Coupling the ILS optimisation algorithm and a simulation process to solve the travelling quay-crane worker assignment and balancing problem

Abstract

In container terminals (CTs), the performance of quay cranes (QCs) is extremely impacted by their operators’ productivity, which makes the QC worker assignment a relevant element in the QC scheduling. Nevertheless, in the literature, this problem was tackled without considering the objectives of balancing operators’ workload and minimising the distance required to move between QCs, even though practitioners underline their importance in maintaining an efficient working environment. Accordingly, and based on a real-case study raised by a CT partner, this paper addresses a novel problem referred to as the travelling QC worker assignment and balancing problem. First, we propose a novel mathematical model with original constraints faced by the company to assign operators to QCs on a daily basis. Second, to find approximate solutions in a reasonable time, a constructive heuristic and an iterative local search (ILS) are proposed and tested on real datasets. We also propose a simulation-optimisation mechanism to evaluate the robustness of the solutions under real-time probabilistic perturbations. The proposed algorithms are integrated into a decision support tool, a network-linked application allowing users in a real CT to generate automatic assignments. The proposed simulation-optimisation procedure helps obtain balanced planning, avoid workload conflicts, and increase productivity.

Keywords:

• Quay crane worker assignment
• workload balancing
• movement minimisation
• robustness evaluation

Acknowledgements

We gratefully acknowledge our colleagues at APM Terminals Tangier, Tangier Med Port, Morocco, for providing our research team with all needed data to accomplish this work, and for giving us the opportunity to implement the Microsoft C# .NET application containing the developed methods in their existing planning system for Go-Live.

Disclosure statement

No potential conflict of interest is reported by the authors.

Additional information

Funding

Part of this work was supported by the National Bank of Belgium (NBB) for the project with contract number BOF.COF.2018.0004.01.