Optimal Path Planning in Cooperative Heterogeneous Multi-robot Delivery Systems

This paper addresses a team of cooperating vehicles performing autonomous deliveries in urban environments. The cooperating team comprises two vehicles with complementary capabilities, a truck restricted to travel along a street network, and a quadrotor micro-aerial vehicle of capacity one that can be deployed from the truck to perform deliveries. The problem is formulated as an optimal path planning problem on a graph and the goal is to find the shortest cooperative route enabling the quadrotor to deliver items at all requested locations. The problem is shown to be NP-hard using a reduction from the Travelling Salesman Problem and an algorithmic solution is proposed using a graph transformation to the Generalized Travelling Salesman Problem, which can be solved using existing methods. Simulation results compare the performance of the presented algorithms and demonstrate examples of delivery route computations over real urban street maps.