2 The Hierarchical Structure of Open Architecture The goal of a hierarchical design is to enhance system scalability and configurability, two key indicators of system openness. Scalability allows the system to expand its functionality and improve performance by adding new hardware interfaces. Configurability enables users to customize the system using existing low-level modules without changing the hardware. Unlike traditional modular structures, the hierarchical approach considers not only functional relationships but also the role and status of control links within the system. It defines inheritance and derivative relationships between components, forming a structured system that goes beyond simple function-based planning.
The hierarchical architecture is applied at all levels of the system, both internally and externally. When components are subdivided according to functional and performance requirements, each substructure maintains the same hierarchical standards and derived relationships. This ensures consistency and flexibility throughout the system.
As shown in Figure 2, the hierarchical CNC system includes a base layer 0, which contains all essential components for basic control functions and necessary hardware/software interfaces for general expansion. Layer 0 serves as the core of the system, ensuring smooth communication between components and maintaining stability and security. Additional layers above layer 0 extend the system’s functionality by adding hardware and open software interfaces. There are two types of extensions: supplementary and parallel. Supplementary expansion adds new interfaces for different control software, while parallel expansion introduces equivalent functional components to meet special control needs or open new control channels. These two forms of extension utilize structural and interface inheritance, allowing for flexible and standardized system modifications.
The motion control module is the core of the CNC system, and open-structured motion control components must support both types of extensions. Parallel expansion is used to increase the number of axes, while additional extensions introduce special functions like complex curve interpolation, position error compensation, and vibration monitoring. As shown in Figure 3, a basic three-axis motion control assembly can be expanded into four-axis and five-axis components, each with additional special functions.
3 Intelligent Development Mechanism of Secondary Development Platform As shown in Figure 5, the secondary development platform uses a guided development model. By leveraging pre-defined information bases, user functional requirements are translated into specific strategies stored in a database. These strategies are then compiled to match the microcontroller core of the CNC system and sent via a parallel port to the simulation development interface. A dedicated storage area is reserved for on-line verification of custom code, ensuring the safety of secondary development. Performance metrics are returned through a verification and evaluation mechanism, providing feedback on the effectiveness of the developed functions.
The secondary development environment supports two methods: language description and guided configuration. The language method uses a structured functional mechanism, defining the algorithm structure of system extensions. Users can input their functional requirements based on prompts, and the platform provides a structured description language (with grammar shown in Figure 6). This object-oriented approach allows for detailed descriptions of CNC component behavior, enabling flexible system configuration. The guided configuration method uses a development wizard (as seen in Figure 7), offering a graphical interface for simpler extensions. Together, these mechanisms form a hierarchical secondary development framework.
4 Conclusion The open CNC system built using a hierarchical structure and micro-control core represents a significant breakthrough in system architecture. The hierarchical design permeates every component of the system, supporting an intelligent secondary development strategy. This framework connects the development, usage, and maintenance of CNC systems, making them truly open throughout their entire lifecycle. Stainless steel fittings are for those fittings made of Stainless steel 316L AISI316 INOX316 . inclduing Stainless Steel Push In Fitting, Stainless Steel Compression Fitting, Stainless Steel Pipe Fitting, stainless steel ferrule fiting, stainless steel check valves and other stainless steel pneumatic and automation connectors Stainless Steel Fitting,Pneumatic Fitting,Quick Coupler,Push To Connect Fitting NINGBO AIHUA AUTOMATIC INDUSTRY CO.,LTD , https://www.iwapneumatic.com
Currently, research and demonstration applications of open control systems both domestically and internationally are primarily focused on the development of PC hardware and software. The essence of these applications is a dedicated use of PCs for I/O interfaces and human-machine interfaces (as shown in Figure 1). However, the structure and performance of such systems are quite limited. First, there is no independent open architecture specifically designed for CNC machining control. While the openness of computers is inherent, it is not tailored to the specific needs of numerical control processing. This approach relies entirely on the computer's structural framework, which lacks consideration for the unique requirements of CNC operations at the hardware and operating system levels, making it difficult to build an effective CNC platform.
Second, industrial PC (IPC) based open CNC systems often fail to guarantee real-time performance and reliability. Since PCs run general-purpose operating systems, they consume significant system resources, with non-NC-related tasks potentially interfering with critical NC functions. This leads to delayed responses and reduced efficiency, increasing system overhead and risking instability. Third, the cost of IPC-based CNC systems is high—motion control cards alone can cost several thousand dollars, making cost reduction challenging. In contrast, embedded microprocessors and programmable chips are much cheaper, and free open-source real-time operating systems further reduce expenses, leading to a better cost-performance ratio.
Fourth, the network capabilities of current IPC-based open CNC systems are limited. They rely on standard computer networks, which do not support the transmission of large data streams required for CNC processing and condition monitoring. As a result, remote applications are mostly limited to program transfers between systems. Additionally, the NC+PC mode typically offers little to no secondary development environment. It provides only basic interface reconfiguration and PLC programming tools, which are insufficient for complex customization. While some systems allow users to modify configurations or add software libraries, this requires advanced technical skills, making the open system less user-friendly and harder to operate.
This paper addresses these issues by focusing on the hierarchical structure of open systems, the network activation mechanism for condition monitoring, and the intelligentization of the secondary development platform.
1 Research Background