If you know the pre-defined destination for each turtlebot, you can write a publisher to move the robot autonomously. There are a few basic things to consider (if you need an autonomous robot) depending on your problem.
- You need feedback. You have to continuously measure the position of the turtlebot on the map. ( you can use odometry to know the distance travelled by the turtlebot and estimate the position of turtlebot on the map).
- If there are obstacles in the environment, you need to sense them and avoid them.
- You may need to plan paths of the turtlebot.
- You need to track the path.
You need to elaborate your question further, because the problem can have various level of complexity.
Regarding the update,
Each of the turtlebot will publish its own positions on the odometry topic (/odom, if I am not wrong). But these positions will be corresponding to robot-frame. What you need to do is transform these positions in robot-frame to earth-frame. You can use a transfromation matrix (consisting of rotational components and translational components, for forward kinematics) for each of the robot, to do the transformation. You can follow this tutorial to learn about coordinate transforms.
Once you get the robot positions in earth-frame, you can use them for formation control.
