A no-cost zone and iso-cost line based control method for an as/rs with a multiple-load s/r machine

In this paper, we propose a control method for an Automated Storage and Retrieval System (AS/RS) with a multiple-load S/R (Storage and Retrieval) machine. The problem environment is an assembly system in which subassemblies are regularly deposited into and retrieved from the AS/RS. Our goal is to optimize the operations of the S/R machine. To achieve this goal, we propose an “iso-cost line” concept and adopt a “no-cost zone” concept to assist us in planning the best route for the S/R machine. To further optimize the S/R machine's operations, the proposed method also considers the relationships between storage items when it is searching for the best storage locations for storage items. A measure called “association strength” is proposed for this purpose. To understand the performance of the proposed control method, the proposed method is compared with other methods through computer simulations. Simulation results show that the proposed method is capable of producing satisfactory results.