Hello,

First, I wanted to let you know that I'm new to ROS and I certainly have a lack of understanding of what I'm doing.

I am currently trying to control the joints of a simple robot in Gazebo. I'm trying to follow this tutorial: http://gazebosim.org/tutorials/?tut=ros_control

My robot is called "bras" and not "rrbot".

I have managed to launch my model in Gazebo whitout any error. However, I cannot launch the command :

 roslaunch bras_control bras_control.launch

Because the consol indicates:

   ~/simulation_ws$ roslaunch bras_control bras_control.launch 
... logging to /home/clement/.ros/log/8f02fa82-51cf-11ec-9d3a-08002781df68/roslaunch-clement-VirtualBox-22458.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://clement-VirtualBox:38753/

SUMMARY
========

PARAMETERS
 * /robot_description: <robot name="droi...
 * /rosdistro: melodic
 * /rosversion: 1.14.12

NODES
  /
    robot_state_publisher (robot_state_publisher/robot_state_publisher)
  /bras/
    controller_spawner (controller_manager/spawner)

auto-starting new master
process[master]: started with pid [22469]
ROS_MASTER_URI=http://localhost:11311

setting /run_id to 8f02fa82-51cf-11ec-9d3a-08002781df68
process[rosout-1]: started with pid [22480]
started core service [/rosout]
ERROR: cannot launch node of type [controller_manager/spawner]: Cannot locate node of type [spawner] in package [controller_manager]. Make sure file exists in package path and permission is set to executable (chmod +x)
process[robot_state_publisher-3]: started with pid [22487]
[ WARN] [1638271244.668825499]: The root link base has an inertia specified in the URDF, but KDL does not support a root link with an inertia.  As a workaround, you can add an extra dummy link to your URDF.

I have read that it can be linked to a bad installation of the roscontrol and roscontroller package. I have installed these packages with the command:

  sudo apt-get install ros-melodic-ros-control ros-melodic-ros-controllers

However, the installation looks to be succesful:

~/simulation_ws$ rospack find controller_manager
/opt/ros/melodic/share/controller_manager

Also, I wanted to know if instead of installing the "ros_control" with the : "sudo apt install..." command; I could have installed it with the command:

 git clone https://github.com/ros-controls/ros_control.git

Thanks for your help

/opt/ros/melodic/lib/controller_manager/spawner