Re: [Paparazzi-devel] turning AP upside down (installing it reversed)

[Andreas Philipp]

Hi,

we are now using the simplest method and it works for us (keeping
"float_dcm" as ahrs):

  <section name="IMU" prefix="IMU_">
   <!-- Calibration Neutral -->
   <define name="GYRO_P_NEUTRAL" value="0"/>
   <define name="GYRO_Q_NEUTRAL" value="0"/>
   <define name="GYRO_R_NEUTRAL" value="0 "/>

   <define name="ACCEL_X_NEUTRAL" value="0"/>
   <define name="ACCEL_Y_NEUTRAL" value="0"/>
   <define name="ACCEL_Z_NEUTRAL" value="0"/>

   <define name="BODY_TO_IMU_PHI" value="0" unit="deg"/>
   <define name="BODY_TO_IMU_THETA" value="0" unit="deg"/>
   <define name="BODY_TO_IMU_PSI" value="0" unit="deg"/>

   <define name="GYRO_P_SIGN" value="1"/>
   <define name="GYRO_Q_SIGN" value="-1"/>
   <define name="GYRO_R_SIGN" value="-1"/>

   <define name="ACCEL_X_SIGN" value="1"/>
   <define name="ACCEL_Y_SIGN" value="-1"/>
   <define name="ACCEL_Z_SIGN" value="-1"/>
  </section>

Thanks Felix!
Andreas


On 09/09/2014 09:07 AM, Andreas Philipp wrote:
> 
> Thanks a lot for your answers Felix!
> 
> Yes, we used "float_dcm" as ahrs (as in the original ENAC airframe file
> for the apogee) which might explain the behaviour. Thanks for hinting at
> the AHRS! Again learned some more details of PPZ ...
> 
> We will try out your suggested options soon ...
> 
> Andreas
> 
> 
> Am 08.09.2014 18:36, schrieb Felix Ruess:
>> Another hint:
>> If the AHRS does not properly support body_to_imu and you don't want to
>> add an upside down option to the imu, you can also simply invert the
>> signs on the y and z axis:
>> <section name="IMU" prefix="IMU_">
>>    <define name="GYRO_Q_SIGN" value="1"/>
>>    <define name="GYRO_Q_SIGN" value="-1"/>
>>    <define name="GYRO_R_SIGN" value="-1"/>
>>    <define name="GYRO_Q_SIGN" value="-1"/>
>>    <define name="ACCEL_X_SIGN" value="1"/>
>>    <define name="ACCEL_Y_SIGN" value="-1"/>
>>    <define name="ACCEL_Z_SIGN" value="-1"/>
>>    ....
>> </section>
>>
>> Cheers, Felix
>>
>>
>> On Mon, Sep 8, 2014 at 5:18 PM, Felix Ruess <address@hidden
>> <mailto:address@hidden>> wrote:
>>
>>     Hi again,
>>
>>     or do something like adding an APOGEE_UPSIDE_DOWN option:
>>    
>> https://github.com/flixr/paparazzi/commit/58e6cf78f69eb6e49501a5774513cc0abf2c3e06
>>
>>
>>     Cheers, Felix
>>
>>
>>     On Mon, Sep 8, 2014 at 5:08 PM, Felix Ruess <address@hidden
>>     <mailto:address@hidden>> wrote:
>>
>>         Hi Andreas,
>>
>>         if you only want to turn it upside down (keeping the x-axis to
>>         the front), just turn it 180deg around the x-axis:
>>              <define name="BODY_TO_IMU_PHI" value="180" unit="deg"/>
>>              <define name="BODY_TO_IMU_THETA" value="0" unit="deg"/>
>>              <define name="BODY_TO_IMU_PSI" value="0" unit="deg"/>
>>
>>         But please not that not all AHRS algorithms properly take this
>>         into account: https://wiki.paparazziuav.org/wiki/Subsystem/ahrs
>>         Which one are you using?
>>
>>         Cheers, Felix
>>
>>
>>         On Mon, Sep 8, 2014 at 5:01 PM, Andreas Philipp
>>         <address@hidden
>>         <mailto:address@hidden>> wrote:
>>
>>
>>             Dear list,
>>
>>             in order to mount an AP reversed (upside down, for accessing
>>             the plugs
>>             easily), what do I have to change in the airframe file? I
>>             couldn't find
>>             any hint in the archive or wiki.
>>
>>             For an Apogee I changed this:
>>
>>                <section name="IMU" prefix="IMU_">
>>                  <!-- Calibration Neutral -->
>>                  <define name="GYRO_P_NEUTRAL" value="0"/>
>>                  <define name="GYRO_Q_NEUTRAL" value="0"/>
>>                  <define name="GYRO_R_NEUTRAL" value="0 "/>
>>
>>                  <define name="ACCEL_X_NEUTRAL" value="0"/>
>>                  <define name="ACCEL_Y_NEUTRAL" value="0"/>
>>                  <define name="ACCEL_Z_NEUTRAL" value="0"/>
>>
>>                  <define name="BODY_TO_IMU_PHI" value="0" unit="deg"/>
>>                  <define name="BODY_TO_IMU_THETA" value="0" unit="deg"/>
>>                  <define name="BODY_TO_IMU_PSI" value="0" unit="deg"/>
>>                </section>
>>
>>             to that (just changing BODY_TO_IMU_THETA and
>> BODY_TO_IMU_PSI):
>>
>>                <section name="IMU" prefix="IMU_">
>>                  <!-- Calibration Neutral -->
>>                  <define name="GYRO_P_NEUTRAL" value="0"/>
>>                  <define name="GYRO_Q_NEUTRAL" value="0"/>
>>                  <define name="GYRO_R_NEUTRAL" value="0 "/>
>>
>>                  <define name="ACCEL_X_NEUTRAL" value="0"/>
>>                  <define name="ACCEL_Y_NEUTRAL" value="0"/>
>>                  <define name="ACCEL_Z_NEUTRAL" value="0"/>
>>
>>                  <define name="BODY_TO_IMU_PHI" value="0" unit="deg"/>
>>                  <define name="BODY_TO_IMU_THETA" value="180"
>> unit="deg"/>
>>                  <define name="BODY_TO_IMU_PSI" value="180" unit="deg"/>
>>                </section>
>>
>>             This works in principle, however, the GCS (PFD) shows that
>>             the AP is
>>             initated reversed first and then needs a long time for
>>             slowly drifting
>>             to the correct position (actually it drifts beyond the right
>>             roll
>>             position and then back like controlled by a low-pass filter).
>>             And maybe associated with this: When flying circles in the
>>             flightplan,
>>             the plane of the circle is tilted about several meters (may
>>             be 20m or
>>             more), leading to one side of the circle being lower than
>>             the other,
>>             which is strange and annoying for climate measurements. The
>>             tilt is
>>             always in the same direction.
>>
>>             What am I missing?
>>
>>             Thanks for any reply,
>>             Andreas
>>
> 
>>
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>>
>>
> 
> 
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