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Investigating Software-based Clock Synchronization for Industrial Networks
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. (Data Communication)ORCID iD: 0000-0002-6942-4229
2021 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A rising level of industrialization and advances in Industry 4.0 have resulted in Industrial Internet of Things (IIoT) gaining immense significance in today’s industrial automation systems. IIoT promises to achieve improved productivity, reliability, and revenues by connecting time-constrained embedded systems to “the Internet”. New opportunities bring with them challenges, and in particular for industrial networks, massively interconnected IIoT devices communicating in real-time,  require synchronized operation of devices for the ordering of information collected throughout a  network. Thus,   a   time or clock synchronization service that aligns the devices’ clocks in the network to ensure accurate timestamping and orderly event executions, has gained great importance. Achieving adequate clock synchronization in the industrial domain is challenging due to heterogeneous communication networks and exposure to harsh environmental conditions bringing interference to the communication networks. The investigative study based on existing literature and the envisioned architecture of the future industrial automation system unveils that the key requirements for future industrial networks are to have a cost-effective, accurate, scalable, secured, easy to deploy and maintain clock synchronization solution. Today’s industrial automation systems employ clock synchronization solutions from a wide plethora of hardware and software based solutions. The most economical, highly scalable, maintainable software-based clock synchronization means are best candidates for the identified future requirements as their lack in accuracy compared to hardware solutions could be compensated by predictive software strategies.

 Thus, the thesis’s overall goal is to enhance the accuracy of software-based clock synchronization in heterogeneous industrial networks using predictable software strategies. The first step towards developing an accurate clock synchronization for heterogeneous industrial networks with real-time requirements is to investigate communication parameters affecting time synchronization accuracy. Towards this goal, we investigated actual industrial network data for packet delay profiles and their impact on clock synchronization performance.  We further analyzed wired and wireless local area networks to identify key network parameters for clock synchronization and proposed an enhanced clock synchronization algorithm CoSiNeT for field IoT devices in industrial networks. CoSiNeT matches well with state-of-the-practice SNTP and state-of-the-art method SPoT in good network conditions in terms of accuracy and precision;  however,  it outperforms them in scenarios with degrading network conditions.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2021.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 311
Keywords [en]
Clock synchronization, Industrial networks, Internet of things, Industry 4.0
National Category
Telecommunications
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:mdh:diva-56095ISBN: 978-91-7485-526-5 (print)OAI: oai:DiVA.org:mdh-56095DiVA, id: diva2:1600536
Presentation
2021-12-10, Gamma, Västerås, 10:15 (English)
Opponent
Supervisors
Funder
Vinnova, 16491Available from: 2021-10-05 Created: 2021-10-05 Last updated: 2021-12-30Bibliographically approved
List of papers
1. Delay and Jitter Analysis in Industrial Control Systems: A Paper Mill Case Study
Open this publication in new window or tab >>Delay and Jitter Analysis in Industrial Control Systems: A Paper Mill Case Study
2021 (English)In: 17th IEEE International Conference on Factory Communication Systems (WFCS) WFCS'21, 2021, p. 99-106Conference paper, Published paper (Refereed)
Abstract [en]

Industrial control systems have strict requirements for time-sensitive applications and clock synchronization services. Performance of such applications is adversely impacted by packet delays and jitters. The impact is especially critical in process industries due to harsh environmental conditions. In this paper, we analyze delays and jitters to assess the performance of time-sensitive applications. To this end, we captured and analyzed round trip delay data retrieved from a paper factory. Analysis shows that a sub-millisecond level average delays and the jitters derived from the observed data are sufficient to meet the minimum 10ms update frequency required for most critical control applications. Moreover, the filtered delay variations at the end devices are less than the recommended 150us, which guarantees an adequate time synchronization accuracy in the factory network. Besides, this analysis can provide significant insights into performance bottlenecks for factory applications.

Keywords
Clock Synchronization, Industrial Automation, Factory Network, Packet Delay, PDV, Round Trip Delay, IIoT
National Category
Engineering and Technology Computer Systems
Identifiers
urn:nbn:se:mdh:diva-54302 (URN)10.1109/WFCS46889.2021.9483601 (DOI)000847076700017 ()2-s2.0-85113823224 (Scopus ID)9781665424783 (ISBN)
Conference
17th IEEE International Conference on Factory Communication Systems (WFCS) WFCS'21, 09 Jun 2021, Linz, Austria
Projects
Future Industrial Networks
Available from: 2021-06-01 Created: 2021-06-01 Last updated: 2023-10-06Bibliographically approved
2. CoSiNeT: A Lightweight Clock Synchronization Algorithm for Industrial IoT
Open this publication in new window or tab >>CoSiNeT: A Lightweight Clock Synchronization Algorithm for Industrial IoT
2021 (English)In: IEEE International Conference on Industrial Cyber-Physical Systems ICPS 2021, 2021Conference paper, Published paper (Refereed)
Abstract [en]

Recent advances in industrial internet of things~(IIoT) and cyber-physical systems drive Industry 4.0 and lead to advanced applications. The adequate performance of time-critical automation applications depends on a clock synchronization scheme used by control systems. Network packet delay variations adversely impact the clock synchronization performance. The impact is significant in industrial sites, where software and hardware resources heavily contribute to delay variations, and where harsh environmental conditions interfere with communication network dynamics. While existing time synchronization methods for IIoT devices, e.g., Simple Network Time Protocol~(SNTP), provide adequate synchronization in good operating conditions, their performance degrades significantly with deteriorating network conditions. To overcome this issue, we propose a scalable, software-based, lightweight clock synchronization method, called CoSiNeT, for IIoT devices that maintains precise synchronization performance in a wide range of operating conditions. We have conducted measurements in local network deployments such as home and a university campus in order to evaluate the proposed algorithm performance. The results show that CoSiNeT matches well with SNTP and state-of-the-art method in good network conditions in terms of accuracy and precision; however, it outperforms them in degrading network scenarios. In our measurements, in fair network conditions, CoSiNeT improves synchronization performance by 23% and 25% compared to SNTP and state-of-the-art method. In the case of poor network conditions, it improves performance by 43% and 26%, respectively.

