Simulation study of miniload-workstation order picking system

This report provides a detailed elaboration on the simulation study of a miniload-workstation order picking system, which was carried out by the Systems Engineering Group at TU/e under the FALCON project. The study is regarded as a starting point towards creating a fast, simple and accurate model for performance analysis based on simulation models. The purpose of this simulation study is to create a detailed simulation model that represents an operating, industrial scale distribution center (DC). As a reference case, an existing DC was selected. The main characteristic of the reference case DC is the use of state-of-the-art Automated Storage/Retrieval System (AS/RS), which is becoming a common practice for large scale DC. The type of AS/RS used in this DC is referred to as the miniload-workstation order picking system, or the end-of-aisle system. Our approach is to create a flexible and modular model architecture such that the model is not restricted to be used only for the reference case. The proposed architecture allows different system structures to be modeled by adding slight changes to the current architecture. The simulation model is built using a process algebra based simulation language $\chi$. The proposed model is structured into three areas and four layers. Furthermore, clustered subsystems and decentralized controls are applied to the model architecture. We validated the proposed model and performed some experiments to evaluate the performance of the DC in terms of flowtime and throughput. Furthermore, we show that different system configurations can be modeled using the proposed architecture. We conclude that our model has covered sufficient details from the reference case and hence can be used further as the base model for evaluating the performance of aggregation methods under development.