Method And Implementation Of NMCSs Based On Clock Synchronization

The primary advantages of a networked motion control systems (NMCSs) are reduction of system wiring, easy of system diagnosis and maintenance, and high system flexibility, etc. The motion control network is the key part of a networked motion control system. In order to achieve high speed and precise of motion, NMCSs requires a control network that supports high-speed synchronous transmission of control command and feedback information with low delay and low jitter. However, the channel of the serial control network is limited and asynchronous essentially, which is a major obstacle for the application control network to the motion control systems. Thereofore investigating this problem and its counter measures has important significance. A solution based on predictive control and clock synchronzation of network was proposed in this dissertation.Firstly the role of the synchronization of the control network in the multi-axes coordinated control was discussed. A distributed interpolation scheme that relies on a clock synchronization of control network was proposed. Effects of network delay on tracking performance of single-axis were analyzed. A compensation method based on time-stamp and predictive control was presented. For the constant network delay, the Smith predictor was presented, where the Zero Phase Error Tracking Controller (ZPETC) and the Youla parameterization were used to improve the tracking accuracy and robustness. By using the Generalized Predictive Controller (GPC) and the message buffer mechanism, the random time-varying network delay can be compensated for. To illustrate the improvement in control performance using the proposed methods, simulation and experiment were presented.Using synchronized clocks in the nodes, delay information can be extracted by including the timestamp to every message. Clock synchronization mechanism of three control network were described. A tuning algorithm of the slave clock was presented. The tuning algorithm does not relay on any specific motion control networks. An ARM7–based implementation of the IEEE1588 protocol was developed.The Maximum allowble delay bound (MADB) of the control network is important for predictive control. Based on the Timed Automata, an analysis method of MADB of the control network was presented. By constructing Timed automata model of network scheduling, model checking can be used for analysis of MADB. Timed automata model of three control networks were established.The improvement of dependability of motion control network can reduce network delay. Effects of EMI on communication were analyzed. The structure of redundant double ring optical network of CANBUS was presented so as to greatly improve the reliability of CANBUS.At last, based on the methods above, a PROFIBUS-based networked motion control prototype system and a CANopen-based networked multi-axes motion control system of shearing machine were realized.