Multiresource-Constrained Flexible Job Shop Scheduling With Fixture Pallets and Setup Stations Under Pallet Automation Systems

Abstract

Pallet automation systems (PASs) are critical in flexible manufacturing for their ability to integrate diverse production resources, such as machines, fixture pallets (FPs), and setup stations (STs). In traditional flexible manufacturing systems (FMSs), loading/unloading typically occurs at machines, limiting the machines' capacity. To address this, in PASs, workpieces are loaded and unloaded from the machines at a limited number of STs, so loading, processing, and unloading are three separate segments. However, the research on PASs is limited, and existing studies mainly focused on machines while overlooking FPs and STs. A critical challenge is the tight coupling between resource selection and operation sequencing. To address this gap, we investigate a multiresource-constrained flexible job shop scheduling problem (MRFJSP) with FPs and STs under PASs (MRFFS). First, a mixed-integer programming model is proposed to minimize makespan. Second, a four-layer encoding scheme and a new decoding method with time period insertion based on the intersection of available time of multiple resources (TPI-IARs) are presented to obtain feasible schedule solutions and shrink the search space. Third, a new search algorithm based on critical paths and points mutation (SACP) is developed to effectively balance exploration and exploitation. Finally, four case studies are designed to demonstrate the validity and effectiveness of this work.