Research And Implementation Of NCUC-Bus Fieldbus Technology

To be high-speed and high-precision is the trend in the development of CNC system nowadays. The pulse or analog interface standard has become the bottleneck to the development of high-performance CNC system. Digital high-speed and high-precision fieldbus becomes the mainstream of CNC communication systems. More than 100 kinds of Fieldbus standards have been set so far. These field buses have different technical characteristics which made them incompatible. Introduction of foreign fieldbus takes lots of money and impede the development of domestic CNC system. Therefore, with the characteristic of our CNC systems, it is of great significance to research fieldbus technology of independent intellectual property. Here the thesis"Research and implementation of NCUC-Bus fieldbus technology"is outspread around the following topics.Based on the study of the technology features and communication mechanism of current foreign fieldbus, and the OSI model, the NCUC-Bus (NC Union of China Field Bus) CNC fieldbus communication model is proposed referred to the control requirement of multi-axes, multi-channel, high-speed and high-precision. Also, the key mechanisms which are conductive to improve the real-time, clock synchronization, and reliability performance of CNC fieldbus are researched based on the simplified communication model. Further, the thesis proposed the hardware interface and overall design of NCUC-Bus fieldbus.After analysis and comparison with real-time Ethernet protocol of IEC 61158 fieldbus international standards, NCUC-Bus adopts such technologies as deterministic communication, simplified protocol processing mechanism, FPGA hardware implementation to ensure the real-time performance; reference to IEEE 1588 precision time synchronization protocol, the thesis proposed NCUC-Bus precision clock synchronization protocol to improve the synchronization accuracy for dual-ring topology; furthermore, redundant hardware architecture with double-loop, real-time data packet retransmission mechanisms, error detection and handling mechanism, enhance the reliability of NCUC- BUS system.Based on the hardware platform which composed by FPGA, CPU, PHY, we integrated the hardware interface and fieldbus communication protocol into the HNC-8 CNC system, developed all-digital servo drives, digital spindle servo drives, PLC module and other products. And finally we conducted functional & performance testing and machining test, successfully applied the fieldbus technology to more than 10 projects which are supported by national CNC major program, such as high-precision horizontal machining center, large five-axes coordinated gantry type milling machine and Turning/Milling machines.