Research And Implementation Of Path Planning For High-density AGV Express Parcel Sorting System

In recent years,with the rapid development of e-commerce,the number of express parcels has increased dramatically.People are demanding higher and higher speed of logistics.The speed of logistics has become the core competitiveness of logistics companies.The sorting of express parcels takes up a considerable part of the whole logistics.Improving the efficiency of sorting express parcels can improve the speed of the whole logistics.Traditional manual sorting efficiency and accuracy have not kept up with the development of the industry.Although automatic sorting systems such as cross-belt sorting machines have high sorting efficiency,they cover a large area and cost a high one-time input.Generally,they can only be found in large sorting centers.Their one-time high input also makes many small and medium-sized logistics companies dread,and once completed,they can't be changed,poor flexible and high energy consumption.Automated Guided Vehicle(AGV)has high flexibility and low energy consumption,which can better adapt to the characteristics of modern logistics such as multi-varieties,small batches and relatively centralized.Therefore,AGV-based express parcel sorting system has become one of the hotspots of intelligent logistics in recent years,and its research has important practical value.In order to improve the sorting efficiency of AGV-based express parcel sorting system,the number of AGV is usually increased as much as possible.In a fixed size site,the increase of AGV will increase the AGV concentration in the site,which makes the AGV concentration in the sorting site higher.In addition,the sorting center usually uses AGV which can walk freely and flexibly to carry packages,which easily causes AGV congestion,or even blockage,and makes the sorting efficiency of the whole sorting system decline sharply.Although the traditional path planning method can plan the shortest path,it can't solve the problem of congestion.Aiming at this problem,this paper proposes a CAA*(Congestion-avoidable A*)algorithm that is able to avoid congestion.Based on the A* algorithm,the algorithm introduces a dynamic attribute node to establish a dynamic environment model.The dynamic attributes of nodes record the AGV passing through the current node and its time points.Based on these information,the number of AGV in a certain time range of each node can be predicted to determine whether the node is a potential congested node.When encountering a potential crowded node during path planning,increase its traffic cost to avoid this potentially crowded node.The simulation of the actual project site shows that the AGV density of the proposed algorithm is 28.57% higher than that of the traditional A* algorithm,The sorting efficiency of the system has been improved by 24.29%.In order to realize the AGV-based express parcel sorting system,this paper simulates the actual sorting site,uses the grid map method to model its environment,designs the direction of grid nodes,and creates an electronic map of one-way road.Planning path for AGV using the CAA* algorithm proposed in this paper to avoid congestion.In order to expand and reduce system coupling conveniently,the system adopts a service-oriented system architecture.The whole system takes the control center as the core.The subsystem provides services to the control center through message bus.The subsystem does not depend on the control center and can be developed independently and run independently.Message Bus uses JSON as Data Transfer Protocol.All AGVs are controlled by centralized management,and the dispatching system and AGV communicate with each other through local area network.The dispatching system detects conflicts in real time when controlling AGV walking,and resolves conflicts according to the types of conflicts.