Visible vibration

ArduCopter
1

Since my monster drone completely crashed I had to build a smaller on: a chinese dji 450 frame and chinese pixhawk 2.4.8.

It flights ok. I built in all the knowledge I gathered from the big one:

  • vibration reduction - balanced props, ballanced motor (+prop), vibration pad.
  • air isolation (barometer) - possibly not perfect yet.
  • high current cables - compass question
  • tuning parameters - optimized for 10" props.

So the vibe values are OK X, Y <5, Vibe Z<20. The raw values are OK too (ACCX, Y < ±3; ACCZ is between -5 and -15.

But the drone (since it is light weight (with battery ~1200gramms) has a visible vibration. Not always, and can’t define a clear rule when. I couldn’t identified a regularity (in automatic landing never - after take off often, but not always).
Here is the link to the log file:
https://1drv.ms/u/s!AotAJyqLFfNV7mUbazJ9xPjaoAPp?e=e6sfTj

Here is another log file from a flight today.

https://1drv.ms/u/s!AotAJyqLFfNV7mbmGa08k3XftBbX?e=L0pOtU
The first short take off shows the situattion when I eliminated the daming pad with a rubber. Here the frame vibration is very high, after I removed this rubber and the vibration values on the pixhawk decreased to a normal and correct value. (Naturally the frame vibration continued.)
I counted it is 7Hz. - can it be in correlation with some filter values (which are 21Hz?)

Thanks for the help in advance,

Szabolcs

2

I cannot recommend chinese Pixhawk clones. They are dangerous and not worth it. Go for a mRO Pixhawk or X2.1 instead.

3

You mean air flow isolation?

Visible vibration might come from flexible arms and badly balanced weight?!

4

Arms are definitely strong enough (not flexible).
Wight is quite well balanced.
So maybe the chinese pixhawk is the problem.

5

I don’t think the Pixhawk causes the issue. If they work they do perform ok. But they might malfunction suddenly and cause a desaster. You should see it in the logs if the sensors are so bad they already cause issues.

6

It doesn’t seems bad. The internal board voltage was low(4.6V), but I added another power source and replaced the shcottky diode to a stornger one, now, it is 5V.

7

which parameter can influence this? I set all the necessary parameters to a 10" prop.
image

8

Set the gyro filter back to 20Hz and give it a try.

9

Ok thanks i will try. When the wether gets back sunny i will try a new fly.

10

HI finally I notcied that the gyrofilter was set to 21. (in the calculation excel there was s comment.
image

image
image747×30 1.88 KB

now I set it back to 42 - which seems solved the issue.
Although the VIBE Z increase from 10-20 region to 20-30 (but yesterday anyway was a high wind), but the visible vibration disappeared completely.

Thanks for the help