Study And Implementation Of Digital Communication Protocol For NC System Based On Ethernet Technology

At present, most of foreign companies use field bus for NC system transmission, such as SERCOS III,PROFINET etc.. These field buses use dedicated hardware equipment, which made them mutually incompatible and high costs. Comparatively, Ethernet technology is mature, low cost and good compatibility. Field bus will be replaced by the Ethernet with the trend. Therefore, the digital communications for NC system based on Ethernet technology is one of most important researches for the next generation NC system. But Ethernet communications delay indefinitely which affects the real-time communications for NC system. Therefore, this dissertation will focus on the digital communications for NC system based on Ethernet technology, resolve the Ethernet communications delay uncertainty and asynchronous communications,and achieve real-time capability, synchronization and reliable performance.The major contributions of this dissertation are as follows: analysis of the domestic and international research status of the all-digital communications, the characteristics of Ethernet technology and the data transmission theory. After analysis of the Ethernet data transmission process of delay,the delay uncertainty and asynchronous communications, a digital communications model is built and the digital communications protocol of NC system which based on Ethernet technology is established, which resolve the Ethernet communications delay uncertainty and asynchronous communications in order to meet the requirements of real-time and synchronization. On this basis, the dissertation studies the problem about the non-periodic data transmission of NC system, and achieves the non-periodic data with real-time data in the cycle of transmission. Furthermore, the error management is used to ensure that the reliability of digital communications for the process of digital communications possible failures. Based on the above analysis and research, the digital communications protocol feasibility in the self-development of all-digital communications NC system which based on the Ethernet technology is validated by experimentation.The digital communications protocol has already applied for patent, and the development of the NC system also participated in the 2007 Beijing International Machine Tool Exhibition. The practice shows, the appliance of protocol achieves real-time capability, synchronization and reliable performance.