Re: [Paparazzi-devel] Lisa/M v2 +Aspirin IMU loss [SOLVED]

[Balazs GATI]

Hi,

I don't really know which sensor fails. We draw the conclusion based on 
a test yesterday: The Lisa/M module with Aspirin was installed in an 
airframe and it was covered with a dark transparent cover. We placed the 
airframe in the shadow and powered up the Lisa. We observed the 
IMU_MAG_RAW, IMU_GYRO_RAW, IMU_ACCEL_RAW messages with the Real-Time 
Plotter. The PFD and the messages showed normal values. If we directed 
the sunlight to the lisa with a mirror, all of the observed IMU messages 
(MAG, ACCEL, GYRO) became zeros in the same time. If we stopped 
mirroring the sunlight, the messages turned back to normal values. It is 
a strange experience, and far from the allday electronic problems, but 
we can explain it only with the sensitivity of the module to the light.

We have an other Lisa/M module. We didn't conducted this particular test 
with this module, but in previous tests it showed very similar behavior 
to the one in the test above. Both Lisa/M (with Aspirin) was purchased 
by Transition Robotics.

I don't know how can I identify more precisely the origin of the problem 
since we don't have any test equippment and knowledge to go more into 
the details.

If you could confirm our conclusion, I would place a warning on the 
Lisa/M and the Aspirin IMU section in the Wiki.

Regards,
 Balazs


2014.09.30. 1:17 keltezéssel, alonso acuña írta:
> Hello. Which of the sensors have this problem?  Have you noticed that
> the horizon slowly keeps accumulating an error and then after some time
> in the ground fixes itself or does it really go crazy and does not fix
> itself?
>
>
>
> On Mon, Sep 29, 2014 at 8:30 AM, Balazs GATI <address@hidden
> <mailto:address@hidden>> wrote:
>
>     Hi,
>
>     after days of bugging we identified the cause:
>
>     the Aspirin IMU is sensitive to light!
>
>     Not to the heating effect of direct sunlight, but even the ambient
>     light on a cloudy day.
>
>     Regards,
>       Balazs
>
>
>
>     2014.09.18. 21:41 keltezéssel, Balázs GÁTI írta:
>
>         Hi,
>
>         thank you for the ideas! I don't think that the sunlight caused the
>         phenomena, because the hardware never was exposed to direct sunlight
>         (8/8 cloud coverage) and in addition our Aspirin IMU is placed
>         directly
>         on the bottom side of the Lisa module.
>
>         I would be eased if somebody could report similar experience by
>         high sun
>         activity, because on Sept. 12th, a CME hit Earth's magnetic field,
>         igniting the most intense geomagnetic storm of the year.
>         (spaceweather.com <http://spaceweather.com>)
>
>         If no similar feedback, then we should conduct further detailed
>         analysis
>         to find the ghost hidden in the system. :)
>
>         Regards,
>         Balazs
>
>
>         2014-09-18 21:05 időpontban Prof. Dr.-Ing. Heinrich Warmers ezt
>         írta:
>
>             Hi,
>             the pressure sensor reacts of sun light.
>             Is that the problem?
>             You have to cover them in same foam.
>             Is the IMU connected separate with same wires?
>             The 168MHz  prevent sometimes well GPS signals.
>             Therefore it is always a  good way to make a shield of metal
>             and use ferrite rings on all wires from and to the autopilot.
>
>             Sometimes the sensor element mpu6000 is defect.
>
>             Regards Heinrich
>
>
>             Balazs GATI schrieb:
>
>                 Hi all,
>
>                 yesterday we experienced the total loss of attitude
>                 calculation of a
>                 Lisa/M v2 (quadshot) with Aspirin IMU in open air. (I
>                 mean the
>                 artificial horizon went wild after we left the
>                 building.) Fortunately
>                 we didnt want to fly, but test the GPS. Finally we could
>                 identify the
>                 problem: the IMU worked only if we provided some kind of
>                 physical
>                 cover to the module. Steel and aluminium sheet, thick
>                 paper worked.
>                 (80g/m2 copy paper and pure hand don't.) We could
>                 explain the
>                 phenomen with the increased sun activity or with some
>                 strange failure
>                 in grounding.
>
>                 Have you got similar experience in the last few days?
>
>                 Regards,
>                   Balazs
>
>
>
>
>
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>
>         ---
>         Balazs GATI, PhD
>         associate professor
>         Department of Aeronautics, Naval Architecture and Railway
>         Vehicles
>         Budapest University of Technology and Economics
>
>         Address:   Budapest
>         Stoczek u 6. J. ép. 423
>         1111
>         Tel:       +(36)-1-463-1960 [1]
>         Fax:       +(36)-1-463-3080 [2]
>         Homepage: http://vrht.bme.hu/ [3]
>
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>
>     --
>     Balazs GATI, PhD
>     associate professor
>           Department of Aeronautics, Naval Architecture and Railway Vehicles
>           Budapest University of Technology and Economics
>
>     Address:   Budapest
>                Stoczek u 6. J. ép. 423
>                1111
>     Tel:       +(36)-1-463-1960
>     Fax:       +(36)-1-463-3080
>     Homepage: http://vrht.bme.hu/
>
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--
Balazs GATI, PhD
associate professor
     Department of Aeronautics, Naval Architecture and Railway Vehicles
     Budapest University of Technology and Economics

Address:   Budapest
          Stoczek u 6. J. ép. 423
          1111
Tel:       +(36)-1-463-1960
Fax:       +(36)-1-463-3080
Homepage: http://vrht.bme.hu/