An Overview of Time Discontinuities of Clock Synchronization Algorithms (1588, Welch-Lynch) and their Effects in Networked Control Systems

E. Martins de Oliveira Jr, M. Lopes de Oliveira e Souza

Abstract:	Current systems such as satellites, aircrafts, automobiles, turbines, power controls and traffic controls are becoming increasingly complex and/or highly integrated as prescribed by the SAE-ARP-4754a Standard. Such systems operate in a real time distributed environment which frequently requires a common knowledge of time among different devices, levels and granularities. The environmental fluctuations, the non-linear dynamics or long lifetimes of these operations cause uncertainties (skew and jitter) in time. So, the common approach in clock synchronization algorithms (IEEE 1588, Welch-Lynch) aims to correct or minimize the time de-synchronizations each one with its own assumptions and peculiarities. However, the common approaches focus on its own assumptions, disregarding the problems that may arise during the application of clock synchronization for networked control systems. The clock synchronization algorithms frequently do not address time discontinuities. Time discontinuities may cause faults or failures in networked control systems among different devices, levels and granularities. This paper presents an overview of time discontinuities of clock synchronization algorithms (IEEE 1588, Welch-Lynch) and their effects in networked control systems. It is based on a review of the literature, discussions, modeling and simulations of a networked control system which requires clock synchronization algorithms (IEEE 1588, Welch-Lynch) among different nodes. The preliminary results of this overview show that: 1) due to the time discontinuity caused by the clock synchronization algorithm (IEEE 1588, Welch-Lynch), the control and response of dynamic systems are degraded; 2) the time discontinuity becomes a design requirement in clock synchronization algorithms of networked control systems; 3) new techniques and analysis must be developed in clock synchronization algorithms schemes to address the time discontinuities for the improvement of next generation systems.
Published in:	Proceedings of the 45th Annual Precise Time and Time Interval Systems and Applications Meeting December 2 - 5, 2013 Hyatt Regency Bellevue Bellevue, Washington
Pages:	134 - 149
Cite this article:	Jr, E. Martins de Oliveira, Souza, M. Lopes de Oliveira e, "An Overview of Time Discontinuities of Clock Synchronization Algorithms (1588, Welch-Lynch) and their Effects in Networked Control Systems," Proceedings of the 45th Annual Precise Time and Time Interval Systems and Applications Meeting, Bellevue, Washington, December 2013, pp. 134-149.
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