Developing a Solution

8/1/16 © Copyright 2016 Stevens Institute of Technology, All rights reserved 1

Course Design

8/1/16 2

Deciding What to Build

& Why

Bringing Solutions to Life

Ensuring Systems Work And Are Robust

Managing Evolution…

Deciding What’s Next

Course Design

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Deciding What to Build

& Why

Defining  the  Problem  

Developing  a  Solu5on  

Formula5ng  a  Proposal  

Concept  Review  

Course Design

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Deciding What to Build

& Why

Defining  the  Problem  

Developing  a  Solu5on  

Formula5ng  a  Proposal  

Concept  Review  

Class Schedule (1 of 2)

Date Week Topic

Feb 1 1 •  Thinking in Terms of Systems

Deciding What to Build and Why

Feb 8 2 •  Defining the Problem

Feb 16 3 •  Developing a Solution

Feb 22 4 •  Formulating a Proposal

Feb 29 5 •  Concept Review

Bringing Solutions to Life

Mar 7 6 •  Building a Functional Model

Mar 14 7 •  Implementing the Functions

Mar 28 8 •  Specifying Components

Apr 4 9 •  Design Review 8/1/16 © Copyright 2016 Stevens Institute of

Technology, All rights reserved 5

Class Schedule (2 of 2)

Date Week Topic

Ensuring the System Works and Is Robust

Apr 11 10 •  Integration and Test

Apr 18 11 •  Modeling and Simulation

Apr 25 12 •  Designing for the Lifecycle

May 2 13 •  Test Readiness Review

Managing Evolution…Deciding What’s Next

May 9 14 •  Technology and Innovation

May 16 15 •  No Class – Final Project Submission

8/1/16 © Copyright 2016 Stevens Institute of Technology, All rights reserved

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Developing a Solution Key Questions:

1.  What is your proposed system concept? What alternative concepts did you consider and why did you select the one you proposed?

2.  How will your proposed concept operate within the larger context to achieve its intended purpose?

3.  What are the key specifications that will drive your system’s design and development?

System Concepts

•  What is your proposed system concept? What alternative system concepts did you consider and why did you select the one you proposed? –  What criteria were used to compare the

alternatives? –  How well did each concept satisfy each of the

selection criteria? –  On what basis was the preferred concept selected?

•  Question on a physics exam at the University of Copenhagen: –  "Describe how to use a barometer to determine the height of a

skyscraper." •  Proposed Solution: “Lower it from the roof on a string and measure

the length of the string.” •  Physics-based solutions:

–  “Drop it from the roof and measure the elapsed time.” –  “Measure its shadow and use proportions.” –  “Turn it into a pendulum and measure the period.” –  “Measure it’s length and use it as a ruler.” –  “Measure the pressure differential.” = the “boring” solution

•  Better yet? – “Offer it to the super in exchange for the answer.” •  The student was said to have been Niels Bohr, the only Dane ever

to win the Nobel Prize for Physics

Creating System Concepts – A Legend?

Innovation

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Idealized Design: How Bell Labs Imagined — and Created — the Telephone System of the Future

•  Imagine a system that meets all the stakeholder expectations perfectly. Then envision how to design and build such a system –  Emphasizes getting the design team beyond

“problem-solving” and into innovation

http://knowledge.wharton.upenn.edu/article/idealized-design-how-bell-labs-imagined-and-created-the-telephone-system-of-the-future/

Dr. Russell Ackoff (1919-2009) Wharton School

University of Pennsylvania

Generating Concepts: Lockheed’s Clarence L. “Kelly” Johnson

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•  Legendary Designer of: P-38 Lightning, Constellation airliner, P-80 Shooting Star, F-104 Starfighter, U-2, SR-71 Blackbird, etc

•  Leader of Lockheed’s Advanced Development Projects—the famous “Skunk Works” –  Motto: Be quick, be quiet, and be on time

•  Kelly Johnson’s “14 Rules of Management” –  E.g. Use small, competent team; understand

the customer; closely monitor cost

Kelly Johnson’s concepts for a twin-engine Army Fighter – 1937

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This concept became the famous Lockheed P-38 Lightning. Over

10,000 produced from 1939-1945

Requirements (1937 Army Air Corps Circular Proposal X-608):

Twin-engine, high-altitude interceptor . Max speed > 360 mph. Climb to 20,000 ft.

in < six min. Must use Allison V-1710 engines with superchargers.

