Abstract: This paper first analyzes the hierarchical structure of a network-based remote control system and proposes a network-based industrial remote control system. The system adopts Microsoft's latest .NET technology, using Visual Basic .NET as the development language, Visual Studio .NET and other software as development tools, SQL Server 2000 as the database platform, and utilizes ASP.NET, ADO.NET, and ActiveX technologies to develop a Web-based remote monitoring system. Keywords: Remote control; Network; SQL 1 Introduction Control systems are products integrating computer technology, control technology, and network technology. They feature strong control functions, ease of operation, and high reliability, and can be conveniently used for production control and management of industrial plants. With the development of network technology, various advanced technologies are constantly emerging, such as remote control and remote manufacturing. This paper applies laboratory remote control technology to industrial sites and designs a network-based industrial remote control system. 2 System Block Diagram The overall block diagram of this industrial remote control system is shown in Figure 1. [align=center]Figure 1 System Block Diagram[/align] 3 Specific Implementation of Remote Control Network Structure 3.1 Field Control Equipment The equipment layer in this paper mainly includes: THJ-2 type advanced process control system, SIEMENS frequency converter, intelligent digital display, various sensors, SIEMENS PLC S7-200, and intelligent acquisition modules, etc. Among these devices, SIEMENS PLC S7-200 acts as a lower-level machine as a controller, serving as a bridge between the field device layer and the field control computer layer. SIEMENS PLC S7-200 is connected to the industrial computer's RS-485 via a PC/PPI cable. The S7-200 CPU integrates a microprocessor, an integrated power supply, and digital I/O points into a compact package, forming a powerful micro PLC. After the program is downloaded, the S7-200 can control the I/O devices according to logical relationships to achieve the application requirements. Various types of expansion modules can also be used to improve the CPU's functionality. In this system, the temperature, weight, and pressure of the expansion tank are controlled using the analog input/output module EM235. 3.2 Field Control Computer The field control computer used in this system is an Advantech industrial PC. In terms of hardware, it has an RS-485 interface and supports ISA and PCI data acquisition cards, making it easy to connect to field devices. In terms of software, it is equipped with dedicated programming software for developing, editing, and controlling custom applications to control the programmable controller. For example, STEP 7-Micro/WIN programming software is used to edit applications and control the S7-200 digital/analog input/output. It also includes MCGS 6.0 network configuration software to display control screens and SQL Server 2000 for data storage. 1. Communication between the Industrial Control Computer and the THJ-2 Advanced Process Control Device Communication between this experimental device and the industrial control computer uses the RS485 serial communication protocol. An RS232/485 converter card is installed on the industrial PC to convert the RS232 communication protocol signals to RS485 communication protocol signals. Communication with all instruments is achieved through the RS485 serial interface on the side of the instrument control console. Two-wire twisted-pair cable is used for communication. The industrial control computer is equipped with MCGS configuration software. In the device window of the configuration software, add the drivers for the AI ​​series intelligent instruments in the device toolbox. First, double-click the general serial port device in the device toolbox, and then double-click the drivers for different models of AI series intelligent instruments to connect them to the general serial port device. The parameter settings of the general serial port device should be consistent with the parameter settings of the intelligent instruments, including the minimum acquisition cycle, communication baud rate, etc. 2. Database Server: In modern industrial production sites, due to the extensive use of various types of control equipment, a large amount of production data is usually generated. This requires the configuration software, which constitutes the core of the control system, to have powerful data processing capabilities to effectively and rationally process this production data. On the one hand, it provides field operators with real-time and reliable images and curves to reflect the field operation status and facilitate corresponding control operations; on the other hand, it also needs to provide enterprise managers with various types of data reports, providing reliable first-hand information for enterprise management. The MCGS configuration software can perform preliminary data processing. This software divides the data processing process into three stages: data preprocessing, real-time data processing, and data post-processing, to meet various needs, as shown in Figure 2: [align=center] Figure 2 Data Processing Flow[/align] 1) Data Preprocessing. In practical applications, the data input or output from hardware devices is generally physical values ​​such as voltage and current within a specific range. These data usually need to be converted to obtain truly meaningful engineering data. For example, data acquired from the AD channel is generally voltage mV values, requiring range conversion, table lookup, calculation, etc., to obtain the required engineering physical quantities. The MCGS system can perform eight forms of data processing on the data acquired from the device's acquisition channels. Various processing methods can be performed individually or in combination. MCGS data preprocessing is closely related to the device. In the MCGS device window, open the device component and set its data processing attribute page to configure MCGS data preprocessing. 2) Real-time Data Processing. MCGS uses a Microsoft Access database by default as its historical data storage database. It employs database technology to manage and maintain the stored data. The database filename and path are set in the main control window properties. During system operation, MCGS automatically performs data storage operations. This is a very effective way to manage user data openly. However, using an Access database is also limited by its inherent characteristics. In particular, when the amount of stored data in a user project is large or when data from a long period needs to be stored, using an Access database can lead to performance degradation due to the large database file size. To address this, MCGS provides a data backup mechanism, storing historical data as multiple flat files in a specified location on the hard drive or connecting to other databases via ODBC. The puffing system uses a SQL Server 2000 database. MCGS can automatically store the collected data into the SQL Server 2000 database. Only the Microsoft SQL Server 2000 server-side component needs to be installed on the database server, and the SQL Enterprise Manager tool provided by SQL Server 2000 can be used to create the database. This is relevant