智慧工廠終端製造設備需整合大量且分散的感測器和致動器，透過現場總線網路進行即時控制和即時資料收集。精密時間同步為工業現場總線網路提供精密且一致的時間戳記，讓所有終端裝置得以即時且同步的運作。典型的運動控制對於時間同步誤差要求必須至少在1微秒以內，然而作為現今自動化設備主流的Modbus現場總線，因為缺乏精密時間同步機制，在分散式協同運動控制的應用上受到很大的局限。本論文參考IEEE 1588標準協定，設計一個基於Modbus協定的精密時間同步晶片，通過Modbus封包傳遞同步封包。精密時間同步除了考量到主從時鐘的時間偏移量和封包的傳輸時間延遲，還針對系統比例誤差進行修正。精密時間同步晶片整合在Modbus現場總線，透過Modbus功能碼的擴充實現系統時間同步，此一晶片每秒進行一次同步，可讓系統時間誤差達到42奈秒，可滿足工業運動控制的精密時間要求。;Smart factory cooperate with a lot and distributed sensors and actuators to realize real-time control and data collection under the fieldbus network. Precision Time Protocol(PTP) is used to synchronize clocks throughout an industrial fieldbus network. It achieves clock accuracy in the sub-microsecond range, making it suitable for motion control systems. Nowadays, Modbus is the primary fieldbus network protocol for automated industrial device. However, the industrial application of Modbus is limited in distributed cooperative motion control because of its lack of time synchronization mechanism. Therefore, we design a PTP chip for Modbus based on IEEE 1588 standard. And the synchronous packets are transmitted via Modbus packets. Besides the time offset between master clock and slave clock, PTP also takes transmission delay into account. In addition, the system error is adjusted by proportional controller. PTP chip is integrated on Modbus through the expansion of function code and it synchronize clocks of network system once per second. Time synchronization accuracy of PTP chip is up to 42 nanoseconds, it is satisfied with the industrial motion control.
