Scheduling cooperative twin automated stacking cranes in automated container terminals

In the considered Automated Container Terminal, twin (i.e., identical non-passing) automated stacking cranes are configured for each block. The twin Automated Stacking Cranes (ASCs) collaborate to serve storage and retrieval requests from opposite ends of a storage block. Since the ASCs are unable to pass each other, there is a handshake area that serves as a temporary storage location so that one crane can start a request and leave it to the other crane to complete it. In this paper, four modes of crane interference are summarized, and a mixed integer programming model is established to minimize the makespan of all requests. For large scale problems, a genetic algorithm is designed. Numerical experiments show that the algorithm is efficient and competitive. A serial of experiments are carried out where it is shown that the method can produce optimum solutions.