Study On The High Speed Digital Communication System Based On SERCOS

The high-speed digital communication between controller and drivers is the key technology of open CNC system. The purpose of this paper is to introduce SERCOS-Ⅱbus technology into CNC system, design and develop a high-speed master and slave network communications modules based on SERCOS-Ⅱbus,and makes the numerical control system based on this structure can exchange real-time data with digital servo, sensor, and PLC-IO through the master and slave network communications modules.First, field bus technology is introduced to the CNC high-speed communications interface,with analyzing the problems of traditional control structures and the requirements on the next generation communication interface. Besides, in the surveying and studying commonly industrial control field bus foundation,the proposal that can build high-speed digital communications systems based on SERCOS technology is chosen. It can satisfy the requirement of strict synchronization requirements and needingcoordination movement among motors in high-speed CNC system.Second, the protocol features and working principle are elaborated and Synchronization mechanism of SERCOS is studied. Then the overall structure of the system is presented. Master-slave's hardware circuit design diagram and the key technologies of each module are introduced. High demands for reliability in industrial environment are taken into account in the design of system hardware. The EMC technology is carried out from the schemes design to PCB layout. And a high reliable hardware circuit design and development is achieved.In system software design, the thesis first introduces the thought of UML and design patterns, and then builds a visual embedded modeling plan. It proposes a general design patterns selection method based on embedded process. Meanwhile it details the whole process and key technology on system software architecture's UML modeling, and discuss the driver development about SERCOS master and slave. In addition, it also points out calculation method of SERCON816 initialization parameter and the key time in periodically transmission stage.Finally, in order to verify system design proposal, technical feasibility and effectiveness, conformance test plan is designed and testing platform based on SDS9-6CNCH for system test. It is shown that SERCOS master and slave network communication module developed by myself meet SERCOS protocol and can control six servo units synchronously run according to prescribed position instruction within 0.5ms control cycle.