:

http://code.google.com/p/arducopter/wiki/AC2_AutoTrim
Austin Suhler December 2, 2012 at 5:46am

I set the quad down on the floor, run level from the mission planner, wait for it to finish, everything shows perfectly level, so I arm, then take off. I get about 4-5 seconds of perfectly stabilized flight, until it starts slowly pitching back and to the right. Correcting for this only adds to the problem, until I'm using almost full correction on the sticks. When I land, it shows the offset. It does re-level by itself once I set it down, more of a it gradual and slow return to level over 4-5 seconds. The HUD just kind of slowly returns to level, like with pre-programmed precision, no snapping, just a perfectly smooth return to level. I can also get this effect just by manually tilting the quad and holding it there for about 8-10 seconds, and again, the instant I set it back down, it's 15 degrees off forward and left, and starts to return back to level over 4-5 seconds again.
John Dell December 2, 2012 at 4:43am

For clarification, after you level your quad the pitch and roll show level....and then they become offset by 15 degrees while left on its own or do you need to do something to get it to show out of level? Does this happen gradually or instantly? Does it ever go back to level or just stay wrong?

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Level automatically adjusting in flight...

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