Study On Digital Communication With High Speed Based On SERCOS In CNC

With the technology development of open CNC and digital servo, how to realize high-speed digital communication between control unit and AC servo driver is becoming the key problem in motion control field. With the requirement of higher control precision and real-time in CNC, interface for analog signals can't meet the requirement. The purpose of this paper is to combine the SERCOS fieldbus technology of motion control with embedded ARM technology to satisfy the requirement of high speed and precision in open CNC, and also guarantee the real-time and the reliability of the data transmission.Firstly open CNC and fieldbus technology are introduced. Besides, the protocol characters and working principle of SERCOS bus are elaborated and the advantages of SERCOS are analyzed. Then the realization structure of SERCOS communication system is presented. Open master and slave SERCOS communication boards are designed based on ARM technology. The key technologies and realization methods of software and hardware are introduced in detail. Master board uses the real-time operating systemμC/OS-Ⅱto manage mission courses and interrupt services, and use USB to communicate with PC. The open and real-time requests are satisfied in the control system. Slave board uses the standard servo interface to communicate with servo drivers. Real-time order transmission and data collection are realized.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 principle scheme to PCB layout. A high reliable hardware plan is achieved. Through the debugging data from practical application, the feasibility of software and hardware schemes of the self-designed communication system based on SERCOS bus and the effectiveness of the functions are verified.Finally, the whole work is summarized. Some suggestions are made on what needs further study.