Self-triggered time coordinated deployment strategy for multiple relay UAVs to work as a point-to-point communication bridge

The use of multiple heterogeneous, low-cost, small Unmanned Aerial Vehicles (UAVs) as a tool in several application domains is becoming increasingly important. One critical aspect to enable the use of such vehicles is the coordination/planning system, whose task complexity increases with the number of vehicles and the communications constraints that arise due to their small size and large distances. In this work, we propose a control architecture for a platoon of relay UAVs that are independent of the coordination system. The platoon task consists in interconnecting the communication link between the possibly mobile command station and a UAV in a mission. The relays are actively driven to deploy, create a network and maintain a desired Quality-of-Service (QoS) level, defined in this paper. We present an architecture that is composed by a waypoint generator based on the network QoS and a Time Coordinated Path Following (TCPF) controller with a method to reduce the frequency of information exchange between the relay UAVs, through the use of a self-triggered control strategy. Exploiting this architecture, it is possible to plan a mission operation for a UAV without the need of considering vehicle-to-command-station communication constraints that will be satisfied by the introduction of the relay-UAVs platoon. Simulation results are provided to illustrate the efficacy of the developed strategy. The self-triggered approach results in significant reduction of information exchange between the relay UAVs, while maintaining the user desired network QoS.