Keywords
Clock Synchronization, Industrial Automation, Cyber-physical systems, Industrial internet of things, Wireless networks, SNTP, NTP, Round Trip Delay
National Category
Engineering and Technology Computer Systems
Identifiers
urn:nbn:se:mdh:diva-53972 (URN)10.1109/ICPS49255.2021.9468174 (DOI)2-s2.0-85112365768 (Scopus ID)978-1-7281-6207-2 (ISBN)
Conference
IEEE International Conference on Industrial Cyber-Physical Systems ICPS 2021, 10 May 2021, Victoria, Canada
Projects
Future Industrial Networks
Available from: 2021-05-28 Created: 2021-05-28 Last updated: 2023-10-06Bibliographically approved
3. Clock Synchronization in Future Industrial Networks: Applications, Challenges, and Directions
Open this publication in new window or tab >>Clock Synchronization in Future Industrial Networks: Applications, Challenges, and Directions
2020 (English)In: 12th AEIT International Annual Conference, AEIT 2020, Institute of Electrical and Electronics Engineers Inc. , 2020Conference paper, Published paper (Refereed)
Abstract [en]

Time synchronization is essential for the correct and consistent operation of automation systems. An inaccurate analysis being a consequence of improper synchronization, can affect automation functions, e.g., by producing false commands and warnings. Industrial systems are evolving from the rigid automation pyramid to a flexible and reconfigurable architecture due to market evolution. The new trends in Cyber-Physical-Systems (CPS), Industry 4.0, and Internet of Things (IoT) are enabling this evolution. Citing a need to understand the future synchronization requirements, this paper envisions the architecture, communication network, and applications of future automation systems. Built on this vision, the paper derives the future needs of synchronization and analyzes them with state-of-art synchronization means. Based on the analysis, we envision the future of synchronization systems for automation systems.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2020
Keywords
Cloud robotics, Cyber Physical Systems, Drones, Factory Automation, Industrial Automation, Industrial Networks, NTP, PTP, Smart Grid, Time Synchronization, UAV, Embedded systems, Internet of things, Network architecture, Reconfigurable architectures, Synchronization, Automation functions, Clock Synchronization, Consistent operation, Cyber-physical systems (CPS), Internet of Things (IOT), Synchronization systems, Automation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-52864 (URN)10.23919/AEIT50178.2020.9241154 (DOI)2-s2.0-85097154159 (Scopus ID)9788887237474 (ISBN)
Conference
12th AEIT International Annual Conference, AEIT 2020, 23 September 2020 through 25 September 2020
Available from: 2020-12-17 Created: 2020-12-17 Last updated: 2023-10-06Bibliographically approved
4. In Sync with Today's Industrial System Clocks
Open this publication in new window or tab >>In Sync with Today's Industrial System Clocks
2020 (English)In: 2020 International Conference on COMmunication Systems and NETworkS, COMSNETS 2020, Institute of Electrical and Electronics Engineers Inc. , 2020, p. 785-790Conference paper, Published paper (Refereed)
Abstract [en]

Synchronization is essential for correct and consistent operation of automation systems. Synchronized devices accurately time-stamp the events and enable timely communication of messages over a communication network. In absence of a common time base, critical functions of automation systems cannot be carried out in a safe fashion. Unsynchronized systems may lead to malfunctions such as false alarms, wrong decisions and erroneous outcomes resulting into serious showstopper for plant operations. Despite technical advances in synchronization, industrial automation systems have lagged compared to telecommunication and financial services in utilization of latest synchronization technology. Thus, there is a need to investigate the adoption of synchronization in industrial networks, its current state and implementation problems. We carried out an extensive literature search in a structured way to study the evolution of synchronization in automation systems. We also investigated today's industrial automation systems and their network topologies to get insight into the synchronization techniques and mechanisms being used. As an outcome of study, the paper highlights the challenges related to synchronization in existing automation networks that need to be addressed in the immediate and short-term future. 

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2020
Keywords
Building Automation, Factory Automation, Heterogeneous communication, IEEE 1588, IEEE 802.1AS, IEEE C37.238, Industrial automation, Industrial networks, Last-mile connectivity, NTP, PTP, Secured synchronization, SNTP, Substation Automation, Synchronization, IEEE Standards, Intelligent buildings, Telecommunication services
National Category
Other Engineering and Technologies Computer Sciences
Identifiers
urn:nbn:se:mdh:diva-47458 (URN)10.1109/COMSNETS48256.2020.9027323 (DOI)000554883200152 ()2-s2.0-85082169343 (Scopus ID)9781728131870 (ISBN)
Conference
2020 International Conference on COMmunication Systems and NETworkS, COMSNETS 2020, 7 January 2020 through 11 January 2020
Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2023-10-06Bibliographically approved

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Gore, Rahul Nandkumar

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