Null Space-Based Formation Control with Leader Change Possibility

This work discusses the implementation and experimentation of a control system designed to guide a multi-robot formation of one aerial and three ground robots, in a trajectory tracking task. The implementation considers three partial formations of two robots, each one associated to a virtual structure, a straight line in the 3D space with its own formation controller. Two of the partial line formations are homogeneous formations of two ground vehicles, and the third one is a heterogeneous formation, involving a ground and an aerial vehicles. All the partial formations have the same reference for position, which is one of the ground vehicles. This also allows to discuss what would happen if this ground vehicle, the reference for all the line formations, and thus for the whole formation, presents a failure, what is considered here, in connection to an escorting mission. The result is that the designed control system is effectively able to accomplish the mission, even upon a failure of the reference robot, what is validated by experimental results also discussed here.