Kelly Johnson’s drawings of concepts for this project

Generating Concepts: How to Get Apollo to the Moon

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•  Three Basic Concepts: –  Direct Ascent (Single huge rocket, Nova, launches large

vehicle to land on and lift off moon for direct return) In 1960, NASA’s favorite, for safety

–  Earth Orbit Rendezvous, EOR. (Two ships launched separately and rendezvous before departure for moon. Land on moon. Direct departure for return to Earth orbit) NASA’s second favorite

–  Lunar Orbit Rendezvous , LOR. (Three components launched on single Saturn V, fly to lunar orbit. Lunar module descends to and ascends from moon. Rendezvous with orbiting Command Module for direct return.) Originally rejected by NASA management as too risky. Championed by 2 groups at NASA Langley, led by Dr. John C. Houbolt, who eventually had to appeal directly to Associate Administrator Robert Seamans

•  By July 1962, the choice. Later recognized as the only way that would have worked by 1969. Later became Constellation’s choice.

•  Allowed simpler, lighter Lunar Module to be optimized for lunar landing. Allowed smaller, simpler Saturn V to be used, instead of huge Nova

•  But assumed lunar rendezvous would be safe—it was

Direct Ascent

EOR LOR

Dr. John C. Houbolt, NASA LaRC

For the full story on the concepts generated for getting a man on the moon, see the excellent article at: http://www.nasa.gov/centers/langley/news/factsheets/Rendezvous.html

Generating Concepts: Burt Rutan and SpaceShipOne

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¤  One of the most creative aerospace designers – m ever ¤  Designed many vehicles including: homebuilt aircraft

(VariViggen, VariEze); corporate aircraft (Beech Starship); the Voyager round-the-world airplane; and SpaceShipOne, winner of the Ansari X-Prize (sent private, suborbital craft into space twice in 1 week)

¤  Known for his innovative design concepts—light weight, highly efficient, unusual layout

¤  Now working on SpaceShipTwo, for commercial suborbital flights by Virgin Galactic

For the full story on the concepts generated for getting a man on the moon, see the excellent article at: http://www.nasa.gov/centers/langley/news/factsheets/Rendezvous.html

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“There is no sense in being exact about something if you don’t even know what you are talking about.”

(John von Neumann, 1950)

Evaluating and Selecting Concepts

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"+" to denote better than required performance "-" to denote lower than required performance

"S" to denote performance on par with the requirement.

Ref: Pugh, Stuart, Total Design: Integrated Methods for

Successful Product Engineering, Addison-Wesley, 1991.

Pugh Matrix is useful for comparing and selecting system concepts.

Joint Strike Fighter Prototypes

Lockheed Martin Boeing

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Apply

Controlled Convergence

Generate New Concepts

Concept Selected

Need Identification Needs Analysis and Requirements Definition

Concept Generation

Initial Number of Concepts Based on the Requirements

Initial Number of Concepts Reduced

New Concepts Added

Iterative Reduction and Addition of Concepts With

Increasing Resolution

Evaluation of Conceptual Solutions

Synthesis of Conceptual Solutions

Analysis of Conceptual Solutions

System concept design is itself an iterative process.

Ref: Pugh, Stuart, Total Design: Integrated Methods for

Successful Product Engineering, Addison-Wesley, 1991.

System Concepts

•  What is your proposed system concept? What alternative concepts did you consider and why was did you select the one you proposed?

–  Assessment Criteria: Broad range of concepts

defined and systematically analyzed against criteria linked to key stakeholder needs.

The System and It’s Context

•  How will your proposed concept operate within the larger context to achieve its intended purpose? –  What are the key operational and other scenarios in

which the system will play an important role? –  Which users and external systems will the system

interact with? –  What sequences describe the interactions between

the system and its external systems for each of the key scenarios?

