An Introduction to Systems Engineering
Source: document of Stevens Institute of Technology
Systems engineering activities present an opportunity for students to do
engineering the way engineers do it.
Students can work together to identify problems or opportunities, explore
alternatives, create models and test them.
The Internet and computer-aided design software make it feasible for students
in multiple locations to work together to develop solutions to complex
engineering challenges.
What is a System?
We are surrounded by systems. Some of them are natural and others are
engineered. The solar system and a beehive are examples of natural systems.
Engineered systems are designed and built to satisfy human needs and wants.
Wireless telephone networks, power generation plants and our highways are
examples of engineered systems.
A system is collection of different elements that interact to produce results that
are not obtainable by the elements alone.
An automobile is made up of thousands of parts and each part must work with
the others if the vehicle is to function as desired.
From a functional viewpoint systems have inputs, processes and outputs. Inputs
are the resources put into a system. Processes combine the resources to
produce the output which can be a product, service or enterprise.
From a physical viewpoint, the system consists of mechanical, electrical and
software components (and even humans) that interact to realize these
functions. Many engineered systems, particularly those that incorporate
electronics, are built in a way to determine if the system is working properly. To
do this the goal of the system and the output are compared. This is called
feedback. Systems also have boundaries. Everything outside the boundary of a
system is part of another system.
Systems Engineering
Engineers have been building systems from the time of the pyramids. It is no
longer possible for a single engineer to plan and execute a complex project.
Generally engineers work in teams. Most engineers are experts in one
engineering discipline such as mechanical or electrical engineering. Systems
engineering is interdisciplinary in that it seeks to improve the way engineers
from different disciplines work together. In the past systems engineers were
usually selected from among experienced engineers who demonstrated good
communication and leadership skills.
Systems engineers are trained to look at the "big picture" as they coordinate
communication among others and the development of products such as
airliners and enterprises such as mass transit and homeland security systems.
Systems engineers work on complex projects. Not all engineering projects are
complex. Although engineers design appliances such as washing machines
these are not complex products.
Systems engineering is widely used in the aviation and defense industries for
activities such as designing and building airliners and submarines. Today's
submarines resemble the fuselage of an airliner, have a nuclear power plant,
serve as the hotel for 100 people, carry advanced weapon and communication
systems and must operate silently underwater. They are truly complex.
Designing airliners requires the expertise of structural engineers, materials
engineers, mechanical engineers, electrical engineers, human factors
engineers and others. Companies designing these and other complex products
use systems engineers to provide leadership and coordinate the work of the
many professionals that contribute to the project.
Industries outside the aerospace and defense domain, such as the automotive
industry, telcom, and IT are also increasingly showing an interest in systems
engineering. One explanation for this is the increased level of electronics and
software in products that only a decade ago hardly had anything. Another factor
is the increased interconnectedness between products that used to live isolation
(e.g. on some cars your power steering now talks directly to your ABS brakes to
help you swerve around obstacles more safely).
Core Principles of Systems Engineering
Engineers create systems for customers but others are also affected by the
systems they design. All those affected are referred to as stakeholders.
Systems engineering activities continue throughout the entire lifecycle of the
system. During the early stages of design it's important to understand the needs
of the various stakeholders and translate this into specific requirements for the
system. Requirements detail what the system must do. After the requirements
are established the focus is on using the engineering design process to
develop, construct/build, test, use, maintain and retire the system. An important
task for systems engineers throughout these phases is to be the "advocate" for
the whole system. This means to ensure that all components of the system
make their assigned contribution to the system, as well as make sure that the
components interact in the way they are supposed to. Assessment should be
ongoing and include a continuous feedback loop to insure that the system is
working properly and provide an opportunity for continuous improvement.
Dr. Rashmi Jain, an Associate Professor of Systems Engineering at Stevens
Institute of Technology, has identified five core concepts of systems
engineering: value, context, trade-offs, abstraction and interdisciplinarity.
Systems provide value when they meet the needs of stakeholders. The context
of a system is important. Engineers need to consider where the products and
processes they design will be used. For example, the engineers who recently
designed double-decker passenger train coaches for New Jersey Transit had to
make sure that the new cars worked with existing systems including the power
lines, platforms, signals and locomotives. Interdisciplinarity supports the
systems approach which is based on the idea that systems design must
consider the needs of all relevant stakeholders and that design teams are made
up of members from many disciplines. This means that a systems engineer
needs to obtain a good understanding of the environment (often referred to as
the problem domain) where the system is used. Although not an expert, he/she
will need a good working knowledge of the different engineering disciplines that
are involved in creating the system.
