Performance analysis for a dual-crane automated storage and retrieval system

Automated storage and retrieval systems (AS/RSs) were first implemented in the 1960s and continue to be installed today, albeit with dramatically evolved technologies. When compared to more manual systems, an AS/RS has the potential to dramatically reduce labour costs, with increased productivity, higher storage density, better order and inventory accuracy, and improved product security. Despite the advantages and widespread implementations, the typical unit-load, single-crane AS/RS is still often characterised by high initial costs and limited maximum throughput. This paper proposes a new design that uses two cranes in one aisle, where the cranes operate cooperatively to increase throughput, thereby allowing a facility that is at capacity to be retrofitted without a complete equipment upgrade and without the need for a new facility. We model travel time of the two cranes and develop system throughput equations. Significant throughput improvement is possible with the new design over a comparable single-crane AS/RS. [Received: 12 September 2022; Accepted 17 July 2023]