Parrot disco wings formation flying project

[Jean-Pierre G]

Hi all,

Thanks a lot for this excellent PID lib that I already use in a home made brewery !

Now I would like to try a more complex project : formation flying of Parrot Disco drones

Github of the current project is here : https://github.com/f2knpw/Parrot-Disco-Formation-flight

I'd like to control distance between the two drones and also bearing, for the slave to join the master trajectory.

For the distance I have estimations of positions (GPS) and speed. I propose to measure distance and tune "throttle" to adjust slave speed as output.

Am I right to say that "proportionnal to measurement" would be a good choice ? and that this PID should be "reversed" -->  increase of speed would decrease distance ?

For the bearing, I have measured that bearing (slave to master) variation is directly proportional to Roll angle of the wing which is also proportional to roll stick value that I can monitor and control.

So bearing should be tuned by a PID taking care of "rollstick value" as output.

I am a little afraid of a few things :

1) how to chain these two PIDs ? Do I have to consider them full independant ?

2) tuning of Kp and Ki will be done in flight... what would be safe values to startup in order to avoid strange behavior in flight ?

3) GPS are quite slowly drifting devices... so even with no motion the two GPS coordinates are slightly drifting... Would it work properly in open air conditions ?

thanks for your comments

JP