Optimal design of AS/RS storage systems with three-class-based assignment strategy under single and dual command operations

This paper presents an extension of the analytical models already proposed by the literature to compute the expected travel time of automated storage and retrieval systems (AS/RS) in three-class-based storage (3-CBS) rectangular-in-time (RIT) storage systems. The authors determined the analytical closed form of the mean travel time for both the single-command (SC) and the dual-command (DC) cycles varying the warehouse shape factor and the ABC turnover curve. The performances obtained by the adoption of the proposed analytical travel time model under different configurations of the warehousing system, i.e., shape, dimension of the classes, and ABC curve, are evaluated and compared. Finally, the optimal boundary limits for the 3-CBS AS/RS, considering both the SC and the DC cycles, are fixed presenting the percentage saving of such configurations toward the common random assignment policy.