Modeling and evaluating the AVS/RS with tier-to-tier vehicles using a semi-open queueing network

The Autonomous Vehicle Storage and Retrieval System (AVS/RS) with tier-to-tier vehicles is modeled as a semi-open queueing network (SOQN). Different storage/retrieval requests in the AVS/RS are modeled as different classes of customers in the SOQN model. Analyzing multiple configurations of an SOQN via computer simulation is time-consuming. Therefore, this article uses some analytical methods to evaluate the performances of a multi-class, multi-stage SOQN with general service time and interarrival time distributions. Two synchronization policies are also compared and the results show that an AVS/RS with virtual synchronization has a better performance than that with physical synchronization.