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

[Hector Garcia de Marina]

Hi Balazs,

I do not have such problem with my aspirin IMU, and I guess nobody here, first time I hear something like that.

In my experience it sounds more a communications problem between the micro and the IMU (SW or HW).

On Tue, Sep 30, 2014 at 9:14 AM, Balazs GATI <address@hidden> wrote:

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
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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/

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