PC-based open CNC system

The mechanical system of the CNC system and the method of its implementation are described in the fully open CNC system.

In the past 50 years, the numerical control system has experienced two stages and six generations of development. After the development of the microprocessor era, with the rapid development of computing technology, information technology and network technology, closed and dedicated systems are increasingly exposed. The inherent problem. Different operating systems, programming languages, man-machine interfaces, communication interfaces, etc., give designers and integrators of CNC systems an attempt to design new systems based on integrated environments in a relatively short period of time, or The integration of the system into different environments creates great difficulties. To this end, people have proposed standardization, that is, open design issues, in order to facilitate parallel cooperation and rapid integration; the most influential research projects are Japan's OSEC, Europe's OSACA, the United States' OMAC. In recent years, foreign parts The design of the numerical control system has begun to achieve its openness within a certain range, such as the MTC200 system of Indramat of Germany and the Acramatic 2100 system of Vickers Electronic System of the United States. At present, domestic research mainly focuses on open CNC system based on software chip, open CNC typography based on Windows 95/NT and open CNC system based on SERCOS fieldbus technology. Open research on open system of m. 1 numerical control system The main purpose of the CNC system is to build a modular, reconfigurable, and expandable system platform, improve the interconnectivity of the control system, and enhance the flexibility and integration of the CNC system. The openness of the CNC system can be roughly divided into three ways, as shown.

1.1 Open man-machine interface This way enables interoperability between the system, between the system and external devices, between the system and the communication network, and between the system and other systems, and can fully utilize the manufacturers for the purpose of maintaining the original CNC. The special function of the chip but the opening of the human-machine interface only provides the user with a way to flexibly customize the operation interface according to their own needs.

1.2 Open Control Kernel Layer Interface This method can determine the composition of system components according to the specific application, and can integrate its own control software module according to the interface protocol.

It can make full use of the role of the PC, use it to complete some real-time non-strong or non-periodic tasks, and strong real-time control tasks can be done by NC or PLC.

1.3 Controlling the kernel layer Fully open This approach is a completely open approach. It is actually a DNC structure, which uses a fiber optic cable to connect the digital servo to a PC-based NC device to form a high reliability. A real-time, complete CNC system; it allows users to develop software modules and hardware modules in specific application areas according to open architecture standards and specifications, or configure system functions on demand without relying on any system manufacturer and developer .

2 PC-based open CNC system hardware structure as a truly completely open, high-end CNC system, it should be as simple as possible in hardware structure, system functions as much as possible through software. The hardware structure of the open CNC system developed by the author, as shown in the bus interface and data exchange protocol, is currently the only international standard for digital servo and transmission data communication. m.SERCOS is connected by fiber optic cable to form a closed loop, according to the servo. Different addresses of the system and PLC, real-time data communication between the computer and the digital servo system is realized by the SOFTSERCANS card inserted in the computer. The real-time data communication mainly completes the data exchange between the command value and the actual value between the PC and the servo. In this system, the data exchange is completed within 2ms.

2.2 Software structure Due to the simplification of the system hardware, the whole development process is mainly software design, software development and operating environment. Windows NT 2.2.1 Real-time control High-precision, high-speed CNC system requires high real-time performance, generally in 1ms. the following. However, under the Windows95/NT platform, if you want to achieve such high timing accuracy, it is difficult to meet the real-time performance of the high-end CNC system through multi-thread programming. Therefore, the NT subsystem is selected in this system, which has its own operating environment and application. Programming interface; its thread management has the highest priority, and it can realize real-time control of the system independently without response message. In this system, RTX4.2 is used to develop applications to realize real-time transmission of cyclic data and some non-cyclic data.

2.2.2 Data exchange between PC and servo Data exchange between PC and servo is realized by means of SOFTSERCANS card. In the software, it is divided into 4 steps. After each step is completed, there is a status return to determine whether the next step is performed: check whether the cable loop is closed; confirm the servo drive in the cable loop, and write the corresponding address into the system parameter; read / Write the system parameters in the servo drive and confirm the status of the drive; data exchange, send the command value from the command value channel to the servo system, and send the actual value from the actual value channel to the PC.

2.2.3 Development of Soft PLC Soft PLC is a key technology based on PC open CNC system using software to achieve control. Since the machine logic is related to the movement of the machine tool, and the control signal is mostly a switch quantity, it is processed by a command method in the software design; if there is an M08 command in the NC program or the operator turns on the cooling switch, the software calls the corresponding subroutine to process To achieve the function of the hard PLC.

3 Conclusion This system has completed the initial design of the overall design. Since SERCOS has more than 30,000 parameters, most of the current systems in SERCOS parameter settings use default values. This is still a big gap for the development of high-speed, high-precision open CNC systems. Deep analysis of each SERCOS parameter The function will be the focus of the next step.

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