Electric van-based robot deliveries with en-route charging

We present a two-echelon electric van-based robot delivery system with en-route charging for last-mile delivery in logistics operations. Each of the vans is equipped with a single robot, and the robots can visit areas with van access restrictions, such as pedestrianized areas or university campuses. The time during which electric vans are carrying robots can be used to recharge the robots, thereby increasing the efficiency of the distribution system. To model the proposed system, we present a mixed integer program. We note that the energy transfer from a van to its robot needs time and will cause the available travel distance of a van to decrease and that of a robot to increase. Focusing on the new time-distance-energy trade-off problem, which increases the difficulty checking the feasibility of any given route, we further propose a greedy route evaluation approach and a linear programming-based route evaluation method. An adaptive large neighborhood search algorithm is presented for solving larger instances. A sensitivity analysis for vehicle charging modes, charging rates, and maximum battery capacities shows that using en-route charging, while appropriately increasing battery level and charging rate can have useful effects on cost.