Abstract: Addressing the issues of insufficient networking, low maintenance efficiency, and high maintenance costs in existing high-power laser cutting machine tools, this paper proposes a cloud server-based remote monitoring system for high-power laser cutting machine tools, leveraging mature GPRS mobile communication technology. A remote monitoring platform is constructed to remotely monitor multiple laser cutting machine tools. A data acquisition intelligent terminal is designed for the remote monitoring system, enabling the transmission of on-site data to the cloud via GPRS technology, providing data support for the rapid diagnosis and handling of high-power laser cutting faults.
introduction
Currently, with the continuous development of laser technology, laser processing technology has also developed rapidly. Laser processing is widely used in sheet metal cutting, engraving, drilling, welding, surface treatment, and other fields. The laser cutting process involves focusing a laser beam onto the surface of a workpiece, using the released energy to instantly melt and evaporate the workpiece, thereby achieving the purpose of cutting and engraving. Laser processing has a cutting speed far exceeding that of traditional cutting technologies, high cutting precision, and can achieve automatic layout.
Laser cutting, with its advantages of high processing speed, no limitation on cutting patterns, and smooth cuts, will occupy an increasing market share in the cutting market [1-4]. With the rapid development of electronics, communication, and internet technologies, laser processing is also rapidly developing towards higher power and higher speed. At the same time, the informatization and intelligentization of laser cutting machine tools are receiving increasing attention. Currently, the working environment in domestic sheet metal processing workshops is relatively poor; processing dust, radiation, and noise all pose challenges to on-site operations.
The laser cutting machine tool can cause varying degrees of harm to the human body. Therefore, remote real-time monitoring of the working status of the laser cutting machine tool and the on-site environmental parameters has become one of the key research hot issues in the laser processing machine tool manufacturing industry [5].
Reference [6] uses a single server based on a common communication interface to collect information such as the machining status and process parameters of CNC equipment in real time for three different CNC systems, including FANUC; Reference [7] uses a network to remotely monitor and manage CNC machine tool machining process parameters, system alarm information, PLC control signals, servo drive parameters, system fault diagnosis, and machine tool maintenance information; Reference [8] uses traditional fieldbus technology and wireless sensor networks.
Real-time data acquisition and processing using an ARMCortex-M3 embedded chip enabled a web-based remote monitoring system for CNC machine tools. With the continuous improvement and development of GPRS technology, it is increasingly being applied in machine tool monitoring [9-11]. This paper proposes a method for high-power laser cutting machine tools, utilizing GPRS wireless communication technology to install a data transmission module at the laser cutting machine tool site. This module transmits the processing status and environmental information of the laser cutting machine tool to a cloud server in real time, thereby achieving remote real-time monitoring of the laser cutting machine tool's status.
1. Overall Scheme Design
Currently, some advanced CNC systems have communication interfaces that can transmit data parameters, enabling remote control of distributed CNC equipment. GPRS can operate online in real-time, supporting multi-point data transmission with low latency, meeting the real-time requirements of general monitoring systems for data acquisition and transmission. With the rapid development of mobile communication technology in China, most areas are now covered by GPRS networks, providing a foundation for large-scale online equipment monitoring. The system has a large transmission capacity, well meeting the needs of transmitting monitoring data, and communication costs are decreasing while its application is convenient. With the widespread use of smartphones, maintenance personnel can browse cloud data through applications, thereby obtaining data before and after CNC machine tool malfunctions, laying the foundation for rapid diagnosis.
This paper takes a Fagor laser cutting machine as the controlled object and constructs a high-power laser cutting machine data acquisition and transmission system based on serial communication and GPRS mobile communication technologies to realize wireless remote monitoring of the laser cutting machine's status. The laser cutting machine remote monitoring system mainly consists of six parts: the on-site laser cutting machine, a camera, a workshop environment acquisition module, an on-site intelligent monitoring terminal module, a cloud server, and a remote monitoring client. The overall structure diagram is shown in Figure 1.
Figure 1 Block diagram of remote monitoring system for laser cutting machine tool
2. Hardware Design
The hardware component primarily involves an on-site intelligent monitoring terminal module. This system uses an STM32 microprocessor and a GPRS wireless communication module as its core. The on-site intelligent monitoring terminal communicates with the CNC machine tool via a serial port and transmits data to the cloud in real time through the GPRS wireless communication module. The cloud server automatically records the uploaded data, and any networked computer can obtain the current working status of the machine tool through the cloud. When the laser cutting machine tool malfunctions, the on-site intelligent monitoring terminal sends fault information to a pre-configured mobile phone number via an SMS service module. Maintenance personnel can then obtain the CNC machine tool fault information via SMS and perform fault diagnosis.
