Abstract: This paper introduces a PLC-based centralized monitoring system for all-mine belt conveyors. The system includes a field control station and a master control station, and establishes a CC-LINK communication network to achieve centralized CRT monitoring of the belt conveyor system equipment. This has yielded positive results in improving production efficiency, reducing on-site operators, and enhancing safety. Keywords: PLC, centralized monitoring, belt conveyor §1 Introduction The safe and reliable operation of the coal mine belt conveyor centralized control system directly affects the mine's economic benefits. To improve the system's reliability and safety, centralized monitoring is essential for comprehensive system protection and centralized control. The intelligent belt conveyor centralized control and monitoring system produced by Tangshan Kaicheng Electric Co., Ltd. is a high-tech product applied to the automation of mine belt conveyors. Based on the "Coal Mine Safety Regulations" and summarizing accidents that occur during mine transportation, this new generation of comprehensive control system was developed with high safety, strong practicality, and advanced features. The centralized control system, together with the dispatch telephone system and industrial television system, constitutes a complete operation, dispatch, and monitoring network, realizing remote measurement, remote signaling, and remote control of the entire system. This system can improve production efficiency, reduce accident rates, shorten troubleshooting time, reduce on-site operators, and increase economic benefits. §2 Description of the Centralized Control System Currently, PLCs remain the mainstay of industrial automation control, providing highly reliable control applications for various automated control devices. This is primarily because they offer safe, reliable, and relatively complete solutions for automated control systems, suitable for the current automation needs of industrial enterprises. In the global industrial computer control field, significant changes have occurred surrounding open process control systems, open process control software, and open data communication protocols. With the birth and further improvement and development of PLC (SoftPLC) control configuration software technology, process control systems based on industrial PCs and equipped with SoftPLC configuration software are gradually developing. For control software, the core of the PLC controller, it provides industrial users with open programming and configuration tools. Furthermore, breakthroughs have been made in open communication network technology, resulting in the integration of PLCs into more open industrial automation control. This system adopts a fully distributed control structure, consisting of an underground control station and a comprehensive operating console. The comprehensive operating center is located in the central control room on the surface. The system utilizes AnS and FX series PLCs from Mitsubishi Electric Corporation of Japan. The control master station and control substations are connected via Mitsubishi Electric's open CC-Link network bus structure. The control substations and sensors are connected via a matrix structure. The control master station and the monitoring host computer on the integrated control console are connected via a CC-Link bus network. The control substations are responsible for data acquisition and control of field equipment. Through monitoring, the entire system's equipment can be monitored and centrally controlled. This system uses Mitsubishi Electric's AnS and FX series PLCs as the main control components, featuring strong moisture resistance and anti-interference capabilities, easy on-site programming and expansion, minimal maintenance, and the ability to achieve software control and automatic system fault detection. The system uses multiple PLCs to form a data transmission network, achieving control at different scales. It completes the monitoring and surveillance of multiple conveyor belts within a system, and together with the ground command and management center, forms a complete monitoring system. §3 Network System Considering the site conditions and control distance of the coal mine, a control master station is set up in the ground control center, using Mitsubishi's large and medium-sized PLC-AnS series. The network uses an open CC-Link bus. Repeaters are added between two control stations with a control distance greater than 1200 meters. Control equipment substations are set up at the conveyor head. The control equipment substations are responsible for on-site signal acquisition and real-time on-site control. The system is a real-time monitoring network structure with complete production monitoring and management functions. It performs real-time data acquisition, transmission, processing, display, recording, and printing of the production process of the main links and related auxiliary links of the conveyor belt transportation system. It performs remote centralized monitoring of the underground conveyor belt system and cooperates with the industrial television system for safety image monitoring to ensure the safety of personnel and equipment. After the monitoring network is implemented, operators can monitor and control the conveyor belt production process on the central control room terminal, and complete the "telemetry, remote signaling, and remote control" of the conveyor belt production and related links, realizing the comprehensive automation of the mine conveyor belt production system. 1. Real-time operation parameter monitoring. 1. **Real-time Process Control:** Each monitoring system collects production parameters in real time, displaying real-time operating conditions, current output, and inventory levels in graphical and report formats. 2. **Real-time Process Control:** Analyzing the collected parameters, each system automatically completes process control, or the real-time production monitoring data can be stored in a historical production data database, enabling historical playback, historical trend analysis, and comprehensive analysis using histograms, pie charts, etc. 4. **Equipment Fault and Analog Quantity Over-Limit Alarms:** When equipment malfunctions or analog quantities exceed limits, the production monitoring and management network simultaneously displays the name of the faulty equipment and provides voice alarms and real-time fault printing. The server stores this fault information in a fault information database for future statistical analysis. 