Warehousing can be expensive because order picking requires considerable vehicular movement and labor hours. Although many previous studies have focused on order picker routing, there exists a lack of research on the simultaneous increase of order picking speed and energy reduction in rectangular warehouses with varying levels of traffic in each aisle. This study accordingly developed and evaluated a mathematical model for determining optimal picker routes considering the total travel time and energy consumed. The results were validated using the brute-force search method and benchmarked with the time-staged (TS) model. The energy savings were determined by comparing a time-optimized use-case (T) with one optimized for both time and energy (TE). Both use-cases provided routes up to 44% faster than the TS and avoided more than 50% of congested paths, and TE which represents the full functionality of our model provided a possible energy savings of up to 17% over T.

Order picking process is considered to be costly processes since takes long processing time and uses a lot of movements. This paper pre-sents a simulation software that utilizes multi-objective mathematical model with a consideration of travel distance and vehicle energy con-sumption. A block stacking warehouse or parallel aisle warehouse is considered in this research and only one picker with his vehicle is utilized. Optimal results of example problems are validated and verified. Finally, conclusion and discussion are given.