Re: [Paparazzi-devel] vibration filter

[Hector Garcia de Marina]

Hi Eduard. What is your sample time in your filter? And what are your rpm in idle? Also what is the sample time in your plots? (The log or telemetry could work at another sample time than the filter).

Have you checked that you are not suffering aliasing in your signal? Try to increase your sample time to be sure.

Another question, idle means for you trimmed flight?

On 5 Jul 2013 04:38, "Stephen Dwyer" <address@hidden> wrote:

Hi Eduardo,

Using a filter can certainly make things worse. We found when using a moving average filter (not the same as a median filter, but similar), we had to "tune" the window size. Too small resulted in little impact, too large distorted measurements too much. To give you an idea, running an Aspirin 1.5 on a TWOG over i2c with a periodic frequency of 120Hz with a window of 4 gave barely noticeable improvements, a window of 8 gave fairly nice performance, and a window of 12 started to give wonky results and behaviour. In addition, we found that filtering gyro data made performance poorer, while just filtering accelerometer data helped. We also noticed differences in the frequencies that affected the gyro and the accelerometer, and each axis was also a little bit different. Definitely take a look at each sensor axis across the whole throttle range, it might provide a bit of insight.

You may have to experiment a bit...

(The moving average filter code is not the nicest, but it is here if you want to look, in the imu_ppzuav.[h|c] files:

https://github.com/scdwyer/paparazzi/commit/ef3efbde8f87dffcfa09941bdb2d32946b3f5775 )

Thanks,

-Stephen Dwyer

On Thu, Jul 4, 2013 at 7:41 PM, <address@hidden> wrote:

The eco guys use a kitchen sponge for reducing vibs on the camera. I did some work on a gas heli here and it seems that a steel wire decoupling also helps significantly (pianowire). The diameter is determined by weight of equipment on top. It does really depend on the spektrum of frequencies that your vehicle generates. I have seen sandwiches of this wire decoupling on plywood, supported by a layer of sorbane or sorbothane (?) and then a really soft material like cheap foam earplugs. Zero vibs on an electric vehicle.

Rgds,

Gerard

On 04/07/2013, at 22:31, Eduardo lavratti <address@hidden> wrote:

Hello friends, i finished 2 airframes this week.
One is a big 3m airplane and other is a 2.6m flywing.
This planes use gasoline engines.

In the flywing i using some vibration mount to help dump the vibration but its not absorbing all low frequency vibration when in idle speed.

I like know if any one tried some kind of filter to reduce the effects ofthis kind of vibration.
I see that some IMU have a MEDIAN_FILTER oprtion so i put this filter in drotek and tried it on my plane.

The result is very bad. It work better without filter.

So, anyone can help ?

kind regards.

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