5. **Production Planning Optimization:** A comprehensive historical database is established on the network server, periodically storing production and operational data to create trend analysis charts of plans and production completion status, providing a reference for future production planning. Based on the external transportation plan, actual equipment status, and coal storage volume, production plans and equipment maintenance plans are rationally arranged to minimize the impact on production. §4 Operator Workstations Based on the functions of the monitoring subsystems, workstations are set up in the monitoring center. The functions of the transportation system monitoring workstations include: 1. Setting different access permissions for different operators, each with their own responsibilities; 2. Providing an interactive, fully Chinese interface operating platform, with intuitive and dynamic display of the operating status and parameters of each subsystem's equipment; 3. Achieving automatic/manual/local control of each subsystem based on the process flow and interlocking relationships; 4. Setting various operating and production process parameters in real time; 5. Monitoring the operating parameters and status of each subsystem's equipment in real time, storing the parameter data on the hard drive, and uploading necessary data to the data server; 6. Monitoring the current status and parameters of each subsystem's sensors in real time; 7. Providing real-time alarms for the fault status of each device and necessary sensors, using audible and visual alarms. Real-time alarms are also printed, and alarm data is stored on the data server for unified management and accident analysis; 8. Allowing users to query and print real-time trends and historical trends for any time period at any time; 9. Allowing users to query and print historical data reports for any time period at any time. §5 Engineer Station In addition to all the functions of the operator workstation, the engineer station also has the following functions: 1. Online modification of the controller program according to process adjustments to adapt to the needs of the new process; 2. Conversion of relevant data from the monitoring system into the mine's information management system; 3. Setting up a color printer to print real-time color images and color trend charts; 4. When an operator workstation of a subsystem malfunctions, the engineer station can be immediately converted into the operator workstation of that subsystem by setting operator permissions. §6 Belt Conveyor Monitoring System This system consists of basic equipment such as belt conveyors and coal feeders. It utilizes control equipment, communication modules, and protection mechanisms for slippage, material stacking, overheating, smoke, longitudinal tearing, dust suppression, speed, deviation, and coal level to meet the requirements of a centralized belt conveyor control and monitoring system. The system uses multiple PLCs to form a data transmission network to achieve control at different scales. It completes the monitoring and control of the entire working process of the belt conveyor and coal feeder within the system, forming a complete monitoring system together with the ground control room. 1) Centralized monitoring of the conveyor belt system, real-time monitoring of equipment status and operating parameters, display of data curves, and recording of important information on the hard drive; 2) Control modes include centralized automatic, centralized manual, and local control, which can be switched between. During normal production, centralized automatic control is used, and the equipment starts and stops automatically from the central control console according to the process requirements; in centralized manual control, each piece of equipment can be operated from the central control console without interlocking or linkage; in local control, operation is performed on-site; 3) Before starting the equipment, a pre-warning signal is sent from the central control console. After a 30-second warning, if the conditions for centralized automatic start are met on-site, the equipment starts automatically in sequence. The start-up process can be stopped on-site using a stop button; 4) Start/stop buttons are provided in the on-site signal box, allowing for on-site stopping at any time. If the equipment is started by the centralized control system, the control system can perform an emergency stop after receiving the stop signal from the site, implementing a fault stop operation; 5) According to the "Technical Specifications", the belt conveyor is equipped with pull-wire switches, deviation protection, low-speed protection, etc., and these signals are all connected to the centralized control system to participate in the emergency stop and interlock stop of the equipment; 6) Real-time alarms are provided for equipment faults and abnormal process parameters, along with audible and visual prompts. General faults only trigger an alarm; in the event of abnormal or serious on-site stops, the faulty equipment and its upstream equipment will be shut down urgently, and the downstream equipment will be stopped with a delayed interlock stop along the coal flow. 6.1 Main Functions of the System: 1. Each piece of equipment is equipped with a local operation control box next to the machine head, with a working mode switch and a local start/stop button; 2. All coal feeding points on the conveyor belts are equipped with coal pile protection and longitudinal tear protection to prevent the escalation of conveyor belt accidents; 3. All conveyor belts are equipped with two-stage belt misalignment switches, with a pair of switches installed approximately every 50 meters. The first-stage misalignment switch is used for fault alarm, and the second-stage misalignment switch is used for fault shutdown; 4. All conveyor belts are equipped with pull-wire switches for emergency shutdown. The installation spacing of the emergency stop pull-wire switches is set at 50 meters, and the belt misalignment protection can be extended to ensure equipment and personnel safety; 5. The public address system adopts a new type of selective dialing telephone system, with an installation spacing set at 200 meters; 6. The tensioning device of the horizontal conveyor belt is hydraulically adjustable. Kaicheng provides a set of belt slack detection sensors, which are controlled by PLC to complete the automatic tension adjustment function of the conveyor belt. 7. Install coal accumulation sensors at the head of the belt conveyor to prevent coal accumulation accidents. 8. Install belt speed sensors on the belt conveyor to detect overspeed and slippage accidents. 