Job Scheduling Optimization Of Cross-tier Shuttle-based Storage System And Retrieval Systems

With the vigorous development of e-commerce,the production mode has gradually changed from "large-scale and small variety" to "small batch and multi variety".At the same time,the operation type of the storage system has changed to focus on picking out and adding in.The Automated Storage/Retrieval System is no longer suitable for the needs,The Shuttle-based Storage and Retrieval System is widely used in the e-commerce storage environment because of its high flexibility and robustness.The Shuttle-based Storage and Retrieval System consists of three main equipment: shuttle,hoist and picking equipment.It is subdivided into the multi-tier system of one shuttle on each floor and the cross-tier system of one shuttle on multiple floors.The Multi-tier system has high efficiency and simple scheduling,but it fails to make full use of shuttle cars and hoists.Although the scheduling of the cross-tier system is difficult,it can ensure that the storage efficiency changes little,improve the equipment utilization of shuttle cars and hoists and reduce the storage cost under certain conditions.Therefore,the cross-tier system is favored in the current production model,The research on cross-tier system has certain practical significance.Job scheduling of shuttle storage system has greatly affects the storage efficiency,and the difficulty of cross-tier system job scheduling is how to coordinate the scheduling of three kinds of equipment,so as to reduce the waiting time between equipment.Taking the storage environment under e-commerce as the background,this thesis selects the cross-tier shuttle storage system of single-loading and double-loading as the research object,takes the overall job scheduling in the system as the research point,takes minimizing the system job time as the optimization goal,and uses the improved gray wolf optimization algorithm to study.Specific work includes:(1)Analyzes the hardware and software composition of the shuttle warehousing system,the operation process of picking and adding warehousing,a variety of parking strategies and scheduling principles,common picking methods and the main factors affecting the efficiency of warehousing operation,so as to lay a foundation for the following research.(2)The working conditions of single-loading shuttle and hoist are analyzed.Considering the advance movement of equipment,the working time of single-loading shuttle and hoist are calculated;Referring to the flexible job shop scheduling problem(FJSP),aiming at the shuttle storage environment,an optimized job scheduling model combined with FJSP problem is established;The grey wolf optimization algorithm is improved from the two directions of initializing the population and improving the global convergence of the algorithm.Several experiments are designed for simulation to prove the effectiveness of the algorithm and the effectiveness of the model.(3)The operation process and working conditions of the double-loading shuttle and the hoist are analyzed.Considering the advance movement of the equipment,the operation time of the double-loading shuttle and the double-loading hoist are calculated according to the different situation of the cargo location information;According to the characteristics of double-loading shuttle and hoist,a scheduling scheme based on cycle division is designed and a mathematical model is established;Using the improved gray wolf optimization algorithm,several experiments are designed for simulation,which proves the effectiveness of the model.Through experiments,the influence of the number of shuttles on the operation time of the storage system under different order sizes is simulated,so as to optimize the storage configuration.