Quadcopter shaking

[mateusvuccaru]

Hi, i've just finished the setup and calibration of my multiwii 2 quadcopter.
When i put it to fly, i noticed it shakes a lot, but its correctly calibrated through multiwii conf.
Just look at the video and see what happens:
http://www.youtube.com/watch?v=Akm20OAR ... e=youtu.be
[youtube]http://www.youtube.com/watch?v=Akm20OAR4JY[/youtube]

[scrat]

Hi, i've just finished the setup and calibration of my multiwii 2 quadcopter.
When i put it to fly, i noticed it shakes a lot, but its correctly calibrated through multiwii conf.
Just look at the video and see what happens:
http://www.youtube.com/watch?v=Akm20OAR ... e=youtu.be
[youtube]http://www.youtube.com/watch?v=Akm20OAR4JY[/youtube]

First of all you must get rid of the vibrations. Then apply 42Hz LPF filter and lower your PID's.

[Andy7]

Nice landing gear!

I wonder if it might help the centre of gravity a little if the battery was mounted under the quad rather than on top?

[mateusvuccaru]

Hi, i've just finished the setup and calibration of my multiwii 2 quadcopter.
When i put it to fly, i noticed it shakes a lot, but its correctly calibrated through multiwii conf.
Just look at the video and see what happens:
http://www.youtube.com/watch?v=Akm20OAR ... e=youtu.be
[youtube]http://www.youtube.com/watch?v=Akm20OAR4JY[/youtube]

First of all you must get rid of the vibrations. Then apply 42Hz LPF filter and lower your PID's.

Sorry, i understand almost nothing about multimotors, this is my first quad.
How can i reduce vibrations?
What exactly is a LPF Filter?

[scrat]

To reduce the vibrations first properly balance propellers. Then balance motors. This is main thing to do and then check quad behaviour.

Prop: http://www.youtube.com/watch?v=2S0ae1A0gAw
Motor: http://www.youtube.com/watch?v=OgvayWfey78

[linuxslate]

The department of redundancy department does not approve of the term:

LPF Filter

[scrat]

The department of redundancy department does not approve of the term:

LPF Filter

?

[Andy7]

Given that LPF is an acronym for low pass filter, I think he's offended by the redundant word 'filter'.
He should come work for the DoP in the uk (Department of pedantry) who are also trying to stamp out the use of the phrase 'NCP Car park'

[mateusvuccaru]

Well, my propellers really were unbalanced. I had balanced they before, now the motors don't shake like before.
I tried to decrease P on multiwii config, but it keeps wobbling between the FRONT_LEFT and the REAR_RIGHT motors.

I'm not ready to sit and cry yet, but i can't find what is happening.
Can someone give me a clue?

[bluecnc]

Your unstable quad looks alot like what happened to mine when the firmware on my board got corrupted when using Multiiwii Win GUI to change the PID's in Windows 8.

I basically had to use Arduino to reprogram the board. I used Vista but I am still nervous changing the PID's. The nice thing about Arduino is, if you bork your settings you can always reprogram and start over. I have done it several times now.

What board are you using?

Rob

[mateusvuccaru]

Your unstable quad looks alot like what happened to mine when the firmware on my board got corrupted when using Multiiwii Win GUI to change the PID's in Windows 8.

I basically had to use Arduino to reprogram the board. I used Vista but I am still nervous changing the PID's. The nice thing about Arduino is, if you bork your settings you can always reprogram and start over. I have done it several times now.

What board are you using?

Rob

My board is a CRIUS 2.0
But i dont think this is my case, because if i change the P or the I i can see the difference.
Yesterday i tried a configuration that looks strange:

By looking to other people's configs, i can see my P is too low and the I is higher. But like this it flies more stable, don't shake like before. but still have a little wobbling that i can't get rid of.

[bluecnc]

Glad you have yours stable. I thought I had my quad set right and was hovering in a slight breeze. It became unstable and came crashing down. Now I am back to square one. Oh well. Thus is the adventure.

Rob

[tovrin]

is it a fast wobble or a slow wobble? these are both PID settings.

[ben74x]

Hi, I've got a similar issue with my GE260 & mini APM ..

Here's a video from takeoff && shaking : https://youtu.be/pkJ91JEZjng

( note at the end, at the left corner, as soon as I've switched between loiter and stabilize mode, this caused fall, as the stab mode woke up 0.5 seconds before hitting the ground ) ..

Here are my basic settings : http://i.snag.gy/eDHIB.jpg
& pid settings : http://i.snag.gy/PTIf7.jpg
( binded to channel 6, didn't notice any change by switching Stabilize Roll kP value .. except if too low (<2.5) it tends to flip over next to an heavy roll command )

Link for the APM logs : http://x24.fr/wobblelogs.zip

Read zilion of things, but I haven't found the cause yet ..don't know where to get the accelerometer values within the logs ..
Thanks for any enlightment

[edsimmons3]

Ben,

It looks like you've got way too little P on pitch and roll... just a guess. Edit: Is that config for multiwii? I don't recognise the software...

Reduce I and increase P for pitch and roll a bit at a time and test fly between each change.

Hope that helps...
Ed

[Cereal_Killer]

Edit: Is that config for multiwii? I don't recognise the software...

That's APM mission planner.


OP I agree your pitch and roll P gains are WAY to low.

[ben74x]

Thanks a lot, I've tried lots of values on the grass with my laptop and some twine attached to a wood log so the quadcopter won't go too far :
Then I've realized a close to 0 P rate value is the thing keeping it stable, so I lowered loiter values as well ( trying this mode caused it crash again ... dah )
6 replaced propellers later + some auto trim, got perfect stable flight ( having some smooth latino dancing move along roll and pitch but that's okay )

[Kbev5709]

Your unstable quad looks alot like what happened to mine when the firmware on my board got corrupted when using Multiiwii Win GUI to change the PID's in Windows 8.

I basically had to use Arduino to reprogram the board. I used Vista but I am still nervous changing the PID's. The nice thing about Arduino is, if you bork your settings you can always reprogram and start over. I have done it several times now.

What board are you using?

Rob

My board is a CRIUS 2.0
But i dont think this is my case, because if i change the P or the I i can see the difference.
Yesterday i tried a configuration that looks strange:

By looking to other people's configs, i can see my P is too low and the I is higher. But like this it flies more stable, don't shake like before. but still have a little wobbling that i can't get rid of.

How can you control it at all with your throttle mid rate set to 0, throttle expo at 43 and your pitch / roll rate and expo set at 90 and 65?
More realistic numbers there would be throttle mid 50, expo 25 to 35, and pitch/roll rate 10 or 20 (or even less) and pitch/roll expo at about 35.