With the rapid development of China's manufacturing industry, the demand for higher precision and production efficiency in machine parts has increased significantly. The automation level of enterprise production processes is also on the rise. Bar materials serve as the primary raw material for various die forgings, roll forgings, and rolling parts. A bar shearing machine is essential for cutting and preparing blanks for these forging processes. Traditionally, shear systems relied on AC contactors and relays for control. However, after years of operation, component aging and frequent equipment failures have become common. Maintenance is complicated due to the large number of discrete components, poor integration, and delays in addressing faults, which hinder smooth production.
To address these challenges, modern high-precision automatic shearing lines now use PLC (Programmable Logic Controller) control systems. These systems offer advantages such as high positioning accuracy, fast response speed, strong anti-interference capability, and stable operation. However, traditional PLCs are not real-time systems, making it difficult to implement complex timing control and offering limited network support. Therefore, high-speed A/D conversion and real-time signal processing from sensors are required. When aiming for intelligent, informational, and networked management of the production process, PLCs may fall short. This has led to the emergence of ARM-based embedded systems, which provide a more flexible and powerful platform for industrial control.
ARM-based systems come with rich peripheral resources, multiple interfaces, and expandable options. They run an embedded real-time operating system, enabling complex control tasks and offering powerful software processing capabilities. These systems combine the features of PCs but at a lower cost compared to industrial computers. Their hardware and software can be customized, allowing for tailored solutions. Additionally, they support large-screen LCD displays for user interaction and can connect directly to local or remote networks, enabling real-time monitoring and management of production.
Based on this analysis, this paper proposes an ARM-based embedded bar shearing CNC (Computer Numerical Control) system. The system is built around an ARM processor and runs an embedded Linux operating system. It supports scalable I/O nodes and various fieldbus interfaces, enabling automatic cutting control, marking, and feed frame adjustments, thus improving bar processing accuracy. It also supports large LCD displays, networking, and an embedded database, enhancing the coordination and supervision of the production process. The embedded database facilitates effective data management and enables adaptive parameter adjustments during processing.
The entire shearing line system consists of a central control unit, a cutting system, a hopper, and an automatic flip feed system. The block diagram of the system is shown in Figure 1. The electrical components include console buttons, display lights, Switches, and motors. The control switches include proximity switches, pressure switches, photoelectric switches, and others. Motors include main motor, discharge motor, baffle motor, and lubrication motor. Additional components like transformers, circuit breakers, and noise filters are also present.
The central control system is based on the ARM9 core board. It expands limited I/O into sufficient control nodes and receives input signals from various switches. According to pre-set parameters, it controls solenoids, relays, and contactors, while sending pulse signals to the servo driver to manage the servo motor. Optical isolation modules are used for interference resistance and level conversion. The 10-inch LCD screen provides a user-friendly interface for setting parameters and viewing system status. The ARM communicates with the inverter and server via RS232 serial ports to enable real-time data exchange, ensuring coordinated operation of the production line.
The ARM9 core board uses the S3C2410X processor with a 6-layer design, featuring a full-featured MMU, low power consumption, and rich interfaces. It integrates numerous functional units, including memory controllers, LCD controllers, serial ports, and more. The core board includes SDRAM, NAND Flash, and other peripherals, with a 2.0mm pin slot for easy expansion. The system runs an embedded Linux OS, supporting various applications and drivers.
The motherboard and I/O expansion board work together to handle USB, serial ports, voltage conversion, and LCD connections. The switching power supply provides 24V at 4A, converting to multiple voltages for different circuits. The ARM9 core board includes three RS232 serial interfaces, with a conversion module for RS485 levels. The USBHOST allows multiple channels for keyboard, mouse, and other devices.
GPIO expansion and isolation circuits are designed as separate boards, expanding I/O ports for better flexibility. Each expansion board has 64 inputs and 64 outputs, connected via flat cables. Two expansion methods are considered: using CPLD or dedicated I/O chips like MAX6957. The system ensures sufficient I/O for switches, indicators, and relays, with optocouplers for isolation and drive modules to improve anti-interference.
Motor control is managed by the inverter, which adjusts motor direction and speed based on ARM signals. Input control comes from the isolated expansion board, with settings for forward, reverse, and speed selection. Other parameters are set via the operator panel.
The CNC system software includes user interface, cut control, fault detection, database management, and networking. With an embedded OS, tasks can run in parallel, using message queues and communication protocols. The software flow chart shows key functions, with details on embedded OS porting, driver development, and application programming. Qt/EmbeddedC++ is used for GUI development, supporting cross-platform compatibility and database connectivity.
Cutting control requires manual and automatic modes, real-time display of process information, fault detection, emergency stop, and security protection. Basic operations involve zeroing the hopper, entering bar data, and adjusting the stopper position for accurate cutting. The system supports weight compensation and real-time position monitoring.
An embedded database supports SQL queries, transactions, and data storage, providing efficient access for industrial control. It helps collect and store data, enabling real-time program restoration and quality analysis. JNI is used to call C/C++ database drivers, solving the lack of JDBC support.
In conclusion, the proposed ARM-based embedded shearing system offers cost-effective, high-precision control, combining Linux, TCP/IP, QT GUI, and an embedded database. It meets modern industrial needs for accuracy, compactness, and low power consumption, representing a technological advancement in existing CNC systems.
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