Re: [Paparazzi-devel] Reply to "How to descent faster? (Famille Chateauvieux-Hellwig)"

[Pascal Brisset]

Hi,

this kind of procedure is available in 
conf/flight_plans/grosslobke_demo.xml (from Martin):

   <block NAME="down" strip_button="Down">
    <set var="lateral_mode" value="LATERAL_MODE_ROLL"/>
    <set var="v_ctl_mode" value="V_CTL_MODE_MANUAL"/>
    <set value="TRUE" var="h_ctl_disabled"/>
    <set value="(-0.6*MAX_PPRZ)" var="h_ctl_aileron_setpoint"/>
    <set value="(0.9*MAX_PPRZ)" var="h_ctl_elevator_setpoint"/>
    <while cond="estimator_z > ground_alt + 220"/>
    <set value="0" var="h_ctl_aileron_setpoint"/>
    <set value="0" var="h_ctl_elevator_setpoint"/>
    <!--deroute block="down_end"/-->
   </block>
   <block NAME="down_end" strip_button="DownEnd">
    <set value="0" var="h_ctl_aileron_setpoint"/>
    <set value="0" var="h_ctl_elevator_setpoint"/>
    <while cond="1.> stage_time"/>
    <set value="FALSE" var="h_ctl_disabled"/>
    <deroute block="wait"/>
   </block>

The trick is to set the h_ctl_disabled variable to disable 
stabilization, put the aircraft in a spiral ... and
restart the autopilot high enough from the ground. Of course, your 
airframe has to handle it (it was the cause of one of the first crash 
with Paparazzi: switching from a manual dive to auto1; Twinstar's wings 
did not support the strong resulting pull)

--Pascal



Famille Chateauvieux-Hellwig wrote:
> Le dimanche 30 août 2009 01:42:16 chris, vous avez écrit :
>   
> > That looks very interesting i will try it.
> > You mean that during the full rudder the IR stabilization should be off
> > if i understood correctly.
> >     
>
> Yes, do not try to stablize anything during the descent. The model will 
> probably do wild figures. That's ok. The point is that it will fly very 
> inefficiently.
>
> My be you should expect a loss of GPS fix. It might be clever to keep this 
> configuration olny for a fixed time (30-60s), then check where you are again.
>
>   
> > How can i do this in the flight plan?
> > Chris
> >     
>
> No clue. You'll probably have to define somtething new for paparazzi. I used 
> this method on regular gliders. My Horus (http://www.horus-uav-systems.de) is 
> not good enough that I've had this kind of problems before...
>
> Another technique that works well for planes with elevators is to fly on the 
> back. It works if you have an asymetrical airfoil (Twinstar, easyglider, 
> Cularis...). On a paparazzi system this sould be only a question of exchanging 
> what is up and what is down... Here again, expect to loose GPS signal if you 
> use a patch Antenna...
>
> Martial
>   
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