In any project, the early design phases are critical in determining its success – that’s especially true when dealing with complex systems. Model-based system engineering (MBSE) offers a structured approach for these early stages that addresses two key aspects: it can enhance communication between all stakeholders and it helps us to check the alignment between design and requirements.
Engineers can use MBSE tools to create visual representations of the system architecture; these models then provide the basis for capturing system requirements and linking them to functions or products.
The aim for the initial design phase should be to achieve a consolidated, high quality baseline that ensures consistency with the needs of the mission or system. In this post, we explore how MBSE is applied in the early design phases and how it can help engineers define a system architecture that fulfils the initial set of requirements in a project.
By Paloma Maestro Redondo, System Engineer and Project Manager
How can MBSE improve system engineering activities?
During the initial stages of a project, system engineers are responsible for establishing a consistent baseline for the design, working together with other stakeholders to define a preliminary architecture that meets the mission requirements. Using an MBSE approach in these activities is an effective method for maintaining consistency and traceability between the different parts of the design and the requirements.
Here, we outline how typical system engineering tasks can benefit from using MBSE processes and tools.
Identifying requirements and functional analysis
Early design phases may consist of conceptual or feasibility studies. In these, the system definition should cover the main mission/project needs but remain abstract and not too detailed. This approach provides flexibility for the next phases, but it is crucial to ensure that we’ve captured and covered all the requirements before continuing.
In large, complex projects, the first phase begins with the identification of the key stakeholders and understanding their needs. System engineers can then define the initial set of user requirements and how they are formalised into requirements, which capture the essential capabilities and constraints of the system or mission.
When implementing an MBSE approach, we can use models right from the early stages. In the MBSE tools, we can also represent the breakdown of the high-level mission requirements into more detailed system requirements; later, these will be translated to functions that the system must perform. A thorough functional analysis and decomposition allows us to gain a comprehensive understanding of the system’s operation, ensuring that every aspect is fully accounted for.
MBSE tools provide engineers with a structured and traceable way to manage requirements, ensuring that all system needs are captured and linked to subsequent design activities. Together with a structured methodology, these tools enable engineers to trace each requirement back to its source, ensuring that nothing is overlooked as the design progresses.
System architecture definition
With the functions clearly identified, the next step is to define the system architecture. This involves organising the system functions into a coherent structure, identifying the components and subsystems needed to realise these functions, and defining the interfaces between them.
MBSE tools like Capella or Cameo Systems Modeler are highly valuable at this stage. They provide functionalities for developing detailed models that integrate functional, physical and behavioural aspects of the system. MBSE tools typically make use of a specific modelling language, and can also have an associated methodology, as is the case with ARCADIA for Capella.
Similar to the process followed in software engineering, identifying the high-level components involves determining the major building blocks that will form the system. When developing complex systems in engineering domains like aerospace or naval design, the system engineers also allocate the functions to physical components, leading to a preliminary system architecture that captures the essential structure and interactions of the system components.
The MBSE models used at the early stages also provide the basis for capturing and linking system requirements to the functional architecture, ensuring traceability and alignment with the mission goals.
Trade-offs and design iterations
Trade-off analysis is a critical part of feasibility studies. In such analyses, different design options are evaluated against each other to determine the best solution. This process involves iterative analysis and optimisation of the system to balance performance, cost, risk and other factors.
Several MBSE tools have integrated functionalities into their modelling environments to perform the analysis and allow engineers to optimise the design and choose the best solution. They can simulate different scenarios based on the architecture that has been previously defined, and refine the system design accordingly. Additional functionalities in the tools can also allow users to verify the requirements based on the simulation results.
In the early stages of the design of a new satellite, for example, engineers might use these tools to evaluate different configurations of solar panels, batteries and payload capacities, and assess their impact on the satellite’s performance, cost and reliability. MBSE allows these iterations to be seamlessly integrated into the overall system model, ensuring consistency and traceability throughout the design process.
An important feature for the tools used in conceptual studies is enabling collaboration between the engineers and other stakeholders. Tools like Starion’s CDP4-COMET allow study participants to work together on the same model, and perform the trade-offs and design iterations in the model while discussing multiple options.
In summary
MBSE provides a consistent and reliable solution for managing the complexity of designing complex systems. By defining the system architecture rigorously, decomposing requirements into functions and allocating these to the physical components, MBSE ensures that every aspect of the system is aligned with the original requirements. This not only improves the clarity and consistency of the design process, but also lays a solid foundation for the subsequent phases of the project life cycle.
As industries and technology continue to evolve, MBSE will become increasingly important in early design stages, allowing engineers to design even more complex projects with confidence and precision.
Find out more
In upcoming posts in this series, we will discuss the use of MBSE in concurrent design studies, and provide guidance on selecting the most suitable MBSE tool(s) for your specific needs. Follow Starion Group on LinkedIn to find out when all new posts are published.
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