[feature] how to multiple fetch control?

[247programmers]

I wanna control 2 fetch or multiple fetchs.

but there are some reference for 1 fetch.

how can I put many fetchs and how can I control them??

I heard that I have to make "group ns="robot1",,, group ns="robot2" " like that...

but its now working.

there have some error.

"cannot parseURDF" or "cannot load controllers" or " No p gain specified for pid. "

there are lots of error and I tried many times.

please I wanna get some document for controlling multi fetchs