A high level Operational Concept describes how the system will work.

A high level Operational Concept describes how the system will work.

System of Interest

Active Stakeholders (External Systems)

Interact with the System in Use

Inputs Outputs

Provide inputs to, but do not interact with, the System

Passive Stakeholders

Inputs

A Context Diagram identifies the system boundary and active stakeholder interactions.

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ATM System

XYZ BankCustomer

UnfriendlyCustomer

ATM Admin

ATM Servicers

Customer Account

DB

NYCENetwork

HW Maint. CIRRUSNetwork

PLUSNetwork

Fraud / Break-inTransactionRequest

TransactionRequest

TransactionRequest

TransactionRequest

Response

Response

Response

Response

Log in /Service

Response

Reports

Log in /Request

RetrieveDeposits

DiagnosticResponse

Fill up w/ Cash

Service

DiagnosticResponse

Credit CardCustomer

Response

Log in /Request

BankManagement

Another Bank'sCustomer

Log in /Request

Log in /Request

Response

Context Diagram Example: Automatic Teller Machine

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•  Cell Phone

•  Passenger Car

Context Diagram Exercise: Now you try one…

26 8/1/16 © Copyright 2011 Stevens Institute of Technology. All Rights Reserved

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General ID

Request forUnique ID

Unique ID

Request for Activity

Deposit Activity

Request forAccount Type

Account Type

Customer BankComputer

ATM

Transaction

Request forDeposit Type

Physical Meansfor Insert

Customer Scenario #1

Deposit Type

Deposit of Funds

Receipt

Main Menu

Request for Amount

Tran Amount (Dtrans)

W/D Activity

Request forAccount Type

Account Type

Request for Amount

General ID

Request forUnique ID

Unique ID

Request for Activity

Customer BankComputer

ATM

Transaction

Request for Fmax

Customer Scenario #2a

Trans Amount (Creq)

Fmax

Receipt

Main Menu

Cust Cash

Sequence diagrams for an automated teller machine (ATM)

✦  Represent the System of Interest as a single lifeline »  Provides a black-box view of the system

✦  Label the arrows with nouns, not verbs »  Focuses on the inputs and outputs, not the act

of exchanging them ✦  Restrict the diagram to first-order interactions

between the system and its external systems »  Focuses on the boundary between the system to

be designed and its context

Special Rules for Sequence Diagrams in Systems Engineering

General ID

Request for Authorization

Unique ID

Request for Transaction

Authorization

Bank Customer

ATM System

Bank Computer

Request for Unique ID

Bank Customer

ATM System

Bank Computer

Enter General ID

Request Authorization

Enter Unique ID

Request Unique ID

Authorize Customer

Request Transaction

Sequence  Diagram   Ac/vity  Diagram  

Two Complementary Views

Reversal  of:  ●  Foreground/background  

●  Persistent/transient  

●   Abstract/concrete  

What do you see?

The System and It’s Context

•  How will your proposed concept operate within the larger context to achieve its intended purpose? –  Assessment Criteria: The external systems with

which the system will interact have been identified, the system boundary has been clearly defined and the interactions between the system and the external systems have been specified from a black box perspective.

Translating Needs into Specifications

•  What are the key specifications that will drive the system’s design and development? –  To what inputs must the system respond and who or

what will provide them? –  What outputs must the system provide and to whom? –  What performance requirements must the system’s

inputs and outputs satisfy? –  What additional quality attributes must the system

achieve?

General ID

Request for Authorization

Unique ID

Request for Transaction

Authorization

Bank Customer

ATM System

Bank Computer

Request for Unique ID

Bank Customer

ATM System

Bank Computer

Enter General ID

Request Authorization

Enter Unique ID

Request Unique ID

Authorize Customer

Request Transaction

Sequence  Diagram   Ac/vity  Diagram  

Defining Inputs and Outputs

Input/output matrices include:

•  Intended inputs –  Resources necessary to produce or influence the production of

desired outputs during each phase of the system life cycle •  Unintended inputs

–  Characteristics, often beyond our control, that arise from the environment in which the systems operates.

