Polygon formation of multiple nonholonomic mobile robots with double-level-control collision avoidance scheme

This paper considers a polygon formation control of multiple robots with nonholonomic constraints enclosing a goal target and double-level-control collision avoidance scheme. Double-level-control scheme consisted of upper-level and lower-level controls are proposed for trajectory generation and tracking control of multi-robot systems. Both upper-level and lower-level controls operate collision avoidance mechanisms based on potential functions. The proposed control scheme guarantees that the group of robots are kept in the polygon formation and driven to a goal, while avoiding collisions during the travel. Moreover, the designed interaction between the upper- and lower-level controls guarantees that the mobile robots are not trapped in local minima or deadlock case. Experiments of the formation of three-robots are conducted to show the performance of the mobile robots in accomplishing a polygon formation while achieving the goal without any collision and no local minima.