1. Introduction With the rapid development of China's civil aviation and logistics industries, increasingly higher demands are being placed on the processing capacity of logistics sorting equipment, and more and more domestic airports are beginning to use automated baggage sorting systems. Automated baggage sorting systems are mechatronic systems integrating computers, industrial control networks, PLCs, and electrical control. They have advantages such as high efficiency, speed, and high integration, and have broad application prospects. Advanced automated sorting technology was previously controlled by developed countries. Currently, most of the automated baggage sorting systems used in major airports in China are imported complete systems, which, although performing well, are expensive. In recent years, some domestic units have developed automated sorting systems with independent intellectual property rights, and these systems have been promoted and applied to some extent. This paper introduces an interface method between an automated baggage sorting system developed abroad and a flight database. 2. Introduction to Automated Baggage Sorting Systems 2.1 Control System Structure The baggage sorting system (BHS) includes both departure and arrival systems. This paper only discusses the departure baggage sorting system. This system adopts a three-level control structure of information network, control network, and remote I/O link. The two departure control computers use the WINDOWS NT4.0 operating system and INTOUCH 7.0 industrial configuration software, with mutual hot standby and dual network cards. Besides forming an Ethernet network with the Airport Computer Integrated System (SI) and the Computer Departure Control System (DCS), they also form an Ethernet network with the lower-level main controller PLC. The PLCs are two large-scale processor PLC-5/80 from AB, with mutual hot standby. Besides forming an Ethernet network with the upper-level computers, they also form a DH+ network with the emergency handling terminal PanelView. The PLC-5/80 not only has rich logic processing capabilities but also very powerful data processing capabilities. The system structure is shown in Figure 1. [align=center] Figure 1 System Structure Diagram[/align] 2.2 Automated Sorting Principle The baggage sorting system (BHS) must exchange data in real time with the Airport Computer Integrated System (SI) and the Computer Departure Control System (DCS). The PLC-5/80 must acquire the following three types of data information. The data flow is shown in Figure 2. A. Flight Information. This information is read from the flight database of the airport computer integrated system by the upper computer of the baggage sorting system and forwarded to the lower PLC. The flight information includes: flight number, destination code, check-in start time, check-in end time, and departure time. B. Message. This message is generated by the check-in computer when passengers check in their baggage and sent to the airport's departure computer system. It is then sent to the upper control computer of the baggage sorting system via the message interface machine. The upper control computer transmits the message to the PLC through the internal LAN. The baggage message contains information such as flight number, destination code, serial number, and number of baggage pieces. C. Baggage Barcode Information. The baggage barcode contains the baggage serial number. It is generated by the check-in computer when passengers check in their baggage and printed as a barcode label, which is affixed to the baggage. When the baggage passes through the scanning station, the barcode information is automatically scanned by the barcode reader and transmitted to the PLC. To achieve automatic sorting, the PLC must compare the received data twice. First, the PLC compares the baggage barcode information and message information one by one. If the baggage barcode information and message information have the same baggage serial number, it determines that the barcode and message belong to the same baggage (the barcode information contains the baggage serial number, and the message contains the baggage serial number and flight number information). Then, the message information is compared one by one with the flights in the flight allocation table in the PLC. If the corresponding information segments are the same (flight number, destination code), it determines that the baggage with this barcode label belongs to that flight. [align=center] Figure 2 Data Flow Diagram[/align] 2.3 InTouch 7.0 Configuration Software InTouch is the central hub for all information interaction in this system. Flight information and message information are sent to the lower-level control PLC through InTouch. InTouch is a human-machine interface (HMI) development tool for industrial control developed by Wonderware, providing the configuration environment WindowMaker and the runtime environment WindowViewer. The system is customized in the configuration environment, including database configuration, screen configuration, and definition of the system's data acquisition and control tasks. These tasks are performed in the runtime environment by executing InTouch QuickScripts, recording and reporting alarm and line history data, and transmitting the data in real time to other tasks on the local station and other workstations on the network. InTouch 7.0 supports Dynamic Data Exchange (DDE) and can be used as a client and server for DDE and SuiteLink communication protocols. Through DDE and SuiteLink, InTouch 7.0 can communicate with other Windows programs, Wonderware I/O servers, and third-party I/O server programs. This system uses Wonderware's Ethernet communication protocol server ABTCP to implement communication between INTOUCH and the lower-level PLC. Consistent with the DDE naming convention, InTouch uses a three-part