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

From: Pascal Brisset
Subject: Re: [Paparazzi-devel] Reply to "How to descent faster? (Famille Chateauvieux-Hellwig)"
Date: Sun, 30 Aug 2009 18:12:29 +0200
User-agent: Thunderbird (X11/20090817)


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 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"/>

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)


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?

No clue. You'll probably have to define somtething new for paparazzi. I used this method on regular gliders. My Horus ( 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...


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