A Study Of Packing Strategy Of Mini-load Automated Storage And Picking System In Medical Logistics Distribution Center

Nowadays, the features of the medical logistics distribution center present a trend that the quantity of the orders is small but the varieties are more. For the drugs which outbound is small amount, the traditional medical logistics distribution center still chooses the "the people to the goods" mode to sort the drugs. The workers walk to the position where the aim drug is, and pick up the specific drug to the order basket. But now, more and more medical logistics distribution center uses another way to sort the drugs, the mini-load automated storage and picking system, to improve the picking efficiency, reduce the worker labor intensity, improve the utilization rate of the warehouse. It’s a "the goods to the people" mode picking system. The system bases on the multi-layer shuttle car system to complete the picking and sorting tasks, and the smallest storage unit is unified specifications box. The shuttle of each layer picks the small box at the same time and transports it to the export of the layer, then the elevation pick it and transports it to the I/O, to complete a line of an order. This paper is going to study the strategy about how to store the drugs in a small box and how to store the different small boxes in the system to improve the picking efficiency.For the packing problem in a box, this paper divided this problem into three aspects:single box single item, single box multi-items, multi-boxes multi-items. The paper used the dynamic planning method to solve packing problem with a same size to improve the loading efficiency of the box, reduce the times of replenishment. When a box need to load multiple items, through the analysis of the medical orders of a period of time to get the correlation between the different items, we use these correlation to cluster the items, and load the items related to the cluster results. This method can achieve a goal that the shuttle only need to pick one box to get many items the order need. When an item of the drug only can be loaded in a box, the packing strategy based on heuristic tired accumulation class algorithm, select the drugs which have the minimum correlation as seeds, and cluster the other items to the different group by the result of the correlation. When an item of the drug can be loaded in different boxes, after getting the results of the K-means clustering algorithm, this paper introduced a concept of membership degree in fuzzy clustering and use it on the result got last step. Based on the membership degree matrix uses a heuristic packing method, making that the relevant in the same box is strong while between the boxes is poor. Eventually using MATLAB to test the method with a real orders of a medical logistics distribution center, proved that the multi-boxes multi-items packing mode optimizes most to the efficiency.For the store-space assignment problem of the system between the boxes, as same as the normal store-space assignment problem, the key is to think the box as a unit not some different items. When there is only an item in the box, we can see each item as a unit; when there are many items in one box, we need to see them as a unit, to analysis the correlation among the boxes, using the improved adaptive DBSCAN clustering algorithm for box clustering, get the store block. According to the characteristics of the multi-shuttle transport system, assign the cluster to the different position of the system. Eventually using MATLAB as a tool to test the method, the result showed that this method does solve the store-space assignment and optimize the picking efficiency than before.