Cyber-physical internet-enabled out-of-order execution considering workload for multi-stage scheduling in hybrid flow shop

Abstract

The growing demand for customization in fast-fashion apparel manufacturing, characterized by high product variety, short lead times, unpredictable order arrivals, and varying batch sizes, has introduced significant challenges to Hybrid Flow Shop (HFS) operations. These challenges are aggravated by the inherent complexity of HFS, which features multiple stages and shared resources. The resulting variability, such as fluctuations in machine availability, processing times, and inter-stage dependencies, necessitates dynamically reallocating resources, reprioritizing jobs, and coordinating buffers among stages. In response, this study presents a Cyber-Physical Internet (CPI)-enabled multi-stage scheduling method to address the challenges of dynamic HFS operations. Firstly, a CPI-enabled HFS is constructed, establishing cyber-physical synchronization through hierarchical gateways at both the shop floor and stage levels. Subsequently, CPI routing tables are developed by multiple information tables, enabling real-time data traceability and visualization throughout the production process. Building on this foundation, this study proposes an Out-of-Order Execution (OoOE) method with dynamic Workload consideration (OoOEW) for HFS scheduling problem. The OoOEW method reduces disturbances in high-variability production environments and enhances scheduling flexibility by incorporating workload balancing across upstream and downstream stages. Finally, a case study is conducted to evaluate the proposed solution in a mass-customization production environment. The experiment results demonstrate that OoOEW significantly outperforms traditional methods, in terms of shop floor throughput and delivery time. The proposed method shows operation flexibility and enhances adaptability under dynamic manufacturing conditions in HFS.