Performance analysis of a clock state estimator for PROFINET IO IRT synchronization

Clock synchronization is essential to support time-based medium access scheduling and distributed control over industrial networks relying on Real-Time Ethernet (RTE). PROFINET IO is one of the most widely used field-buses in large automation plants. The PROFINET IO Isochronous Real Time (IRT) implementation includes a Precision Transparent Clock Protocol (PTCP) for network-level synchronization. A similar scheme is also used in the second version of the Precision Time Protocol (PTP), standardized as IEEE 1588-2008. Unfortunately, synchronization uncertainty typically grows in the case of long chains of cascaded clocks. In this paper, the accuracy of a clock state estimator based on a Kalman filter is analyzed in the context of PROFINET IO IRT networks. The proposed estimator can be used to compensate the time offsets of every node with respect to the reference master, thus improving synchronization accuracy in the case of long linear topologies beyond the limits of other existing solutions. The presented results are obtained from multiparametric simulations based on the features of real hardware devices.