2.1 Introduction to System Engineering

Question 1

What is systems engineering?

Answer 1

There is a wide range of systems engineering
definitions, each of which is subtly different because it tends to reflect the particular focus of its source.
The common themes are:
1- A top-down approach (as distinct from the bottom-up approach of traditional engineering disciplines).
2- A formal focus on requirements engineering—ensuring that we get the requirements right.
3- A focus on the system life cycle, rather than just on acquisition
4- Ensuring that the system is optimised and balanced
5- Integration of large number of specialisations and disciplines involved
6- Management of all aspects of the system life cycle.

Question 2

TOP-DOWN approach

Answer 2

So, in systems engineering, we begin by addressing the system as a whole, which facilitates an understanding of the system, its environment and its interfaces.
System-level requirements can then be developed.
Once these are understood, the system is then broken down into subsystems and the subsystems further broken down into assemblies, and then into components until a complete understanding of the system is achieved from top to bottom.
This top-down approach is a very important element
of managing the development of complicated systems. By viewing the system as a whole initially and then progressively breaking the system into smaller elements, the interaction between the components can be understood more thoroughly, which assists in identifying and designing the necessary interfaces between components (internal interfaces) and between this and other systems
(external interfaces).
Perhaps the best example is the ANSI/EIA-632
approach to top-down development. The system is descomposed into enabling products. Process continues on until the leaves of the tree where a work package to allow the task to be allocated to an individual or a small team.

Question 3

Design and integration in bottom-up approach

Answer 3

While design is top-down, integration is bottom-up.
On the right-hand side of the diagram we have the
flip side of top-down design—bottom up integration as components are developed and tested, integrated into assemblies which are tested and integrated into subsystems which are integrated into the system and final tested for the desired system properties.

Question 4

System life cycle

Answer 4

1-The development of a complete and accurate definition of system requirements fundamental to project success and is a primary focus of systems engineering.
2-The life cycle of a system begins with business needs, which are translated into a large number of statements of requirement that form the basis for the logical design and subsequently elaborated further to form the physical architecture.
3-These transitions must be managed by a rigorous
process, called requirements engineering, which is aimed at ensuring that all relevant requirements are included (and all irrelevant requirements excluded).
Poor requirements cannot be rectified by good
design.
4-Once requirements have been collected, the systems engineering process then focuses on the derivation and decomposition of these requirements from the
system level right down to the lowest constituent component (requirements flowdown). This involves: elicitation, analysis, definition, validation and management of requirements. Our objective to have a complete set of unambiguous requirements from the stakeholders.

Question 5

Requirements Traceability

Answer 5

Essential for effective management.
Through traceability, design decisions can be traced from any given system-level requirement down to a detailed design decision (we call that process forward traceability).
Similarly, any individual design decision must be able to be justified by being associated with at least one higher-level requirement (we call that backward traceability).

Question 6

Life cycle focus

Answer 6

Systems engineering is focused on the entire system life cycle and takes this life cycle into consideration during decision-making processes.
A life-cycle focus requires a focus on the capability system, not on the product—the result is a focus on what is called life-cycle costs (LCC), or whole-of-life costs, or sometimes the cost of ownership.

Question 7

System optimization and balance

Answer 7

Consider the impact of incorporating an F1 engine in a small family car—the engine may be optimised for performance but it will destroy the remainder of the drive train that has been designed for a much less powerful engine. Additionally, the F1 engine is capable of propelling the car far faster than is safe given its suspension and brakes and much faster than is allowed by the legal speed limits.
It follows that a number of subsystems may need to
be suboptimal (or at least constrained in some manner) to allow their combination (the system) to be optimal.

Question 8

Integration of specializations / disciplines

Answer 8

Systems engineering aims to manage and integrate the efforts of a multitude of technical disciplines and
specialities Rarely is it possible for a complicated system to be designed by a single discipline. I.e. Consider an aircraft with their own complexity but also all the additional constrains to be taken in account. The aim of systems engineering is to define the tasks that can be completed by these disparate disciplines and specialities and then to provide the management
to integrate their efforts to produce the system that
meets the users’ requirements. In modern system developments, this function is all the more important because of the complexity of large projects and their contracting mechanisms, and the geographic
dispersion of contractor and subcontractor personnel across the country and around the world.

Question 9

Management

Answer 9

While systems engineering clearly has a technical role and provides essential methodologies for
systems development, it is not limited simply to technical issues and is not simply another
engineering process to be adopted. Systems
engineering has both a management and a technical role.
Project management is responsible for ensuring that the system is delivered on-time and within-budget, and meets the expectations of customers. The trade-offs
and compromises implicit in those functions are
informed by the products of systems engineering.
Additionally, the scope of the project is defined by
the work breakdown structure, which is the result of requirements engineering.
Systems engineering, requirements engineering, and project management are therefore inextricably
linked.