Lot-streaming in energy-efficient three-stage remanufacturing system scheduling problem with inequal and consistent sublots

The well-accepted three-stage remanufacturing system scheduling aims to achieve intelligent and green remanufacturing by reasonably coordinating limited resources in the system involving disassembly, reprocessing, reassembly production stages. Currently, the lot-streaming production mode is increasingly favoured by scholars and enterprise managers due to its remarkable performance in reducing machines' idle time and improving production efficiency. This paper investigates an energy-efficient scheduling issue for three-stage remanufacturing systems under the lot-streaming environment where each large-sized lot is split into its constituent small-sized sublots whose sizes may be inequal but remain consistent among various operations. Foremost, a dual-objective optimization mathematical model aiming at concurrently minimizing the makespan and total energy consumption is built. Then, since its NP-hard property, an improved fruit fly optimization (IFFO) algorithm is accordingly introduced. IFFO adopts a problem-specific three-layer encoding mechanism that contains three key pieces of scheduling information, i.e., lot sequence, machine assignment, and lot size splitting. Besides, based on the lot-streaming property, two distinct decoding strategies, i.e., sublot preemption and lot preemption are also correspondingly integrated. In addition, several effective optimization techniques, such as the simulated annealing-based replacement mechanism and Sigma method, are also employed to seek high-quality Pareto solutions. A real case and several designed random small/large-sized instances are tested on IFFO and its peers under three performance indicators. To obtain a convincing and solid conclusion, the Wilcoxon signed-rank statistical test is executed as well. The overall experimental results show that IFFO is feasible and effective in addressing the studied problem.