Abstract
This paper studies the problem of creating an optimal flight schedule for a heterogeneous fleet of helicopters tasked with transporting personnel to, from, and between offshore installations. The problem can be modelled as a rich vehicle routing problem and combines the following properties from the vehicle routing literature: pickup and delivery structure, heterogeneous fleet operating out of multiple depots, multi-trip, and temporal synchronization of transportation tasks. We present compact and extended mathematical models of the problem, where the extended model is based on generating all trips apriori. When solving the extended model we apply delayed constraint generation (DCG) to parts of the model to speed up the solution process. Computational results are presented that show that the extended formulation and solution method can solve realistic instances of the problem within one hour. The results further show that the DCG method works significantly better than using lazy constraints from a commercial solver, especially when the number of transportation tasks requiring temporal synchronization becomes large.
Highlights
Since the discovery of the Ekofisk field in 1969, the Norwegian oil and gas sector has developed into the country’s largest industry (Norwegian Petroleum, 2020a)
An exact solution method to the multi-trip vehicle routing problem (VRP) is proposed by Mingozzi et al (2013), while an exact method for an extension of the problem which include both time windows and limited trip durations is given by Hernandez et al (2016)
The problem can be modelled as a rich vehicle routing problem, which includes a pickup and delivery structure, heterogeneous fleet of vehicles, multiple trips, multiple depots, and temporal synchronization of transportation tasks
Summary
Since the discovery of the Ekofisk field in 1969, the Norwegian oil and gas sector has developed into the country’s largest industry (Norwegian Petroleum, 2020a). It happens that certain personnel travel back and forth between a heliport and an installation on a single day to perform some key task, in which case they must be given sufficient time at the installation to perform their intended task To transport their personnel, each operator has a fleet of helicopters at its disposal. Due to the limited number of helipads (usually just one) at an offshore installation, it is necessary to ensure that no two helicopter routes are scheduled to visit the same installation at the same time The objective in this problem is to design a set of routes for the helicopters to fly, minimizing costs associated with operating a helicopter and the distance flown, while transporting all personnel from(to) their intended origin(destination), and adhering to all the limitations described above.
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