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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Thanks for confirming that original 3dr APM also has the same issue, anyone else with a original 3dr APM having the same issue?

It's easy to knock off cheap means poor hardware. I actually find the micro APM to be innovative, it's really small. The micro osd and telemetry is also small and works.

I also saw a thread on the pixhawk an original one suffering from similar issues. My cheap clone hk pilot32 works fine on 3.2 and 3.2.1

I will check my vibration logs, but my APM sits on a top deck that is isolated by dampening balls. The APM is attached by a thick but sturdy foam tape. It also flies very well on stabilize mode, so I am doubtful it's the IMU. Does stabilize rely solely on the IMU?
For the record I have the same issue in both Alt hold and Loiter. Haven't tried with 3.1.5 yet.

It's help alot. Is someone  reported it on buglist?

From reading about the issue it seems to be related to 3.2.1 beeing a lot more sensitive to vibration. Not sure if that is a conclusion everyone woul agree with and I'm not sure if that is a bug either. Hopefully some developer is looking at it because the new flight modes are quite neat. It is not possible to be 100% vibration free.

i definitely agree with that...cause I have 3.2.1 on another copter that doesnt have as much vibration and it works fine...so its that 3.2.1 is more sensitive to vibration than 3.1.5 for sure....

Could you do IMU log and post what maximum vibration level do you have on copter? 

Methodics described here: http://copter.ardupilot.com/wiki/initial-setup/assembly-instruction...

I have noticed that my quad tends to lose altitude when moving forward fast in AltHolt and Loiter. I always put this down to some aerodynamic effect, but should this actually be happening? Loiter/AltHolt in hover seems ok. Never tried 3.1.5 - started on 3.2.

Hi guys,

We can only help if we have good data logs to look at. So far only Rolf has posted logs.  I had a look at them, and can't see much. His vibration levels do seem fine.  For the short segments he's in Loiter, the motors are clearly pulsing.  There is a negative correlation between climb rate and throttle output, but impossible to say if this is cause or effect. The logging resolution is not high enough to see which happens first.

I do notice that his Alt Hold PIDS are exactly the default settings.  These might need to be tuned.

The talk of "bugs" is a bit premature.  Keep in mind, we have over 10,000 users, and there are only a handful of people complaining of a problem.

Is this only happening on APM-class hardware?  Or Pixhawk as well?

I agree it's too early to call it a bug but it is an issue at least some have.
Problem for me with getting logs except the weather is that the pulsing is so bad it's hard not to crash (I'm still waiting for spare parts from my last flight) beeing sort of a noob pilot. I deleted my logs from my last crash by mistake while trying to figure out what was wrong and configuring everything again. If it's fine again with 3.1.5 I may give it a try when getting a bit more confident and prepared for it to go wrong.
It would for sure be nice to hear some success stories as well :)
Mine is an APM by the way.

Hardly going to be a handful of people Rob, I have 3 APM's doing this with vibration isolation platforms. A 330mm quad, a 525mm quad (just retired this frame and now in a H- quad, same problem) and a 680mm hex. None of these had issues with old firmwares. I have a time issue at present to spend looking into tuning and pids, it may be simply fixed, will definately post details when I've the chance to look further on.

Hi Rob,

Thanks for posting.  I will try to post a log after 2 weeks, going away and using my quads.  I think I can help a bit as I got both APM and Pixhawk class FC.  Here is what happened to me.

I have a V550 (TBS Discovery Clone), using HK Pilot32 (Pixhawk clone).  When I bought a HK APM micro set I decided to replace the pilot32, as pilot32 was big and the APM micro will enable me to put the battery inside the frame.  V550 with HK Pilot32 runs very well from 3.1.4 -> 3.2

After replacement of APM micro with 3.2.1 on the V550, I found the alt hold and motors where hunting down a lot.  I thought it was due to barometer not being covered properly.  I tried 4 different materials/ways to cover the baro and I was able to make it better, but not good.  I decided to lower the throttle acceleration, which made the quad sluggish.  However this did not cure it, even after several attempts of manual tune.  I decided to put the Pilot32 back, upgraded to 3.2.1 and the V550 is back to it's very stable and crazy fast response nature.

Here is a post when I was attempting to use the APM on the V550, before I decided to put the Pilot32 back.  There is some data flash logs link on that post.


I then built a new frame H600 (QAV 550 clone) and used the APM micro on it.  With AUW 1.3kg which means I am at 50% power for hover.  It ran really very very well.  So I just thought, maybe my V550 is not as stable.  The H600, has a top deck that is floated by rubber balls.  The APM also sits on a thick double sided foam tape.  

240fps proof with APM 3.2.1 the H600 is very stable alt hold


After being happy with the bare frame I decided to add payload on it (gimbal, fpv, etc.).  This moved the AUW from 1.3kg to about 1.6kg.  To my surprise the issue I saw on the V550 manifested on the H600 as well.  The altitude hold was very sketchy, the motors started to pulsate as well.  I had a few very hard landings, only way to keep in holding altitude is to use stabilise mode which also makes the motor smooth.  This is the only time I looked at the dataflash logs, which is a cool feature of the APM.  Actually its only the time I downloaded the Pilot32 as well, and showed me some interesting stuff.  Anyway I can't see much in terms of the barometer, aside from the fact it kinda over compensates for things.  I even tried to put the hover to 65% which is closer what is needed for the heavier AUW, this made it worse.

I saw this post, then decided to downgrade to 3.1.5 and the H600 flew well and stable.  The battery life was a bit shorter than I expected, but it was stable.  I had to abort my H600 build and get my trusty F450 with Naza back online, as I was going away and would want to have some good video footage.

In summary it doesn't seem to affect Pixhawk class hardware, only APM in my case.  Also it only manifested when I moved the AUW beyond the 50% hover on 3.2.1, and instantly fixed by downgrade to 3.1.5.  After I come back I will rebuild the H600 and get some logs and see what the vibration is like for both 3.1.5 and 3.2.1.

Again thanks.

Yes, strangely I noticed the problem wildly accentuated by increasing AUW on my h-quad, doesn't correlate to 50% power with mine though as this model is very over-powered.


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