Integrated automated guided vehicle dispatching and equipment scheduling with speed optimization

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Integrated automated guided vehicle dispatching and equipment scheduling with speed optimization

Xing, Zheng / Liu, Haitao / Wang, Tingsong / Chew, Ek Peng / Lee, Loo Hay / Tan, Kok Choon

Abstract The loading and unloading processes at quay and yard cranes are often studied separately, despite that integrated scheduling of the two processes could benefit in improving productivity and increasing profit. We consider an automated container terminal, in which the discharging and loading tasks at quay and yard cranes are fulfilled by a homogeneous fleet of automated guided vehicles (AGVs), and the traveling speed of AGVs can be adjusted. We formulate the problem into a mixed integer programming model that minimizes the total makespan of cranes and energy consumption of AGVs simultaneously. To address the problem, we develop a three-phase approach, where the problem is firstly reformulated as a digraph, and then a adjusting heuristic and a branch-and-bound procedure are used to optimize the assignment of tasks to AGVs and yard cranes. After the aforementioned two steps, the speed optimization process is executed to obtain the final schedule. Numerical results demonstrate the efficiency and effectiveness of the proposed approach and also justify the value of taking account of the AGVs speed optimization.

Highlights • Studying an integrated scheduling problem with variable vehicle speed at ports. • Reformulating the AGV dispatching problem as the format of directed graphs. • Proposing a modified bottleneck and branch&bound approach.