Cyclic hybrid flow shop scheduling problem with limited buffers and machine eligibility constraints

In today's competitive world, each company which is involved in production activities should try to adjust its production scheduling with customers' order. This reality was one of the principals of emerging just-in-time philosophy which tries to fulfill each customer's order in exact size of his demand and at the earliest time which is preferred by him. This is the main reason why those industries which produce high variety of goods have been trying to change their production policy from batch production of a single type to batch production mixed of different types which is called minimal part set. With this motivation, cyclic policy which also attempts to reduce work-in-process inventory arouse in production systems. Although hybrid flow shop is one of the most important and notable problems in sequencing and scheduling, there has not yet been any research that considers use of cyclic policy in hybrid flow shop. This problem is which this paper tries to peruse. Moreover, we try to reduce the gap between theoretical and practical problems by considering unrelated parallel machines, eligibility, and limited buffer constraints. In this paper, a mixed integer linear programming model is proposed at first. Because of the NP-hard nature of the problem, some heuristics and metaheuristics are proposed for solving the problem and are compared then. At last, all the results show that a simulated annealing method using some embedded heuristics in it is an effective approach for solving this problem.