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Re: [Paparazzi-devel] fixed point complementary quaternion AHRS in fixed


From: karlito
Subject: Re: [Paparazzi-devel] fixed point complementary quaternion AHRS in fixedwing
Date: Wed, 02 Jul 2014 09:42:00 +0200
User-agent: Roundcube Webmail/0.9.2

OK, I think I going to learn how to read, and then I get back to making things fly...

Thank a lot ;)


Le 2014-07-01 18:31, Felix Ruess a écrit :
Hi,

Observe your build output!
It clearly warns that PERIODIC_FREQUENCY should be least equal or
greater than AHRS_PROPAGATE_FREQUENCY

You are running the fixedwing firmware with the standard 60Hz periodic
frequency (rotorcraft runs at 512 by default).
If you want to run the main loop at the same rate on fixedwing
firmware, you have to <configure name="PERIODIC_FREQUENCY"
value="512"/>

Also don't set V_CTL_THROTTLE_SLEW_LIMITER to zero, you will get a
division by zero as you can see in the warnings....

Cheers, Felix

On Tue, Jul 1, 2014 at 5:39 PM, karlito <address@hidden> wrote:

I disabled the AHRS_GRAVITY_UPDATE_COORDINATED_TURN, and putted the
IMU configuration in the fixedwing airframe file (attached), but the
issue remains.

I forgot to specify that the initialisation works fine. The first
approximation (when stating the autopilot) is ok, but then the
amplitude of the movements are very small compared to reality.

Thanks a lot.

Have a nice day.

Sent from my crane.

On 01-07-14 17:08, Felix Ruess wrote:

Hi Karlito,

the difference in ahrs int_cmpl_quat [2] is that
AHRS_GRAVITY_UPDATE_COORDINATED_TURN is enabled by default for
fixedwing firmware (but only relevant if you USE_GPS).

And you are using different IMU calibration... try with the same one
(the one in your rotorcraft file if that one works)...

Cheers, Felix

On Tue, Jul 1, 2014 at 2:22 PM, karlito <address@hidden>
wrote:
Hello,

I'm working on the Delfly
(https://www.youtube.com/watch?v=tNPfD9l14Js [3]), I would like to
make it autonomous with paparazzi. In my case I would like to make
it go forward first, and the eventually make it hover (like in the
video).

For that reason I started using the fixed wing firmware. But when I
use the fixed point complementary quaternion AHRS algorithm, I get
an attitude that is very small in amplitude compared to the reality.
For example pitching up 90° will make it display 10° on the PFD.

I then tried with he rotorcraft code. In that case it works
perfectly, my PFD displays something very close to the reality.

I joined the two airframe files that I use for my tests.

What could be the reason for this comportment.

Thanks a lot.

Have a nice day.
--
Sent from my crane.

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Links:
------
[1] https://lists.nongnu.org/mailman/listinfo/paparazzi-devel
[2]
https://wiki.paparazziuav.org/wiki/Subsystem/ahrs#Complementary_Quaternion_.28fixed_point.29
[3] https://www.youtube.com/watch?v=tNPfD9l14Js

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