Re: [Paparazzi-devel] Issue with Body_to_Imu and DCM

[Christophe De Wagter]

Hi Felix,

After struggling with this problem for too long, one day we needed to fly so I hacked the code [https://github.com/paparazzi/paparazzi/blob/aspirin2/sw/airborne/subsystems/imu/imu_aspirin2.h]: LISA_M_LONGITUDINAL_X is the name of the define (not in master branch) that was hacked in place. I would have preferred to introduce an IMU2AHRS conversion that can do only 90-degree stuff, keeping the AHRS2BODY for fine tuning (like: 5 degrees up). Still not sure how to solve, but the define above is probably not preferred as for instance you can not put the lisa upside-down without the need for a new define. 

Also see: https://github.com/paparazzi/paparazzi/issues/93

-Christophe 

On Wed, Feb 15, 2012 at 1:28 PM, Felix Ruess <address@hidden> wrote:

Hi Jochen,

if you want to try out the version on the dev branch, you can use int_cmpl_quat with mag for heading.

I'm not aware of any problems there, but I haven't tested the centrifugal force correction for flying coordinated turns in real flight yet (weather too ugly). It works perfectly in simulation. It also works very well on quads, but obviously with the coordinated turn corrections.

If you want to use the GPS for heading, that needs a bit of thought of when/how to initialize the heading, since at initialization on startup you don't have any gps heading information (you are not moving yet).

If you want to stay on master and/or want to use float_dcm you should either turn the imu, switch the channels (so you don't have to turn the imu) or fix float_dcm to deal with this correctly.

Cheers, Felix

On Wed, Feb 15, 2012 at 1:08 PM, Jochen Rieger <address@hidden> wrote:

Thanks for answer.
I have a fixed wing, it is recommended to use DCM. Should i use int_cmpl_quat on fixed wing or better turn the IMU?

Regards.
-Jochen

2012/2/15 Felix Ruess <address@hidden>

Hi Jochen,

what AHRS algo are you referring to?

http://paparazzi.enac.fr/wiki/Subsystem/ahrs has the current status

So if you are on the dev branch, you are fine using int_cmpl_quat, it will deal with all BODY_TO_IMU rotations correctly.

float_dcm does not handle this correctly, patches are welcome! 

But due to limited time, I'm not going to fix that one. I would recommend to use int_cmpl_quat anyway.

Cheers, Felix

On Wed, Feb 15, 2012 at 9:44 AM, Jochen Rieger <address@hidden> wrote:

Hello, in my airframe, i need to turn the board on the z axis.

I set the angle in the airframe file to:

     <define name="BODY_TO_IMU_PHI"   value="RadOfDeg( 0. )"/>
    <define name="BODY_TO_IMU_THETA" value="RadOfDeg( 0. )"/>
    <define name="BODY_TO_IMU_PSI"   value="RadOfDeg( 90. )"/>

It is possible that i will have problems?
Because in the wiki there are problems with Body_to_imu and the AHRS.

Also the USE_MAGNETOMETER is not tested, current status?








Thanks for informations.

Regards.
-Jochen

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