A local fan monitoring system based on CAN bus

Preface

    Coal mine gas accidents are a type of mining accident in my country. In order to eliminate or reduce gas accidents, the State Administration of Coal Mine Safety has put forward a clear 12-word gas disaster prevention and control policy and three standard gas management solutions. Underground ventilation is a key factor in gas disasters. Only by ensuring underground ventilation, monitoring the underground gas volume fraction, and taking corresponding measures can the safe production of coal mining enterprises be guaranteed. Local fans refer to underground fans, which are one of the most important ventilation equipment produced by coal mining enterprises. Local fans can effectively adjust the gas volume fraction of underground working faces, effectively avoid gas explosions, and also ensure the life safety of working face workers. With the development of computer technology, communication technology and network technology, gas monitoring systems have been widely used. This paper proposes a coal mine local fan monitoring system based on CAN bus.

1 Local fans and local fan monitoring

    The most critical equipment in the coal mine ventilation system is the underground fan or local fan. The coal mine production ventilation system includes the main fan and the local fan. The main fan is usually installed on the ground and is mainly responsible for the ventilation of the entire mine; the local fan is usually installed on the underground working face and is mainly responsible for the ventilation of each excavation tunnel. In order to prepare for various excavation working faces, each tunnel in the mine needs to continuously build, expand and renovate the working face, and a large amount of minerals and toxic gases are often produced during the excavation process. It is the task of the ventilation system to ensure smooth ventilation during the excavation process, create a good air environment, and dilute or discharge coal, gas or other mine dust. Coal mining enterprises generally use local fans to continuously deliver fresh air to the excavation working face or tunnel, and at the same time discharge the mine dust or coal gas from the excavation working face or tunnel out of the mine for local ventilation and gas supply. However, if the volume fraction of gas or CO in the excavation working face is too high, it will cause the local fan to stop running or gas explosion, and even cause a fire in serious cases. In this sense, it is very necessary to install a local fan monitoring system. The local fan monitoring system based on CAN bus designed in this paper is such a monitoring system. The system mainly monitors the gas volume fraction, CO volume fraction and other parameters of the local fan, grasps the gas outflow law, and further adopts reasonable strategies to reduce the gas volume fraction, take ventilation measures, and take measures such as power outage or alarm to prevent gas explosion accidents. The local fan monitoring system of coal mines is generally installed in the coal lanes, semi-coal rock lanes or other excavation working faces with gas outflow in the mine. The gas volume fraction in these places is relatively high. By monitoring the gas volume fraction in these places, it can be discovered in time whether the gas accumulation exceeds the upper limit of gas explosion.

2 Local fan monitoring system based on CAN bus

    2.1 System Design

    The overall structure of the local fan monitoring system based on CAN bus is shown in Figure 1.

    The system includes field monitoring layer, process monitoring layer and operation management layer. The integrated monitor of the field monitoring layer is installed on the underground working face and is set by the underground ventilation manager or remotely controlled by a remote computer. The integrated monitor mainly monitors the environmental information, fan status and power supply control of the working face to ensure the safety of power supply and ventilation in the mine. The USB-CAN bus adapter mainly realizes the data communication between the integrated monitor and other information systems of the enterprise. All the information monitored in the CAN bus network is uploaded to the monitored PC. Similarly, the monitoring information received from the PC is sent out through the CAN bus network. The main monitoring computer is installed in the monitoring room. The relevant monitoring equipment is connected using the CAN bus structure. The main monitoring computer processes the monitored data and is responsible for the management of the enterprise database. The results are stored or transmitted to the relevant enterprise application server for the relevant personnel of the coal mine enterprise to browse or operate. Users outside the enterprise can access the enterprise's network server through the B//S mode to query relevant monitoring information and network application information.

    2.2 Hardware System Design

    The hardware system is mainly composed of a field integrated controller and a USB-CAN communication adapter. They both use Atme189C52 as the control core, through which they communicate with other interfaces for data exchange and control operations (see Figure 2).

Figure 1 Overall structure of the local fan monitoring system

Figure 2 Schematic diagram of the hardware structure of the on-site integrated monitor

    The field integrated controller circuit is composed of CPU core control module, human-machine interface module, CAN bus communication interface module, fan fault monitoring module, environmental information monitoring module circuit, etc. The monitoring module is responsible for real-time monitoring of environmental information and other motor faults. The human-machine interface module is responsible for the interaction between the monitoring system and relevant managers and operators. The communication interface is responsible for data communication between the field monitoring layer and the remote monitoring layer and the management layer, ensuring that the underground working face data is transmitted back to the monitoring layer in a timely manner, so as to serve the correct decision-making of the enterprise management. [page]

    The USB-CAN bus adapter consists of three main modules: CAN bus universal communication interface module, USB interface module and CPU core control module, which provides guarantee for the real-time data monitored by the on-site monitor to be transmitted back to the monitoring room.

