– Objective function: Eq. (1) designates the total traveled distance to be minimized in accordance with the set of system constraints.
– System constraints: Constraints (2) and (3) impose that each node is visited only once by one vehicle. Constraints (4) ensure the continuity of vehicles’ pathways. Constraints (5) enforce the capacity constraint of the vehicles. Constraints (6) and (7) ensure that each used vehicle starts and ends at the depot. Constraints (8) discard vehicles’ sub-tours.