A Framework for Executable Systems Modeling

Systems Modeling Language (SysML), like its parent language, the Unified Modeling Language (UML), consists of a number of independently derived model languages (i.e. state charts, activity models etc.) which have been co-opted into a single modeling framework. This, together with the lack of an overarching meta-model that supports uniform semantics across the various diagram types, has resulted in a large unwieldy and informal language schema. Additionally, SysML does not offer a built in framework for managing time and the scheduling of time based events in a simulation. In response to these challenges, a number of auxiliary standards have been offered by the Object Management Group (OMG); most pertinent here are the foundational UML subset (fUML), Action language for fUML (Alf), and the UML profile for Modeling and Analysis of Real Time and Embedded Systems (MARTE). However, there remains a lack of a similar treatment of SysML tailored towards precise and formal modeling in the systems engineering domain. This work addresses this gap by offering refined semantics for SysML akin to fUML and MARTE standards, aimed at primarily supporting the development of time based simulation models typically applied for model verification and validation in systems engineering. The result of this work offers an Executable Systems Modeling Language (ESysML) and a prototype modeling tool that serves as an implementation test bed for the ESysML language. Additionally a model development process is offered to guide user appropriation of the provided framework for model building

Model-Based Systems Engineering Approach to Distributed and Hybrid Simulation Systems

INCOSE defines Model-Based Systems Engineering (MBSE) as the formalized application of modeling to support system requirements, design, analysis, verification, and validation activities beginning in the conceptual design phase and continuing throughout development and later life cycle phases. One very important development is the utilization of MBSE to develop distributed and hybrid (discrete-continuous) simulation modeling systems. MBSE can help to describe the systems to be modeled and help make the right decisions and partitions to tame complexity. The ability to embrace conceptual modeling and interoperability techniques during systems specification and design presents a great advantage in distributed and hybrid simulation systems development efforts. Our research is aimed at the definition of a methodological framework that uses MBSE languages, methods and tools for the development of these simulation systems. A model-based composition approach is defined at the initial steps to identify distributed systems interoperability requirements and hybrid simulation systems characteristics. Guidelines are developed to adopt simulation interoperability standards and conceptual modeling techniques using MBSE methods and tools. Domain specific system complexity and behavior can be captured with model-based approaches during the system architecture and functional design requirements definition. MBSE can allow simulation engineers to formally model different aspects of a problem ranging from architectures to corresponding behavioral analysis, to functional decompositions and user requirements (Jobe, 2008)

Review of the safety engineering techniques for a complex ship system

Marine industry is leaning towards the autonomous vessels; and advanced technologies are being developed for autonomous operations. However, this rapid technological change has increased the level of complexity in ship systems. As the interactions between components are increasing further and software are getting imbedded into components, the nature of risks in modern systems can be different than in the traditional systems; where the risks were mostly limited to human errors and component failures. However, for identifying risks in modern systems, it is first important to understand the system composition and the behavior of components. Since traditional system-safety engineering techniques, developed for the relatively simpler systems in past, are still dominant in marine industry. These techniques may not be able to cope with the risks due to increasing complexity.This paper reviews and identifies a suitable modelling approach and a risk analysis method for a complex ship system. A modern modeling approach known as Systems-Modeling Language (SysML) and a modern risk analysis method known as Systems-Theoretical Process Analysis (STPA) are reviewed and compared with widely used traditional methods known as the Tree structure method and Fault Tree Analysis. SysML is a graphical modeling language that presents structural composition, component functions, behavior, constraints and requirements of a complex system. STPA is a risk analysis method that aims to identify and mitigate risks in a complex system. The review and comparison results are presented in the paper.The results of this study suggest that the modern methods are more suitable than the traditional methods when the functionality of each method are considered. However, as the modern methods are more detailed, and are focused on the functionality, they are relatively complex and require more resources for the analysis in comparison to the traditional methods. Some viable solutions to improve the drawbacks of SysML and STPA, and possible future research topics are presented.Peer reviewe