    The CPU core control module uses MCU Annel 89C52 as the control core. 89C5 is the most widely used chip in the field of industrial control. It is mainly responsible for the information exchange between the CAN bus controller and the USB controller, including simple information processing. The system directly uses the CAN bus universal communication interface module as the CAN bus universal module, and directly replaces the USB-CAN bus adapter and the field integrated monitor. The CAN bus universal communication interface module mainly includes the CAN bus controller, the CAN bus transceiver, and the CAN bus electrical isolation photoelectric coupler 6N137, etc.

    2.3 Software System Design

    The software system includes two types: embedded software and host computer monitoring platform software. The embedded software includes field integrated monitoring software and USB-CAN adapter software. Field integrated monitoring software includes two aspects: manual program and automatic program. The so-called manual program refers to the part debugged according to the keyboard. The operator confirms the status of the system according to the keyboard and performs fault detection according to the mechanical response. The so-called automatic program refers to the program that the system runs automatically to ensure the normal operation of the entire system. As soon as the system is powered on, it will automatically initialize, perform corresponding equipment power supply and other status detection, and start monitoring gas volume fraction at the same time. The power supply and other status detection and judgment of the equipment are as follows: as soon as the equipment is powered on, the system automatically determines whether the equipment is faulty. If it is faulty, it will alarm and start other fans to prevent accidents such as gas explosions.

    The USB-CAN adapter firmware program implements the information exchange between the CAN bus and the USB bus. The USB-CAN adapter uses the interrupt method to communicate with other peripheral chips through the CPU core module of the adapter. The most commonly used chips are CH375 and SJA 1000. They have different divisions of labor. CH375 is usually responsible for receiving interrupt service programs, while SJA100() saves interrupt service programs in RAM and makes corresponding flags. For example, after the system main program completes initialization, SJA100() will set the flag bit to 1, indicating that the system is transmitting data to the other party.

    The host computer monitoring platform software is installed on the monitoring PC. In order to monitor the status of the underground working surface and the value of environmental parameters more intuitively and in detail, the system requires a more intuitive camera that can display real-time information and can timely process and manage the real-time data information being reported. The host computer monitoring platform software includes the following functions.

    (1) It has the function of network monitoring and can send commands to the relevant field integrators according to the self-designed CAN bus data format. It can also randomly set the air volume, automatically cut off the power and rotate the fans.

    (2) It has the functions of real-time monitoring, automatic analysis of gas volume fraction, automatic alarm and related fan equipment fault analysis. It can parse the data on the on-site integrated monitor through the CAN bus communication protocol and display it on the system's video interface, and save the parsed data in the system. If it is judged that the gas volume fraction exceeds the standard, it can make a fault analysis in time, and immediately alarm and stop power supply.

    (3) The system has the function of historical data query. It can query the monitoring historical data or gas volume fraction and other information according to time or tunnel, gas volume fraction, fault type, etc., and perform corresponding data analysis on these historical data to derive rules and provide a theoretical basis for underground fan management.

    (4) With the basic information management function of the fan, the system shall perform relevant editing, type or performance parameter management on the fans on each working face or excavation platform. At the same time, the relevant tunnel number, tunnel cross-sectional area, tunnel length, and average tunneling speed of the corresponding working tunnel can also be managed to provide guarantee for monitoring gas volume fraction, etc.

    (5) It has the function of system user management, and divides system users into two categories according to their permissions: administrators and ordinary users. System administrators can add and delete users, and can also set user permissions. It manages the database operation permissions of ordinary users and administrators, and at the same time, records the login information of administrators and users to improve the security of the system database.

    According to the design requirements of the software system functions, the module function design of the system is shown in Figure 3.

Figure 3 System function module diagram

3 Conclusion

    The software system of the coal mine local fan monitoring system based on CAN bus adopts C/S architecture. The development environment of the software system adopts Delphi2006, the upper computer monitoring software is developed with Delphi2006, and the database management system adopts SQIServer2000. The test shows that the system meets the design requirements, realizes the functions of each module, and provides guarantee for the safe production of coal mine enterprises.