Solving steel coil ship stowage-planning problem using hybrid differential evolution

As an important optimisation problem in the finished product terminal of an iron and steel enterprise, the steel coil ship stowage-planning problem is to determine the stowing locations for the planned coils on a ship. Although the problem has attracted attention, the research has focused only on the optimisation for the ship. In this study, the problem is investigated from the view of improving operation efficiency of the cranes on the quay and in the warehouse. For this purpose, an integer-programming model is established to minimise the coil dispersion on the ship and the moving distance of the warehouse cranes by determining the stowing locations and loading sequence of the coils. To improve the solution efficiency, a two-level hybrid differential evolution (TLDE) composed of a continuous DE and a discrete DE is designed to assign the coils to the rows on the ship, and then allocate locations for them. Further, a subpopulation-based local search and a human experience-based heuristic are developed to further adjust the coils within each row and to produce initial population for TLDE, respectively. Extensive comparison experiments are performed to demonstrate the proposed algorithm. Numerical results confirm that TLDE is an efficient method for solving the SSPP.