Performance Evaluation Of RMMR System With Different Deep Lane Under Zoning Policy

Based on the advantages of the RMMR system,the application of the RMMR system is an idea to solve the two major problems of "how to improve the operational efficiency of the storage system" and "how to use limited land resources to meet the rapidly growing storage demand".The RMMR system completes the picking and replenishment operations by robots carrying movable shelves.It is very suitable for e-commerce distribution centers with a wide range of products and large demand fluctuations.This paper takes the robot in the RMMR system under the zoning policy as the research object.Aiming at the single picking process of the robot,the expected travel time model of the robot under the condition of the single-deep layout for RMMR and the uniform motion state is developed.Next,the walking process of the robot in the uniformly variable motion state when the random storage strategy and the fixed storage strategy used in each zone respectively,and the walking process of the robot in the uniformly variable motion state under the condition of multi-deep layout are studied.We calculated separately expected travel time corresponding to the four system characteristics.By comparing with the results of numerical experiments,the expected travel time calculated in this paper has very high accuracy.This paper analyzes the influence of the parameter combinations composed of the proportion of different zones' storage positions and the probability that the pods in different zones are determined as the target pods on the expected travel time of the system.The results show that:(1)Under zoning policy,when A-class-goods is stored in the middle of the pods storage area,the lower limit of the turnover grade of A-class-goods should be guaranteed to be as high as possible within a reasonable range;(2)When the system characteristics and assumptions studied in this paper are met,and under different parameter combinations,the zoning policy of A-class-goods stored in the middle of the pods storage area is always better than that of A-class-goods stored in at both ends of the pods storage area.This paper calculates the difference between the expected travel time when the random storage strategy and the fixed storage strategy are adopted in each zone under different parameter combinations.The calculation results show that,on the basis of satisfying the relevant assumptions and system characteristics proposed in this paper,when the system planning and design decision makers choose the storage strategy in each zone based on the expected travel time,the random storage strategy and the fixed storage strategy have almost completely equivalent effects under different parameter combinations.Under the condition of some fixed parameters,this paper studies the optimal layout of the system under different index constraints.The results show that:(1)If the expected travel time is used as a reference index for planning and design,the optimal solution corresponding to the lane depth d =1 is the global best optimal layout;(2)If the three indexes of expected travel time,space utilization,and time cost of occupied lane are considered at the same time,the feasible combinations formed by the weights of the indexes within certain conditions correspond to the optimal system layout.The decision makers can determine the layout plan based on the weight range.The main research significance of this paper is as follows:(1)This paper provides a system analysis method.According to the characteristics of the system,this paper analyzes the travel process,evaluates the system performance with the expected travel time model and different parameter combinations,and optimizes the system layout.(2)This paper provides the basis of the optimal design.In order to improve the system space utilization,this paper studies the system's lane depth.The research process of the optimal layout of the system under fixed parameters provides a reference basis for system decision-makers to optimize the design.(3)This paper provides a comprehensive analysis method of multiple decision-making indexes.In a multi-deep lane system,this paper solves the optimal layout of the system under fixed parameter conditions based on three planning indexes: expected travel time,space utilization,and time cost of occupied lanes.The entire analysis process can be used as a reference process for decision-makers to comprehensively analyze the influence of multiple decision-making indexes on the system layout.