naming convention to identify data elements in the I/O server program, including VIEW (application name), TAGNAME (subject name), and ActualTagname (item name). To obtain data from another application, the client program (InTouch) opens a channel to the server program by specifying these three items. In addition, it must know the name of the application providing the data value, the subject name and item name of the application containing the data value. When another Windows application requests a data value from InTouch, it must also know these three I/O address entries. The I/O type tag name must be associated with an access name, which contains information used to communicate with other I/O data sources, including the node name, application name, and topic name. 3. Communication Protocol Introduction 3.1 Dynamic Data Exchange (DDE) Dynamic Data Exchange (DDE) is a communication protocol developed by Microsoft that allows applications in a Windows environment to send/receive data and instructions to each other. It establishes a client-server relationship between two concurrently running applications. The server application provides data and accepts requests from other applications interested in that data. The requesting application is called the client. Some applications (such as InTouch and Microsoft Excel) can act as either a client or a server program simultaneously. DDE uses a three-step naming convention to identify data: a. Applications: The name of the DDE dialog application. b. Topics: The dialog topics supported by the server. A DDE application name can have multiple topics to distinguish the type of dialog. c. Items: The specific data item names under the dialog topics. 3.2 Open Database Connectivity (ODBC) ODBC is a standard interface developed by Microsoft for accessing different databases, based on Structured Query Language (SQL). An application can access heterogeneous databases through this universal interface. Accessing an ODBC data source requires ODBC driver support. First, the data source must be registered using an ODBC manager. The manager establishes a connection between ODBC and the specific database based on the database location, database type, and ODBC driver information provided by the data source. Thus, as long as the application provides the data source name to ODBC, ODBC can establish a connection with the corresponding database. 4. Flight Database Interface The flight database SYBASE pre-enters flight information for the entire day based on the flight schedule. SYBASE is a client/server architecture database management system that supports SQL as the query language. The baggage sorting system's host computer, equipped with SYBASE client software, retrieves flight information from the SYBASE flight database and sorts the flights according to their check-in start time. Baggage chute resources are limited. The baggage sorting system always allocates chutes to the flights that check in first within a given timeframe. When a flight's check-in is complete, it is deleted and a new flight is added. This necessitates that flight information read from the flight database be processed before it can be used by the baggage sorting system. InTouch's data processing capabilities are limited. This system accesses Sybase via Excel, processes the read flight information, and then InTouch reads the processed data from Excel. Excel is a powerful spreadsheet software with rich data processing, charting functions, and various functions and tools. Excel's VBA (Visual Basic for Applications) macro language is a subset of Visual Basic, offering powerful functionality and simple, fast data processing methods. Multiple macros developed in Excel VBA are used to access the flight database and process and organize the data. First, Excel periodically accesses the database by customizing query times, reading the updated flight information into a table. Then, based on the actual availability of chutes, a chute allocation table is customized, adding the appropriate number of flights and sorting them by check-in start time. Each flight is then assigned a chute, establishing a one-to-one correspondence between flights and baggage chutes. Flights to a single destination occupy one chute, while flights to multiple destinations occupy multiple chutes. An identical display screen to the Excel flight allocation table is created in the INTOUCH upper-level interface, reading all the data from the Excel chute allocation table. This completely replicates the Excel chute allocation table in the INTOUCH database. Through the Ethernet I/O server ABTCP, the lower-level PLC reads the chute allocation table into its own database, establishing a one-to-one correspondence between flights and baggage chutes on the lower-level PLC. The PLC determines which flight the baggage belongs to by receiving two additional pieces of information: the baggage barcode and the message. This determines the flight number of the baggage and thus its chute number. 5. Conclusion While Excel provides convenient and quick access to the flight database, allowing the baggage sorting system to accurately allocate baggage to designated chutes, the background flight database causes chutes to be reassigned upon system restart, leading to baggage confusion. Converting the flight database to a front-end database would preserve the previous chute allocation data after a system restart. Furthermore, chutes are allocated based on flight destinations. When a flight has multiple destinations, it occupies multiple chutes. If chutes are insufficient, baggage from flights currently checking in without available chutes will be largely abandoned. Changing the chute allocation rules so that multi-destination flights share a single chute can improve this situation and reduce baggage abandonment. Therefore, these two points represent the next technical challenges for system upgrades.