1.Background
The initial form of transfer warehousing is basicInvoicing (Invoicing software mainly focuses on the management of inventory, purchasing and sales, and WMS focuses on material handling, storage and sorting operations within the warehouse; the former addresses the ability to manage goods, and the latter is a process guidance and standardization system for warehouse operations based on the former. The initial form is positioned at The warehousing module in the quality inspection system; therefore, it only undertakes a relatively fixed and simple physical purchase, sale and inventory process, and has no other decision-making, process, etc. ability. In its initial form, it only operated a few self-operated sites, and the inventory volume was at a level that could be handled manually. However, with the rapid development of the business, the volume of goods returned to the warehouse continued to grow, and the system's operating efficiency was facing increasingly serious challenges. Bottleneck challenge.
1.1 Introduction to transfer warehouse
Based on the above background, we have developed a brand newWMS system, which is different from the purchase, sales and inventory system; the Zhuanzhuan WMS system is based on the WMS standard Designed a process and management model that is more suitable forsecond-hand goods. Since then, Zhuanzhuang said goodbye to the inefficient and single-function purchase, sale and inventory system and moved towards A new chapter in creating a smarter and more advanced WMS standard warehouse. In this process, the introduction of automation equipment is crucial; with the cooperation of system process optimization, it will improve warehouse operation efficiency and reduce labor costs. And achieved a great leap forward in operation mode.
1.2 Evolution of operating modes
With the rapid development of Zhuanzhuan business, higher requirements have been put forward for the efficiency and accuracy of contract fulfillment warehousing; with the help of system process optimization iterations and the introduction of auxiliary hardware equipment, Zhuanzhuan Warehouse has achieved three major leaps in its operating model.
The nouns involved in the above picture are explained as follows:
- PDA: Handheld terminal device (Android system).
- DPS: Lighted electronic shelves.
- Assembly line: A production organization method that connects work processes in a streamlined manner.
- AGV: AGV intelligent handling robot.
- Conveyor line: A conveyor belt that transports goods continuously.
In the process of transforming from paper orders to paperless and unmanned, Zhuanzhuan built its own equipment control system (WCS).
2. Equipment Control System (WCS)
The WMS system mainly focuses on the BS architecture system belonging to the software layer in business-related processes; however, the introduction of automation hardware will inevitably require dealing with the hardware layer, which requires a system for docking and controlling the hardware; refer to the industry standard, so we introduced the equipment control system, referred to as WCS (hereinafter referred to as this name).
2.1 System architecture
WCS is a management control system between the WMS system and the PLC (programmable logic controller) system. On the one hand, the WCS system interacts with the WMS system, accepts WMS system instructions, and sends them to the PLC system, thereby driving the production line to produce corresponding operations. On the other hand, it reflects the status and data of the PLC system in real time, and provides interface debugging for the PLC system and production lines. The following figure shows the architecture diagram of Zhuanzhuan WCS:
2.2 Communication protocol
The hardware devices connected to WCS support communication in different forms. Therefore, the communication protocols currently used by the WCS system include the following categories. The application scenarios of each protocol are explained in detail below.
2.2.1 HTTP
HTTP Hypertext Transfer Protocol is the cornerstone of the Internet, and HTTP itself is very popular and applicable. Among the hardware connected to WCS, it is mainly used in equipment with simple software and hardware interaction and hardware manufacturers supporting HTTP; for example: the sorting chute used in the warehouse (a device used to allocate goods to different exits according to their attributes), From the perspective of interaction, the sorting chute only needs to request the background interface once to complete the operation.
Interaction process: Take a photo and scan the QR code -> Request product export -> Execute distribution
2.2.2 SSE
SSE is a technology that only sends text messages from the server to the client in a browser-based WEB application. It is based on the persistent connection in the HTTP protocol and is a lightweight long connection protocol introduced by the HTML5 suite. The main application is a scenario where only the server pushes to the client; for example: automatically receiving and printing picking tasks (in the WMS operation process, picking orders need to be automatically printed based on the picking status). In this scenario, the printer service acts as a client The client needs to automatically execute printing tasks according to business processes; in addition to the scheduled polling method, SSE is more convenient in this scenario.
