This paper presents the design of a decentralized cooperative control law that allows a mobile robot group to establish and maintain a specific geometry formation while the robots moves along a predefined trajectory. The leader-follower approach control strategy was implemented, because this method specifies a unique reference to lead the group. As a result of the research, it was proved a cooperative control system that permits a set of robots to keep one specific formation while the group performs a predetermined mission. This control system helps to avoid obstacles; furthermore, it permits to modify the formation or make roles changes inside the group. Finally, this control system was checked in simulation and subsequently it was implemented in a real set of robots.