A Flexible Job Shop Online Scheduling Approach Based on Process-tree

The flexible job shop scheduling problem (FJSP) is one of the most difficult NP-hard combinatorial optimization problems. It is extremely difficult to solve the FJSP with the disturbances of manufacturing environment, which is always regarded as the flexible job shop online scheduling problem. This paper proposes a new method based on Process-Tree to solve this type of scheduling problem. Process sequence of a job can always be described as one of the three types of Process-Trees given in this paper. To manufacture a job, assignment of operations to machines is determined by considering the Process-Tree, together with the status of job shop and appropriateness of machines and auxiliary device for producing the job’s features. In this paper dispatching rules are used to generate the scheduling, and simulation results reveal that the presented approach performs well in flexible job shop online scheduling problem.