2.1 Hardware Design of On-site Intelligent Monitoring Equipment
The hardware of the on-site intelligent monitoring module consists of a 32-bit microprocessor, a data display unit, a GPRS wireless data transmission module, a data acquisition module, and a data storage module. The system hardware schematic diagram is shown in Figure 2.
Figure 2 Hardware schematic diagram of the on-site monitoring equipment
The STM32F103VBT6 microcontroller from the STM32 series is selected as the main control chip. The SIM800E module from SIMcom is used for GPRS data transmission. The SIM800E is a dedicated GPRS data transmission module that supports multiple TCP/IP connection protocols and methods, single-step and multi-step development environments, and transparent and non-transparent transmission modes. It supports TCP and UDP protocol stacks on both the server and client sides. In this system design, the SIM800E module is connected to serial port 2 of the STM32 microcontroller to achieve communication between the GPRS module and the microcontroller. A 3.5-inch true-color touchscreen is used for display to enable human-computer interaction.
2.2 Camera Surveillance Hardware Design
Image acquisition utilizes a serial camera module, specifically the LJ-DSC02 series serial camera manufactured by Chengdu Lanju Technology. This 2-megapixel camera features a built-in OV series high-performance CMOS sensor, directly outputting JPEG images and transmitting data via RS232 or RS485. It is equipped with six 850nm night vision LEDs for infrared illumination. In this system, the LJ-DSC02 is connected to serial port 1 of the microcontroller to acquire camera data.
2.3 Hardware Design of Environmental Acquisition Module
Environmental parameter acquisition utilizes the GK-508F module, which can acquire 16 channels of analog signals and supports RS232, RS485, and MODBUS protocol interfaces. In this system, the main data acquired during laser cutting machine operation include ambient temperature, humidity, pressure, power supply voltage, current, and cooling fan temperature.
3. Software Design
In the Keil development environment, terminal control software is designed. The software is mainly divided into system initialization module, data acquisition module, data analysis module, touch screen display module, and communication module.
After the intelligent monitoring equipment starts up, it first enters the system initialization module. After initialization, data acquisition begins. The data acquisition part mainly includes the acquisition of CNC machine tool operating parameters, camera images, and on-site environmental parameters. After data acquisition is completed, it enters the data analysis module. After analysis, the data is displayed and stored. Finally, it enters the communication subroutine for remote data transmission. After data transmission is completed, it enters the next loop. The software flow is shown in Figure 3.
Figure 3 Software control flowchart
System initialization primarily involves initializing the clock, interrupts, GPIO, and serial port. After completion, it sequentially communicates with the CNC machine tool, serial camera, environmental acquisition module, and GPRS module. The laser cutting machine tool CNC system uses an asynchronous serial communication protocol. When the on-site monitoring equipment program runs, it first sends a handshake request to the CNC system. If the handshake is successful, it receives various parameter data from the CNC system; if the handshake fails, it sends a fault display interface. In the data processing and analysis module, the laser processing machine tool's process parameters, NC program, pitch error compensation parameters, workpiece coordinate data, etc., are categorized and saved, and then transmitted to the cloud server via GPRS. When a command to update data is received from the cloud server, the CNC machine tool communication management module notifies the CNC machine tool to modify communication parameters and update the data.
The serial camera module acquires camera images via a microcontroller. During power-on initialization, the serial port is opened and the image resolution is set. During normal communication, it continuously executes the following steps: start image acquisition, acquire image data, end image acquisition, and upload. The data analysis module compares the acquired data with set values; if alarm conditions are met, a signal is sent to the alarm subroutine. For convenient human-machine interaction, a data display module using a 4.3-inch true-color touchscreen from DWIN is included to display data and view alarm information. To prevent data loss due to network failures, a data storage module is installed on-site to store acquired data and alarm information locally on an industrial SD card, ensuring data security.
When the GPRS module communicates, it first initializes the parameters, which mainly include: SIM card number, DNS service settings, GPRS service password, APN settings, IP address, TCP port number, etc. After the system is powered on, a TCP communication is automatically established. After successful communication, the smart terminal module and the cloud can wirelessly interact with each other.
4. Conclusion
Practice has shown that the field intelligent monitoring terminal designed using the STM32 microcontroller and SIM800LGPRS communication module is small in size and low in power consumption. It can interface with the CNC system of laser cutting machine tools in real time. Through this terminal, the field data of the laser cutting machine tool can be transmitted to the cloud server via wireless network. Through the cloud service monitoring client, maintenance personnel can provide users with convenient and fast technical support, which has good practical significance and promotion value.
