I have a problem after updating AC to 3.2.1 from 3.1.5.

When in Loiter, the the speed of the motors rev up and down/pulsate quite rapidly. This was working fine when I was using previous versions of arducopter.

I have downloaded the logs, and have looked into accX, accY and accZ. These seems to be inside the range specified in the wiki at arducopter. (Log_vibrations.bin)

Please have a look at the Log.bin, and note the difference between ThrIn and ThrOut when I'm in Loiter mode.


Anyone having any idea what the problem may be?

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Hi Leonard - I think you'll find no-one on this thread can try 3.3 as they are all on APM.

So can we safely say that the issues that they are experiencing on this thread are unique to APM and not Pixhawk ?


I am too is experiencing this problem. Has anyone solve this yet? I used to fly AC 3.2 on bigger quads and flies smooth in all modes. Then I recently purchase the fat phantom shell  425mm from infinity hobby and installed my other APM 2.6 (running AC 3.2 also)  on it. Then started to experience motor pulsing in ALT Hold and other GPS related modes. Please see attached log


Mine was vibrations and some tunning. Solve it.

Thanks. I made sure my vibrations were on the limits. What did you tune, may I ask? Thanks

Try autotune first and them you can do fine tunning, http://diydrones.com/forum/topics/ac-3-1-autotune-support-discussio...

Done that. but will try it again and see if anything change.

Tried to graph my BaroAlt, Dalt and Alt and found out it's not tracking all together.

Here's my vibes

This looks like the classic vibration issue. It looks like it is just ok in stabilize but as soon as you put a PID loop around the accel it blows up.

You may get away with dropping your Thr_Accel_P and I by 50% but vibrations are the cause of the problem. You can add vibration isolation or fix it at the source.

Hi Leonard,

Thanks! I thought it was still on the vibration limits. Pardon my ignorance, but what do you mean by as I put PID loop if I may ask? I strictly followed the wiki regarding vibration dampening using kyosho zeal. Should I use the 3M foam tape instead?

Also is it necessary to not have the gimbal installed while performing autotune? 

Hi Elvin,

What I am saying is the additional accelerations caused by Alt Hold are just enough to mess up the inertial prediction of height and climb rate. It is close to the breaking point before and Alt Hold pushes it over the edge.

Vibration dampening can be a fussy thing to get right, especially on the APM. Make sure there is nothing flopping around that could hit on the frame. Make sure wires connected to the APM are secured and won't flop around too much but leave enough length so they aren't tight. Make sure all screws are tight and your battery is secured hard against the frame.

The best vibration isolation I have found is the latex foam sold by Hobby King with some thin double sided tape (I use carpet tape). I use squares approximately 12mm on the side. This can tear during a crash so make sure you check it if you crash hard.


If you have the gimbal installed during autotune make sure it is powered. If you find the tune isn't good then try without the gimbal.

Elvin:after tunning you need to solve vibrations, don't think that only being under limits, you are ok with vibes, the pixhawk add more vibrations measure I hope for this problem Leonard can clarificate better; I finally changed my hole copter trying component by component that produce vibration including the APM for a Pixhawk but, in case, tired,  I mounted on a tower of isolation systems (not recommended but works for me) I have this  http://www.hobbyking.com/hobbyking/store/__76727__APM_Flight_Contro... and over there, the pads on the four corners that come with the controller, better idea is become with less isolation and add more if you need or change them and test until your copter performed well, I have the two extreme, my other copter, the controller is hard fixed, no isolation and performs nice, 

Thanks Leonard and Cala!

Changed my damping pads to moon gel and got less vibration on the X & Y but not that good on the Z. Checked all wires and any possible components that can transfer vibration thru the APM. Still, the problem exists. Any Idea why the vibrations on the Z axis is not that good compared to the XYÉ

Cala I guess you're right, I too have another APM 2.6 on a 800mm quad and spend less time setting it up and flies great in all modes and I've been flying it for over a year already. Just decided to build a 400 size now and facing this problem. 

Do you guys think I should switch to pixhawk in my case? I guess my APM is not right for my new frame (which is a fat phantom shell 425mm from infinity hobby).

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