What is exact fixed frame name?

It is for [mastering mobile manipulators]]
I tried to follow as tutorial, but I think something is wrong.
Please let me know how I could fix this.

Hello @hki,

In depends on the situation, but in general terms, the fixed frame you have to select is robot_base_link. Note also that in the RobotModel display, you have to set the Robot Descrpition parameter to robot/robot_description. Here you have an image showing you the proper configuration:

Also, could you please tell me which is the Chapter you are following here? So that in case there’s something wrong in the instructions, I can fix it.