Routing optimization for last-mile delivery with a truck and multiple heterogeneous robots

Abstract

Recently, innovative delivery approaches for last-mile logistics receive attentioin due to rising package quantities, various environmental issues, and high customer expectations. In this study, we propose a delivery routing model to find an optimal route for the flock of a single truck and multiple heterogenous robots carrying customer parcels from a single depot to multiple customers. We consider two types of customers: customers served by a truck and customers served by robots. The goal is to minimize the total delivery time to serve all customers no later than the delivery deadlines. After the rendezvous with the truck at a customer node, a robot needs to be loaded on the truck. Since the old batteries in returning robots need to be recharged before the robot leaves for the next trip for delivery, in general, the robot cannot be remobilized for another delivery at the same node at which the robot is loaded on the truck. We relax this assumption by considering the battery swapping option. In other words, the old battery of robots returning after delivery will be replaced by a new one if the robot needs to leave for the next customer at the same node, assuming that the delivery truck has enough replaceable batteries for robots. In our managerial study, we vary the number of available delivery robots, the driving range and payload capacity of robots and their speed, to assess their impact on the quality of service and delivery costs in two areas with different topographic characteristics.