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Browse Prior Art Database

Visibility of Time Synchronization Accuracy in Industrial Network Management System

IP.com Disclosure Number: IPCOM000178369D
Original Publication Date: 2009-Feb-13
Included in the Prior Art Database: 2009-Feb-13
Document File: 2 page(s) / 110K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The frequency / frequency drift of quartz or oscillator within field level devices is not available within network management system. Additionally, the management system lacks of any information about the synchronization accuracy of the field devices. If the field level devices send the frequency / frequency drift of quartz to SINEMA-M (Product of the Siemens AG), then SINEMA-M could intelligently decide on when to change the IOD (input-output device) as due to this IOD, the overall time synchronization accuracy within that the IO system is going beyond the acceptable limits.

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Visibility of Time Synchronization Accuracy in Industrial Network Management System

Idea: Vivek Kulkarni, DE-Munich; Matthias Scheffel, DE-Munich; Sandeep Misra, DE-Munich

The frequency / frequency drift of quartz or oscillator within field level devices is not available within network management system. Additionally, the management system lacks of any information about the synchronization accuracy of the field devices.

If the field level devices send the frequency / frequency drift of quartz to SINEMA-M (Product of the Siemens AG), then SINEMA-M could intelligently decide on when to change the IOD (input-output device) as due to this IOD, the overall time synchronization accuracy within that the IO system is going beyond the acceptable limits.

In order to support applications that demand for strong real-time requirements like motion control, distributed stations interconnected by a network must be synchronized with a minimum accuracy of one microsecond. A typical small-scale real-time automation system consists of one input-output controller (IOC) that communicates with a number of input-output devices (IODs) to exchange data between sensors and actuators. Each IOD has an internal clock (slave clock) that must be synchronized to the master clock of the IOC. The clocks are based on oscillators whose frequency is inevitably altered by various influences such as temperature or vibrations. Synchronization within the network is created and maintained by exchanging time information between the nodes. When applying the precision time protocol IEEE 1588 for example, the IOC continuously distributes the actual master time and the IODs determine the station-dependent delay after which the data reaches them to compensate for processing and propagation times. However, there is no default feedback of the synchronization status from the IODs to any other node.

From a network management point of view it is desirable to monitor the time synchronization performance in order to make sure the system is functioning properly. At each IOD, a synchronization algorithm adapts the local slave clock to the estimated master clock utilizing time stamps. On the one hand, actual time stamps of the master clock are transferred in packets from the IOC to the IODs. On the other hand th...