E-mail: f.arrichiello(at)unicas.it

Home page: http://webuser.unicas.it/arrichiello.

Tutor: Prof.  S.Chiaverini, Università degli Studi di Cassino

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Coordination control of multiple mobile robots   ___________________________________________________________________________________________________________

Summary of the thesis

The research described in the thesis concerns the coordination control of robotic systems composed by multiple autonomous vehicles. In particular, the research focuses on the control aspects for multi-robot systems, i.e., how to define the motion directives for each vehicle of the team to achieve missions in a coordinated way. The main motivations of a research in this topic can be found in the several advantages that multi-robot systems present respect to single autonomous robots, e.g., improving the mission efficiency in terms of time and quality, achieving tasks not executable by a single robot or proving flexibility to the tasks execution.

The main contribution of the thesis can be found in a behavior-based approach, namely the Null-Space-based Behavioral approach (NSB), to control generic multi-robot systems while achieving different formation control missions in dynamic scenarios. The approach, inherited from closed loop inverse kinematics techniques for industrial manipulators, has been developed in a proper mathematical framework and has been tested experimentally or in simulation with different robotic systems, i.e., to control a single mobile robot, a platoon of grounded mobile robots, a fleet of autonomous marine surface vessels and a team of mobile antennas.

The thesis is organized as follow:
• Chapter 1 presents an introduction to Multi-Robot Systems (MRSs). Thus, starting by the definition of a MRS, and after some considerations concerning the meaning of cooperation among multiple vehicles, the chapter presents an overview and the state of the art of the research in the field by describing the main applications of MRSs, the principal control structures and algorithms proposed in literature, and the global characteristics of MRSs.

• Chapter 2 is aimed at giving to the reader the basic notions concerning the motion control problems for autonomous vehicles. In particular, it presents the basic motion control problems for grounded mobile robots and for autonomous marine surface vessels.

• Chapter 3 describes the main characteristics of the NSB. First, the NSB is introduced in its theoretical and mathematical characteristic in comparison with the main behavioral approaches proposed in literature. Then, the different approaches are compared both in simulative and experimental studies while controlling a single autonomous vehicle. Finally, an experimental case study where the NSB controls a single mobile robot during a kick-to-goal mission is presented.

• In Chapter 4, details about the application of the NSB to the control of multi-robot systems are presented. In particular, after the definitions of the task functions for MRSs, and after some considerations about the NSB implementation aspects, a set of experiments performed with the setup available at the LAI (Laboratorio di Automazione Industriale) of the Università degli Studi di Cassino are illustrated. These experiments consist in several formation control missions performed with a platoon of 7 Khepera II mobile robots that communicate through Bluetooth connections with a remote unit.

• In Chapter 5, the extension of the NSB to the control of fleet of marine surface vessels and of platoon of mobile antennas will be presented. In particular, the NSB has been tested in numerical simulation in the Matlab/Simulink environment while controlling a fleet of autonomous surface vessels with particular actuation systems (partially or fully actuated depending on the velocity of the vessels) while navigating in a complex environment in presence of sea current. Moreover, the NSB has been tested in numerical simulation in the Matlab/Simulink environment while controlling a platoon of mobile antennas with limited communication range, i.e., the NSB is aimed at coordinating a team of antennas moving in the environment while keeping a communication bridge between one agent and a fixed base station.

• In Chapter 6 some concluding remarks are presented.

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