Re: [Paparazzi-devel] quadroter spektrum example firmwares

[David Conger]

Hi Felix,
That does help a lot.
I ask because I had a strange thing happen with a flight. After
takeoff instead of flying to STDBY it did wild circles that got larger
and larger until I abandoned the flight and clicked the "Land Here"
button. It hit a tree and gravity took over. Surprisingly only a foot
from one leg broke. Some glue and it is good as new and ready again.

It was a surprise as I had done tests before where it took off, nicely
flew to STDBY and hovered nicely and then landing without surprises.

I have never done the calibrate magnetometer step using ardrone
control so I had wondered if that was the cause. I have logs from that
flight. They are longer than they have to be as it was dark and it
took me a long time to unplug the battery because I was walking around
looking for the plastic leg that broke (little 3cm piece).

-David


On Wed, Jan 29, 2014 at 1:45 PM, Felix Ruess <address@hidden> wrote:
> Hi David,
>
> see the 'autorun' attribute for module periodic functions [1] for
> starting/stopping of them.
> In the generated doc I pointed to earlier it says that for the geo_mag
> module it is set to LOCK, meaning it will always run.
>
> About the mag calibration:
> I don't really know much about the ARDrone specifically...
> But the magnetometer calibration is something totally separate from the
> setting of the local magnetic field.
>
> - The mag calibration will - well - calibrate your mag mounted in the
> airframe (hard- and soft iron effects).
>   This (theoretically) makes it possible to actually measure the local
> magnetic field without the distortions from your airframe.
> - To calculate the true heading (w.r.t. geographic north), you need to (at
> least) know the local magnetic declination.
>   Like with a compass, declination is enough if you always place your sensor
> in the horizontal plane and are not too close to the poles...
>   But since an aircraft doesn't quite always stay in the horizontal plane
> ;-), you can only properly calculate it if you have the full vector of the
> local magnetic field (including the not insiginificant inclination).
>
> The latter already requires a "calibrated" magnetometer and is what the
> geo_mag module provides (or you do by hand by setting AHRS_H_[X|Y|Z])
>
> Hope that clears it up a bit...
>
> Cheers, Felix
>
> [1] https://wiki.paparazziuav.org/wiki/Modules#In_the_module_file
>
>
>
> On Wed, Jan 29, 2014 at 8:58 PM, David Conger <address@hidden>
> wrote:
>>
>> I wanted to ask that same question. Thank you Felix for answering it.
>> I have read the URL you gave and have more questions.
>> 1. In GCS under settings/modules I see I can start/stop the module.
>> The documentation you gave implies to me that there is no need to do
>> this start/stop because it is automatically called. Is this the case
>> or is there a specific sequence to follow. I see on the Wiki for
>> ARDrone if you fly autonomously you are to use the iPad app and do a
>> mag calibration after power up and before flight. Is this still
>> required?
>> -David
>>
>> On Wed, Jan 29, 2014 at 2:20 AM, Felix Ruess <address@hidden>
>> wrote:
>> > Hi Jake,
>> >
>> > I guess we can remove one of the examples...
>> > The geo_mag module sets the local magnetic field vector at startup when
>> > you
>> > get a gps fix.
>> > See http://docs.paparazziuav.org/latest/module__geo_mag.html
>> >
>> > Cheers, Felix
>> >
>> >
>> > On Wed, Jan 29, 2014 at 2:07 AM, Jake Tarren <address@hidden>
>> > wrote:
>> >>
>> >> I checked the wiki, and I read the actual .xml files, and it seems like
>> >> the only difference is the geo mag module before the servos driver=PPM
>> >> section.
>> >>
>> >> What's the geo mag module for?  What different hardware do I need for
>> >> it?
>> >>
>> >> Thanks.
>> >>
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