Scheduling the operations of a double-load crane in slab yards

Abstract

This paper studies a double-load crane scheduling problem (DLCSP) in steel slab yards. A slab yard stores slabs in stacks. To prepare for use in production, some slabs need to be moved from one place to another. These movement tasks are performed by a double-load crane which can hold up to two slabs simultaneously. Given a set of tasks and possibly precedence relationships among them, the scheduling problem is to allocate the tasks to double-load operations and determine the schedule for the crane to perform the tasks so as to minimise the makespan. The problem is first formulated as a mixed integer linear programming (MILP) model with variables representing the order of tasks. Based on properties of the problem, it is then reformulated from a crane operation perspective. Computational experiments are carried out on practical data collected from a steel company. The results show that both models can solve practical sized problems optimally, with the second model being more efficient.

Keywords:

• slab yard
• crane scheduling
• double-load crane
• MILP model

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China (2016YFB0901900), the Fund for Innovative Research Groups of the National Natural Science Foundation of China (71621061), the Major International Joint Research Project of the National Natural Science Foundation of China (71520107004), the Major Program of National Natural Science Foundation of China (71790614), General fund of the National Natural Science Foundation of China (71472081), and the 111 Project (B16009).