5 Nonlinear Stable Formation Control using Omnidirectional Images Christiano Couto Gava 1 , Raquel Frizera Vassallo 1 , Flavio Roberti 2 and Ricardo Carelli 2 1 Universidade Federal do Espítiro Santo 2 Universidad Nacional de San Juan 1 Brasil 2 Argentina 1. Introduction There are a lot of applications that are better performed by a multi-robot team than a single agent. Multi-robot systems may execute tasks in a faster and more efficient way and may also be more robust to failure than a single robot. There are even some applications that can not be achieved by only one robot and just by a group of them (Parker, 2003; Cao et al., 1997). Another known advantage of multi-robot systems is that instead of using one expensive robot with high processing capacity and many sensors, sometimes one can use a team of simpler and inexpensive robots to solve the same task. Some examples of tasks that are well performed by cooperative robots are search and rescue missions, load pushing, perimeter surveillance or cleaning, surrounding tasks, mapping and exploring. In these cases, robots may share information in order to complement their data, preventing double searching at an already visited area or alerting the others to concentrate their efforts in a specific place. Also the group may get into a desired position or arrangement to perform the task or join their forces to pull or push loads. Although multi-robot systems provide additional facilities and functionalities, such systems bring new challenges. One of these challenges is formation control. Many times, to successfully perform a task, it is necessary to make robots get to specific positions and orientations. Within the field of robot formation control, control is typically done either in a centralized or decentralized way. In a centralized approach a leader, which can be a robot or an external computer, monitores and controls the other robots, usually called followers. It coordinates tasks, poses and actions of the teammates. Most of the time, the leader concentrates all relevant information and decides for the whole group. The centralized approach represents a good strategy for small teams of robots, specially when the team is implemented with simple robots, only one computer and few sensors to control the entire group. In (Carelli et al., 2003) a centralized control is applied to coordinate the movement of a number of non-holonomic mobile robots to make them reach a pre-established desired formation that can be fixed or dynamic. There are also the so called leader-follower formation control as (Oliver & Labrosse, 2007; Consolini et al., 2007), in which the followers must track and follow the leader robot. The Open Access Database www.i-techonline.com Source: Computer Vision, Book edited by: Xiong Zhihui, ISBN 978-953-7619-21-3, pp. 538, November 2008, I-Tech, Vienna, Austria