Model Based System Engineering for the development of System on Chip

Abstract. Model Based System Engineering (MBSE) has been utilized in auto manufacturing industries, airplane manufacturing and maintenance, and factory process automation industries. These are some of the complex fields. As SoC design is a complex process and requires years of work, MBSE can reduce time, complexity, reuse, and maintenance costs. It seems a fruitful idea/decision to take MBSE into use in SoC design depending on the previously mentioned elements. System on Chip (SoC) is obtaining the interest of many big companies. Therefore, MBSE will represent a huge competitive advantage once it is taken fully into the systems engineering roles of SoC. The existence of geographically dispersed teams, complexity of systems, interdisciplinarity, personalized system description, and their integration can be enabled by MBSE. As an emerging paradigm for the systems of the 21st century, MBSE paved the way for creating successful systems (for the companies) that are end to end connected. This research focuses on making use of MBSE in SoC. The thesis will show how SoC processes can be implemented in one complete model with top to bottom approach. Firstly, the traditional systems engineering approach has been explained with its tools and examples. Secondly, the need for taking up MBSE by the systems engineers is expressed. This contains the applications, use in modern systems, and benefits of MBSE. Moreover, MBSE methodology tools, languages, and their use in SoC is illustrated with examples. As SoC development is a huge and complex process; therefore, a small component of the chip has been taken in consideration for the purpose of understanding and making of the thesis. MBSE is a model-based approach hence a language needs to be present to produce these models and that language is SysML and OPD/OPL. SysML language and MagicDraw tool is used for expressing the architecture of the system. MagicDraw supports several external evaluators for evaluation of expressions and MATLAB is one of them. With MagicDraw we can do simulations, input parameters, and analyze data by processing on it using algorithms developed in MATLAB

Review and comparison of the modeling approaches and risk analysis methods for complex ship system.

Marine industry is leaning towards autonomous vessels with companies such as Rolls-Royce and Kongsberg leading the development. However, this rapid technological change invites greater risks and responsibilities for marine professionals. Ship systems are getting more complex with time as the interactions between components are increasing and software are getting embedded. As a result, the nature of risks in modern systems can be different than in the traditional systems, where the risks were mostly limited to human errors and component failures. However, for identifying risks in modern complex systems, it is first important to understand the structural composition of the system, and the component’s behavior, functions and interactions. Although, modern systems are quite different than traditional systems, traditional system-safety engineering techniques developed are still widely used. This thesis aims to review a modern modeling approach known as Systems Modeling Language (SysML) and a risk analysis method known as Systems-Theoretical Process Analysis (STPA); and compare them against widely used traditional methods known as the Tree structure method and Fault Tree Analysis (FTA). SysML, developed in 2006, is a graphical modeling language which presents structural composition, component functions, behavior, constraints and requirements of a system. SysML aims to support the analysis, specification, design, verification and validation of complex systems. STPA, developed in 2011, is a risk analysis method which aims to identify and mitigate risks in a complex system. Unlike traditional methods such as Fault Tree analysis (FTA), STPA focuses on risks due to the unsafe control actions and component interactions. Furthermore, STPA can be also used during the early phases of the system development process to generate safety constraints and requirements for a safer design of the system. This thesis also includes a workshop with Rolls-Royce where FTA, STPA, SysML and the Tree structure method were applied to a sample complex ship system. The results and feedback received from the workshop are presented and analyzed. The results suggest that the modern methods such as SysML and STPA are more suitable than traditional methods for modeling and identifying risks in a complex ship system if the results of the method’s implementation are considered. SysML presents several aspects of systems in a model which are missing in the Tree structure method, such as the requirements of a system, and behavior and interaction of components. Furthermore, it also provides a model that can be used as a tool for conducting an analysis of a system. Similarly, STPA succeeds on identifying higher number of risks related to component interactions and human errors in comparison to FTA, as STPA analyzes all possible control actions in a system, whereas FTA only analyzes the risks that are known to the analysts. However, some drawbacks of SysML and STPA have also been identified. Although the methods are suitable for complex ship systems, the methods have higher degree of complexity and require more time for an analysis in comparison to traditional methods. Furthermore, some solutions to improve the identified drawbacks of SysML and STPA are proposed in this thesis. Finally, some viable future research topics to improve the research results are presented

Search-based system architecture development using a holistic modeling approach

This dissertation presents an innovative approach to system architecting where search algorithms are used to explore design trade space for good architecture alternatives. Such an approach is achieved by integrating certain model construction, alternative generation, simulation, and assessment processes into a coherent and automated framework. This framework is facilitated by a holistic modeling approach that combines the capabilities of Object Process Methodology (OPM), Colored Petri Net (CPN), and feature model. The resultant holistic model can not only capture the structural, behavioral, and dynamic aspects of a system, allowing simulation and strong analysis methods to be applied, it can also specify the architectural design space. Both object-oriented analysis and design (OOA/D) and domain engineering were exploited to capture design variables and their domains and define architecture generation operations. A fully realized framework (with genetic algorithms as the search algorithm) was developed. Both the proposed framework and its suggested implementation, including the proposed holistic modeling approach and architecture alternative generation operations, are generic. They are targeted at systems that can be specified using object-oriented or process-oriented paradigm. The broad applicability of the proposed approach is demonstrated on two examples. One is the configuration of reconfigurable manufacturing systems (RMSs) under multi-objective optimization and the other is the architecture design of a manned lunar landing system for the Apollo program. The test results show that the proposed approach can cover a huge number of architecture alternatives and support the assessment of several performance measures. A set of quality results was obtained after running the optimization algorithm following the proposed framework --Abstract, page iii

