Severe vibration issues

Info and discussion about the original AQ v6 flight controller

Re: Severe vibration issues

Postby Max » Sat Jul 19, 2014 9:07 pm

s_sergiu wrote:Can you please specify what exactly in the code you modified to get more filtering of Acc/Gyros ?

kinderkram wrote:Max changed MPU6000_DRATE_SLOTS to 80 (100Hz) which was 40 (200Hz) before in mpu6000.h


Technically, it's only GYO output which is getting averaged over a longer time period. To change ACC output as well, you'd need to change MPU6000_SLOTS value. :geek:

-Max
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Re: Severe vibration issues

Postby s_sergiu » Mon Jul 21, 2014 1:50 pm

Max and Kinderkram thank you for reply.

Sergiu
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Re: Severe vibration issues

Postby epyonxero » Mon Jul 21, 2014 9:27 pm

Do you have a video of the multicopter in flight? Im curious if your problem is similar to mine where the vehicle kind of bounces up and down in PH.
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Re: Severe vibration issues

Postby chschmid » Mon Jul 21, 2014 9:45 pm

Bouncing up and down is usually a navigation altitude Tuning Problem. Check the wiki. There is a nice vid explaning this behaviour and Tuning.

Cheers
Christof
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Re: Severe vibration issues

Postby hogster » Wed Jul 30, 2014 8:38 pm

Hi Max,

Just to let you know I finally got around to trying your test firmware ... and it's exactly the same as before :(

A short while after hovering it starts making its quiet *zing zing zing* oscillation and starts drifting in a certain direction quite noticeably (in this case backwards). If I give inputs on the sticks to keep the platform level, the HUD tells me the platform is tipping forwards :(

As you can see from the attached ACC plot, I'm still fighting a strange biased vibration which tends to be more positive than negative on Y and more negative than positive on X :| The full log file is available to download here if anyone would be so kind as to try and debug this problem with me:

http://www.horizonimaging.co.uk/rcgroup ... es/30-7-14

I've got some M3 rubber mounts here which I will try placing between the chassis and the AQ as a last resort ... I don't know what else I can try :(

Many thanks for any input chaps, it's much appreciated :)

David
Attachments
2014-07-30_2019 ACC plots.png
ACC plots
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Re: Severe vibration issues

Postby LPR » Wed Jul 30, 2014 9:28 pm

Max

I tried your mod firmware on my octo and there was a big change in how is flew.

The wobble was completely gone with the change in firmware. I'm afraid I did not look to see the version I was flying with probably around r396.

The only change from defaults was to lower tilt rate D to 24600 for both firmwares.

The large octo with 17' x 5.5 props does have divergence in alt/pos hold. I'll try lowering D some more but I have two ESC32 and the rest are Simonk ESC so what could be some of the cause for divergence.

I'll upload the two videos tonight.

Larry
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Re: Severe vibration issues

Postby LPR » Thu Jul 31, 2014 4:17 am

Here's the links to the youtube videos.

https://www.youtube.com/watch?v=YweLrqGU4Wc

https://www.youtube.com/watch?v=d8JrLrhD9bE

Both videos are of the octo with default settings except for tilt rate D at 25600.

Larry
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Re: Severe vibration issues

Postby hogster » Fri Aug 29, 2014 7:03 pm

Hi all,

A month later, slightly better news :)

I've now tried mounting the AQ on the four M3 rubber damper I mentioned earlier, and the 'zing zing' noise has gone! I was able to hold a very stable hover in my small garden in slightly windy conditions. Also the platform didn't have its tendency of wanting to fly in a particular direction as it used to do here:

viewtopic.php?f=36&t=3542

Strangely, the vibration level is the same, if not worse than before, see attached. :|

Interestingly, I've just spotted the 'zinging' noise in the MOT plots from my flights back in July – it's clearly visible as very sharp individual spikes. These spikes are *not* visible in the MOT plots from today's flight, but the MOT data is a lot more noisy.

I don't really know what to make of this – in one respect it's better, and in the other respect it's worse! :roll:

I will experiment making the mounts softer still and report back ... can't promise it will be immediately though ;)

Many thanks for any and all advice,

David
Attachments
2014-07-30_2019 MOT plots.png
MOT plots from last month with the hard mounts. Not as noisy but with 'zinging' quite clearly visible
2014-08-29 ACC plots.png
ACC plots from today – noisier than before =( Maybe because it was more windy? ...
2014-08-29 MOT plots.png
MOT plots from today. Noisy but no 'zinging'
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Re: Severe vibration issues

Postby SuperSharpShooter » Tue Sep 16, 2014 9:59 pm

Max wrote:Hi David,

You could try the attached firmware and see if it helps at all. This has more filtering applied on the MPU6000 gyro/acc DIMU sensor (otherwise it's the same as the other experimental builds). With the current default filtering, the PID controller may tend to amplify small/high frequency transitions, which could appear as severe vibration issues (both in the logs and in how it behaves in the air).

Start with default PID Rate/Angle values. Set motor mix pitch/roll values to defaults (+/-100 for an X8). Test in manual mode and see if the altitude oscillations and/or motor surging is improved/eliminated. Check if controls are sufficiently crisp/precise.

This makes a big improvement on 2 of my systems when switching to DIMU, both using decent quality ESCs flashed with SimonK's firmware (HK Blue 30A). Both use 10 - 12" props, and hover is around 45% of potential motor output. The difference is less pronounced if the system is more loaded down (eg. 65% for hover), or if using slower motor/prop.

If you try it, please let me know how it feels.

-Max


Hi Max, I'm trying to use this firmware of yours, but I cannot get the motors to do anything other than spin at idle speed after arming and raising the throttle. I'm using ESC32s via PWM, and have a DIMU installed. This copter has been working fine (other than being impossible to tune perfectly) with r396. I've been struggling to get it to fly perfectly smoothly despite balancing the motors and props to perfection and spending a very long time PID tuning with limited success.

I've tried resetting the mixer and setting it up fresh but ended up with the same result of motors spinning at idle but no response to throttle.
-Glenn
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