Systems Engineering

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Systems Engineering

• Designing, implementing, deploying and operating
  systems which include hardware, software and
  people
• Objectives
• To explain why system software is affected by
  broader system engineering issues
• To introduce the concept of emergent system
  properties such as reliability and security
• To explain why the systems environment must be
  considered in the system design process

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What is a system?

• A purposeful collection of inter-related
  components working together towards some common
  objective.
• A system may include software, mechanical,
  electrical and electronic hardware and be
  operated by people.
• System components are dependent on other system
  components
• The properties and behaviour of system components
  are inextricably inter-mingled

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What is a system?

• A purposeful collection of inter-related
  components working together towards some common
  objective.
• A system may include software, mechanical,
  electrical and electronic hardware and be
  operated by people.
• System components are dependent on other system
  components
• The properties and behaviour of system components
  are inextricably inter-mingled

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Problems of systems engineering

• Large systems are usually designed to solve
  nasty problems
• Systems engineering requires a great deal of
  co-ordination across disciplines
• Almost infinite possibilities for design
  trade-offs across components
• Mutual distrust and lack of understanding across
  engineering disciplines
• Systems must be designed to last many years in a
  changing environment

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Software and systems engineering

• The proportion of software in systems is
  increasing
• Software-driven general purpose electronics is
  replacing special-purpose systems
• Problems of systems engineering are similar to
  problems of software engineering
• Software is (unfortunately) seen as a problem in
  systems engineering
• Many large system projects have been delayed
  because of software problems

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Emergent properties

• Properties of the system as a whole rather than
  properties that can be derived from the
  properties of components
• Emergent properties are a consequence of the
  relationships between system components
• They can therefore only be assessed and measured
  once the components have been integrated into a
  system

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Examples of emergent properties

• The overall shape and size of a physical system
• This depends on the composition of components.
• The reliability of the system
• This depends on the reliability of system
  components and the relationships between the
  components.
• The usability of a system
• This is a complex property which is not simply
  dependent on the system hardware and software but
  also depends on the system operators and the
  environment where it is used.

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Types of emergent property

• Functional properties
• These appear when all the parts of a system work
  together to achieve some objective
• For example, a bicycle has the functional
  property of being a transportation device once it
  has been assembled from its components
• Non-functional emergent properties
• Examples are reliability, performance, safety,
  and security
• These relate to the behaviour of the system in
  its operational environment
• They are often critical for computer-based
  systems as failure to achieve some minimal
  defined level in these properties may make the
  system unusable.

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System reliability

• Because of component inter-dependencies, faults
  can be propagated through the system
• System failures often occur because of unforeseen
  inter-relationships between components
• Honey-baked ham
• It is probably impossible to anticipate all
  possible component relationships
• Hardware
• Software
• Operator

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Reliability relationships

• Hardware failure can generate spurious signals
  that are outside the range of inputs expected by
  the software
• Software errors can cause alarms to be activated
  which cause operator stress and lead to operator
  errors
• The environment in which a system is installed
  can affect its reliability
• E.g., placement of a system intended to operate
  at room temperature near an air conditioner

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The shall-not properties

• Properties such as performance and reliability
  can be measured
• However, some properties are properties that the
  system should not exhibit
• Safety - the system should not behave in an
  unsafe way
• Security - the system should not permit
  unauthorised use
• Measuring or assessing these properties is very
  hard
• How do you know you are safe or secure?

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System architecture modelling

• An architectural model presents an abstract view
  of the sub-systems making up a system
• May include major information flows between
  sub-systems
• Usually presented as a block diagram
• May identify different types of functional
  component in the model

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Functional system components

• Sensor components
• Actuator components
• Computation components
• Communication components
• Co-ordination components
• Interface components
• All are now usually software controlled

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Hierarchies of Systems
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Intruder alarm system
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Component types in alarm system

• Sensor
• Movement sensor, Door sensor
• Actuator
• Siren
• Communication
• Telephone caller
• Coordination
• Alarm controller
• Interface
• Voice synthesizer

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ATC system architecture
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Inter-disciplinary involvement
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Embedded systems

• Computing systems are everywhere
• Most of us think of desktop computers
• PCs
• Laptops
• Mainframes
• Servers
• But theres another type of computing system
• Far more common...

