Multi-vehicle path planning for non-line of sight communication

This paper presents the formulation and hardware results of a mixed-integer linear programming approach to online connectivity-constrained trajectory planning of autonomous helicopters through cluttered environments. A lead vehicle must execute a certain mission whereby wireless line of sight communication to its ground station is lost. Relay helicopters are therefore introduced that must position themselves in such a way that indirect line of sight connectivity between the leader and the ground station is always maintained. The corresponding coordinated multi-vehicle trajectory optimization is tackled using both centralized and distributed receding horizon planning strategies. Binary variables are used to capture connectivity, obstacle- and collision avoidance constraints, extending earlier formulations to model nonconvex obstacles more efficiently. Simulation, hardware in the loop, and flight test results are presented for a centralized two-helicopter mission. Simulation results for a distributed scenario are given as well