Re: [Paparazzi-devel] sparkfun 6dof / imu sensor mounting

[Christophe De Wagter]

If the BODY_TO_IMU would be done in the imu rather than the ahrs file, it would solve the problem of simplified ahrs filters. Or even better!?: do this rotation between imu and ahrs so it is not in all AHRS files or all IMU files but just in the main.c

just an idea...

I can add the chip-on-imu signs in the header for the sparkfun3000 if I have a good picture of the orientations.

-Christophe 

On Tue, Oct 4, 2011 at 1:47 PM, Felix Ruess <address@hidden> wrote:

I agree with Antoine that BODY_TO_IMU  should be enough, but this is currently not the case for all ahrs algorithms.
E.g. ahrs_float_dcm still assumes you the IMU and body frame are the same when computing the accel and gps updates.
Same goes for mag with other algorithms.

I think we should update all ahrs algos to make it possible to just set IMU_TO_BODY to define the mounting position,
although the downside will be that we need a little more computing power.

So Bernie, right now you are better of changing the signs, although this is basically a hack.

Cheers, Felix

On Tue, Oct 4, 2011 at 3:53 AM, Bernard Davison <address@hidden> wrote:
> Thanks for the correction Antoine. :-)
> I'll update my airframe.
>
> Cheers,
> Bernie.
>
> On 04/10/2011, at 12:03 PM, antoine drouin wrote:
>
>> I disagree about using signs to describe the orientation of the IMU -
>> signs should only reflect the way sensors are mounted on a particular
>> model of IMU  ( and hence should be hard coded in the specific IMU
>> header ) - you want to set the signs so that sensor readings are
>> correct with respect to the IMU frame.
>>
>> BODY_TO_IMU should be enough to describe the orientation of the IMU
>> with respect to the vehicle body
>>
>> hth
>>
>> Poine
>>
>> On Tue, Oct 4, 2011 at 1:16 AM, Bernard Davison <address@hidden> wrote:
>>> Hi Sven,
>>>
>>> Changing the orientation is very easily achieved.
>>> From the configuration on this page http://paparazzi.enac.fr/wiki/IMU/SEN-10121 just change
>>>                <define name="BODY_TO_IMU_PHI"   value="RadOfDeg(0)"/>
>>>                <define name="BODY_TO_IMU_PSI"   value="RadOfDeg(0)"/>
>>>                <define name="BODY_TO_IMU_THETA" value="RadOfDeg(0)"/>
>>> as required. This is assuming you have it mounted the right way.
>>>
>>> If you have it mounted sideways or upside down then you may need to adjust
>>>                <define name="GYRO_P_SIGN" value="1"/>
>>>                <define name="GYRO_Q_SIGN" value="1"/>
>>>                <define name="GYRO_R_SIGN" value="1"/>
>>> and
>>>                <define name="ACCEL_X_SIGN" value="1"/>
>>>                <define name="ACCEL_Y_SIGN" value="1"/>
>>>                <define name="ACCEL_Z_SIGN" value="1"/>
>>>
>>>
>>> In my airframe I have
>>>                <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"/>
>>>                <define name="BODY_TO_IMU_THETA" value="RadOfDeg(10)"/>
>>> because I have it mounted upside down and back to front…
>>> Once you have it mounted in your airframe and flashed the configuration, check the messages and PFD to make sure that changes are reported correctly.
>>>
>>> Cheers,
>>> Bernie.
>>>
>>> On 03/10/2011, at 7:37 PM, Sven Lorenz wrote:
>>>
>>>> Hi,
>>>>
>>>> I was happy and surprised that the sparkfun 6dof IMU (*) is working "out-of-the-box" with the ppzuav-IMU module. Well done ;-)
>>>>
>>>> Is there a way to allow for the mounting position of such a sensor in a "general" way? From the code I can see only hardcoded orientations for aspirin and ppzimu.
>>>>
>>>> Cheers!
>>>> Sven
>>>>
>>>>
>>>> (*)sparkfun 6dof IMU is a nice and tiny module with ITG3200 and ADXL345 connected via I2C
>>>> http://www.sparkfun.com/products/10121
>>>>
>>>>
>>>>
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