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Embedded systems overview

• Embedded computing systems
• Computing systems embedded within electronic
  devices
• Hard to define. Nearly any computing system other
  than a desktop computer
• Billions of units produced yearly, versus
  millions of desktop units
• Perhaps 50 per household and per automobile

Computers are in here...
and here...
and even here...
Lots more of these, though they cost a lot less
each.
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A short list of embedded systems
Anti-lock brakes Auto-focus cameras Automatic
teller machines Automatic toll systems Automatic
transmission Avionic systems Battery
chargers Camcorders Cell phones Cell-phone base
stations Cordless phones Cruise control Curbside
check-in systems Digital cameras Disk
drives Electronic card readers Electronic
instruments Electronic toys/games Factory
control Fax machines Fingerprint identifiers Home
security systems Life-support systems Medical
testing systems
Modems MPEG decoders Network cards Network
switches/routers On-board navigation Pagers Photoc
opiers Point-of-sale systems Portable video
games Printers Satellite phones Scanners Smart
ovens/dishwashers Speech recognizers Stereo
systems Teleconferencing systems Televisions Tempe
rature controllers Theft tracking systems TV
set-top boxes VCRs, DVD players Video game
consoles Video phones Washers and dryers

• And the list goes on and on

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Some common characteristics of embedded systems

• Single-functioned
• Executes a single program, repeatedly
• Tightly-constrained
• Low cost, low power, small, fast, etc.
• Reactive and real-time
• Continually reacts to changes in the systems
  environment
• Must compute certain results in real-time without
  delay

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An embedded system example -- a digital camera

• Single-functioned -- always a digital camera
• Tightly-constrained -- Low cost, low power,
  small, fast
• Reactive and real-time -- only to a small extent

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Design challenge optimizing design metrics

• Obvious design goal
• Construct an implementation with desired
  functionality
• Key design challenge
• Simultaneously optimize numerous design metrics
• Design metric
• A measurable feature of a systems
  implementation
• Optimizing design metrics is a key challenge

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Design challenge optimizing design metrics

• Common metrics
• Unit cost the monetary cost of manufacturing
  each copy of the system, excluding NRE cost
• NRE cost (Non-Recurring Engineering cost) The
  one-time monetary cost of designing the system
• Size the physical space required by the system
• Performance the execution time or throughput of
  the system
• Power the amount of power consumed by the system
• Flexibility the ability to change the
  functionality of the system without incurring
  heavy NRE cost

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Design challenge optimizing design metrics

• Common metrics (continued)
• Time-to-prototype the time needed to build a
  working version of the system
• Time-to-market the time required to develop a
  system to the point that it can be released and
  sold to customers
• Maintainability the ability to modify the system
  after its initial release
• Correctness, safety, many more

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Design metric competition -- improving one may
worsen others

• Expertise with both software and hardware is
  needed to optimize design metrics
• Not just a hardware or software expert, as is
  common
• A designer must be comfortable with various
  technologies in order to choose the best for a
  given application and constraints

Hardware
Software
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Robotic System
Video
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Robotic System

• Mecanica Control Computacion
• Ingeniería de reversa (servomecanismos,
  controlador, programación)
• Mecánicas (cabeza, tobillos), comunicación
  inalámbrica, hardware para control,
• Sistema de programación, interfaz
  bidireccional para los servos
• Percepción
• Sensores Visión, Infrarrojos, Unidad Inercial
• Reconstrucción 3D Monocular
• SLAM Visual
• Odometría visual, Navegación Inercial (IMU),
  SLAM Visual, etc.
• Obtención de Modelos y Desarrollo de Simulador
• Geométrico, Cinemático, Dinámico
• Control Cinemático y Dinámico
• Control articular, control cinemático, control
  dinámico (ZMP, FRI)
• Aplicaciones
• Reconocer pelota, Evitar y reconocer obstáculos
  y marcas, Caminar hacia la pelota, conducir la
  pelota, Penalties (tirar y parar), coordinacion
  con otros robots, Pruebas RoboCup, Futbolistas.

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Robotic System Application
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Electric SCADA System
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Web-Based Software System
http//people.csail.mit.edu/hal/mobile-apps-spring
-08/videos/flare.mpg
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Key points

• System engineering involves input from a range of
  disciplines
• Emergent properties are properties that are
  characteristic of the system as a whole and not
  its component parts
• System architectural models show major
  sub-systems and inter-connections. They are
  usually described using block diagrams
• System component types are sensor, actuator,
  computation, co-ordination, communication and
  interface

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Conclusion

• Systems engineering is hard! There will never be
  an easy answer to the problems of complex system
  development
• Software engineers do not have all the answers
  but may be better at taking a systems viewpoint
• Disciplines need to recognise each others
  strengths and actively rather than reluctantly
  cooperate in the systems engineering process