Vibration damping techniques

[steve fh]

I think that the people writing the code for the controllers should look to make a "compensation" for the vibrations on the copters, as I think this is what is done on the WKM, NAZA & WKH controllers do,

There is alot to be said for making the software deal with vibration.

My quad would not fly using MeggaP on my AIOP V2 board. Swithched to MultiWii and and selected and changed the frequency filter and it flew well with no twitches with unbalanced props and motors.

I then used the GUI sensor traces to dynamically balance the props and motors and saw more improvement but nothing on the improvement the MultiWii filter.

My main reason for tackling vibration is that it reduces wear and tear on mechanical parts and less fatigue failure.

[teslahed]

Here is my setup with moongel;



There is a nylon M3 bolt holding the camera down on the top of the quad (though a hole in the camera base) which compresses the moongel and holds the camera to the quadcopter. I can still wiggle the camera backwards and forwards a few mms.

The sticky out bit mounted between the 2 base plates has moongel taped above and below it, between it and the wood, again to absorb vibrations. I have also used tape and a piece of double sided foam sticky tape to stick the moongel to the quadcopter here as i don';t trust it to hold without something more than just the gel - the gel is not sticky enough!

I';ve done before and after videos with the moongel - it definitely helps;

Up into the Sunset above Lancaster, UK - before moongel

GOPR0003 - after moongel

[steve fh]

This is how ive mounted mine.
Cut out some copper plated board larger than the FC. Put a nut and bolt in each corner. Then used O-rings to suspend it between the bolts.
Used moongel to fix the board to the quad.

I would think a significant amount of the gain here is that you have more than doubled the mass you are isolating from the main copter frame.

These controller boards are so light that just about any mounting is close to rigid up until the point you get unacceptable support for the board as the heavy mass is acting on the lighter mass.

From an engineering point of view it is far more effective to isolate a low mass that generates vibration (such as motor and prop) from a heavy mass (such as the rest of the frame).  This also has benefits that you are protecting the frame and all components from the fatigue effects of vibration with lifetime and reliability benefits for ESC';s etc

[icedfusion]

The way I mount my boards now is to sandwich a piece of moongel between two pieces of thin double sided sticky foam. I then attach this to a case which the FC of choice sits in. This has worked on APM2.0, various MWC and CC3D. I would not mount my FC';s in any other way.

ice.

[neagron]

thanks for that will give it a try,Marty. :scotland:

[rickp]

This looks very interesting:

   http://www.extremetech.com/extreme/149623-mit-releases-open-source-software-that-reveals-invisible-motion-and-detail-in-video

Be interesting to see if that could show where vibration is occurring on a multi-rotor. Maybe worth uploading some video and giving it a go. See http://videoscope.qrclab.com/.

[rickp]

FWIW - I remounted my APM2.5 on my rctimer quad onto double-height moon-gel pads on the bottom plate. Above the APM i had a foam pad betwee it at the top plate. This seems to work better than my previous methods (foam-sandwich). This has reduced the vibration to this:



On the hexacopter, I';ve put the APM2 onto a copper-plate, and mounted the plate using ear-plugs. Be interesting to see how that compares - though won';t be for a little while as I blew up an ESC last night (don';t ask)...

[teslahed]

I';ve just had a go at making some simple vibration dampers using M3 nylon spacers, spare M3 nylon threaded rod and some silicon fuel line (purchased from a local model shop).

I haven';t tested them in flight yet.

[teslahed]

Until recently i have had ';align gyro gel'; under my sensor boards on my multiwii flight controllers to help absorb vibrations that would otherwise affect the sensors on the board.



I got hold of some moongel which is similar but much softer. It works really well at smoothing out high definition video recorded on GoPros and similar.



I thought i would try the moongel in place of the align gyro gel as it might do a better job at smoothing out the vibrations.

The result was that the quadcopter became totally unflyable. It was oscillating backwards and forwards with feedback wobbles as if i had a bent motor axle or something.

My conclusion is that you can have too much vibration damping and if you soften out the forces acting on the sensors too much they stop working properly.

[Gaza07]

Excellent test Chris I always thought moon gel would be a bit on the soft side 

[kym]

I';m with Gaza -- you have to ...er... go hard.

I have some fpv rc trucks around the place and while the little cameras seemed to be fine mounted plastic to plastic, the handycams and spycams I mounted on them came back a big blur. I tried various foams, gel packs, rubber feet, hard and soft packaging I recycled from various shippers... nothing made much of a dent in the vibes.

Finally I tried some rubber feet from the local $2 store -- the kind you put under kitchen chairs. Big improvement.

I also found that old standby double-sided foam tape -- aka window weather strip -- works v well.

There are the low-freq and high-freq components and it seems too hard and you end up with some high-freq buzzing getting through; but back off that a little and you';re into the middle of a bit of a notch filter.

Now doodling with the Seeker/Locust I see "Ali" from OFM has backed off his el-cheapo design for a Hero mount. Originally it had (in the wording of one bit of paper that came with it) "5 senior rubber mounts".

