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Unreliable barometric altitude (Arduplane 2.30)

Posted by Gábor Zoltán on March 25, 2012 at 11:25am

Just got into this about 2 weeks ago, and really enjoyed it.

It is so much fun! :)

 

But today I experienced this pitch down and dive hard unexpected movements that my plane made.

I took off 3 more times, everything seamed ok, in the begining, but suddenly it happened again, and again. Luckily i did not crash.

 

Then it was time to check the logs. And i saw this. 6000m???!!!

 

Have you experienced such a thing?

 

3690922563?profile=original

 

 

 Please help.

At this point, i can not trust my APM anymore.

And it does feel bad. :( 

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Replies

  • Omar Achraf July 3, 2012 at 9:15pm

    Did someone had problems with your APM1 barometric sensor BMP085? My one is providing a strange measure of 116353 for the GND_ABS_PRESS and 2200 deg for temperature. To check this I used the barometer test code at ArduPlane2.34\libraries\AP_Baro\examples\AP_Baro_BMP085_test\AP_Baro_BMP085_test.pde
    the value of 116353 is higher than 101325.0 producing a number higher than 1 in the calculation.
    I tested it byusing the APM Planner test option airpressure that shows the same value for GND_ABS_PRESS and 220 for the temperature.

    Hi,

    I replaced the IMU board to other I have and the readings are then 91754 for GND_ABS_PRESS and 20 deg for temperature. So with this other IMU it is workin ok as showed by the test program as well by the Planner test option and HUD.

    To my APM to work with that IMU having this faulty sensor I replaced de mix from 0 to 1 to use GPS only for altitude.

    It is common to this BMP085 sensor to be faulty? Did someone have similar problem?

    regards,
    Omar

  • Developer
    Andrew Tridgell March 26, 2012 at 10:25pm

    I've just pushed out ArduPlane 2.31 to fix this bug. Thanks to Randy for the fix!

    Cheers, Tridge

  • Andre K. March 26, 2012 at 12:40pm

    Randy , could you please comment on how this is possible ?

    bad GPS fix, gives me realistic,changing altitude with a huge offset.

    http://youtu.be/LhRxeRjXG5Y

  • Developer
    Randy March 26, 2012 at 6:22am

    I know what this is and it's my fault.  It occurs when the raw pressure from your barometer crosses 32.7 degrees while in flight.

    There's a problem with the barometer filter in 2.5 arducopter and 2.3 arduplane.  We just found and fixed it and this went out in 2.5.3 of arducopter yesterday but I forgot that 2.3 of arduplane had the same bug.

    I'll talk to tridge and see when we can push out a fix.  Sorry about this.

  • Andre K. March 26, 2012 at 5:28am

    check that you have good GPS fix -

    GPS altitude is not used by default - (as far I can see from the source)

    Still I've seen my plane at 7000m for several minutes, after bad GPS (lost fix) - while real altitude was ~100m.

    This is very dangerous - in case of lost GPS fix in this case, the plane would descend until it meet terrain if it was in any AP mode..

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