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Making complexity comprehensible

21 February 2017

Chris G Jones, group leader at Frazer-Nash Consultancy, discusses how using Model-Based Systems Engineering (MBSE) can help you to assure your designs and understand the impact of change

Traditionally, multi-disciplinary engineering projects rely on vast quantities of data to manage their designs – masses of detailed documents, spreadsheets and requirements databases. While these tools store huge amounts of information, as a design matures and its complexity increases it can become more difficult to visualise the ‘bigger picture’, to see if a system’s overall purpose is being met. This can increase project risk, as dependencies between systems are missed and incompatibilities arise after design changes, causing costly downstream issues.

The use of a Model-Based Systems Engineering (MBSE) approach makes these large quantities of complex information understandable, through generating a diagrammatic model that enables the representation and exchange of information. Being able to see systems and requirements visually, rather than having to switch between multiple textual sources of data, allows the rapid interrogation of complicated system interfaces and dependencies. Without altering the design process, MBSE centralises and contextualises requirements and design data, providing assistance in understanding potential project risks.

MBSE centralises and contextualises requirements and design data

MBSE can be used from requirements capture to acceptance, building up an entire system design in the model; or can be applied retrospectively to existing systems as a design assurance exercise, looking at the impact of new requirements across the flow of the system. The information can also be output in a range of formats to share with other stakeholders, including web-based viewers and automatically generated reports.

Taking a new drive design concept, for example: the first step would be to identify the overarching requirements for the drive. These might be to deliver a specific amount of torsional effect to a particular device; whilst meeting regulatory requirements; and within precise costing parameters. These requirements can be defined as a collection of interrelated blocks, then broken down further into tiers of interrelated sub-requirements. As these are added to the MBSE model it shows the requirements and sub-requirements, and the links between them, diagrammatically, supporting clarity around interdependencies and enabling the identification of optimal solutions that fit whole-system needs.

Existing systems

But MBSE doesn’t only have to be used at the start of the design process – it can be used for design assurance of an existing system, particularly when considering making a change. An existing drive system, for example, may need to be upgraded to improve its functionality. Using existing drive data, a model is created with MBSE that shows how it has been designed and what it was meant to do. Then the new requirements are added – for example, to specify the performance requirements of an upgrade to the control system hardware and software. Using the system model it is possible to explore the interplay of systems and analyse the impacts of proposed changes on related systems, spotting mistakes or essential dependencies very quickly.

Designers, whether creating a design concept or assuring design, are able to work from a central, single source model using MBSE; with its facility for simultaneous editing meaning any change is instantly visible to all design stakeholders, who can assess the flow-down impact. This reduces the potential for design incompatibilities – particularly important when different departments are creating distinct elements of a product or system that need to be joined together. For programme and project managers this means costly and time-consuming reworking at a later stage can be avoided, with delivery to the end-user more quickly, and perhaps even more cheaply. In regulated industries, such as aerospace or defence, MBSE also allows an approving authority to look at the system and its relationships at a higher level, providing confidence that the design is coming together to meet its overall requirements.

The MBSE approach has the potential to evolve alongside the design life cycle – meaning it can be used throughout the life of a platform or programme. Simplifying large requirement and design programmes, through supporting decision-making and assurance, and facilitating the understanding of stakeholders, means that MBSE can deliver maximum value to both new and existing projects.

Key Points

  • Model-Based Systems Engineering makes these large quantities of complex information understandable, using a diagrammatic model
  • As well as new projects, MBSE can be used for design assurance of an existing system, particularly when considering making a change
  • The facility for simultaneous editing means any change is instantly visible to all design stakeholders, who can assess the flow-down impact