But on u-tube Ali is disappointed with the lack-of-support the feet give (for one thing, the hourglass grommets are the only thing keeping your little camera from a fall) and ended up suggesting to glue the mount to the airframe with double-sided tape and just wrap the camera in foam inside the carry  basket.

[bunnygirl80]

Hi guys,

My pennies worth. I use this anti-slip gel sheeting. It';s cheaper than moongel and does a good job. It';s also very sticky and ideal under batteries to stop them moving around.

http://www.ebay.co.uk/itm/New-Magic-Sticky-Pad-Non-Anti-Slip-Mat-for-Phone-mp3-GPS-cellpho-PP06-/121086947180?pt=LH_DefaultDomain_3&hash=item1c31582f6c

Stef 

[teslahed]

I';ve just ordered myself a few of those anti slip mats - they look useful.

[teslahed]

Well my anti-slip mats turned up - they look good but i haven';t tried using any yet.

In the mean time i have been trying to balance the motors on my sporan quadcopter. I have used a method stef introduced me to where i';ve built a little motor arm with a speed controller and servo tester that i can use to mount motors one at a time and then check for vibrations using a ';vibrometer'; app on my android smartphone. I used an arm from an old low quality Chinese quadcopter kit that is far too bendy and flexible - it would make for a terrible quadcopter (which is why i didn';t build it) but works great for showing up vibrations on badly balanced motors.



It works quite well.

I use a cable tie wrapped around the motor to check for the light side by moving the cable tie around the motor 90 degrees at a time and then spinning the motor up and down and listening for the noise it makes whilst watching the graphs on the vibrometer app. Once i find the spot where the vibrations seem the least i mark it with a marker pen then take the cable tie off and start putting on little squares of tape. I keep adding tape and then spinning the motor up and down - the vibrations will reduce as i get closer to the perfect amount of tape, then increase again when i had added too much. Once i';ve found the perfect balance i remove the motor from the jig and do the next one.

I';ve not test flown since doing this but my motors definitely seem to be running smoother. Hopefully it will make a difference.

[kym]

Of course there are PTZ mounts and PTZ mounts.
The el cheapo that came with the Seeker/Locust was intended to sit on 5 hourglass-type grommets. One half of the hourglass sits in a hole in the mount; the other in a corresponding hole in the airframe.

But "Ali" at OFM made a little video where he showed how sloppy the mount was. He then suggested just double-sided taping it to the airframe and putting 2 layers of plastic -- hard foam outside and soft foam inside -- immediately around the camera in the basket, and using rubber bands and/or zipties to hold the camera+surrounds in the basket.

He then showed a clip from a Seeker with that mod, and it did seem a lot smoother.

It';s on u-tube somewhere; I';m too lazy and my network link is lousy this time of day.

P.S. I';m also putting rubber under my motors on the Seeker; just neoprene pads meant to stick under chair legs, but with some punched holes for the bolts and any axle that sticks out that side of the motor.

P.P.S. I was trying several motors and have gone back to HobbyKings prop 28 kv 1000 provdrive.
Without the prop holder bolted on they were smooth up to full revs; just sat on the bench without having to be bolted down. With the prop holders there was a bit of buzzing, but nowhere near as bad as the Turnigies kv 1100 I';d experimented with, and the Sunnyskies kv 800 I had great hopes for given how snug the prop holder bolted on and how exactly aligned were the holes; they were by far the worst with a positive growl from the engines if they just sat on the benchtop with high revs.

[hoggdoc]

In my quest to improve vibration damping on my quadcopter I';ve found some (allegedly) better gyro tape;

http://www.ebay.co.uk/itm/160692941621?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Mine';s on it';s way over from Hong Kong so I';ll get to try it out in a couple of weeks...

I have some of this and use it between my Camera and Gimbal.  I still have Jello in Videos, but I am now looking at other areas to reduce the Vibes.

[hoggdoc]

Ive just been having a browse through GLB as you do  and came across these http://www.goodluckbuy.com/m3-anti-vibration-rubber-tube-for-ptz-installation-x4.html
I wonder if they are any good, I didnt think rubber was that good for anti vibes and silicone was better 

[attachimg=1]

I use something similar to these to suspend my Quadframe.com Gimbal from the frame.  I still have a lot of vibes getting through to the camera even when using both the isolators and the gummy blue stuff under the camera.

[Gaza07]

Do you balance your props ?

[hoggdoc]

Looks good - but I';d be worried about the copper shorting the ESC connections, even though there looks to be plenty of clearence...

Love thought and engineering that went into your design, but IMHO it is an over-kill.  Can I ask, did you have problems that were flight controller / vibration linked?  If so did this design fix the issues.

My point is this if you can';t clearly show that a design accomplishes what it was designed to do, what is the point.  Granted I look at this as really cool and really appreciate your efforts, but do it accomplish something.

HD

[Tango21Delta]

Having tried various techniques to reduce the vibrations to the APM 2.5 I have found that once all the normal culprits are taken care of, props, motors, cables etc simple foam ear plugs work really well.
Just cut 5 of them to size with a craft knife blade and fit them to the case with double sided tape. One on each corner and one in the middle of the APM case. Push firmly down to fix the tape, the plugs will distort but will reassert themselves after a couple of minutes. At £1.59 for 10 it makes a cheap but efficient low tech alternative.

