Experiments of Formation Control with Collisions Avoidance using the Null-Space-Based Behavioral Control

In this paper an approach to formation control with collisions avoidance of a multi-robot system is presented. The proposed technique, namely the null-space-based behavioral control, is a behavior based approach aimed at coordinating a platoon of mobile robots while performing different missions. The overall mission is firstly decomposed in elementary tasks and, for each of them; a motion reference command to each robot is elaborated referring to an inverse kinematic approach. The proposed technique is novel in the way it combines the output required by each task in order to obtain the final motion command for each robot; in details, it uses a hierarchy-based approach that uses the null-space projection to handle multiple, eventually conflicting, tasks. The proposed technique has been experimentally validated while performing a formation control mission with a platoon of 5 Khepera II mobile robots; during the mission a change of formation is commanded that requires the vehicles to avoid collisions among themselves and with external obstacles