Abstract: This paper elaborates on the PCC-based electrical control system of a new coal mining machine developed by Xi'an Coal Mine Machinery Co., Ltd., from the three aspects of the control system, hardware design and software design. Keywords: PCC; Coal Mining Machine; Reliability; Remote Monitoring and Fault Diagnosis 1 Introduction The coal mining machine is the main equipment of the fully mechanized mining face, and its normal operation determines the production efficiency of the fully mechanized mining face. The reliability of the coal mining machine depends on the design and manufacturing of the mechanical parts and their reasonable use, as well as the completeness and effectiveness of the electrical control system. If we compare a coal mining machine to a person, the mechanical parts are the limbs and torso, while the electrical parts are the brain. Therefore, the electrical control system is crucial in a coal mining machine. Currently, the controllers of the electrical control systems of domestically produced coal mining machines are basically PLCs of various brands. Although PLC-controlled coal mining machines have monitoring and fault diagnosis functions and can generally meet the requirements, the harsh working environment, numerous parts, and complex structure of coal mining machines mean that operators cannot promptly grasp the various operating parameters of the machine, potentially leading to malfunctions. To improve the uptime of coal mining machines, it is necessary to add remote monitoring and fault diagnosis functions. Furthermore, due to the excessive labor intensity of miners in fully mechanized mining faces, there is an urgent need to reduce it, necessitating the establishment of automated fully mechanized mining faces. Therefore, the coal mining machine must have a memory-based cutting function. Additionally, due to space limitations in the coal mining machine's electrical control box, using a fieldbus system would improve the reliability of the electrical control system while also facilitating installation and maintenance. To enable coal mining machines to have remote monitoring, fault diagnosis, and memory-based cutting functions, and to utilize a fieldbus system, it will be difficult to meet these requirements without innovation in the electrical control system. To adapt to development, Xi'an Coal Mining Machinery Company developed a new electrical control system using B&R Industrial Automation's PCC (Programmable Computer Controller) as the controller. 2. Design of the Coal Mining Machine Electrical Control System The coal mining machine is a multi-motor linked mechanical device with high technical requirements. It operates in damp, dusty, vibrating, and high-gas mines, under complex and changing working conditions. Its large weight and inertia, coupled with requirements for easy operation and low failure rate, place high demands on the design of the coal mining machine's electrical control system. The block diagram of the coal mining machine's electrical control system is shown in Figure 1. (1) Control Computer (using B&R PCC) The control computer (composed of a CPU module and communication block of the 2003 series PCC) is the core of the coal mining machine's electrical control system. When the coal mining machine is working normally, the traction direction, acceleration and deceleration control of the frequency converter, the lifting and lowering of the left and right rocker arms, the opening and closing of the brake, the temperature monitoring of the left and right cutting motors, the temperature monitoring of the traction transformer, the current sampling of the traction and cutting motors, as well as the constant power protection, zero-crossing protection, gas power-off protection, and cutting motor overload protection of the coal mining machine are all realized through the control computer. The control computer receives data from the digital input module and the analog input module, and transmits the instructions to the solenoid valve group through the digital output module. It transmits the parameters of the coal mining machine to the display computer through the communication interface, and transmits the instructions to the main frequency converter through the communication interface. (2) Digital Input and Output Module The digital input module mainly receives the instruction signals issued by the end station, remote control and control panel buttons. The digital output module mainly transmits the controller's instructions to the solenoid valve group to control the lifting and lowering of the coal mining machine rocker arms, the start and stop of the cutting motor, and the opening and closing of the brake. (3) Analog Input Module The analog input module mainly receives analog signals such as the current of the cutting and crushing motor, the temperature of the traction transformer, the cutting and crushing motor, the angle of the rocker arm, and the concentration of gas, and then sends them to the control computer. (4) Display Computer (using B&R PP series HMI) The display computer provides a rich and user-friendly HMI, which vividly displays the following data information to the user: • Input and output status of the coal mining machine control computer • Current and temperature of the cutting motor and traction motor • Temperature of the traction transformer • Traction status and traction speed of the coal mining machine • Working status and fault information of the coal mining machine • Data, working status and fault information of the frequency converter, etc. 3 Hardware System