Precise clock synchronization for industrial automation and other networked applications

Abstract:

High precision clock synchronization has emerged as a key enabler for real-time control over shared networks, and the requirements on synchronization precision and on the number of nodes which can be synchronized with this precision are ever increasing. We consider the synchronization solution
offered by the standard IEC 61158 Type 10, called PROFINET, which is an Ethernet which satisfies industrial requirements. Messages carrying precise timing information are propagated in the network to synchronize the slave clocks to a master clock. The current solution is discussed and embedded
into the real-time industrial automation context, and the problem is examined both from a theoretical and a practical viewpoint. The synchronization problem is shown to be a combined estimation and tracking control problem in each of the local clocks, given periodic noisy information transmitted over a communication channel. We give results on synchronization performance under various scenarios. In addition, we examine how to obtain in each slave an optimal estimate of the master time at desired moments. To this end a probabilistic state-space model is introduced which quantifies the uncertainties and represents the relations between the system variables. Then an advanced controller is derived, which produces an optimal reconstruction of the master time at each slave in the sense of minimizing
the mean square error of the estimator and minimizing a quadratic cost function for the controller.

Presentation Slides

Biography:Dragan Obradovic received his B.E. and M.E. degrees in Mechanical Engineering in 1980 and 1985 from the University of Belgrade, Serbia, the latter parallel to holding a Research Engineer position in the Institute Mihailo Pupin. In 1990 he received the Ph.D. degree in Mechanical Engineering from the Massachusetts Institute of Technology, Cambridge, USA. After finishing his PhD, he stayed at MIT until the end of 1991 in the position of a Postdoctoral Fellow at the Laboratory for Information and Decision Systems (LIDS). Since 1992, Obradovic has been with Siemens Corporate Technology, Automation and Control Systems Department, in Munich, Germany where he currently holds a position of Principal Research Scientist. In addition, between 2001 and 2010 Obradovic taught as an Industrial Lecturer in the international “Masters of Science in Communication Engineering (MSCE)” program within the EE Department at Technical University Munich.