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Re: [Paparazzi-devel] int_cmpl_quat and bungee takeoff

From: Felix Ruess
Subject: Re: [Paparazzi-devel] int_cmpl_quat and bungee takeoff
Date: Fri, 3 Aug 2012 16:46:34 +0200


See the thread from last year on this topic:
With some nice plots Antoine made showing this problem.

Quick recap on the basic principle of all these pure attitude filters:
When you launch on a bungee you get a high acceleration forwards, which means that the "correction" via accelerometers during that time is wrong. The pitch angle computed from the acceleration measurement (assumed to be only gravity) will be positive (pitch up) even if you are flying level in reality. Hence it tries to correct downwards.

The int_cmpl_quat estimator was mainly written/tuned for quadrotors near hover condition. I think it has a higher "gain" on the correction via accelerometers than the float_dcm and hence the effect is stronger there.


Possible solutions (as already discussed several times):

Cheers, Felix

On Fri, Aug 3, 2012 at 8:47 AM, Reto Büttner <address@hidden> wrote:
The guys of ZHAW Switzerland faced the same nasty nose down behaviour
when bungee launching and were not able to solve it.

How has OSAM of Utah State (or someone else) avoided this problem?

Regards, Reto

2012/8/3 Eduardo lavratti <address@hidden>:
> Today i do 5 perfect flights using float_dcm and bungee takeoff.
> For the last flight i used int_cmpl_quat but when i release the bungee the
> flywing fly for about 10 meter and loss altitude / crash.
> Does anyone know if "AHRS_GRAVITY_UPDATE_NORM_HEURISTIC: lower the gain of
> the gravity update based on a acceleration norm heuristic (e.g. good for
> bungee takeoff)" need to be used ?
> This is the 10th attemp to use int_quat and i ever hae problem with bungee
> takeoff.
> regards
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden

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