Potential design concepts should be evaluated based on tradeoffs such as cost,
time and performance. The goal is to select the optimal solution and recognize
that there is no perfect solution for all stakeholders. A tank-like automobile
designed to prevent injury during every crash would be inefficient to drive and
probably too expensive to build. Instead engineers have focused on seat belts,
air bags and designing the structure surrounding the driver and passengers to
reduce the forces transferred to them during a crash.
Abstraction is another element of the systems engineering process. Engineers
need the ability to abstract a design concept independent of the solution. It's
important to consider a wide range of alternative and not select a specific
solution too soon. For example, early in the space program NASA wanted
astronauts to be able to take notes in a zero gravity environment. They spent
millions to develop a ball point pen that would work. Russia solved the problem
by having their astronauts use pencils.
Systems engineers are also concerned with risk management. Risk
management involves identifying what may go wrong in a system and then
planning to prevent it or solve the problem should it occur. For example, many
companies manufacture components for their products in multiple locations so
that a tornado or other natural disaster will not totally disrupt production of the
final product.
Systems and Global Engineering
Our global economy creates opportunities and challenges. The US economy is
growing very slowly compared to that of many other countries. This creates an
opportunity to sell consumer products in countries that have rapidly growing
economies. It has become increasingly common for a product to be designed in
one location, tested at another site and manufactured at a plant thousands of
miles away. Since labor costs make it expensive to manufacture in the United
States many companies have their products manufactured in China, India and
other developing countries. Advanced communication systems including the
Internet, and Computer-Aided Design software have helped to make this a
common practice. In addition, a combination of global and systems engineering
makes it possible to take advantage of the expertise of engineers and
companies located throughout the world. A good systems design will facilitate
this type of collaboration, by creating modular subsystems that reduce the
amount of micro-management needed to coordinate the development effort.
The new Boeing 787 Dreamliner, which will have a fuselage built of 50 percent
carbon fiber, is being assembled from components produced by 43 companies
at 135 sites around the world. This approach has presented challenges.
Manufacturing problems are causing costly delays. Boeing hopes that its
systems engineers will be able get the project back on track shortly.
Systems Engineering Glossary
Abstraction
Boundary
Context
Customer
Engineering
Feedback
Gantt Chart
Input
Interdisciplinarity
The ability of engineers to think of design concepts that are not dependent on specific solutions.
A separation between the interior of a system and what lies outside.
The users, other systems and other features of the environment of the system that the system will
interact with.
The organization or individual that has requested (and will pay for) a product or service.
The application of scientific principles to practical ends.
Information about the output of a system that can be used to adjust it.
A project management tool in the form of a bar chart showing the start and finish dates of activities
A material, service or support item that is processed by the system.
People from different disciplines working together to design systems.
Lifecycle
Important phases in the development of a system from initial concept through design, testing, use,
maintenance, to retirement.
Mission
An undertaking that is supported by the system to be designed to be successful (e.g. space missio
Optimization
Output
The process of choosing the best alternative that will satisfy the needs of the stakeholders under t
constraints given (e.g. cost, schedule and available technology).
What is produced by a system.
Process
A set of activities used to convert inputs into desired outputs.
Project
An activity having goals, objectives, a beginning and an end.
Requirement
Risk Management
A statement of required behavior, performance and other characteristics of the system to be
developed.
A process of identifying what can go wrong and making plans that will enable a system to achieve
goals.
Specifications
Stakeholder
System
Systems Approach
System Design
System Integration
Systems Engineering
The technical requirements for systems design.
An individual or group affected in some way by the undertaking. Stakeholders are valuable source
for requirements.
A set of interrelated components working together to produce a desired result.
The application of a systematic disciplined engineering approach that considers the system as a
whole, its impact on its environment and continues throughout the lifecycle of a project.
The identification of all the necessary components, their role, and how they have to interact for the
system to fulfill its purpose.
The activity of integrating all the components of a system to make sure they work together as
intended.
The orderly process of bringing a system into being using a systems approach.
Trade-off
losing one quality or aspect of something in return for gaining another quality or aspect.
Value
The benefit enjoyed by the stakeholders of the system when the system is in operation.
Validation
Testing to insure that the created system actually provides the value intended to its stakeholders.
we build the right system?).
Verification
The process of proving that a finished product meets specifications and requirements. (Did we bui
the system right?)