robot formation in ROS

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Hi, I'm going to work with ground mobile robot formation in ROS, using turtlebot to do some experiments in simulator like stage. However, there's a tough problem.

The velocity command in ROS is made up of linear velocity and angular velocity while a vast number of formation algorithms result in velocity in 2D vector. Is there any method to make a translation? What if the algorithm generates target point to each robot? How to generate ROS velocity,namely Twist, to make diff-drive robots like turtlebot arrive in such points. I don't think using navigation stack is a good idea.

I'd appreaciate it if anyone can give me some advice or some related package in ROS.