Re: [Paparazzi-devel] Lisa/M Aspirin IMU Vibration Problems

[Stephen Dwyer]

Hello,

I have started a page on Vibration in the wiki, as it seems more and
more people are having issues with it:
http://paparazzi.enac.fr/wiki/Vibration

Woz, we had major vibration problems (including huge throttle
dependent attitude estimation drift), but with some insight from
Christophe De Wagter we got it under control. However, we had lots of
room and payload weight leeway in our solution. If doing it again, I
would use a solution closer to what Christophe describes with four
small corners of foam. Discussion is on the vibration page.

If anyone wants to add to that page, either personal solutions/case
studies or some theory etc, or maybe links to other good discussions,
feel free!

Thanks,
-Stephen Dwyer

On Fri, Feb 24, 2012 at 2:09 AM, Christophe De Wagter
<address@hidden> wrote:
> When possible we put the battery + autopilot + all weight we can find that
> needs to fly on 1 piece of wood, which is mounted on the fuselage using 4
> small corners of foam.
>
> The best results are in a combination of both mechanical damping and
> software filtering. Please note these are NOT equivalent. E.g. in your plots
> the bias of the gyro seems to change significantly at certain throttle
> settings (which is to be expected and can not be undone with filtering
> afterwards). And also note that a low-pass filter on the gyroscopes is
> almost never useful.
>
> The smaller the weight, the looser the dampers you need. E.g. to dampen a
> lisa-m board four pieces of 4x4x10 milimeter of packing-foam in the 4
> corners are probably stiff enough.
>
> -Christophe
>
>
>
> On Fri, Feb 24, 2012 at 9:29 AM, Chris Wozny <address@hidden> wrote:
>>
>> All,
>>
>> I'm running into enormous issues from throttle vibrations. After
>> looking at the data from one of our flight tests, there's a very high
>> correlation between the motor vibrations and the noise in our IMU
>> readings. I've included plots and also ranges below. Most of the
>> values below should be reading 0, but instead there is substantial
>> deviation. How have people damped their vibrations in extremely tight
>> space or seen this much deviation in sensor data? I know that there's
>> code for low pass filtering the gyro values, but is there something
>> for accelerometers as well with int_cmpl_quat?
>>
>> gp_range: -133.0658 to 139.7247
>> gq_range: -210.5803 to 228.9202
>> gr_range: -107.8851 to 109.6058
>> ax_range: -22.4756 to 44.2783
>> ay_range: -18.2686 to 33.1533
>> az_range: -55.9863 to 35.9473
>> phi_range: -10.0023 to 35.5467
>> psi_range: -18.9091 to 10.1885
>> theta_range: -18.1581 to 41.1144
>>
>> - Chris
>>
>> _______________________________________________
>> Paparazzi-devel mailing list
>> address@hidden
>> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>>
>
>
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>