Research On The Key Technologies Of Networked Motion Control System

Motion control system plays a key role in manufacturing automation. Manufacturing industry puts forward higher requirements for the efficiency, precision and flexibility of motion control system. An open control structure is needed in order to achieve these goals, so that the networked motion control system (NMCS) is proposed. With the development of real-time Ethernet, NMCS is becoming more and more popular. In this paper, the model of the NMCS, the real-time and synchronization mechanism of Ethernet and some other key technologies of NMCS to improve the performance of motion control system are researched.Firstly, the model of networked control system is researched. The network induced delay and real-time performance of different action trigger mechanisms are analyzed and compared. Control model of the networked control system with delay is built and simplified according to the real-time and synchronization property of motion control system. The effects of communication cycle and network induced delay to the stability, steady-state error and dynamic performance are researched with this model, and then some design criterions to diminish the network effects are established.Based on the design criterion from the NCMS model, the real-time and synchronization mechanisms of Ethernet are researched. A real-time Ethernet for motion control system named EtherMAC (Ethernet for Manufacture Automation control) is proposed from a system point of view. Time-deterministic communication can be achieved by using cascaded line topology and summation frame. High precision communication period can be achieved by employing a FPGA-based slave node to manage the communication cycle, in this way, the real-time demand for the master node can be weakened, and hard real-time performance can be achieved even the master node without any dedicated hardware or hard real-time operating systems. A distributed clock based synchronization mechanism is proposed to achieve high synchronization precision. With the online compensation mechanism, the effect of crystal error on the distributed clock can be compensated.Based on the previous work, the reliability and functional safety of EtherMAC are researched. The faults of communication network are analyzed. The last node arbitration, automatic repeat request, forward error correction mechanisms and redundant ring topology are employed to realize the reliability of EtherMAC according to different applications. The black channel technology is applied to simplify the functional safety model of EtherMAC. The simplified network uses cyclic redundancy check, sequence number, time stamp, time expectation and some other measures to detect corruption, incorrect sequence number, unacceptable delay and connect failure errors in communication. The functional safety solutions based on EtherMAC are proposed and the safety function response time is analyzedThen, the networked motion control system based on EtherMAC is researched. A FPGA-based slave node implementation method is proposed, and the intellectual property (IP) core which supports EtherMAC data link layer protocol is developed. Forward delay less than520ns between adjacent slave nodes can be achieved by modifying the frame online. The protocol framework of master node is given, and a PC-based software motion control system is proposed. A hierarchical open-architecture software motion control system is developed. This architecture not only allows the application developer use the high level programming languages, but also supports the CoDeSys which is an integrated development environment compliance with the international industrial standard IEC61131-3. A high speed fine interpolation algorithm, a parametric hardware fine acceleration/deceleration algorithm and a contour error control algorithm based on EtherMAC motion control platform are proposed. The advantage of performance and openness are also demonstrated.An EtherMAC prototype system is built at last, and its real-time performance is tested according to several experiments.