Intra-aisle robotic picking with onboard tote lift takes longer per cycle
Resource-Performance Trade-offs in Intra-Aisle Robotic Picking: A Discrete-Event Simulation Comparison of Shuttle Configurations With and Without an Onboard Tote Lift
Robotics
Summary
This study looks at two ways of organizing robotic pickers in warehouse aisles that have two levels. One method uses two separate robots for each level, while the other uses just one robot with a special part to lift totes to the upper level. The researchers found that the single robot with the tote lifter takes more time to finish the picking cycle compared to using two robots, even though it uses fewer machines. However, this comparison is specific to their experiment setup and does not cover costs or overall system capacity.
What this means in practice
- •For warehouse operations managers: Decide on robotic picking setups by comparing cycle times when choosing between two robots or one with a tote lifter across two storage levels.
- •For industrial automation engineers: Evaluate the trade-off between robot count and order cycle time when designing shuttle systems for multi-level warehouse picking aisles.
Authors
Mohsen Reda Mahmoud Moursi
Abstract
This study compares two implemented intra-aisle robotic-picking configurations through discrete-event simulation. Without an onboard tote lift, two level-captive shuttles serve the two tested levels; with the lift, one shuttle remains on its horizontal level and its onboard mechanism moves the order tote to allow picks from the adjacent upper level. Thirty configuration-task-size experiments (n = 1-15 locations; ten replications each) yield 300 replication-level cycle-time observations. Two-sided Welch tests are applied to the replication means, with Holm adjustment across the 15 comparisons. The onboard-tote-lift configuration has longer mean cycle time at all tested task sizes. At n = 15, the means are 299.477 and 333.231 s/cycle, respectively: a 33.753 s increase (11.27%). The corresponding cycle-time-derived item rates are 180.314 and 162.050 items/h (-10.13%). These rates are calculated as 3600n divided by the scenario-mean cycle time; they are not measurements of the combined concurrent capacity of two level-captive shuttles. Importantly, task locations are sampled from different eligible-level sets in the two configurations, so the result concerns the implemented configuration-and-task-generation packages, not the isolated effect of a five-second tote-lift operation under identical picked locations. The study quantifies a cycle-performance difference alongside a reduction from two dedicated shuttles to one within the tested two-level block; it does not quantify system-level maximum throughput, investment cost, or reliability.