Flexible pallet automation system scheduling with limited fixture-pallets and material-pallets: A case study from an engine manufacturing enterprise

Pallet automation system (PAS) is crucial for enterprises to organize and schedule limited resources, such as fixture-pallets (FPs) and material-pallets (MPs). In customized production, FPs are often insufficient and unbalanced. To address this, MPs are prepared to store workpieces to release FPs' capacity. In this way, FPs are utilized for processing, while MPs are leveraged for storage. However, existing studies mainly focus on fixtures that are fixed to machines and rarely consider FPs and MPs. To address this gap, this paper investigates the flexible pallet automation system scheduling with limited FPs and MPs (FPASFM). Firstly, a mathematical model is established to minimize the makespan. Secondly, a five-layer encoding strategy, a new decoding method, and a feasibility correction strategy are integrated to obtain feasible solutions. Thirdly, an improved meta-heuristic algorithm with rule-based initialization and critical path mutation (IMHRC) is proposed. Finally, effective initialization rule combinations are identified through experiments with 36 different rule combinations. 15 real-data case studies show that IMHRC outperforms six other algorithms. Additionally, IMHRC significantly reduces makespan by 59.66 % and 45.90 % for two real orders, while enhancing resource utilization. IMHRC demonstrates the ability to obtain superior solutions in a shorter time, with its advantages in large-scale problems, effectively meeting the practical demands of enterprises in real-world production environments.