A clock state estimator for PTP time synchronization in harsh environmental conditions

Abstract

In industrial automation networks based on the Precision Time Protocol (PTP) large temperature changes as well as mechanical shocks and vibrations may severely affect the performance of the local oscillators clocking the network nodes, thus making accurate time synchronization challenging. This problem is particularly critical in large industrial networks with long linear paths, as multiple uncertainty sources tend to accumulate while PTP event messages are forwarded towards the slave clocks. In this paper, the performance of a clock state estimator based on a special Kalman filter as well as on a detailed model of the PTP communication mechanism is described. The reported simulation results when the network nodes are subject to changeable environmental conditions provide interesting guidelines to keep synchronization accuracy in industrial networks within given boundaries.