Bi-objective operation optimization in multi-shuttle automated storage and retrieval systems to reduce travel time and energy consumption

The automated warehouses currently in widespread use maintain highly efficient operations at the cost of consuming a large amount of energy. This study first considers the problem of operation optimization in multi-shuttle automated storage and retrieval systems (AS/RSs) to reduce both time and energy consumption. A time and energy bi-objective integer programming model is proposed to jointly optimize the storage/retrieval (S/R) location assignment and S/R scheduling for a multi-shuttle AS/RS. The adaptive variable neighbourhood search algorithm and Lagrangian relaxation algorithm are developed to tackle large-size instances. The results demonstrate that the bi-objective model is effective at finding the compromise solution considering travel time and energy consumption simultaneously. The decrease in travel time is obtained at the expense of increasing energy consumption and vice versa. The study provides valuable insights for warehouse managers to operate a time-efficient and energy-efficient automated warehouse.