Multi-vehicle simulation support about px4-flightgear-bridge

[Jaeyoung-Lim]

Multivehicle support would be awesome!

@slimonslimon For the port configuration, this script might be useful to compare how it is done for gazebo

[slimonslimon]

Thank you for your comment!
Our solution for FG will work in a little bit another way because we need to spawn multiple types of vehicles.

I'm close to working example now.

@Jaeyoung-Lim Do you have some experiences with communication and orchestration of multiple vehicles? And are you able to run current Px4<->FG SITL?

[slimonslimon]

Now, there is an experimental branch flightgear-multi, which supports:
make px4_sitl_nolockstep flightgear_plane___multi
And you are able to run it multiple times. You only need to connect FG to the server manually, for now. (It will be automated later.)

There is one other problem with selecting "empty" "px4id" - now it counts running px4 instances - this can work only on the first run. (You cannot restart any instance separately)

[Jaeyoung-Lim]

@slimonslimon IMHOI I would prefer moving the multivehicle sim to a separate script, rather than making it part of the make target (e.g. the script link I linked above) so that we can be more versatile on the number of vehicles.

For example, for gazebo you can specify arbitrary number of vehicles and targets through the script

[slimonslimon]

Thank you for your comment! I will improve this later.

[slimonslimon]

The last problem of selecting PX4 ID was passed to user start script - it should be set by environmental variable in the experimental branch

but this problem is not part of the FG bridge, It is the problem of start scripts.

The bridge has multi-vehicle support.