APM 2.5 - Height keep on increasing ?

Posted by Drone-University.com on May 18, 2014 at 4:34am

Hi,

This is my third APM (1 multicopter / 2 planes)

On the multicopter one, height keeps on increasing, from the real height (0,50 meters) by about 1 meter per minute.

I have the little foam and a piece of tape on the plastic cover as usual. This is working on both others 2 APM 2.5

How can I solve that ? 

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Replies

  • Developer
    Randy May 18, 2014 at 6:05pm

    My guess is that it could be weather affecting the barometer but it's also be that heat is affecting the barometer.

  • Jim Frantz May 18, 2014 at 12:19pm

    You do have the baro sensor covered with no light shining on it - right?  Even bright room lighting can do it.  

    Try powering up the APM with a battery and see if the baro altitude keeps rising or stabilizes.   If it is rising you may want to see the link below for a possible plan to a solution maybe:

    http://diydrones.com/forum/topics/ac3-1-rc5-spi-speed-problem

    Jim

  • 3D Robotics
    Chris Anderson May 18, 2014 at 10:21am
    It sounds like you may not have mounted the APM on vibration damping foam as required.
    • Drone-University.com > Chris Anderson May 18, 2014 at 10:25am

      Thx guys. Hello Chris.

      This problem happens while motors are off (APM is connected through USB to MP), t4 vibrations are not the problem is this particular case. Must me something else.

      Would it be some slightly increasing internal temp tricking the barometer to think the air is less dense and thereforr altitude is increasing ? 

    • Drone-University.com > Drone-University.com May 18, 2014 at 10:44am

      I forgot to mention that the increasing altitude is the one showing on the quick window of the MP flight data screen.

  • Jim Frantz May 18, 2014 at 9:19am

    Check for:

    • excessive vibrations
    • eliminate any chance of sun getting to the APM's baro sensor
    • check that the stick position is exactly centered during stabilized flight hovering
    • and that the natural barometric pressure is not changing.  

    You can check some of all of these using the Terminal CLI interface in Mission Planner.  To see if the pressure sensor is thinking it's holding altitude go to the CLI and check the data logs.  As I recall baro alt is in the CTUN record.  More accurately in altitude hold mode it holds the barometric altitude which is not the same as the actual distance above a reference point on the ground.

    Better yet get a sonar for this application of hovering low to the ground where a fixed distance is desired.

    Jim 

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