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Old Feb 25, 2012, 12:03 PM
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United Kingdom, England, Devon
Joined Dec 2011
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Quadcopter Oscillation Issues

Hi Guys,

Hoping someone might be able to give me some tips on how I can tune my PID settings to smooth out the flying on my Cadtomotion quad.

Recently fitted a Wii Gyro and Auto Level - LLC + ITG3205 Gyro + BMA180 Acc after which I've been having issues. Since fitting it I've been getting oscillation issues with auto level turned on and off.

Have tried lowering the P auto level to 5 but still no real improvement (guessing I need to tweak the gyro settings too but am looking for some advice ).

Also balanced the props and motors as I thought it might be vibration but this hasn't solved the issue.

The oscillation can also be felt when I hold the quad and got to 50% throttle...

Here are my base settings - the only thing i've tried to tune is level which I changed from 9 (shown here) down to 5 but this didn't really improve anything:


And a pic of the quad:



Any help or suggestion appreciated
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Old Feb 25, 2012, 12:15 PM
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Dampen the sensors also you should turn D down. Don't enable auto level until you get gyro working fine.
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Old Feb 25, 2012, 12:33 PM
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Quote:
Originally Posted by chaosdestro0 View Post
Dampen the sensors also you should turn D down. Don't enable auto level until you get gyro working fine.
Thanks for the reply.

So turning down D on pitch and roll should help a bit - by around 5 maybe?

Any recommendations on dampening the sensors?
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Old Feb 25, 2012, 12:40 PM
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Originally Posted by DV8ER View Post
Thanks for the reply.

So turning down D on pitch and roll should help a bit - by around 5 maybe?

Any recommendations on dampening the sensors?
I use sponge for dampening, it flies OK at the moment so I think it works. D=Derivative value. The derivative term slows the rate of change of the controller output, if it's too high then it's slowing it down too much! Which means that it has to overshoot to compensate for the undershooting of the correction thrust.
I don't know much about this stuff, so be aware I might be drastically wrong.
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Old Feb 25, 2012, 12:55 PM
RTFM // copter damaged
warthox's Avatar
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dampen the sensors
use lpf for the itg
which esc do u use? maybe they are not fast enough.
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Old Feb 25, 2012, 12:57 PM
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Also a bendable construction could be a reason. Use stiff centerplates and fasten your screws very tight.
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Old Feb 25, 2012, 01:03 PM
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You should get it flying smooth before worrying about autolevel. Arm oscillations in gyro only mode is usually because P is set to high. If you start with the default settings and get oscillations try lowering P slightly. Changing sensors will often require you to retune settings. P is the gain of the gyro turn it up till it oscillates then back off slightly. I is the correction over time turn it up until it stops drifting and continue turning it up until it locks in the angle and does not float up in the front when you release stick. D controls how quickly it settles after making a attitude change.
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Old Feb 25, 2012, 01:18 PM
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Quote:
Originally Posted by chaosdestro0 View Post
I use sponge for dampening, it flies OK at the moment so I think it works. D=Derivative value. The derivative term slows the rate of change of the controller output, if it's too high then it's slowing it down too much! Which means that it has to overshoot to compensate for the undershooting of the correction thrust.
I don't know much about this stuff, so be aware I might be drastically wrong.
Sounds like its worth a try, thanks

Quote:
Originally Posted by warthox View Post
dampen the sensors
use lpf for the itg
which esc do u use? maybe they are not fast enough.
Hey warthox, thanks for the reply - its thanks to your vids that I got into quadcopters.

What does lpf for the itg mean (sorry noob)?

The sensors are attached the daughterboard which is mated to the xcopter board which all together is hard bolted the the chassis... maybe if I attach this using a few layers of double sided foam tape it might take out some of the vibrations.

ESCs are 10 Amp Hobbywing Pentium ESC

Pic of how the two boards are mated to the chassis - I have tried adding some rubber washers but get the impression this is not enough dampening:


Quote:
Originally Posted by zerosight View Post
Also a bendable construction could be a reason. Use stiff centerplates and fasten your screws very tight.
It has two plates either side of the arms with two bolts running through - construction seems very stiff and strong.
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Old Feb 25, 2012, 01:31 PM
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Here is an excellent video on PID tuning.

OpenPilot TV Episode 2: PID Tuning (36 min 51 sec)
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Old Feb 25, 2012, 01:48 PM
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>>Pic of how the two boards are mated to the chassis<<

You can add a thousand rubber washers and you won't get any isolation. The bolts are transmitting all the vibration from your frame to the board. You need to isolate the bolts.

LPF = low pass filter.
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Old Feb 25, 2012, 01:58 PM
RTFM // copter damaged
warthox's Avatar
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esc are ok.
u should definitely dampen the sensors itself. i use 3 layers of double sided mirror tape.
most of my quads fly perfect with default pids.

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Old Feb 25, 2012, 02:19 PM
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Quote:
Originally Posted by pug398 View Post
You should get it flying smooth before worrying about autolevel. Arm oscillations in gyro only mode is usually because P is set to high. If you start with the default settings and get oscillations try lowering P slightly. Changing sensors will often require you to retune settings. P is the gain of the gyro turn it up till it oscillates then back off slightly. I is the correction over time turn it up until it stops drifting and continue turning it up until it locks in the angle and does not float up in the front when you release stick. D controls how quickly it settles after making a attitude change.
Thanks for the info bud.

Quote:
Originally Posted by milo12 View Post
Here is an excellent video on PID tuning.
Thanks mate

Quote:
Originally Posted by SeismicCWave View Post
>>Pic of how the two boards are mated to the chassis<<

You can add a thousand rubber washers and you won't get any isolation. The bolts are transmitting all the vibration from your frame to the board. You need to isolate the bolts.

LPF = low pass filter.
I thought that might be the case, rubber bolts would be amazing... LOL

Is LPF a setting in multi wii or adding dampening - sorry bit slow today.


Quote:
Originally Posted by warthox View Post
esc are ok.
u should definitely dampen the sensors itself. i use 3 layers of double sided mirror tape.
most of my quads fly perfect with default pids.

Cool thanks - the old gyro in the main board had 2 layers of that tape and that seemed fine... on the daughter board the sensors are hard attached without this padding...

I agree - I think the sensor dampening is to blame here - looks like I'm going to have to do some modifying.
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Old Feb 25, 2012, 03:05 PM
RTFM // copter damaged
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Originally Posted by DV8ER View Post
Is LPF a setting in multi wii or adding dampening - sorry bit slow today.
u have to set the lpf in the multiwii fw before uploading.
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Old Feb 26, 2012, 12:09 AM
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One thing that stands out is your high YAW "P" value and the RATE. I would back it off to about 7 with a rate of 0.2 and see if that makes an improvement.
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Old Mar 01, 2012, 03:20 PM
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Joined Dec 2011
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Thanks for all the comments guys - Ian at cadtomotion is kindly adding some dampening to the sensor for me, highly recommend his quads and his customer service is amazing (if anyone would like a review of his 350 quad let me know).

In the mean time i've flown with gyro only, lpf, extra dampening and pid tweaks and got this video today. Excuse the music and camera work - one of the guys was kind enough to capture it on his iPhone for me.

Cadtomotion 350 Quadcopter (2 min 7 sec)
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