Integrated optimisation of consolidation and stowage planning of steel coil ships using differential evolution

Consolidation plan (CP) and stowage plan (SP) of coil ships are to assign steel coils onto ships and decide specific loading location for each coil, respectively, which are two correlative and adjacent plans in the finished product logistics of iron and steel industry. In this paper, we focus on the problem of making an integrated plan of CP and SP (C&SPP), which is important and rarely studied, to try to achieve systematic optimisation from the perspectives of the product terminal, shipping companies, and customers, simultaneously. First, according to the practical situation, an integer programming (IP) model is established to optimise ship loading, transportation timeliness, and operation efficiency. Then, to improve calculating efficiency, the IP model is simplified (SIP) by reducing the dimensions of variables. After that, based on the problem features and algorithm behaviour, an improved differential evolution algorithm is proposed in which an element-dependent strategy is designed to set control parameter, a guided operator is constructed to generate mutant individual and an iteration-based mechanism is introduced to dynamically adjust the parameter and mutation strategy, respectively. Finally, extensive experiments are carried out to evaluate the proposed method, and the numerical results demonstrate its effectiveness in solving practical scale C&SPP.