Optimization Research Of 3-Dimensional "Part-to-Picker" Combined Sorting System Considering Order Structure

With the development of "Industry 4.0" and "Made in China 2025",smart logistics has become the main direction for the transformation and upgrading of the logistics industry.Warehousing is the most important part of the logistics,and its investment cost and operational efficiency affect the total cost and response speed of the entire supply chain of an enterprise.The 3-dimensional "part-to-picker" combined sorting system uses elevated 3-dimensional shelf to store items,and a variety of intelligent robots realize storage and sorting operations,which can quickly achieve multi-variety sorting and complete pallets picking of large-volume orders efficiently,with its more flexible picking mode,more efficient and higher flexibility,has become an intelligent warehousing system with great development prospects.Orders are the power source of the 3-dimensional "part-to-picker" combined sorting system.The system stores and sorts items according to the order.At present,there are few studies on the combined analysis of the order structure and intelligent warehousing systems optimization.The complex and changeable order structure has seriously affected the operational efficiency of the warehousing system.Considering the order structure,planning and designing the 3-dimensional "part-to-picker" combined sorting system,and customizing the operation strategy that matches the order structure has important theoretical and practical significance for the application and promotion of the system.Therefore,this thesis mainly conducts the optimization research of the 3-dimensional "part-to-picker" combined sorting system that considers the order structure,and takes the order structure factors into consideration in the designing and the operation strategies optimization.First,a design optimization method based on the 3-dimensional "part-to-picker" combined sorting system considering the proportion of order items picking is proposed.Previous studies on the design optimization of the sorting system defaulted to the universality of orders,and the design parameters of the sorting system were determined by the requirements of system efficiency and storage capacity.This thesis introduces the concept of order matrix in the design and optimization of the sorting system for the first time,and uses the order matrix to identify the order picking ratio to characterize the order structure,and then proposes a system design optimization method that considers the order picking ratio.In this thesis,a closed queuing network model is constructed to evaluate system performance,and the mean value analysis is used to solve it.On the other hand,this article constructs a multi-objective system design model,and uses the non-dominated sorting genetic algorithm to solve it to obtain system design parameters that match the order picking ratio,mainly including the number of storage tiers,aisles,and columns in the pallet storage area.The number of storage tiers,the number of aisles and the number of columns in the totes storage area,the number of picking workstation,and the number of rail-guided vehicles combinations.Secondly,an outbound optimization method based on the 3-dimensional "part-to-picker"combined sorting system considering the order structure is proposed.The 3-dimensional "partto-picker" combined sorting system is divided into the pallet storage area and totes storage area according to the different storage containers,which can realize pallet picking,case picking,and item picking.For the first time,this thesis studies the matching problem of order structure characteristics and equipment operation in the aspect of system output optimization,and defines the item picking ratio and order intensity to identify the order structure characteristics.In addition,this article redefines the total order picking time as an evaluation indicator for output optimization,and proposes a heuristic order dividing algorithm that considers the order structure.According to the order structure characteristics and the matching rules for the output capacity of the two warehouse areas,it is summarized into three types:considering the proportion of order items picking,considering the capacity of the totes storage area,and considering the capacity of the pallet storage area.Finally,the effectiveness of the algorithm is verified through numerical experiments,and the interaction between the pallet and tote capacity,the output efficiency of the pallet storage area and the tote storage area,the order intensity,the item picking ratio and the order dividing algorithm are summarized,which provides reference for warehouse operators to better use the system.Then,a replenishment optimization method based on the 3-dimensional "part-to-picker"combined sorting system considering the order structure is proposed.The replenishment operation refers to the pallet storage area replenishing goods to the tote storage area,and the same item of the order in the wave is combined to calculate the required picking quantity,and the order is uniformly performed replenishment operations.This thesis proposes a replenishment strategy that matches the order structure,defines the item’s order frequency,order intensity,order density,and wave size to identify the order structure characteristics.By analyzing the structure parameters of the order picking within the wave,finally determining the number of items allowed for overstocking.The proportion of the number of items allowed for overstocking is to better weigh the contradictory relationship between the storage space of the tote storage area and the replenishment tasks and shorten the replenishment operation time within the wave.This thesis adopts the regression analysis method.Firstly,a simulation model is established through FlexSim software,13,440 order structure combinations are set,and according to the proposed replenishment strategy process,the experimental results are counted and the optimal plan parameters are selected,and then the MINITAB software is used to solve the relationship between replenishment optimization parameters and order structure parameters with the best subset regression analysis and stepwise regression analysis.Finally,the validity of the regression function is verified by numerical experiments,and the order structure parameters are analyzed and summarized on the system’s equipment replenishment tasks,storage space occupation,and replenishment operation time,which provides a reference for replenishment adjustments.Finally,this thesis proposes a comprehensive optimization method for the picking process of the 3-dimensional "part-to-picker" combined sorting system considering the order structure.The comprehensive optimization of the 3-dimensional "part-to-picker" combined sorting system is carried out from the two processes of replenishment and sorting.The comprehensive optimization of the system considers the picking scenarios of multi-wave orders and divides the orders into multiple batches according to the delivery time requirements.In the wave,the replenishment operations are first carried out in a centralized manner and then picked according to the order and item order.This thesis proposes a comprehensive optimization method for the whole process of matching order structure for the first time,which comprehensively considers order structure such as order picking ratio,order intensity,order density,wave size,wave number,item picking ratio,and item order frequency,etc.,and customized heuristic rules and dynamic order dividing algorithm.In addition,this thesis defines the total multi-wave operation time of the system as the optimization goal,establishes a comprehensive optimization model,and improves the simulated annealing algorithm to solve the model.In the algorithm design,the influence of order structure parameters is considered to realize the dynamic adjustment of the algorithm with the change of order structure.Finally,the actual operating orders of the enterprise are used to verify the effectiveness of the algorithm,and the influence of the frequency of item ordering,the number of waves,and the orders of different quarters on the optimization performance are analyzed.The results show that the comprehensive optimization algorithm of the whole process proposed in this thesis can greatly shorten the total operation time of the system.