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Re: [Paparazzi-devel] Magnetometer issue.

From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] Magnetometer issue.
Date: Fri, 30 Sep 2011 20:59:10 +0200

Dear Dr Hwarmers,

The current implementation uses 3 magnetic vectors and attitude correction. It is the feedback loop that is less stable than with GPS correction at high feedback gain precisely because of this attitude dependance.

I would be interested in seeing any other implementation if possible.

On Sep 29, 2011 2:15 PM, "Prof. Dr.-Ing. Heinrich Warmers" <address@hidden> wrote:
> Dear Christophe,
> i think the magnet sensor interface in the DCM Implementation is wrong.
> The attitude and the three magnet fled components must be considerd
> when calculating the yar angle.
> I have a free and correct GPL implementation also for correcting hard
> magnet materials near the sensor.
> I can mail it to you if you want.
> regards
> Heinrich
> Christophe De Wagter schrieb:
>> Dear Luiz,
>> At this moment there are still 3 known issues with
>> lisa+fixedwing+magnetometer combination.
>> 1) The magnetometer code for fixedwing with <subsystem name="ahrs"
>> type="float_dcm" /> is not good yet and the attitude filter becomes
>> easily unstable at higher lattitudes.
>> 2) IMU data might not fit lower modem rates (9600bps) and then
>> messages are dropped which can cause for instance the GCS not to
>> populate while messages do arrive (when ALIVE message fails to find
>> some free bandwidth).
>> 3) Last but not least: the current I2C implementation does not work
>> with all sensor combinations (could e.g. happen when adding
>> magnetometer). It can happen that IMU stops working after a while. A
>> totally new lowlevel driver is in the make to be released as soon as
>> possible but it is a lot of work.
>> -Christophe
>> On Thu, Sep 29, 2011 at 2:27 AM, Luiz Flavio Felizardo
>> <address@hidden <mailto:address@hidden>> wrote:
>> there is something wierd with my setup and I cant figure it out,
>> anybody would mind to help? :D
>> It's something with my magnetometer, I had to comment this line
>> (<define name="USE_MAGNETOMETER" />) cause with the magnetometor
>> up (this line uncommented) the system go crazy and even stop
>> working. I checked the Ivyprobe and the messages log it seems that
>> the system is overloaded with magnetometer information and dont
>> have enough spare link to send or do the other functions. Is there
>> any way to limit the amount of messages the magnetometer sends!?
>> Or, if u dont think thats the problem do you have any ideas?
>> Lisa/L with IMU Aspirin system. Fixedwing Airframe.
>> Thanks very much.
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