9. Install smoke sensors in the belt conveyor roadway to detect smoke concentration and prevent fire accidents. 10. Install temperature sensors on the main drum of the belt conveyor to monitor the drum temperature at all times, and equip it with an automatic water spraying device to automatically spray water and cool the main drum when it overheats. 11. Install a start-up warning device every 100 meters on the belt conveyor to issue a warning signal before the equipment starts, prompting relevant personnel to immediately move away from the equipment. 12. Real-time current monitoring function of the motor can detect potential faults in some mechanical equipment; real-time monitoring and analysis of motor current during operation, alarm when current exceeds the limit or changes suddenly occurs, and shutdown when the situation is serious. 13. Enables interlocking between the coal feeder and the conveyor belt, and interlocking with existing conveyor belts, with automatic, manual, and maintenance control modes; 14. Developed advanced matrix control functions in both software and hardware, saving on main cable costs; 15. The automatic control system has good resistance to damp heat and interference, and its structure allows for rapid maintenance or replacement of components in underground conditions. Based on the underground coal mine environment, the control box uses a stainless steel structure, and other components employ anti-corrosion measures; 16. Can perform emergency shutdown, sequential shutdown, or issue alarm audible and visual signals according to the nature of the conveyor belt system fault; 17. The operating status, fault type, and fault location of the conveyor belt can be centrally displayed on the control panel; 18. Explosion-proof soft starters or explosion-proof frequency converters are integrated into the monitoring system; 19. Multiple operating modes. Control modes include: centralized linkage, centralized manual, local linkage, local manual, and start-prohibition, making the system flexible and reliable in operation. In centralized mode, all equipment is operated by the operator in the control room via a host computer; 20. Multiple process selection. In linkage mode, the transportation process can be selected according to the process. The conveyor belt starts in the direction of coal flow and starts after a delay according to the conveyor belt speed and length to reduce running time; when starting under heavy load, it starts in the direction of coal flow; the system stops automatically after a delay when there is no coal; 21. Complete information processing function. Alarm information, operating parameters, operation records and other information are automatically formed into a standard format database file and stored on the hard drive for a long time for the information system to call; 22. Realize centralized system monitoring and computerized management of production data 1) The interface is intuitive and user-friendly, easy to operate and full of functions. It has vivid dynamic screens and full Chinese display, and also has real-time alarm monitoring, safety confirmation mechanism and data recording function. There are no special requirements for operator quality and training is simple; 2) Alarm information and important operating parameters are recorded on the hard drive, and data tables and curves can be retrieved at any time; 3) Production data is stored on the computer hard drive and can be called by the management information system as needed. 6.2 Enables data sharing between the automated control system and the production management system. The computer management workstation is equipped with an information management system. Decision-makers can remotely access the monitoring host computer through the management workstation according to their respective permissions to obtain on-site production data reports, equipment management information, and production statistical analysis. 6.3 Features fault self-diagnosis. When transmission problems such as disconnection or interference occur, the network will automatically detect them and issue an alarm. 2. PLC fault self-diagnosis. When the PLC scanner and adapter malfunction, the system will determine the fault through network communication and issue an alarm; when the PLC I/O module malfunctions, the CPU will detect the fault and its details through the I/O module status bits, and the system will issue an alarm. 3. Sensor and signal line fault diagnosis. When analog sensors or signal lines experience disconnection faults, the PLC will determine the fault through measured values ​​and issue an alarm. 6.4 Easy Maintenance 1. The I/O modules use detachable terminal blocks. In case of a fault, the control room will issue an audible and visual alarm, and replacement can be completed within minutes. 2. The system is easily expandable. New equipment or subsequent engineering work can be easily added to nodes, and the program can be modified online via the network. 3. The system has a self-diagnostic function, which can promptly report fault time, location, type, and other information, making maintenance easier. 6.5 Features of the Centralized Control System This centralized control system has the following features: 1. It uses advanced controllers, ensuring good real-time performance, high reliability, and fast data processing speed. 2. It adopts a fully distributed control structure, providing high system security. When a control failure occurs on the surface, the underground system can still achieve centralized control operation. 3. The communication network is fast, has a long distance, and high reliability. 4. The interface is intuitive and user-friendly, easy to operate, and has complete functions. The human-machine interface not only features vivid dynamic graphics and a full Chinese display, but also includes real-time alarm monitoring, a safety confirmation mechanism, and data logging functions; 5. Reduced wiring costs: the use of a long-distance communication network makes wiring more convenient and significantly reduces cable usage; 6. Convenient maintenance and low operating costs: The system is easily expandable, nodes can be added at any time, and the program can be modified online from the central control room via the network. The controller and network have high reliability, resulting in minimal maintenance workload; 7. Drawing on the lessons learned from various mine belt conveyor systems, specific measures have been taken to increase equipment reliability, such as selecting advanced and reliable controllers and network products.