2.2.3 WebSocket
WebSocket is a new protocol launched under the HTML5 standard. Its main feature is to realize full-duplex communication between the client and the server. As a full-duplex communication protocol, it allows both requesting parties to send data to each other. According to this feature, warehouse applications are mainly used in scenarios where WCS and hardware require two-way communication; since some hardware supports only wired connections, in order to achieve server-side cloud control, we provide local< a i=1>WebSocket client is used to connect localized hardware to the cloud. For example: to light up electronic shelves (inventory shelves with lighting capabilities), in addition to the server pushing the lighting instructions to the electronic shelves, you also need to pay attention to the results of the execution of the lighting instructions.
In the WebSocket long connection application scenario, our solutions to some of the problems encountered by long connections are as follows:
- WebSocket client hot backup; in some scenarios, long-connection clients need to maintain high availability; therefore, the approach adopted for such scenarios is to use Keepalived to implement multi-machine hot backup for two local physical machines, and provide VIP services to external parties. ;The process is as follows:
- WebSocket messages are lost; the handling strategy for the scenario of long connection message loss is as follows:
- WebSocket heartbeat reconnection implementation; connection channel idle timed heartbeat, timeout reconnection. As shown below:
2.2.4 TCP
The application scenario of the TCP protocol is mainly that the control programs provided by some manufacturers only support TCP; for example: a photo camera of a certain Kang manufacturer. In the WMS application scenario, the camera is responsible for recording the delivery time of the order in the delivery assembly line; the package reaches the camera through the conveyor belt After entering the photo area, the camera will automatically take photos, save them and upload key data to WCS.
2.3 System monitoring
The WebSocket long connection client monitoring page is as shown below. This page can monitor the real-time status and real-time hardware configuration of all WebSocket long connection clients.
The WebSocket long connection message monitoring page is as follows. After connecting to the company's Prometheus monitoring system, real-time monitoring and early warning of indicators such as the amount of message loss and the number of message retries of the WebSocket long connection can be carried out.
3. Equipment empowerment business
The above describes the types of hardware we connect to WCS and the protocols we use. How do these hardware empower our business? Next, let’s take a look at the implementation of the device in the WMS process (refer to 1.2 for the device name below).
3.1 Warehousing business
The warehousing business refers to the process of putting products on shelves in the system and generating inventory. The main process is: scan the product barcode -> select the shelf location -> enter the shelf quantity -> release inventory; analyze from this process , the first three stages require human operation; for these three stages, our equipment is used in different operating modes as follows:
As can be seen from the above table, as the degree of automation of the operation mode increases, fewer and fewer steps are required for manual operation, and the efficiency of the operation becomes higher and higher.
3.2 Warehouse out business
The outbound business refers to the process of goods carrying out outbound delivery tasks and deducting inventory. The main manual operations are: picking -> sowing -> review; for these three nodes, we have added corresponding automation equipment. , the following is a comparison under different modes:
- Picking
- sowing
- Outbound - review
3.3 Others
In addition to the above-mentioned devices embedded in the process, there are also some devices that are completely localized and deployed; that is, some hardware that does not interact with the system can also assist the system process to be accurate and fast in certain scenarios. Some hardware and application descriptions for the following applications:
3.3.1 Abnormal rejection baffle
The application scenario is: In the automated outbound assembly line, there may be some hardware failures that cause outbound documents to not flow normally; such abnormal data will be automatically pushed out of the normal assembly line when passing through the abnormal removal baffle scanning head and handed over to warehouse personnel. Manual processing.
3.3.2 Automatic packaging machine
After the outbound personnel perform the outbound review process, the goods and other invoice accessories have been placed in the package. At this time, you only need to place the package on the assembly line, and the package will be automatically packaged and delivered to the logistics collection office.
4. Summary
With the rapid growth of Zhuanzhuan business, the requirements for warehousing capacity are also increasing. To this end, we have introduced automated equipment into the entire process, optimized system strategies in a targeted manner, and strengthened the combination of software and hardware to better support business development. This article aims to share Zhuanzhuan Warehousing's ideas for building a WCS system and its practical experience in the application of automation equipment on the basis of fully considering its own business characteristics.
5. Reference links
- https://en.wikipedia.org/wiki/Warehouse_management_system
- https://zhuanlan.zhihu.com/p/29401678?utm_source=wechat_session
About the author
Tu Zhiwu Contract fulfillment business middle-end R&D
Zhuanzhuan is a technical learning and exchange platform for R&D centers and industry partners, regularly sharing frontline practical experience and cutting-edge technical topics in the industry.
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