An analytical performance investigation of RCS/RS under a class-based access structure over the stack height

The requirements for modern storage systems are steadily increasing due to limited space, cost, time, and personnel. Robotic compact storage and retrieval systems (RCS/RS), where containers are stacked and arranged in a block layout with robots operating from above, offer a promising solution. Some systems benefit from a self-sorting effect, where robots relocate previously moved containers after accessing non-directly accessible ones, resulting in demand-based sorted stacks. Despite various analytical models for automated storage systems, RCS/RS remain under-researched. Apart from two distinct papers on performance evaluation, there are no general, fast, and easy-to-use tools to assess system throughput under demand-based access patterns. Additionally, the performance benefits of self-sorting have not yet been studied. This paper presents an analytical approach to predict RCS/RS performance using a class-based access structure. A discrete event simulation validates the model, and an optimization example demonstrates the model’s broad applicability and ease of use.