Evaluating Automated Guided Vehicle (AGV) Use in Distribution Centers
- Single-tethered picking: Each picker was assigned to an AGV instead of a forklift truck.
- Double-tethered picking: Each picker was assigned to two AGVs to fulfill two orders simultaneously.
- Zone-to-zone picking: We divided all aisles in the DC into multiple zones and posted a picker in each zone. While AGVs moved from aisle to aisle on their own, pickers loaded AGVs in their zones.
After we spent several days in a Walmart DC to understand and document its unique operations and processes, we developed and implemented a simulation system model to recreate the DC’s current operations virtually. We validated the system by comparing the model key performance indicators (KPIs) with the actual KPIs, and we established that both were very close.
Next, we developed simulation systems to model single-tethered, double-tethered and zone-to-zone picking options, using smart algorithms to route pickers and AGVs. Finally, we packaged these simulation algorithms into a decision support system to create multiple scenarios. Users could view each scenario’s simulation through the visual animation of pickers and AGVs, and then analyze any scenario’s results via reports, charts, and graphs.
- Our simulation systems proved that they were excellent representations of real-world scenarios. The proof: Our simulation KPIs were within two percent of the DC’s actual KPIs.
- From a cost point of view, we decided that single-tethered picking by AGVs was the best method. Contrary to our initial intuition, zone-to-zone picking wasn’t as effective, since pickers spent too much time waiting for AGVs.