Modeling the Flying Sidekick Traveling Salesman Problem with Multiple Drones

This paper considers a version of the flying sidekick travel- ing salesman problem in which parcels are delivered to cus- tomers by either a truck or a set of identical flying drones. The drones’ flights are limited by the battery endurance and each flight is made of a launch, a service to a customer, and a return: launch and return must happen when the truck is stationary. These operations require time and when multi- ple drones are launched and/or collected at the same node, their order becomes relevant. The proposed model takes into account the order of these operations as a scheduling problem, because ignoring it could lead to infeasible solu- tions in the reality due to the possible exceeding of drones endurance. We propose a set of novel formulations for the problem that can improve the size of the largest instances solved in the literature. We provide a comparison among the formulations, between the multiple drones solutions and the single drone ones, and among different variants of the model.