Real-time hoist scheduling for multistage material handling process under uncertainties

Significance: Zhao et al. have recently developed an interesting mixed-integer linear programming (MILP) model for real-time hoist rescheduling in a multistage electroplating line. In this letter, we reformulate the hoist movement constraints in their model. Due to this reformulation, we obtain a more compact MILP model in terms of the number of constraints and variables. Computational experiment shows that our improved model can be solved several times faster than Zhao et al.'s model. Such a reduction in computation time is significant in a real-time hoist rescheduling context.