面向工厂自动化无线网络的时间同步方法

Time Synchronization Method of Wireless Network for Factory Automation

时间同步技术是保障工厂自动化无线网络高实时性与高可靠性的支撑技术.工厂自动化无线网络技术指标要求时间同步的精度成为同步方法的重心,在商用的IEEE 802.11硬件平台上,设计并实现了基于时分多址(time division multiple access,TDMA)机制并由时钟偏差测量、时钟偏差预测和时钟漂移补偿3部分算法组成的高精度时间同步方法.实验证明由于该同步算法相对于传统的双向同步算法加入了时钟偏差预测与补偿机制,使其有精度高、可靠性高、自适应性强等优势,有助于实现工厂自动化无线网络微秒级的TDMA时隙调度.

As one of the key technologies in wireless networks, time synchronization is the supporting technology of factory automation wireless network that guarantees high reliability and high real-time. The high rate and simply effective topology of IEEE 802.11 make it become the best protocol for wireless network of factory automation. This paper first analyzes the importance of clock synchronization precision for high reliability and high real-time in factory automation and proves that high time synchronization precision is the important goal for wireless network in factory automation. Then it designs and realizes the high precision time synchronization method of wireless network for factory automation based on TDMA mechanism on commercial IEEE 802.11 hardware. The high- precision time synchronization method includes three algorithms that are clock skew measurement, clock skew prediction, and clock skew compensation, which are interlocked in one cycle of superframe of TDMA mechanism for high precision of time synchronization. Experiments show that through measurement, prediction and compensation, the time synchronization precision is improved obviously relative to the traditional two-way time synchronization algorithm. The high reliability and strong adaptability of this method adapt to the factory environment, and the high precision of time synchronization is helpful to realize the TDMA timeslot schedule in microsecond of wireless network for factory automation.