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

[John Burt]

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