Q: The rommel command generates an error: SpawnModel: Failure - model name turtlebot3_waffle already exist.
A: This is a known issue with the rommel command (or roslaunch sternformost
rommel.launch command). Nothing to worry about! Gazebo might show a black
screen after generating this error. Still, nothing to worry about. Just
wait and the world with the TurtleBot3 will be loaded eventually. The
loading process might take some time, due to the large amount of
models. Just sit back and relax, everything will be alright.