[smg id=247]

[hoggdoc]

Here is my setup with moongel;



There is a nylon M3 bolt holding the camera down on the top of the quad (though a hole in the camera base) which compresses the moongel and holds the camera to the quadcopter. I can still wiggle the camera backwards and forwards a few mms.

The sticky out bit mounted between the 2 base plates has moongel taped above and below it, between it and the wood, again to absorb vibrations. I have also used tape and a piece of double sided foam sticky tape to stick the moongel to the quadcopter here as i don';t trust it to hold without something more than just the gel - the gel is not sticky enough!

I';ve done before and after videos with the moongel - it definitely helps;

Up into the Sunset above Lancaster, UK - before moongel

GOPR0003 - after moongel

I have tried the moon gel on my Hexa, still not getting g rid of the Jello effect. Dude what is that on your head?

[teslahed]

I have tried the moon gel on my Hexa, still not getting g rid of the Jello effect. Dude what is that on your head?

FPV helmet - details in the FPV thread;

http://www.multi-rotor.co.uk/index.php?topic=1738.0

If you can';t afford Fatsharks building some kind of head mounted screen with a sun shield is a must.

[Biffa]

If you can';t afford Fatsharks building some kind of head mounted screen with a sun shield is a must.

Very few people can carry it off Chris and make it look good, you do though and Gok would be proud

[burgerman]

I am always fascinated when I see 1001 anti vibration cures. I decided that instead of trying to cure the vibes I would just get rid of the vibration. Then no need for any of that stuff.

So I properly balance props. And motors. And my GoPro is stuck to my TBS Disco with plain old servo tape. And even at 1080p in super bright sun, no jello and as sharp as can be.  You just need to learn to balance props. I use 9 or 10 inch props, various makes, and the quad is heavy. Never have any image quality issues.

Here';s a short 1080 high quality vid. It will need to be downloaded to desktop to play, as its 60fps.

http://www.wheelchairdriver.com/gopro/shapes-1080.mp4  Gyro gain too high, but no jello and simpsons sky!

Also if anyone is interested in way more range: http://www.wheelchairdriver.com/12x.htm 

You don';t need a 12x for this to work...
This is super neat, and works very reliably. And I get at least 4x the range if not more. And its better through houses and trees too. Makes you feel far less worried.

[rsmith21]

Have a look at this http://www.multi-rotor.co.uk/index.php?topic=4447.msg36224#msg36224

[burgerman]

Well all I do is rough balance the prop. Fit it to the motor on the quad. Then connect a spare speed controller, and slowly ramp up the rpm till you feel the vibes at the "worst" with your fingers on the little plastic part that hangs down to land on.

Then I sand, or add varnish (or tiny bits of insulation tape temporarily) to get the BLADE balance as good as poss. It will still vibrate as this only sorts out the heavy blade. It also needs side to side balance.

Here I stick tiny bits of tape to motor can and re test. If adding weight makes it worse, stick it the other side? Better? Try more or less? Better? Keep going until there is NO vibration detectable with your fingers at this worst case RPM. This is usually about 1/4 throttle.

If your fingers are not sensitive enough, stick a lolly pop stick to the landing plate and have the bottom of this in a glass of water. That shows balance better than any laser pointer.

When you get this right, there really is no need for any fancy anti vibe rubbish, and its all free. 

More importantly, it FLIES better. That controller sees all those vibes and does "jello" too with your stability... And it SOUNDS smoother and you just know its right.   

Listen to the motors in that vid below. Remember this is solidly mounted on that type of tape that car number plates are stuck on with...  Its better still with gyro tape. But I do this to check balance.

After you do this a few times it becomes easy and quick.
_____________

Here';s a short 1080 high quality vid. It will need to be downloaded to desktop to play, as its 60fps. There is a tiny frame jump now and again - windows movie maker frame rate mismatch, not jello!)

http://www.wheelchairdriver.com/gopro/shapes-1080.mp4  Gyro gain too high, but no jello and simpsons sky!

Also if anyone is interested in 4x plus better range on any 2.4 gear: http://www.wheelchairdriver.com/12x.htm 

[amicu1]

This is how I installed my gimbal. I get no jello.

http://youtu.be/lMamQp7_B5A

[doofer]

You can use Tattoo Gun Grommets (Donut and Nipple type) to help combat vibration, they have a 3mm (M3) hole and are dirt cheap (100 for a couple of quid delivered), all sorts of colours and even available in different softness/hardness if you search a bit for them, get them on Amazon and eBay...

http://www.ebay.co.uk/itm/like/360767425185?lpid=83&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=83&ff19=0

Self Amalgamating tape as used on Sat Dishes is a good cheap dampener too but will cure and eventually harden if exposed to UV.

[Toledodave]

I also had issues with my FC due to hard mounting and too many vibrations led to inaccurate accelerometer readings. So I suspended my FC with small rubber bands. Works like a champ now.

[nub]

hmmm did u try o rings on pillars?