Accelerometer Calib PixHawk 3.3.3 Question

Hi All,  (Quad PixHawk 3.3.3  >> MP 1.3.37)

 I realize that this may be a trivial question to those

 who have their own Calibration techniques well sorted,

  however, my question is -

  During the Accel Calibration procedure -

         One is prompted to 'Level Auto-Pilot' -

            1) Do one position the Craft such that the PixHawk Unit itself is at Level?,

                 which was  pre-mounted on the Craft during the assembly

           2) or Does this mean that you place the Craft on a Level surface.

            3) Both options  correct?

      I would say 2)  Assuming of course one have mounted the Pixhawk as

          close to the Centre position of the Craft and as level as possible, at assembly.

   I am looking forward to your valuable feedback, thank you.

Regards,

Gerhard

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Replies

  •  To me, technically both are correct. Essentially, you want your craft to be level during normal flight, or for the pixhawk to know what 'level' is for your craft. Installing mine, I made sure that the pixhawk is true and level in relation to the craft itself and then, when calibrating, I used small spirit levels that I can clip onto the frame in two orientations to ensure the craft is perfectly level.
    So, in doing that, and with the pixhawk  installed level relative to the craft, and with the craft level relative to the earth, then 'level' will be the same orientation for them both.

    If your pixhawk is crooked on the craft and you have calibrated the pixhawk to level off the craft or it's installed crooked, then the pixhawk will level itself and the craft will be 'off kilter', which I should think will mean the motors are constantly going to have to fight to fly true because they are also now not level.

    • Hi Doug,

      Thanks for your reply.

      I take your point to ensure that -

      Pixhawk unit installed level to to the craft, the craft level to to 'ground'.

      I assume here that the IMU's on the PixHawk are used to 'sense' the orientation, eg level.

      If that is the case, I think that, once the the craft is positioned level, the pixhawk unit will accept the reading

      from the imu's as 'level' whether it is 'true' level or not.  This reading will then be used as 'level' and deviations from that during flight is used by the FC to determine its 3D orientation in the air. If I am wrong in this reasoning, then please correct me.

      I admit this is the first time I am using Pixhawk, so therefor my very basics questions to understand the

      practical calibration procedures to ensure I get the best results.

      I have done the Accel Calibration now with the Craft being place on a 'prepared' level area.  I have noticed with a bubble compass on top of the PixHawk unit, that the unit is a bit off-level, even though the Craft is now positione  on a level surface.  I continued doing the accel calibr and some value '19...' was reported, according to MP voice.  Which params hold these values, where can I review it?  Is this reported value of '19' correct, well, acceptable?

      I proceeded with the compass calibr using the rotating 'chair' method.

      All the 'white' dots were hit and the samples were > 1200

      The Compass #1 (external) offset > -140, 34, -74  == calc ~162, which is lower than 600 (should be)

      according to wiki >> http://ardupilot.org/copter/docs/common-compass-calibration-in-miss...

      I am not sure whether this Compass offset is 'good' or 'bad' ??

       Compass #2, internal, -300, -55, -192   >>Not used.

      Which other parameters can I look at to evaluate whether the Craft's Calibration is 'acceptable'

      or in fact 'good'.   Which are the go / no-go calibr params one can review?

      I am going to do a test flight in the new day to evaluate my findings.

      Any other helpfull info or comments/video examples are very welcome, thank you very much.

      Regards,

      Gerhard

      Compass Calibration — Copter documentation
This reply was deleted.

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