Hi Folks,
A few Weeks ago i switched from dji naza to a 3dr pixhawk controller. Sadly I cant get my quad to fly. Its a TBS Discovery with longer arms and 2814er Motors. The pixhawk is Positioned in the place that is normally for the dji naza. In the upper frame the gps module is right above the pixhawk. I also habe telemetry and minimosd mounted and all functional. Die all the basic setup and calibration, compass accel and so on. On my first flight trying to take oft in stabilize the quad is drifting to the right heavily. And in general its flight characteristics are horrible. I had GPS 3D lock and thought maybe loiter will hold it a little steady in its Position but after switching to loiter the copter immediately lifted up straight into the sky and off to the right.... It was out of my view within seconds and crashed into a field a few 100 meters away. I could localize it after quite a while and thankfully it only had minor damages. Then after repairing everything today i gave it anothet try. Again calibratet everything and took off in stabilize. This time it tried to move forward and i had a hard time keeping it steady hovering. Again GPS 3d lock and everything i tried alt hold mode and it took off into the sky again, this time i was able to rescue it with switching back into stabilize. Then loiter, exactly the same behavior. Whats wrong with my setup? I cant get it to at least hover steady or hold its altitude...
Any help is really appreciated!
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Replies
Ben, starting with any DJI autopilot is not a good ideea. It's an extremely beginner-friendly system, that will actually teach one to gude the flying machine, not to fly it.
The GPS and Simple/Supersimple modes (equivalent to Naza IOC) will not save the day. You will have to tune your Pixhawk to the TBS. Given that you went with 350-ish watts 2814 motors instead of the usual 150 watts 2216, means your bird is overpowered and at half-throttle, which ArduCopter takes as granted for hover, your TBS will climb.
For all your problems, there are procedures and parameters to adjust. The accelerometer calibration is best done with a spirit level on the frame. I use a $5 photo double-unit, the kind that can be mounted in the camera light shoe. Then, first lift is for saving trims. Wiki: http://copter.ardupilot.com/wiki/autotrim/#Save_Trim
Then you'll have to adjust THR_MID. Mine, on a dead-cat with 2814/710kV on 4S and 11x5 E-Props is at 428. Yours can be lower, depending on setup and weight. Once you figured out THR_MID, you'll have to check Alt-Hold and see if it hovers at altitude. If it bobs, lower your Throttle Accel parameters a bit. P and I. For my bird, the defaults of 1.5 and 0.75 were too high. 1.2 and 0.6 are closer to mark.
Once you have your Alt-Hold working, get a fresh LiPo and do the Autotune. Wiki: http://copter.ardupilot.com/wiki/autotune/
Even after autotune, your bird won't fly perfect. If you look at Rate_P and Rate_I in both pitch and roll, you'll see identical values. That's the software "best guess", and it's acceptable but not perfect. You'll have to manually tune each P and I to perfection. You can skip this fine-tuning and get straight into loiter, and your bird will stay glued in the spot, but you'll see that if for instance you apply yaw, it will bank, sway a bit and hunt back for the position. Naza does this all the time, so you may find acceptable, but I once had a hexa spin around its center for a full minute (APM 2.0 AC 2.7) so I know it's possible and i like to achieve that level of tuning whenever possible.
Good luck!
Thanks for the heads up, attached the files I hope these are the correct ones?
Both flights I did today, logging was set to almost everything.
2014-05-18 15-40-57.log
2014-05-18 15-10-55.log
@Ben,
Providing tlogs and/or data logs of your TBS's performance with the Pixhawk will greatly improve the ability of members to troubleshoot your issues.
Regards,
TCIII Admin