Re: [Paparazzi-devel] modifying AP behavior re HOME position and flight modes

[Gautier Hattenberger]

Hello,

If you to have a flight plan with relative position, take a look at the 
basic.xml and especially the function NavSetGroundReferenceHere() in the 
Geo init block. If it is called at the beginning, the reference will be 
set at your launch point. By the way, this reference is different from 
the HOME point unless you have x=0 and y=0 (which is usually the 
case...). The HOME is only the center of the circle in failsafe 
navigation mode.

For the behavior when telemetry is lost, what you want is the default 
behavior. The way to change it is to add an exception in the flight plan 
(something like <exception cond="datalink_time > 22" deroute="Standby"/>).

For the behavior when RC is lost. In manual and auto1, HOME mode is the 
default behavior (by the way, this can be change by setting RC_LOST_MODE 
to PPRZ_MODE_AUTO2 for example). By default in AUTO2, when the RC is 
lost, the mode stays this way. If you want to change this, you should 
use a exception in your flight plan:
- add #include "radio_control.h" in the header section
- before the blocks section, add a section
<exceptions>
   <exception cond="rc_status==RC_REALLY_LOST" deroute="Standby">
<exceptions/>
where the Standby block could be a circle around the HOME point.

It should work, let me know if not.

Gautier

John Burt a écrit :
> Dear Paparazziphiles,
>
> I'm developing a Paparazzi based UAV system to aid biological research 
> in remote field environments. In some circumstances, I will need to be 
> able to occasionally operate the UAV a) with limited or no real-time 
> telemetry link (i.e., no ground station), and b) from launch sites 
> that were not pre-planned in advance. From my reading of the 
> documentation and code, and my early test flights using GCS, I think I 
> may need to modify the AP code to get the features I need. Can someone 
> please offer any advice on how to do the following:
>
> a) Operate the UAV with no radio telemetry link. To get this, I think 
> I need to disable the trigger that aborts mission with loss of 
> telemetry signal? Also, I'd like to change the mode behavior to work 
> like this:
> - loss of RC TX signal in _any_ mode for X seconds = abort and home to 
> launch site
> - loss of telemetry link = no change
>
> Does this require a change to the C code (and where), or can this be 
> configured in an XML config file?
>
> b) How can I set up the AP code to execute a single flight plan that 
> is centered on the launch point, wherever it is? As I understand the 
> current flight plan config, all waypoints are relative to the HOME 
> waypoint, _but_ the HOME waypoint is itself a fixed (absolute) GPS 
> position specified in the flight plan. How can I modify this behavior 
> so that HOME is set at launch time? For example, imagine this scenario 
> (which does not use a ground station link):
> - On a remote road, I stop my truck and pull out my UAV, put in a 
> fresh battery, and turn on the AP and RC TX w/ mode switch set to 
> MANUAL. When the AP GPS reports a sat fix, I switch to AUTO1 mode, 
> which tells the AP that this position is now HOME. I then launch the 
> plane and switch to AUTO2 mode, allowing the plane to fly a course 
> relative to the launch point based on a pre-programmed flight plan. If 
> I switch off the RC TX, then the UAV will abort the mission and return 
> to the launch point (HOME).
> - At the end of the mission, I land the plane, drive ten miles down 
> the road, and repeat above step from the new launch point.
>
> Thank you in advance - Paparazzi is an amazing project and I'm very 
> excited about the possibilities of using it in research and 
> conservation applications.
>
> John Burt
>
>
>
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