Modeling drones

Transportation Optimization includes the capability to model drones with ground transportation assets, enabling users to deploy drones that make deliveries in coordination with trucks. The trucks serve both as a mobile depot, where drone launches and retrievals are performed, and a delivery asset. Transportation Optimization determines where and how to incorporate drones into the logistics operations to improve last-mile delivery and reduce cost.

Drone truck delivery supports a number of features, including:

• Define various drone types by payload, speed and battery

• Assign drone types to ground vehicles as potential companions in performing delivery

• Allow for fixed and linear endurance models to determine the effective flight range

• Override point-to-point flight distance and time with transit matrix

In modeling drones, keep the following in mind:

• A shipment destination may be served by either a truck or a drone, as defined in the Customers and Sites tables. Locations where the Drone Eligible column is set to "Yes" can be served by drones or by trucks. Locations where Drone Eligible is set to "No" must be served by trucks only. The Drone Eligible value does not have an effect with source locations or the sites to which trucks are assigned (depots).

• Use the Drone Assignments table to define pairing between drones and their carrier trucks. You can pair multiple drone types with a truck and Transportation Optimization will select one that is optimal to use for deliveries. For a given truck-drone type combination, the total number of drones deployed will not exceed the Available Units. The truck is assigned to a depot through the Asset Availability table.

• A sortie is a delivery carried out by a drone consisting of a sequence of locations: a launch stop, a delivery stop, and a rendezvous stop (where the drone returns to the truck or depot). In the Drones table, you can define activity times incurred for the sortie:

  • Before the drone is launched, either from the truck or from the depot, the time required to swap or charge the battery and to load the shipment is defined in the Fixed Launch Time.

  • The time required to perform delivery at customer locations is defined in the Fixed Service Time.

  • The time required to retrieve the drone, either on a truck or at the depot, is defined in the Fixed Retrieval Time.

• Each drone visit, or sortie, covers one customer only. Over the course of a route, there can be multiple sorties. The Fixed Drone Cost is applied once regardless of the number of sorties performed.

• Drones support two flight enduring models: fixed and linear. If the values for both models are defined, the more restrictive model takes priority.

  • In the fixed endurance model, the flight range is independent of the drone speed and payload. You can define the fixed flight range, measured in minutes, in the Max Flight Time column in the Drones table.

  • The linear endurance model assumes that the energy consumption is a linear function of shipment weight and requires three parameters defined. First, define the power consumption rate per unit weight, measured in watt/lb, in Consumption Rate. Second, define the power consumption rate to keep an empty drone moving or hovering, measured in watt, in Empty Load Consumption Rate. The third parameter is the energy of the battery loaded on the drone, measured in kJ. You define this in Battery Capacity.

The following are assumptions regarding behavior with drones and trucks:

• A carrier truck may serve other customers in between drone launch and retrieval locations while the drone is serving the customer.

• Drones must return to the truck before the range is reached or before the battery is exhausted. Drones are launched with a full battery from the trucks. The linear energy consumption model assumes that the power consumption rate during different flight phases, takeoff, cruise, landing and hovering, is the same.

• The launches and the retrievals of drones only take place when the truck is at the stops (including the depot).

• For a given route, only one sortie is performed at a time.

• Drones are in the air during delivery. Therefore, the service time takes up flight duration as the drone is hovering. A drone must remain airborne while waiting to rendezvous with the truck if the range/battery allows. If the battery life or range isn't long enough for a rendezvous, the sortie will not be scheduled, even if the drone has enough power for the delivery stop.

Drone modeling scope

Drones are supported for standard outbound routes with round trip only. Interleaved routes and tours are not supported (the Optimize Fleet Size option is not selected).

Starting from the first drone-eligible customer in a given route, the algorithm traverses through all the drone-eligible customers in the route, following the original order of route stops, and tries to generate a sortie for each. As long as the travel time and maximum flight time/battery allows, the first drone eligible customer may actually be served by the drone straight from the depot. In the diagram below, one possibility is that the travel time between the depot and customer 1 is too long (due to restricted flight zones for example) for the algorithm to schedule drone delivery to it.

Input and output tables for drone modeling

These input tables provide the means for configuring drone types, assigning drones to ground vehicles and defining overrides to the travel time or distance between pairs of locations:

• Drones – Use this table to define the drone types including their maximum flight time, battery capacity, energy consumption per distance unit, load capacity and activity time requirements.
• Drone Assignments – Use this table to associate the drones with transportation assets (carriers), specifying the number of drones available per asset.
• Drone Transit Override – If required, define the distance and travel time from origin to destination locations per drone type.

A set of sortie-specific output tables and additional columns in other output tables provide thorough reporting including the stop, service and segment details of the drone sorties:

• Transportation Drone Summary – This table provides a high level overview of the number of drones used per carrier.

• Sortie Summary – Similar to the Route Summary, this table provides summary information about the sorties that a drone carries out including total distance and time, total weight, volume and quantity, and other time-based metrics.

• Sortie Details – This table provides detailed information about each sortie carried out by the drone, including details about specific activities, sortie capacity, and load/unload metrics.

• Sortie Segments – This table details the metrics of each leg of the sortie, including distance and flight time, and start and end times per leg.

• Sortie Stops – This tables provides the location, pickup and delivery details for each stop on the sortie. It also reports on the range at arrival and range when leaving the stop.