Joint Order Batching, Batch Assignment And Sequencing, And Routing Problems On E-commerce Warehouse

Warehouses and logistics play a key role in online to offline business.For manual warehouses,order picking is an important process in warehouse distribution center.With demands for faster services,if each order is given a due date,it is crucial for fast order picking.When a set of orders arrive,the orders are grouped in batches,and pickers are assigned to a number of batches,then the picker begins to pick the batch one by one.One batch means a picker routing job,which should pick all items in the batch.When the batch is picked completely,the completion time of the order equals to the completion time of the batch.The tardiness is defined by the order completion time and due date.It is significant to optimize tardiness to improve service level.The above-mentioned processes are closely connected,while previous literature only studied specific aspects.Thus,this paper studies the integration problems of order batching,batch assignment and sequencing and picker routing innovatively and establishes a mixed integer programming model.Due to the NP-hard property,the problem is applied with heuristic algorithms.First,the initial solution is generated by using the earliest start date rule or the improved saving method.Then,the problem of order batching,batch assignment and sequencing is solved by using variable neighborhood descent algorithm and variable neighborhood search algorithm.The 2-opt method and Simulated Annealing algorithms are applied in picker routing.Numerical and simulation results show that,while optimizing the picking process simultaneously,we can reduce the total tardiness further.When the time window of order is urgent or the quantity is large,the initial solution given by the improved saving method is better than the earliest start date rule.Finally,we compare the impact of different heuristic algorithms on experimental results.