Cooperative control of unmanned aerial vehicles

The use of unmanned aerial vehicles (UAV) for military missions has received growing attention in the last decade, with civilian usage also starting to expand. Apart from the obvious advantage of not placing human life at risk, the lack of a human pilot also enables a wealth of new operational paradigms. To realize these new paradigms, the UAVs must have a high level of autonomy and, often, work cooperatively in groups. With the development of UAV systems that have significant processing, communications, navigation, and sensing capabilities, the stage has been set to deploy cooperative control algorithms that effectively increase the capabilities of UAV teams beyond what can be accomplished by individual vehicles. Extensive research has been conducted in recent years on the development of novel cooperative decision and control algorithms to enable effective and efficient utilization of group capabilities. This special issue presents a sampling of solution approaches to problems involving cooperative control of UAVs, with an emphasis on the ‘outer-loop’ and decision-making aspects of the problem. It brings together papers that cover a broad range of cooperative control topics, such as vehicle/task assignment, sensor coverage, cooperative patrol, multi-player games, and sequential resource allocation. In this context, cooperative control is the study, development, and implementation of algorithms that either enable a group of UAVs to perform missions that cannot be accomplished individually, or else improve the team efficiency over that which can be achieved by UAVs acting as independent agents. Owing to the multidisciplinary nature of cooperative decision and control problems, the papers in this issue do not fit neatly within the standard feedback control paradigm. Some aspects of cooperative control, such as formation control and cooperative motion, which are perhaps more familiar to control engineers, are not emphasized. It is our hope that readers will nevertheless find the papers interesting and accessible. Operations involving teams of cooperative agents face numerous fundamental challenges, including computational complexity, information uncertainty, communication constraints, operator interaction or mixed initiative control, and adversary action. The papers in this special issue address a cross-section of these fundamental challenges. These challenges appear in cooperative control problems in forms such as combinatorial solution space, sensor capabilities and limitations, hardware systems capability, operator delays and operator errors, prediction of and reaction to enemy actions, and communication system limitations. In this special issue, the papers are arranged according to the four sub-topics that address task assignment, optimal distributions, multi-player differential games, and mixed initiative control. Task assignment: The first two papers of the issue address task assignment. This is the problem of allocating vehicles to perform tasks, with aspects of task scheduling and path planning commonly also involved. The task assignment problem is dominated by the fundamental difficulties of computational complexity, information uncertainty, and implementability. The first paper, ‘A Robust Approach to the UAV Task Assignment Problem’, by Alighanbari and How, explores methods to construct and deploy UAV assignment algorithms that are insensitive to uncertainties