to the puffing explosives database. Database tables are automatically generated in the specified database according to the needs and settings of the control layer. A key database table used is "Vacuum Degree" in the "Expanded Explosives" database. Note: For data objects that are not group objects, they are stored as independent objects based on changes, and as members of group objects, they are stored periodically. The same object uses two different storage methods and is stored in different locations within the data file. When a single data object is stored, the data value mainly reflects the change of that object's value over time, while the data stored for group objects focuses on recording the values ​​of all its members at the same moment. A data object that is not a group object may be a member of multiple group objects simultaneously, and may be stored in several places, with each part of the stored data being independent. Generally, group objects are used for storage because storing group objects simultaneously stores all members of the group object. In the historical data database, each group object corresponds to a data table, and its members correspond to corresponding fields. If a single variable is defined and stored, then that variable corresponds to a table and field in the historical database. If there are many variables, the number of tables in the database will be large. In practical engineering applications, multiple engineering physical quantities are related. Historical reports and curves need to display the historical data corresponding to multiple variables simultaneously. In this case, group objects are used to ensure the simultaneity of the stored data, making the comparison of historical data for multiple variables physically meaningful. 3) Data post-processing. Data post-processing in configuration software is essentially the processing of the historical database. The historical data in the database is extracted to obtain data and information truly useful to the user. Then, these data and information are displayed or printed visually through functions such as historical curves, historical tables, Excel report output, and data browsing. This paper uses the ADO.NET component in ASP.NET to access stored data. ADO.NET reads SQL Server database tables, using expanded vacuum degree data as an example to illustrate the implementation of ADO.NET reading SQL Server data. 3.3 Web Server Implementation The web server is the key to the entire system, acting as a relay. It mainly includes five processes: login interface, experimental parameter setting interface, experimental result display interface, Socket server, and Socket client program. Its structure is shown in Figure 3. [align=center]Figure 3 Web Server Structure Diagram[/align] The login interface, experimental parameter setting interface, and experimental result display interface are all dynamic web pages built using ASP.NET. The Socket client program and Socket server program are written in VB.NET. Setting up both the Socket server program and client program in the Web server simultaneously allows the modified experimental parameters to be sent to the industrial control computer in a timely manner, enabling online real-time parameter adjustment. Simultaneously, the sampled values ​​sent back by the industrial control computer are written to an XML file. Experimental parameters are transmitted from the parameter setting interface to the Socket client program. They communicate using Microsoft Message Queues and execute concurrently. The Socket server program writes the sampled values ​​sent back by the industrial control computer to the XML file. The experimental result display interface simultaneously reads this file and converts the data into graphical representations for the user. 1. The dynamic web pages—login interface, experimental parameter setting interface, experimental result display interface, and configuration demonstration interface—are all implemented using ASP.NET. Different databases are used for login, parameter setting, and experimental result display, while the configuration demonstration interface uses ActiveX components. The following describes how to embed the MCGS configuration interface into a webpage using ActiveX components: First, open VB, create a new project, add an index for the browser component in the ActiveX Toolbox, create a browser component on the form, and adjust its size. 2. Message Queues - MSMQ As can be seen from the architecture, this system adopts a multi-module, multi-process model. To improve system speed, processes need to execute concurrently. To ensure coordinated work between processes, a corresponding mechanism is necessary. This mechanism should have low coupling and high reliability. Microsoft Message Queues (MSMQ) is a communication mechanism that meets these conditions, providing a reliable asynchronous and loosely coupled communication mechanism. MSMQ Implementation Principle: The message sender puts the information it wants to send into a container (called a message) and saves it to a message queue in the system's shared space; the local or remote message receiving program then retrieves the message sent to it from the queue for processing. Because MSMQ uses asynchronous communication, neither the sender nor the receiver needs to wait for a success message before executing the remaining code, thus enabling concurrent process execution. The message format is user-defined and can be easily encrypted. Since MSMQ represents packaged service requests, when logs are required, only a copy of each message needs to be automatically generated for the relevant log queue, which is beneficial for system recovery and security. 3. Data Exchange Process Using DDE The system in this paper uses DDE hotlinking, with Excel used as an intermediate cache unit between MCGS and browser data. Variables Dat01-Dat100 are defined in the MCGS "Real-time Database" window. According to project requirements, some variables need to be output by DDE, while the rest are input by DDE. Select the "DDE Connection Management" menu item from the "Tools" menu in the MCGS configuration environment. 3.4 Proxy Server The proxy server software used in this system is Sygate, a gateway server configuration software that is easier and more user-friendly than Wingate. Sygate is a software that allows users on a local area network (LAN) to share an internet connection with other users on the LAN, enabling two or more computers to access the internet simultaneously. It supports various access methods including Modem, ISDN, Cable Modem, and ASDL. It only needs to be installed on the computer with a modem on the LAN, making it an excellent solution for multi-computer internet sharing. In addition to sharing the internet connection, proxy services can also improve access speed and save bandwidth by utilizing cache stored on the local computer's hard drive. The author's innovation lies in the fact that remote control technology is a comprehensive technology involving multiple fields such as control, networking, computers, and databases. This paper delves into the design of a network-based industrial remote control system from a system integration perspective, implementing the design of a remote client and a web server. 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