A two-sided picking model of M-AS/RS with an aisle-assignment algorithm

The mobile automated storage/retrieval system (M-AS/RS) has overcome the manual operational problems of mobile storage systems (MSSs). However, it remains a single-sided picking model with an integrated multi-level conveying device (IMCD) running in a right-angled path. To enhance the picking performance, the present paper proposes that the IMCD path be modified to run in a straight-line path. A picking-aisle-assignment algorithm is developed to reduce the number of picking aisles in which the IMCD is required to run. This proposed picking-aisle-assignment algorithm, together with the modified IMCD movement action and a ‘no-skip’ approach to arranging a picking sequence, are used to construct a two-sided M-AS/RS. Simulations of the proposed model are undertaken, and the results demonstrate that the two-sided operational model proposed in this paper addresses the weaknesses of the existing single-sided M-AS/RS model, especially in environments characterized by poor ventilation or the movement of heavy products.