Roll Problem With My New Ugly Pixhawk Octocopter

[baddox]

I'm new to the Pixhawk and Arducopter in general, so I'm wondering if any of you guys have experience with it or APM and help me out. This is my first venture outside of the KK2 world!

I'm working with all stock Arducopter 3.1 settings, octocopter, plus configuration.


It wants to roll to the right. I can only even it out with full left input. The accelerometer is calibrated, and the artificial horizon in Mission Planner displays correctly. All radio channels display correctly in Mission Planner. Motor order and direction was verified via the "motors" command. Prop direction and flight controller orientation have been triple-checked (at least).


Also, I find the throttle to be ridiculously hot. The little bursts at the beginning are a single "notch" in the Taranis' ratcheted throttle stick. When I take off, that's two or three notches, so well below 25% throttle.


Also, the pitch (elevator) is reversed, even though it looked like it was showing up correctly in Mission Planner. That one's an easy fix, but it feels weird.

Here's the video from my maiden indoor test (center yellow prop is the "front"):

https://www.youtube.com/watch?v=dXdoukJW7Zo&feature=youtu.be

 

[Mustang7302]

I would suggest that your APM is 180* out of phase with the front of the copter. If it want to roll heavily in one direction, it is trying to level itself with what it thinks is counter input but is really just exaggerating the issue. This is also supported by your pitch input to craft response being backwards, despite being correct in the configuration utility.

 

[Dumpster Jedi]

I This is also supported by your pitch input to craft response being backwards, despite being correct in the configuration utility.

Is that set from the Tx? I had a similar issue with my quad and discovered that the aileron throw functioned in reverse from what would be the intuitive guess. The monitor function on the KK2.1 verified that the right-left as showing on the Tx was actually left-right as shown on the KK2.1.

I'm still rather new at this so my guesses aren't as educated as some, but it might be worth looking into just to be sure that your stick directions translate properly to the FC.

 

[cranialrectosis]

I think he is suggesting the board is mounted backwards on the copter.

Octo copters have a tendency to be high powered on the throttle. As a quad, this config would probably launch at 50%. As an octo, it is suited to carry a mighty payload which it doesn't appear you have added.

 

[Tritium]

Definitely unstable. Have you been to the Arducopter Wiki or the 3DR forum? I have not yet purchased a Pixhawk but do have a true APM 2 and a 2.1 clone. ESC's calibrated? Your throttle response is very strange (you knew that though).

Thurmond

 

[baddox]

I would suggest that your APM is 180* out of phase with the front of the copter.

I don't think it can be that, since the artificial horizon in Mission Planner displays correctly when I move the octocopter around.

 

[Tritium]

So a copter tilt to the right causes the Artificial horizon to tilt left (downhill right to left)?

Thurmond

 

[baddox]

Yes, just like what you would observe the horizon doing if you were in the aircraft facing forward.

 

[Mustang7302]

Then the issue could is that you have the motors plugged in in the wrong order. I found it odd that the MultiWii (also a Arduino based flight controller) has ports going from the bottom to the top for a ascending order; perhaps you've got motor one where motor eight should be, and so forth.

 

[baddox]

The motors fire up in the order they're supposed to when I do the "motors" command line test.

 

[Tritium]

It sure acts like the sensors do not think it's level even though the artificial horizon thinks it is.
The only thing I can think of that would cause the sensors to accumulate this much error is vibration!

Thurmond