Model-BasedSystemsEngineering

System is an integrated set of elements, sub-systems or assemblies that accomplish for a defined objective. Elements could be:

• Products
• Software
• Hardware
• Processes
• People
• Information
• Techniques
• Facilities
• Services

System can be decomposed to elements treated as a black box.

System hierarchy is a way in which different elements of a system are organized and structured. The hierarchy helps us understand how various components interact and work together to achieve a common goal.

Core Concepts of Systems Engineering

Systems engineering has evolved significantly, addressing the complexities of modern product development. The practice aims to mitigate risks associated with complex systems, focusing on the connections between components.

Lifecycle

Each product has the following stages

• Concept
• Development
• Production
• Utilisation
• Support
• Retirement

Processes behind life-cycle are dinamic, iteractive and recursive.

Iteration - repeating process to improve product by using newly available information

Recursion - applying the same process at finer levels of details (for exaple decomposing system to the elements

Life-cycle methods:

• Waterfall method- specified, sequential process that follows a predetermined sequence. Used than requirements are defined and will not change in future
• Incremental and iterative method - after each step product is checking for meeting expectation. If meets - new requirements are to be defined. If not - product improves to meet expectations
• Vee method - product evolves over time from stakeholders requirements, to the system concept and finally to elements design. At first system is decomposing, than components are developed and verified and than components are integrating to a system. Iteration is optional after components integration

Lifecycle process categories

All life cycle processes (about 30 in 15288 standard) can be splitt in four categories

• agreement processes - formalize methods and expectations between organization. They needs to define responsibilities, project and technical functions.
• organizational project enabling processes - focused on needed resources to accomplish goals. They needs to define environment in which work is performed, project processes and lifecycle model in use, required resources to accomplish project and quality measurement processes
• management technical processes - focused on managing allocated resources to reach the goals. They need to track costs, and milestones, to align efforts with plans and to correct planning to avoid shortfalls.
• technical processes - focused on technical tasks at any point of life cycle. They need to realize and apply the processes to create the system which meets stakeholder requirements.

Cost of Corrective Actions

A study highlights that correcting issues during the requirements phase is significantly cheaper than making changes later in the design, build, or testing phases, with costs increasing dramatically at each stage.

Return on Investment (ROI) in Systems Engineering

Higher levels of systems engineering capability correlate with better project performance, with a study showing a 57% success rate at high capability levels. Investing around 14% of total program costs in systems engineering yields a substantial ROI of of 7:1, with projects lacking systems engineering seeing a much lower median investment of only 7% there is a 3.5:1 ROI

MBSE

Model-based system engineering is a formalized application of modeling to support system requirements, design, verification and validation thru all lyfecicle of the development

Key concept is model-based definition (MBD) which used to define system in digital format (cad models, manufacturing and performace models)

MBSE focused on is focusing on development, management and controlling system

Using MBD thru entire enterprise reduces cost, improves performance and open way for easy product improvement:

• improves communication between deweloping teams
• improves quallity
• reduse time and cost for test and integration

Models

In the context of systems engineering, a model that represents a system and its environment is of particular importance to the system engineer who must specify, design, analyze, and verify systems, as well as share information with other stakeholders

Models can represent physical form, functionality or behaviour. Different models are using different programs with

1. its own language with unuque rules and objects (constructs) to build the model (abstract synthax)
2. set of symbols to represent objects (concrete synthax).
3. semantics to provide meaning of the objects

Functional modeling languages consists of:

• Data flow diagrams (DFD)
• Integration definition for structural modeling (IDEF0)
• Enhanced Functional Flow block diagram

Structural modeling technics includes:

• Data structure diagrams
• Entity relationschips diagrams
• Object modeling techniques

System engineering works with Systems Modeling Language (SysML) which overlaps with Unified Modeling Language (UML).

It is important to use verification of the model when applying MBD.

Verification ensures you build the system right and validation is that you build the right system

SysML

UML is a software engineering modeling language enabling communication and visualisation with respect to program structure and details.

SysML is a graphical modeling language developed to support system engineering. It is human-readable and and supports XML and AP233 data exchange formats for mashin readability.

SysML builds uppon UML and they have many in common. SysML allows to modify 3 diagrams

• activity - focuced on behaviour - specified transformation of inputs to outputs thru conctrolled system of actions
• block definition - focused on structure - describes the relationschips between blocks
• internal block diagram - structure - desctibe internal structure of the block in terms of parameters and connectors

And adds 2 diargams

• Requirement
• Parametric - structure - ise to express constrains and equatuons

Also SysML extends UML

• Item flows
• Value properties
• Allocations

UML diagrams(?):

• Sequence diagram - behaviour - provides representation of a messaged-based behaviour
• State machine diagram - behaviour - represents lifecycle of the blocks and event-based behaviour
• Use case diagram - behaviour -provides to dedcribe functionality of the system in terms of goals or means
• Package diagram - structure - used to organise system using hierarchi and can add user - defined properties (verification methods..)

Top level requirement diagram - represent text-based requirements

Four pillars of SysML

1. Steucture
2. Behaviour
3. Requirements
4. Parameters

To implement SysML used Continious Product Improvement Stategy to gradually implement components of the process.

Existing systems:

• Magic draw
• Tau and Rapsody
• Artisian Studio
• Visio

MBSE Framework

To use MBSE the framework is requiered. Frsmeworks can be focused on a single component, or series of components

Analysis framework consists of variety of simulation tools: nastran, ansys, mathlab. It should be able to transfer automaticaly results from one analysis to the subsequent. Framework should have execution engine to iterate analysis until requered solution reached. It can also include version control to update elements without impacting the architecture of analysis. In some frameworks results can be checked against requirements.

Examples:

• Siemens HEEDs is an example, that can search alternative design configuration
• LMS Imagine Lab - automate mechatronics systems creation
• Phoenix integration model center
• Dasault iSight - optimisation and design of experiments

Resources for Systems Engineering

Key resources include

• INCOSE Systems Engineering Handbook,
• SEBoK,
• ISO/IEC/IEEE
• 15288 standard, and the
• NASA Systems Engineering Handbook.

These resources provide a comprehensive understanding of systems engineering principles and practices. Understanding Systems and Their Architecture

Useful links

https://sebokwiki.org/