Hey all,

 

I'm having some real problems getting my new guy to take off.  This is everything from the jDrones kit (except in the Xaircraft hexa frame), 850Kv motors, 20 Amp ESC's, hexa PDB, 10x45 props, APM1.0.  On takeoff, the copter wants to move to the right, and will not lift (at least at the throttle percentage I'm willing to give it).  At higher throttle, the motors start to vibrate to what seems like a dangerous extent.  This is what I believe is the main problem, but I'm having a lot of trouble figuring out what is going on.  I was hoping the community might be able to chip in on the issue and help me get off the ground.  

 

Here is a link to the above video of the problem:

http://youtu.be/_nj9vihERHU

 

Thanks in advance for any help!

 

Blaine Hoyt

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It's hard to tell in the videos- which way is your APM facing? Do you have the servo connectors pointing exactly toward the back of the hexa?

My RC Pins point away from that little yellow ball.  So I believe the answer to your question is yes.

did you really make sure it was level when you hit the level button doing setup. this is REALLY important. it affects how it flys.

I don't really see a problem here - it's better to get it up faster than to try keeping it in place on the ground - hopping on the ground can cause the copter to overcompensate and even flip.

I think you should do a hand test - hold it firmly(!) in your hand, arm it, and raise a throttle. See how it reacts. If it wobbles it can be just a PID setting problem. If it twitches it can be a PID problem as well or a very bad vibration. How is your board mounted? On this "type" of frame (in my case it was naza F450) the best mount for sensors was by a few blobs of hot glue in corners - foam tape didn't do any good. YMMV.

I'd do this:

1) mount board on hot glue

2) tune Rate_P down (P=0.06, I=0, D=0.1)

3) try again (it will most likely not be flyable - very lazy and "rubbery")

4) tune Rate_P up in 0.01 increments until it starts wobbling again, then decrease slightly - you can try increasing D

5) tune Stab_P up until it starts wobbling (much slower than what Rate_P does), then decrease slightly

And remember that it's pointless to judge anything it does under 0.5 height - really.

Thanks all for the help!  Turns out I was just pussyfooting around the controls and throttle.  As per Jan, I changed up my RATE_P and am seeing better results.  It's still pretty dang tough to fly, so it definitely needs a lot of tuning.  I'll post a video of it here in a little bit with my most recent settings, maybe someone can help me out with that.

The vibration in the props still seems like it might be too much, but I can't figure out what's going on there (tried using multiple different pairs of props, have the correct diameter inserts, etc.).  

Anyway, thanks for all the help!

Blaine

No problem. It will always vibrate slightly at different RPMs, that's what multicopters do. I personally never had to balance props or motors, not even when the prop hit something solid and snapped some material at the end. But in the end it comes out to vibration properties of the frame and some software filtering (aka problem masking) properties :-)

Post a video of how it hovers and we'll likely be able to give you a few hints.

Enjoy

Here's the latest and greatest video:

RATE_P is set to 0.144 I and D settings are 0. STB_P is 4.5 and STP_D is 0.005

 

If I change the P to 0.07 it stops fidgeting enough, but it's definitely still not stable.  Also, when I give it pitch/roll it seems like it is barely responding.

Yeah, Rate_P is too high in the video. If you tune it down you need to increase Stab_P to be able to control it.

Blaine, we are running the same machine; APM1 on XAircraft Hexa with Jdrones Kit!!! And I experience almost the same problems. It never lifts staight-up. Difficult to control. Motor vibration is very bad. Even I balance the prop, upgrade the prop mount, the vibration is still there at high throttle.

The good news is, it's getting better in v.2.5 even with the default (new) PID setting. Reducing rate_p and stab_p a bit help improve stability but still far from flying it hand-free. Hope I will soon find an appropriate PID setting for this thing. 

Anyway, I still cannot solve the vibration problem.... Is it a hardware problem? Motor or frame or else???

I'm back!

So, after adding foam to dampen the vibrations to the APM, most of my issues were resolved, and it flew pretty well...

After not using it for like a month, it now wants to flip over (to the right) when I give it any throttle.  Attached is a pic of the raw sensor readouts at rest, it looks like the Accel X is higher than it should be.  

Is this too high? Also, would this cause the flipping, and if so, how do I fix it?

Let me know if there's any more info you guys need, and thanks in advance,

Blaine Hoyt

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