Dynamic scheduling in flexible assembly system based on timed Petri nets model

作者:Zhang, WJ*; Freiheit, T; Yang, HS
来源:Robotics and Computer-Integrated Manufacturing, 2005, 21(6): 550-558.
DOI:10.1016/j.rcim.2004.12.002

摘要

This paper investigates a scheduling model for optimal production sequencing in a flexible assembly system. The system features a set of machines working together in the same workspace, with each machine performing a subset of operations. Three constraints are considered: (1) the precedence relation among the operations specified by the assembly tree; (2) working space that limits concurrent operations; and (3) the variation of process time. The objective is to find both a feasible assignment of operations to machines and schedule tasks in order to minimize the completion time for a single product or a batch of products. The assembly process is modeled using timed Petri nets and task scheduling is solved with a dynamic programming algorithm. The method calculates the time required precisely. A detailed case study is discussed to show the effectiveness of the model and algorithm.