  Multi-robot formation control enables robots to cooperate as a working group
in completing complex tasks, which has been widely used in both civilian and
military scenarios. Before moving to reach a given formation, each robot should
choose a position from the formation so that the whole system cost is
minimized. To solve the problem, we formulate an optimization problem in terms
of the total moving distance and give a solution by the Hungarian method. To
analyze the deviation of the achieved formation from the ideal one, we obtain
the lower bound of formation bias with respect to system's parameters based on
notions in information theory. As an extension, we discuss methods of
transformation between different formations. Some theoretical results are
obtained to give a guidance of the system design.