Integrating life cycle assessment in model-based systems engineering

The emergence of smart products has led to the development of an increasing number of multidisciplinary systems. For the successful development of such systems, a holistic approach is necessary, such as model-based systems engineering (MBSE). It is argued that certain product development activities could be integrated and improved with MBSE, one such activity being the assessment of environmental impacts. This article presents a case study on the usage of Life Cycle Assessment (LCA) on a MBSE system model. In the study a technical system is modelled with views according to the MagicGRID approach. The scope and goal of the LCA are defined by using SysML diagrams and elements. Additionally, different system variants are modelled to explore the capability of comparing LCA studies. At the end of the case study, the benefits, limitations, and shortcomings of the integration are discussed

A process model in platform independent and neutral formal representation for design engineering automation

An engineering design process as part of product development (PD) needs to satisfy ever-changing customer demands by striking a balance between time, cost and quality. In order to achieve a faster lead-time, improved quality and reduced PD costs for increased profits, automation methods have been developed with the help of virtual engineering. There are various methods of achieving Design Engineering Automation (DEA) with Computer-Aided (CAx) tools such as CAD/CAE/CAM, Product Lifecycle Management (PLM) and Knowledge Based Engineering (KBE). For example, Computer Aided Design (CAD) tools enable Geometry Automation (GA), PLM systems allow for sharing and exchange of product knowledge throughout the PD lifecycle. Traditional automation methods are specific to individual products and are hard-coded and bound by the proprietary tool format. Also, existing CAx tools and PLM systems offer bespoke islands of automation as compared to KBE. KBE as a design method incorporates complete design intent by including re-usable geometric, non-geometric product knowledge as well as engineering process knowledge for DEA including various processes such as mechanical design, analysis and manufacturing. It has been recognised, through an extensive literature review, that a research gap exists in the form of a generic and structured method of knowledge modelling, both informal and formal modelling, of mechanical design process with manufacturing knowledge (DFM/DFA) as part of model based systems engineering (MBSE) for DEA with a KBE approach. There is a lack of a structured technique for knowledge modelling, which can provide a standardised method to use platform independent and neutral formal standards for DEA with generative modelling for mechanical product design process and DFM with preserved semantics. The neutral formal representation through computer or machine understandable format provides open standard usage. This thesis provides a contribution to knowledge by addressing this gap in two-steps: • In the first step, a coherent process model, GPM-DEA is developed as part of MBSE which can be used for modelling of mechanical design with manufacturing knowledge utilising hybrid approach, based on strengths of existing modelling standards such as IDEF0, UML, SysML and addition of constructs as per author’s Metamodel. The structured process model is highly granular with complex interdependencies such as activities, object, function, rule association and includes the effect of the process model on the product at both component and geometric attributes. • In the second step, a method is provided to map the schema of the process model to equivalent platform independent and neutral formal standards using OWL/SWRL ontology for system development using Protégé tool, enabling machine interpretability with semantic clarity for DEA with generative modelling by building queries and reasoning on set of generic SWRL functions developed by the author. Model development has been performed with the aid of literature analysis and pilot use-cases. Experimental verification with test use-cases has confirmed the reasoning and querying capability on formal axioms in generating accurate results. Some of the other key strengths are that knowledgebase is generic, scalable and extensible, hence provides re-usability and wider design space exploration. The generative modelling capability allows the model to generate activities and objects based on functional requirements of the mechanical design process with DFM/DFA and rules based on logic. With the help of application programming interface, a platform specific DEA system such as a KBE tool or a CAD tool enabling GA and a web page incorporating engineering knowledge for decision support can consume relevant part of the knowledgebase

THE INTEGRATION OF RELIABILITY, AVAILABILITY, AND MAINTAINABILITY (RAM) INTO MODEL-BASED SYSTEMS ENGINEERING (MBSE)

Model-Based Systems Engineering (MBSE) methods have developed a strong foothold in the design space in industry. These methods have proven fruitful when the right method is applied to the right problem. Reliability, Availability, and Maintainability (RAM) and associated techniques are equally important. Currently, there is a gap in applying a methodology to integrate the two in the design process, particularly when the design is complex. This work attempts to provide a methodology that results in the successful integration of RAM and MBSE that can be used during the early phases of design. The methodology was developed after an extensive literature review, followed by validation of the methodology through a use case where each step of the method is applied to a turbine fuel system. The application of the seven-step methodology demonstrate its validity and acts as a simple blueprint for the integration of RAM and MBSE techniques to effectively inform a design effort.NSWC Crane; 300 Highway 361, Crane, IN 47522Lieutenant, United States NavyApproved for public release. Distribution is unlimited