Design B&R's programmable computer controller (PCC) combines the advantages of traditional PLC and industrial PC, such as the former's high reliability, flexible expandability and environmental adaptability, and the latter's multi-tasking processing mode, high-speed computing power, high-level language programming and open communication. PCC is one of the most advanced control technologies in the industrial field, featuring time-sharing multitasking, high-speed computing power, large-capacity memory and storage units, and powerful communication networking capabilities. PCC has become the fastest-growing industrial motion control device today because it possesses many unique advantages. It effectively addresses the reliability, safety, flexibility, convenience, and economy issues that are of general concern in the industrial control field. The main characteristics of PCC are as follows: (1) High reliability and strong anti-interference capability; High reliability is one of the most prominent features of PCC, with a mean time between failures (MTBF) of hundreds of thousands of hours. Due to the frequent continuous day and night production processes in industrial settings, harsh industrial environments, and severe electromagnetic interference, PCC has adopted a series of measures to address these issues. The main method is to implement opto-isolation on all input/output (I/O) interface circuits, effectively suppressing the influence of external interference sources on PCC. (2) Easy to design and install, short debugging cycle, and simple maintenance; (3) Rich variety of modules, good versatility, and powerful functions; (4) Small size and low energy consumption; (5) Powerful Automation Studio software development platform. The electrical control system of the MG650/1630-WD coal mining machine developed by Xi'an Coal Mining Machinery Co., Ltd. selected the following automation products from B&R to form the system according to the actual control requirements: (1) Control computer (i.e., 2003 series PCC). As shown in Figure 2, the control computer consists of 7CP570.60-1 and 3IF722.9. 7CP570.60-1 is a 2003 series PCC. Its CPU is Celeron 300, 64 MB DRAM, and the communication interfaces are: USB, RS232, and Ethernet. 3IF722.9 is a communication board, which includes the following communication interfaces: CAN, RS485, and RS232. The control computer controls the main frequency converter through the RS485 interface, communicates with the display computer on the coal mining machine through the Ethernet interface, and exchanges data with the display computer hundreds of meters away from the coal mining machine through the CAN interface. (2) The digital input/output module is shown in Figure 2. Two 7DM465.7 modules were selected for the digital input/output module. Each 7DM465.7 module has 16 inputs and 16 outputs. (3) The analog input module is shown in Figure 2. One 7AT324.70 and three 7AI354.70 modules were selected for the analog input module as needed. All four modules are plugged into the adapter module 7AF101.7. Each 7AT324.70 module has four temperature inputs, and each 7AI354.70 module has four analog inputs. (4) Display Computer (i.e., B&R Power Panel series HMI) As shown in Figure 2, since HMI displays are required in two locations several hundred meters apart, two display computers, 4PP320.1043-31 and 4PP420.1043-75, are selected. Among them, 4PP420.1043-75 also has the function of data transmission relay. 4 Software Design PCC adopts a runtime qualitative time-sharing multitasking operating system. Multitasking means that when the computer starts several programs at the same time, it can also run some programs in the background in an orderly manner. A complete application is usually composed of several tasks (program blocks or subroutines). Not all tasks need to be executed within the same time frame. For some tasks that do not need to be executed frequently, the priority of tasks can be distinguished to ensure that the program can run quickly and efficiently. PCC programming software Automation Studio is an object-oriented programming language that can use the IEC61131 programming language, as well as Basic and ANSI C high-level languages. Automation Studio integrates various development tools: • Project hardware configuration • Project software configuration • Graphical display • Maintenance and diagnostics • Libraries and function libraries. Automation Studio provides many standard function libraries, which greatly improve the programming speed and efficiency of programmers. Based on the requirements of the control system and the characteristics of the B&R PCC, the software design uses ANSI C, utilizing the PCC's multi-tasking technology to divide the complex control logic into eight tasks for separate completion. The flowcharts of several tasks are shown in Figures 3 to 6. [align=center] [/align] 5 Conclusion The aforementioned coal mining machine has been successfully applied in the fully mechanized mining face of the Meihuajing Coal Mine of Shenhua Ningxia Coal Group, initially realizing remote monitoring and fault diagnosis functions as well as memory-based cutting functions. Its electrical control system is stable and reliable, basically leveraging the advantages of the PCC. Based on this, there is still significant room for improvement in the electrical system of the coal mining machine. References: [1] Chen Boshi. Automatic Control System for Electric Drive [M]. Beijing: Machinery Industry Press, 1992. [2] Qi Rong. Programmable Computer Controller Technology [M]. Beijing: Electronic Industry Press, 2006.