Vibration Measurements on the APM

[rickp]

For those of you with an APM with logging, here';s a quick guide on how to log your vibrations.

The first thing is to turn on RAW logs. These are quite verbose, so I';d turn ';em off once you';re done.

• Connect up the APM to your PC
• Start Mission Planner, but do not connect
• Select Terminal
• In the window, type "log" and then "enable raw"

Now go for a quick test flight outside of the ground effect. Doesn';t need to be long, 30seconds is fine. Land and disarm to ensure the data is saved. Now extract the logs:

• Connect the APM to your PC
• Start Mission Planner, but do not connect
• Select Terminal
• Click ';Download Logs';
• Select the log (normally the latest log or select all) and download it - this can take a while
• Once downloaded, select ';Browse logs'; and load the one you just downloaded

You should now have the log viewer window up. Scroll down the log until you find a line that starts RAW. Scroll across until you find the accelerometer columns, and select ';graph this'; for each direction and see a graph like the one attached.

Reasonable values are +5 to -5 for x and y, and -5 to -15 for z - though I';d try and do better if you can as it will improve the flight characteristics.

You can now turn off RAW logging by following the instructions above but putting ';disable raw';.

I';ll try and do a screen cast after Easter to it';ll be easier to follow...

[neagron]

       Very good post Rick,thank you,Marty.    :scotland:

[benchmark]

Thanks for the detailed explanation.

Now i know what i will be doing tomorrow .

I am happy we have APM experts on the forum. 

[benchmark]

I have moved my APM 2.5 from the tricopter unto a DJI F450 flamewheel quad frame, Tricopters are just not for me

It has helped as great deal with the compass deviation problems. Now my compass only deviates 1-2 degrees when i throttle up the motors .
My craft still deviates a little bit to the left on forward motion even though i have entered the correct declination.

As regards the vibration RAW file graphs , i just did the above recommended and i fall within the +5 to -5 range except for a couple of spikes on the Z axis.

here is a screenshot

[rickp]

As regards the vibration RAW file graphs , i just did the above recommended and i fall within the +5 to -5 range except for a couple of spikes on the Z axis.

Looking good! Spikes wouldn';t worry me too much. I';ve seen an issue a number of times where the download loses sync and gets data into the wrong columns. Probably happens to me as I';m running Mission Planner in a VM on my mac.

Also, you';ll get spikes on a ';firm'; landing

I';ve just remounted my Hexa';s APM onto a gel on a copper plate, which is in turn mounted using ear plugs. Pretty pleased with the results after a quick test flight this evening, with new rc-timer carbon fibre props. Feels really locked in, probably needs dialing back a little bit...

[benchmark]

I just did a new RAW vibration check, i do not think that its that bad is it?
I am running 1.2.9b firmware with MP 1.2.40

[attachimg=1]

[rickp]

Looks great :)

[Gaza07]

Here';s a capture of mine showing from take off to landing I think the big bump is the landing followed by a rock on the skids 
My Apm is only mounted on thin double sided sticky foam tape so the results probably arent to bad 

[attach=1]

[optiplex]

heres my graph today, finally can measure the vibrations with the new apm board
Green is without a nice foam i found, called here in israel "miracle foam" and red is with the foam
the green is actually with the Kyosho Zeal ... expensive and dont do the job

[DarrenG]

Just followed this guide to grab some raw log data and, looking at the graph, I have some work to do in this area!  Might explain my issues with Alt Hold and Loiter where my quad starts climbing.

Currently the APM is mounted on a hard foam bed with the entire platform mounted on 4 rubber stand-offs. Am I best binning the foam and trying a gel pad that i have or combining the two?  Haven';t balanced the props yet as the balancer has gone AWOL in the post.

[firey1]

thought i would join the club
my apm is mounted on a old heli blade holder double sided taped

good loiter and running V3 rc2

[titeuf007]

how does it possible to check compass noisy??

[rickp]

More vibration reduction - on my reptile, I have the APM mounted onto small pieces of double-layed moongel at each corner, and the whole thing held down with a velcro strap to the bottom board. This gives really great performance!



Bit of a bouncy landing (oops) - but the rest looks rock solid

[Gaza07]

That is a good result I think I might mount mine differently now as its only on double sided sticky foam tape and the vibes are deff getting to it 

[rickp]

Gaza - yes, I was pleasantly surprised as to how good it was. On the hexacopter, I had to resort to a metal plate to give it some mass - but its still not as good as the reptile. In fact, looking at the last log - the hexacopter looks a bit marginal, but it flies superbly so not changing anything yet!



