Study on the Job Shop Fuzzy Dynamic Scheduling Based on Virtual Pre-scheduling

Dynamic job shop scheduling is a frequently occurring and highly relevant problem in practical fuzzy manufacture environment. Previous research suggested that periodic rescheduling improves classical measures of efficiency; however, this strategy had the undesirable effect of compromising stability and this lack of stability could render even the most efficient rescheduling strategy useless on the shop floor. In this research, the concept of the virtual scheduling pool was proposed and the heuristic virtual dynamic scheduling algorithm was also presented on the basis of this concept. This algorithm allows efficiency and stability to be balanced in a way that is appropriate for each situation. The contradistinctive simulations between the algorithm presented in this paper and the one based on the strategy of the temporal decomposition show that the algorithm presented is effective and feasible as well as the scheduling strategy of the former excels of the later in performance measures as a whole