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A State-based Extension to STPA for Safety-Critical System-of-Systems
Volvo Construction Equipment, Eskilstuna, Sweden.ORCID iD: 0000-0003-4756-7285
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. RISE ICT/SICS Västerås, Sweden.ORCID iD: 0000-0001-8891-033X
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.ORCID iD: 0000-0001-5269-3900
2019 (English)In: 4th International Conference on System Reliability and Safety ICSRS-2019, 2019, p. 246-254Conference paper, Published paper (Refereed)
Abstract [en]

Automation of earth moving machinery enables improving existing production workflows in various applications like surface mines, material handling operations or material transporting. Such connected and collaborating autonomous machines can be seen as a system-of-systems. It is not yet clear how to consider safety during the development of such systemof- systems (SoS). One potentially useful approach to analyze the safety for complex systems is the System Theoretic Process Analysis (STPA). However, STPA is essentially suitable to static monolithic systems and lacks the ability to deal with emergent and dysfunctional behaviors in the case of SoS. These behaviors if not identified could potentially lead to hazards and it is important to provide mechanisms for SoS developers/integrators to capture such critical situations. In this paper, we present an approach for enriching STPA to provide the ability to check whether the distributed constituent systems of a SoS have a consistent perspective of the global state which is necessary to ensure safety. In other words, these checks must be capable at least to identify and highlight inconsistencies that can lead to critical situations. We describe the above approach by taking a specific case of state change related issues that could potentially be missed by STPA by looking at an industrial case. By applying Petri nets, we show that possible critical situations related to state changes are not identified by STPA. In this context we also propose a modelbased extension to STPA and show how our new process could function in tandem with STPA.

Place, publisher, year, edition, pages
2019. p. 246-254
Keywords [en]
Hazard Analysis and Risk Assessment, Systemof-Systems, Autonomous Machines, STPA, Safety, Petri Net
National Category
Engineering and Technology Computer Systems
Identifiers
URN: urn:nbn:se:mdh:diva-46270DOI: 10.1109/ICSRS48664.2019.8987632ISI: 000545634000039Scopus ID: 2-s2.0-85080111187ISBN: 978-1-7281-4781-9 (electronic)OAI: oai:DiVA.org:mdh-46270DiVA, id: diva2:1377764
Conference
4th International Conference on System Reliability and Safety ICSRS-2019, 20-22 Nov 2019, Rome, Italy
Projects
ITS-EASY Post Graduate School for Embedded Software and SystemsAvailable from: 2019-12-12 Created: 2019-12-12 Last updated: 2025-10-10Bibliographically approved
In thesis
1. Safety Analysis of Systems-of-Systems
Open this publication in new window or tab >>Safety Analysis of Systems-of-Systems
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Safety-critical systems may fail dangerously with severe consequences to the health of the involved humans, costly equipment, the environment, or other valuable assets of a stakeholder. For these classes of systems, the developers are obliged to analyze each potentially hazardous situation thoroughly. In addition, any identified hazardous situation needs to be considered for risk reduction measures, including adjustments of the system's design, additional safeguards if the hazards cannot entirely be removed by design, or warning information to users.  

An essential activity in the development process is the safety analysis, where hazards related to the system under development are identified, and the risks are evaluated and classified. This classification stipulates the rigor of complying with safety standard requirements and directing the development and verification activities. Several techniques for safety analysis have been identified in the literature and are applied in industrial development processes.

The technical evolution enables moving from developing single systems with specific features towards attaching several independent systems to a system-of-systems.On top of the trend towards connectedness, there is also a trend towards more and more automation. In the vehicle domain, autonomous vehicles can collaborate to achieve specific goals, like transporting goods in warehouses, transporting containers in automated ports, or transporting material in off-road environments.

Autonomy brings in new challenges when ensuring product safety and functional safety for single systems due to the lack of a human operator as a fallback solution.Further, when autonomous vehicles collaborate in a fleet, the safety analysis becomes more complex since their interaction and interoperability bring forth new hazards not identifiable with a safety analysis of a single system. Our research aims to bridge this gap and provide solutions for specifying a system-of-systems and finding and developing suitable safety analysis methods.

To understand the challenges and current practices, we have studied industrial projects where systems-of-systems are developed. We have applied safety analysis methods to our industrial cases and found limitations of finding hazards related to a system-of-systems. As part of our research, we have developed extensions to the safety analysis methods to support the analysis of a system-of-systems. We have developed the Safe System-of-Systems (SafeSoS) method which is a structured and hierarchical process to discover and document a system-of-systems characteristics on three primary abstraction levels. Additionally, we utilize model-based formalism to describe the System-of-Systems’ characteristics on each level. Our research results support engineers in the industry when designing a safety-critical system-of-systems.

Abstract [sv]

Safety-critical systems may fail dangerously with severe consequences to the health of the involved humans, costly equipment, the environment, or other valuable assets of a stakeholder. For these classes of systems, the developers are obliged to analyze each potentially hazardous situation thoroughly. In addition, any identified hazardous situation needs to be considered for risk reduction measures, including adjustments of the system's design, additional safeguards if the hazards cannot entirely be removed by design, or warning information to users.  An essential activity in the development process is the safety analysis, where hazards related to the system under development are identified, and the risks are evaluated and classified. This classification stipulates the rigor of complying with safety standard requirements and directing the development and verification activities. Several techniques for safety analysis have been identified in the literature and are applied in industrial development processes.The technical evolution enables moving from developing single systems with specific features towards attaching several independent systems to a system-of-systems.On top of the trend towards connectedness, there is also a trend towards more and more automation. In the vehicle domain, autonomous vehicles can collaborate to achieve specific goals, like transporting goods in warehouses, transporting containers in automated ports, or transporting material in off-road environments.Autonomy brings in new challenges when ensuring product safety and functional safety for single systems due to the lack of a human operator as a fallback solution.Further, when autonomous vehicles collaborate in a fleet, the safety analysis becomes more complex since their interaction and interoperability bring forth new hazards not identifiable with a safety analysis of a single system. Our research aims to bridge this gap and provide solutions for specifying a system-of-systems and finding and developing suitable safety analysis methods.To understand the challenges and current practices, we have studied industrial projects where systems-of-systems are developed. We have applied safety analysis methods to our industrial cases and found limitations of finding hazards related to a system-of-systems. As part of our research, we have developed extensions to the safety analysis methods to support the analysis of a system-of-systems. We have developed the Safe System-of-Systems (SafeSoS) method which is a structured and hierarchical process to discover and document a system-of-systems characteristics on three primary abstraction levels. Additionally, we utilize model-based formalism to describe the System-of-Systems’ characteristics on each level. Our research results support engineers in the industry when designing a safety-critical system-of-systems.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2022
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 355
Keywords
System-of-Systems, Safety Analysis, Hazard Analysis, Model-based Development
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:mdh:diva-56680 (URN)978-91-7485-542-5 (ISBN)
Public defence
2022-01-14, Zeta (och Zoom), Mälardalens högskola, Västerås, 13:00 (English)
Opponent
Supervisors
Available from: 2021-12-06 Created: 2021-12-04 Last updated: 2025-10-10Bibliographically approved

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Fröberg, JoakimPunnekkat, Sasikumar

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