Multi-robot formation based on RSSI power level and radiation pattern

This paper studies a formation control scheme to achieve a ‘dispersion’ of a group of robots using the Received Signal Strength Indication (RSSI) measurements of their on-board wireless nodes as feedback signals and their antenna radiation patterns (which is not omnidirectional in most of the cases) as a distance sensor between pairs of robots. In this sense, the multi-robot coordination evolves from a distance formation control to a power-based dispersion strategy. Thus, with the use of feedback through RSSI levels, the heading angle between the agents and the differences of its orientation angles, the control law becomes decentralised, avoiding the need of distance sensors. The result applies to a group of robots with a directed spanning tree topology, with root in the leader and the rest of followers are formed with respect to a unique local leader. The approach considers distinct radiation patterns found in Bluetooth or WiFi communication devices. As the approach ensures the convergence to desired values of RSSI, then a connectivity between the wireless nodes can be adjusted to maintain a desired communication data rate and wireless coverage by the robots posture. Simulations and real-time experiments illustrate the performance of the system.