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Using SpaceWire Time-codes for Global Synchronization of PLL-Based Local Clocks

Bahls, Thomas and Bihler, Markus (2018) Using SpaceWire Time-codes for Global Synchronization of PLL-Based Local Clocks. Univeristy of Dundee. International SpaceWire Conference 2018, 14-18 May 2018, Long Beach CA, USA.

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Official URL: http://2018.spacewire-conference.org/downloads/2018SpWProceedings.pdf


Abstract In a control application all sensors and actuators have to be able to perform their functions in a specific time to guarantee the desired control cycle. To achieve an exact actual system state a synchronization of the different sensor measurements is necessary. This guarantees that all acquired values are in a very small period of time and not spread over the whole control cycle. Otherwise, a noiser system state would result. The simplest way to synchronize those measurements is with cyclic triggering. This can be either an external request via communication or generated locally by a timer. Both approaches work well in a monolithic system approach with a central unit due to the existence of a common clock domain. However, a distributed system consists of multiple monolithic systems connected via communication, each with a separate clock domain. Due to the communication delay from unit to unit, and the differences between the local clocks, a synchronization according to the presented approaches is only possible by introducing a global clock domain. With time-codes SpaceWire already includes a mechanism to distribute time over a network. However, the communication delay regarding the time-code distribution is not considered. In systems consisting of large networks which have to be synchronized in very small cycles (e.g. high dynamic robots see [1]) this aspect is not negligible. This approach introduces a global time distribution by synchronization and runtime compensation. The synchronization is based on digital phase locked loops (PLLs) which align the units’ local time to the occurence of SpaceWire time-codes. The runtime compensation of the time- code distribution in the network is based on statistical evaluation.

Item URL in elib:https://elib.dlr.de/120401/
Document Type:Conference or Workshop Item (Speech)
Title:Using SpaceWire Time-codes for Global Synchronization of PLL-Based Local Clocks
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Bahls, ThomasUNSPECIFIEDhttps://orcid.org/0000-0002-9935-2676UNSPECIFIED
Date:14 May 2018
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Page Range:pp. 109-112
Publisher:Univeristy of Dundee
Series Name:SpaceWire - 201 8 Proceedings of the 8 th International SpaceWire Conference California, 2018
Keywords:Global time, Synchronization, Local time
Event Title:International SpaceWire Conference 2018
Event Location:Long Beach CA, USA
Event Type:international Conference
Event Dates:14-18 May 2018
Organizer:Univerity of Dundee, ESA, JPL, Microsemi
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space System Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Space System Technology
DLR - Research theme (Project):R - Medical Assistance Systems [SY]
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Robotics and Mechatronics (since 2013) > Mechatronic Systems
Deposited By: Bahls, Thomas
Deposited On:28 Nov 2018 11:07
Last Modified:28 Nov 2018 11:07

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