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


From: Chris Wozny
Subject: Re: [Paparazzi-devel] Issue with Body_to_Imu and DCM
Date: Sat, 18 Feb 2012 21:00:21 -0700

Christophe,

Will this hack will allow me to set the orientation of Lisa/Aspirin if
it's not being mounted in the way that Joby Robotics intended? Per my
other thread, I used BODY_TO_IMU, but it seems as if you don't want us
to change the orientation of the IMU that way, only minute changes.

- Chris

On Wed, Feb 15, 2012 at 7:55 AM, Christophe De Wagter
<address@hidden> wrote:
> 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
>>>>> _______________________________________________
>>>>> Paparazzi-devel mailing list
>>>>> address@hidden
>>>>> https://lists.nongnu.org/mailman/listinfo/paparazzi-devel



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