Hi, how can I subscribe the node(topic cmd_vel) of turtlesim to the node of my model?

edit

via command line:

You can remap topics with /old_topic:=/new_topic. In your case:

rosrun turtlesim turtlesim_node /turtle1/cmd_vel:=/my_gazebo_robot/cmd_vel

via launch file:

Within the node, you can use the remap tag.

<node pkg="turtlesim" type="turtlesim_node" name="sim">
  <remap from="/turtle1/cmd_vel" to="/my_gazebo_robot/cmd_vel" />
</node>

You can check if either method worked with rostopic list and rostopic info /my_gazebo_robot/cmd_vel. Note that /my_gazebo_robot might be several directories deep (such as if you have a base controller).