# Simulation-Based Performance Analysis for a Novel AVS/RS Technology with Movable Lifts
## 2 Literature Review on AVS/RS  
AVS/RS is first studied by [PERSON] [5] by proposing analytical conceptualization tools based on the characteristics of autonomous vehicle systems. He models the system to estimate expected performance metrics as a function of important system attributes such as storage capacity, rack configuration, and fleet size. The models are demonstrated for an exemplary problem and compared with analytical conceptualization tools. In a later study, [PERSON] [6] proposed a state equation model to predict the proportion of dual command cycles in autonomous vehicle storage and retrieval systems using interleaving. Although  
Figure 1: A shuttle-based storage and retrieval system (SBS/RS) from a single aisle view. the proposed model has some limitations, it is a useful tool for estimating the storage and retrieval cycle times in autonomous vehicle storage and retrieval systems. Differently, [PERSON] et al. [7] proposed cycle time models for class-based storage policies in a unit-load automated storage and retrieval (S/R) system. The proposed model is based on a queueing network approach to achieve sufficient accuracy and computational efficiency for system design conceptualisation applications. By considering non-Poisson arrivals, [PERSON] et al. [8] investigated approximation strategies for transaction waiting times in Autonomous Vehicle Storage and Retrieval Systems (AVS/RSs). Based on the simulation validation, the proposed strategies can reduce the amount of error in estimated transaction waiting times by about 80% compared to static approximations. Different from the above studies, [PERSON] et al. [9] conducted a simulation-based experimental design for unit-load (UL) automated storage and retrieval systems based on autonomous vehicle technology to identify factors influencing several performance metrics. To benchmark the warehouse solutions, they apply the method of Design of Experiment (DOE). In a later study, [PERSON] and [PERSON] [10] study simulation-based design for AVS/RS. They experiment several AVS/RS configurations by simulating their models and present various outputs from the multiple runs. A practitioner may select the best design based on his/her requirements. By introducing semi-open queueing network with class switching [PERSON] et al. [11] investigated the performance effects of AVS/RS design decisions by using an analytical model. A decomposition-based approach was developed to evaluate system performance of AVS/RS. The numerical studies provide various insights that could be useful in the design of AVS/RS. Performance comparison of two automated warehousing technologies, AVS/RS and crane-based AS/RS, was presented by [PERSON] and [PERSON] [12]. The results show that AVS/RS could provide better performance if the layout is also considered in the warehouse design. [PERSON] et al. [13] modelled an SBS/RS by an open queuing network model to estimate the performance of the SBS/RS in terms of lift and shuttle utilisation. For benchmarking the analytical model, they compare the results of the analytical models with the results of the simulation model. The proposed analytical models show good estimates for the performance indicators of SBS/RS. In a later study, [PERSON] et al. [14] presented the main design trade-offs for SBS/RS by using simulation. They completed their study for several warehouse design scenarios for tier-captive shuttle vehicles. Different from [PERSON] et al. [13; 14], [PERSON] [15] proposed an analytical travel time model for calculating single command and dual command cycle times for double-deep Shuttle-Based Storage and Retrieval Systems (SBS/RS). The proposed model takes into account the real operating characteristics of the elevator's lifting table and the shuttle carrier with the condition of rearranging blocking totes to the nearest free storage location during the retrieval process of the shuttle carrier. [PERSON] et al.