Re: [Paparazzi-devel] is ALT_KALMAN really necessary?

[Pascal Brisset]

Hi,

Here is a screenshot of altitude and climb plots of a recent flight 
(yesterday, with a Funjet, Tiny2, LEA 4P):
- In the lower plot, we can observe that it is stable flight: during 
80s, the altitude change by only +-1m
- In the upper plot, in blue is plotted the GPS climb (in m/s); the 
average of it is about -0.4m/s, a clearly wrong value
(integrated over 80s, it would lead to a descent of 32m). I don't know 
how the u-blox kalman filter can output such crazy speed values and we 
cannot rely on them as inputs of the vertical control loop. In red is 
plotted the climb output of our basic kalman filter, using only the GPS 
altitude. They are correctly centered around 0. Unfortunately, they are 
late ...

Look at your own  measurements and decide it is possible to directly use 
the GPS climb values ...

--Pascal

Zouhair Mahboubi wrote:
> Hi,
> I have two questions regarding the kalman filtering in the tiny 2.1.1:
>
> 1-Do we really need the ALT_KALMAN filter? the instructions say to use 
> the 4G navigation mode on the u-blox, which already has its own 
> filtering subroutines.
>
> 2-When ALT_KALMAN is defined and ALT_KALMAN_ENABLED is set to true, 
> the estimator.h gets compiled with:
> #define EstimatorSetSpeedPol(vhmod, vhdir, vz) { \
>   estimator_hspeed_mod = vhmod; \
>   estimator_hspeed_dir = vhdir; \
>   if (!alt_kalman_enabled) estimator_z_dot = vz; \
> }
> This means that the vz from the GPS is not actually passed to the 
> alt_kalman function? does that mean that the GPS altitude ends being 
> differentiated to obtain estimator_z_dot? I thought the entire idea 
> behind filtering is to 'mix' the measurement and its derivative to 
> obtain a more accurate result...
>
> What's even more worrisome is that when the estimator_init function 
> calls EstimatorSetSpeedPol(0., 0., 0.) the estimator_z_dot does not 
> get initialized...
>
> Am I missing something here?
>
> Thanks,
> Zouhair
>
>
>
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> > Today's Topics:
> >
> >    1. Successful auto landing (chris)
> >    2. A successful auto landing (chris)
> >    3. Re: A successful auto landing (Andrew S)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sat, 10 Oct 2009 20:53:23 +0300
> > From: chris <address@hidden>
> > Subject: [Paparazzi-devel] Successful auto landing
> > To: address@hidden
> > Message-ID: <address@hidden>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > Today i had a wonderful experience as i achieved a very successful 
> > auto landing.
> > All the parameter were correct and the glide path was spot on.
> > It really landed slowly exactly on the predetermined spot.
> > Chris
> >  
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Sat, 10 Oct 2009 20:54:22 +0300
> > From: chris <address@hidden>
> > Subject: [Paparazzi-devel] A successful auto landing
> > To: address@hidden
> > Message-ID: <address@hidden>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> > Today i had a wonderful experience as i achieved a very successful 
> > auto landing.
> > All the parameter were correct and the glide path was spot on.
> > It really landed slowly exactly on the predetermined spot.
> > Chris
> >
> >
> >
> >
> > ------------------------------
> >
> > Message: 3
> > Date: Sun, 11 Oct 2009 14:26:46 +0400
> > From: Andrew S <address@hidden>
> > Subject: Re: [Paparazzi-devel] A successful auto landing
> > To: address@hidden
> > Message-ID: <address@hidden>
> > Content-Type: text/plain; charset=koi8-r
> >
> > Hello Chris!
> > Congratulations, this is your great step to success :)!
> > Did you use the standard "basic" flight plan, or custom (your own)? 
> > Did you took into account the wind?
> > By the way, when I tryed to make the landing procedure with 
> > simulator, I found out that simulator dont have wind info. Is it only 
> > my bag, or this should be? Andrew
> > 10.10.09, 21:54, "chris" <address@hidden>:
> >
> > > Today i had a wonderful experience as i achieved a very successful 
> > > auto landing.
> > > All the parameter were correct and the glide path was spot on.
> > > It really landed slowly exactly on the predetermined spot.
> > > Chris
> > > _______________________________________________
> > > Paparazzi-devel mailing list
> > > address@hidden
> > > http://lists.nongnu.org/mailman/listinfo/paparazzi-devel
>
>
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