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Re: [Paparazzi-devel] fixedwing landing with ultrasonic sensor

From: Reto Büttner
Subject: Re: [Paparazzi-devel] fixedwing landing with ultrasonic sensor
Date: Tue, 3 Sep 2013 11:35:58 +0200

The ZHAW (Switzerland) implemented an advanced Paparazzi landing using both ultrasonic sensor and angle of attack sensor:
The key to good landing is controlling the approach though a controlled AOA (Angle of Attack) for speed control and height via engine power (controls the total energy in the system). When there is time for flaring (when your sonar sensor gets some signal or one to two meters above ground) you increase the amount of AOA with some function (linear should be good enough for the start).
AOA can be measured with a vane (with a rotational sensor potentiometer) or by subtracting gps vector from airplane nose direction (might be the other way around).
I remember there was a branch from Paparazzi called ZHAW or similar. you might find some code there but I am not so sure...

2013/9/2 Refik Sever <address@hidden>
Hi Tobias,

I'm glad to hear that. We can also help and test your work. We have
installed a SRF08 sensor.

By the way, energy control wants to increase the airspeed, sometimes by
diving. Will that create a problem in landing?


-----Original Message-----
From: paparazzi-devel-bounces+refiksever=address@hidden
[mailto:paparazzi-devel-bounces+refiksever=address@hidden] On
Behalf Of Tobias
Sent: Monday, September 2, 2013 6:36 PM
Subject: [Paparazzi-devel] fixedwing landing with ultrasonic sensor


work is in progress :-)
sensor is already installed and tested (made two flights) unfortunately i m
a little short on time right now but you can start wit something like this

    <block name="land">
      <call fun="gls_init(WP_AF,WP_SD, WP_TOD, WP_TD)"/>
      <call fun="nav_compute_baseleg(WP_AF, WP_TD, WP__BASELEG,
      <circle radius="nav_radius" until="NavCircleCount() > 0.5"
      <circle radius="nav_radius"
us))*10), 10 > fabs(GetPosAlt() - WaypointAlt(WP__BASELEG)))"
    <block name="final">
      <exception cond="(ground_alt + 10 > GetPosAlt())" deroute="final2"/>
      <call fun="gls(WP_AF,WP_SD, WP_TOD, WP_TD)"/>
    <block name="final2">
      <exception cond="(2 > sonar_distance)" deroute="flare"/>
      <call fun="gls(WP_AF,WP_SD, WP_TOD, WP_TD)"/>

the flare could be done by just reducing the airspeedsetpoint - at least
with the energy control this will lead to a really smooth flare

for further implementation I recommend to use a separate function in
guidance.c since this update rate is much higher.
but as I said work is in progress ;-)

cheers Tobi
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