Ros control robot arm to move，what knowledge should I learn?

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Follow the moveit tutorials using python or c++ to script the Panda arm through a range of motions visualising in rviz.

http://docs.ros.org/melodic/api/movei...

If you have your own xacro definition of a robot, use the setup assistant to generate the files necessary. Again follow the moveit tutorials to use them.

Better yet, take a bunch of meshes, perhaps using 3D CAD software to make your own and write a xacro file for a more complex robot and then do the above.