The climbouts at the end were great fun - that thing has so much power

[pendragon6667]

This is my graph my apm 2.5 is in a 3dr plastic case mounted on a copper faced pcb board with zeal type gel which in turn is mounted on an o ring supended boad with align gyro gel on this board is also my receiver and 3dr radio for extra weight. The o rings are on metal 20mm upstands, all this is on an sk450 quad. What do you think guys

[Hands0n]

Coming really late to this party  ::)  Here';s mine, mounted with some double-sided foam pad supposedly made for FCs and sold all over the place.  It looks marginal compared to some of the better results on here. Something to work towards with some different materials.

[Raf]

My Vibes after mounting APM on Omnimac APM Mount V1.5
I';m happy with results 

[attach=1] [attach=2]

[Hands0n]

An awesome result there Raf.  That Omnimac APM mount is certainly doing the trick.  Nice low vibes.

[HowDoIfly]

What he ^ said, very nice low vibes.

[dirtyharry]

foam ear plugs with the tops cut off and glued down with evostick.
works amazingly well

The little vero board has a 4 way dil switch so I can isolate the esc';s and balance each prop/motor/hub assembly as one unit  ( feel vibes by hand) . Also lets me filter 2 esc becs to run the flight controller.

[arnonel]

Anyone used steel rope trick for vibration damping? Any suggestions on thickness required or where to buy?

Sent from my Nexus 5 using Tapatalk

[guest2350]

Anyone used steel rope trick for vibration damping? Any suggestions on thickness required or where to buy?

Sent from my Nexus 5 using Tapatalk

I bought a metre of it from b&q a few weeks back for less than a quid!
About 1-2mm I think would be good but to get a good mount takes up space with this method IMO.

[Desmoboy]

Hi Guys

This is not to question the values for good performance but where do they come from, Are they objective or subjective ?

I have X & Y values of less than 3 but 10 for Z.

Regards
keith

[Hands0n]

Hi Keith

The values are handed down from the Arducopter developers.  A fundamental change was introduced in Arducopter 3.1 (I think it was, it may have been 3.0) that used the accelerometers to aid Alt Hold in addition to the Barometer. It meant that much finer control was possible by being able to detect [particulary] any Z movement that would indicate the altitude varying, or beginning to vary. 

So, with that sensitivity came a need to eliminate as much vibration reaching the Flight Controller as possible.  The developers, knowing their particular algorithms for measuring movement, have defined the boundaries that should be met.

Edit: Here';s some most recent info in a bug and a link URL that shows importance of getting the vibration management right: https://github.com/diydrones/ardupilot/issues/1009#issuecomment-50440571

Here';s the story - read the comments also - Z is heavily implicated in the fly away response: http://diydrones.com/forum/topics/fly-away-please-help-me-figure-out-why

Anecdote:
My own personal experience of this is of a total loss fly away one late night. I was fitting an APM into a 450 quad that previously had a MultiWii Pro FC.  I knew about the vibration elimination requirements but still nipped out into the garden for a quick test hover.  It was reasonably okay at first. Then, for some stupid reason, I flipped Alt Hold on, the quad shimmied, the quad shammied, and then the quad sped off vertically into the night sky at full power never to be seen again.   

Since then I have built several APM-based multi-rotors and have paid particular attention to running IMU logging to measure vibration before attempting any auto-assist modes other than Stabilise. Exactly as suggested in the Arducopter wiki.

HTH

[Desmoboy]

Hi
Thanks for the quick reply, i have read those links and am encouraged by the fact that the Pixhawk processor is apparently  less susceptible to this issue.

Happy that the values come from the developers, that';s good enough for me !

The mystery to me is why the  Z limit is higher than the X or Y .

[Desmoboy]

This is my output

[Hands0n]

My thinking is that Z vibration is inevitable given the entire physics of multi-rotor flight. So while using Z movement detection to help smooth out altitude hold the developers have had to allow for a higher minimum amount, beyond which the auto correction is applied. Hysteresis I believe it is called.

I can';t view your chart from here. Will have a look next time I';m on a big screen ::)

Sent from my Nexus 5 using Tapatalk

[Desmoboy]

Either way i';m quite encouraged, i had thought that because my Z was so large especially compared to the other 2 that i had a serious issue to overcome.

I had not initially seen that the Z value was acceptable as that level   and everyone else';s is very similar anyway.

[Hands0n]

Have you seen the Arducopter wiki page on this subject? It is here: http://copter.ardupilot.com/wiki/ac_measuringvibration/

The suggested Z range is -15 to -5 which yours is well within - in fact your Z vibes are almost nonexistent!  Thats rather awesome really   

Arducopter X, Y and Z vibration limits
[attach=1]