Hybrid formation control of the Unmanned Aerial Vehicles

An essential issue in the formation control of Unmanned Aerial Vehicles (UAVs) is to design a reliable controller in their path planner level to handle all interactions between the continuous dynamics of the system and inherent discrete nature of the decision making unit, which has been embedded to coordinate the control submodules. In this paper, we have proposed a new approach of hybrid supervisory control of UAVs for a two-dimensional leader follower formation scenario. The approach is able to comprehensively capture internal relations between the path planner dynamics and the decision making unit of the UAVs. To design such a hybrid supervisory controller for the formation problem, we have introduced a new method of abstraction, based on polar partitioning of the state space. Furthermore, we have utilized the properties of multi-affine vector fields over the polar partitioned space. Within this framework, we design a modular decentralized supervisor in the path planner level of the UAVs to achieve two major goals: first, reaching the formation and second, keeping the formation. In addition, an inter-collision avoidance mechanism has been considered in the controller structure. The approach is robust against uncertainty in the initial state of the system, in the sense that it can bring the follower UAV to the desired position, starting from any arbitrary initial position inside the control horizon. Moreover, the velocity bounds are applied through the design procedure so that the generated velocity references can be given to the lower level of the control hierarchy, as the references to be followed. (C) 2010 Elsevier Ltd. All rights reserved.