The concept of CNC system architecture
Computer-controlled machine tools are developed by integrating the latest achievements in modern computer technology, automation control technology, sensor and measurement technology, and mechanical manufacturing technology. They are typical mechatronic products.
Although CNC systems vary greatly in their system design methods and implementation, their basic components and principles are similar. As a typical computer application system, any CNC system cannot function without the support of both hardware and software. Through the coordination of system control software and hardware, the input, data processing, interpolation, and information output of the CNC system are rationally combined and managed, controlling the actuators to enable the CNC machine tool to perform machining in an orderly manner according to the operator's requirements.
The hardware of a CNC system is the material basis for the system's operation, and can usually be represented as shown in Figure 2.1.
The basic system of a dedicated computer consists of a CPU, bus, program memory, data memory, and peripherals. The device support layer, consisting of input control, motion control, programmable machine tool controller (PMC), and basic input/output interfaces, can connect to various external devices and systems.
The software of a CNC system is the soul of the system's ability to achieve ever-changing control functions. It generally consists of an operating system, CNC management software, and control components. The operating system provides a basic software development platform and operational support; the CNC management software is responsible for the input and output of part machining programs, system status display and fault diagnosis, and coordination and scheduling of various CNC functional software; the control software is responsible for completing the machining control functions of the CNC system, including part program interpretation, data processing, tool compensation, interpolation calculations, position control and speed control of each coordinate axis, and control of machine tool auxiliary devices.
The hardware and software of a CNC system constitute its platform. It is called a system platform because, on the one hand, it provides complete control functions for the CNC system; on the other hand, it allows for appropriate functional expansion and development based on this platform.
The way a CNC device's system platform is constructed is generally referred to as the CNC architecture. It includes the division of the system's hardware and software components, and the connections and constraints between these components, such as topological relationships, synchronization relationships, and communication protocols. Therefore, the CNC system architecture not only provides a reference framework for system analysis, design, and construction, but also serves as the foundation for guiding the system's expansion, updates, maintenance, and secondary development throughout its entire lifecycle.
Therefore, research on system architecture is not only directly related to the development cycle and cost of the ChIC system, as well as the performance and lifespan of CNC products, but also to the cost and convenience of integration, use, and maintenance by intermediate and end users of the CNC system. With the development of CNC technology, system architecture is attracting increasing attention from all sectors.
Open Approach to CNC System Architecture
There is still considerable debate regarding the definition of open architecture. According to the IEEE definition of an open system: an open system should be able to run on multiple platforms, interoperate with other systems, and provide users with a unified user interface.
These basic requirements should also be followed for an open CNC system. An open control system should have a fully modular structure. Interchangeability, scalability, portability, and interoperability between modules are fundamental characteristics of an open system.
To address the challenge of making closed, proprietary systems more open, various system developers and research institutions have proposed multiple solutions. These can be broadly categorized into three approaches based on the level of openness. These approaches differ in their level of openness, implementation difficulty, and the resulting openness effects, as shown in Figure 2.2. In the figure, the dashed lines divide the control system into two layers: the Human-Machine Control (MMC) layer and the control kernel layer. The control kernel is the core component of the CNC system, responsible for real-time machining process scheduling and control, and is generally associated with system real-time performance. The three approaches are distinguished by their different handling of these two layers of openness.
