Mesh stability of formations of unmanned aerial vehicles

Co-ordinated maneuvers are becoming more and more important in military as well as civilian applications. Advances in sensing, communication and computation are aiding in the design and development of advanced control technologies for these distributed, multi-vehicle systems. Some of the applications where coordinated control of a multi-vehicle system is required are, automated highway systems, formation flying of unmanned aerial vehicles for military surveillance and coordinated ocean floor mapping for autonomous underwater vehicles. For successful formation maneuvers of these vehicles we need to design the controller and communication structure so as to achieve classical stability of the formations. In addition to classical Lyapunov stability, one can imagine that these formations need to have the property of damping any disturbances which may and will arise in the course of operation. This thesis is concerned with the analysis and design of cluster controllers which achieve such disturbance damping. Roughly speaking, this property of disturbance damping and error attenuation is called mesh stability.; The contributions of this thesis can be seen in three parts. The first part concerns analysis of a cluster of linear dynamical systems. It is shown that it is not possible to get scalable clusters if the cluster controllers focus only on the local information. The second part is analysis of a nonlinear look-ahead interconnected system. Sufficient conditions guaranteeing mesh stability have been presented. The results obtained using the Lyapunov theory based approach are compared with the input-output gain results for linear systems. Third part is the applications of the above theoretical results to a case of formation flying of unmanned aerial vehicles. A nonlinear helicopter model is used to test the results offered by previous theoretical work. As an initial step, a regulation layer controller based on differential flatness and dynamic surface control is designed for the helicopter. The thesis ends with some suggestions for future work along the directions presented in the main part.