Managing External Temporal Constraints in Manual Warehouses

Most of the warehouse operations are still performed manually despite the increasing development and adoption of automated warehouse solutions. Planning human workers in a warehouse is a complex task because managers have to consider issues such as start and end times of shifts, breaks, and incentive payment schemes. When warehouses have temporal restrictions on the processing time of inbound trucks or when they have deadlines for outbound orders, these constraints impact the schedules and cost of employing human workers. In this environment, warehouse management has to consider the temporal restrictions from external entities as well as the limited resources available at the warehouse. In this thesis, we study the impact of external temporal constraints in three operational planning problems at manual warehouses. We develop mathematical models for the problem, propose solution approaches for them and conduct computational experiments to derive insights.

The first study in the dissertation explores integrated scheduling and assignment of trucks to dock doors in unit-load cross-dock facilities with mixed mode dock doors. The processing time of both inbound and outbound trucks at the cross-dock are constrained by time windows.  In the second study, we investigate order picker scheduling problem in distribution centers where order picking operations are constrained temporally by predefined time windows for delivery of orders to the staging area of the warehouse. In the final study, we consider the impact of delivery time windows at customers on the capacity requirements of three warehouse processes – order picking, staging and loading.