Performance Analysis of a Class-Based Robotic Compact Storage and Retrieval System

Abstract

Warehouses are often characterized by low cube utilization, which becomes an issue with land scarcity and increasing land prices. Robotic Compact Storage and Retrieval Systems (RCS/RS) have been developed to increase space utilization. They do not require traditional picking- and cross-aisles. In such a system, a grid-based storage space contains bins stacked on each other. Moreover, robots operate on the roof of the system to lift or lower bins in stacks while transporting them between storage locations and ports. The question is what the dimensions of an RCS/RS should be because operation times for the system differ based on the speed of robots, as well as the x-, y- and z-dimensions and the number of bins. To minimize the expected operation time of a robot to complete storage/retrieval operations, we embed a discrete formulation of the generalized assignment problem in an enumeration over the z-direction to determine the optimum allocation of bins to locations in a three-dimensional class-based storage space and the best dimensions of an RCS/RS with the proposed algorithm in a reasonable time frame. We consider three classes of bins based on different skewness values for activity levels. Our optimization model can be used to design a new RCS/RS or analyze an existing RCS/RS based on its current system parameters. © IISE and Expo 2023.All rights reserved.