•  Desired outputs –  Required outputs over all system life cycle phases. Upon

development and deployment, the system should demonstrate the realization of these outputs

•  Undesired outputs –  Undesired characteristics which, if anticipated in time, can be

minimized 34

Sample Input/Output Matrix

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Inputs Outputs

Intended Unintended Desired Undesired

Signal Pulse shape, data rate, signal to

noise ratio

Electrical noise Data rate, accuracy

Error rate, false alarm rate

Electrical Nominal voltage Surge voltages and timing

Voltage, current, frequency stability

Electromagnetic interference, electric shock

Mechanical Activation force Shock and vibration

Movement, resistance

Acoustic noise levels

Environmental Normal temperature

range

Temperature and humidity extremes

Particle density, air flow

Heat, effluents

Input/Output Performance

•  Quality –  Accuracy, precision, error rate, security…

•  Quantity –  Size, throughput, number, intensity…

•  Timing –  Frequency, response time, availability…

Being Clear About Requirements

Customer Needs •  Language of the Stakeholders •  What the customer wants •  May be subjective

System Specifications •  Language of the Engineers •  What the engineers build •  Must be objective

Translated into

Quality Function Deployment

Relevant Design Parameters

Desired Stakeholder

Characteristics

Ref: J.R. Houser and D. Clausing, “The House of Quality,” Harvard Business Review, May-June 1988.

Quality Function Deployment Mobile Phone Example

Customer Needs

Relevant Design Parameters Length Width Weight COG Roughness Curvature

“Feels Good in the Hand”

•  Terminology –  Use “Shall” to indicate the limiting nature of a

requirement –  Statements of fact use “will” –  Goals use “should” –  This scheme should be agreed to by all key stakeholders

at the outset! •  Grammatical Construction

–  A subject (The XYZ System…) –  The word “shall” –  A relation statement (e.g., less than or equal to) –  The minimum acceptable threshold with units

Rules for Writing Requirements

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•  Use Proper Grammar –  “The system shall stop the flow of liquid hydrogen in 0.5 seconds or less.

The liquid stopping time is measured from the time the control signal for stopping is received until the flow through reaches zero.”

•  Avoid Compound Predicates –  “The system shall fit ..., weigh ..., cost ...” (this causes traceability

problems)

•  Avoid Negative Predicates –  “The system shall not ...” (attempt to turn this into a positive statement

of what the system shall do).

•  Avoid Ambiguous Terms –  Verbs: “optimize,” “maximize,” and “minimize”

–  Adjectives: “adaptable,” “adequate,” “easy,” “flexible,” “rapid,” “robust,” “sufficient,” “supportable,” and “user-friendly

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Rules for Writing Requirements

Characteristics of a “Sound” Requirement

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Attributes of individual requirements

Unambiguous Every requirement should have only one interpretation

Understandable The interpretation of the requirement should be clear

Correct Consistent with what the system is required to do

Concise No unnecessary information is included in the requirement

Traced Each requirement is traced to some document or statement from the stakeholders – the rationale should be captured and verifiable

Traceable Each derived requirement must be traceable to a “system” requirement via an explicit tracing scheme

Design independent Requirements should not impose an implementation approach or solution or technology

Verifiable A finite, cost-effective approach has been defined to ensure that the requirement has been attained

Characteristics of a “Sound Set” of Requirements

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Attributes of a set of requirements

Unique Requirements are not overlapping or redundant

Complete (a) Everything that the system is required to do throughout its life cycle is addressed; (b) responses to all possible (realizable) inputs throughout the system’s life cycle are defined; (c) the document is clear and self contained; (d) there are no “tbd” or “to be reviewed” statements.

Consistent (a) Internal – no two subsets of requirements conflict; (b) external – no subset of the requirements conflict with external documents or stakeholders from whom these requirements have been derived.

Comparable The relative priorities of the requirements in included.

Modifiable Changes to the requirements can be made with relative ease, and with a method to ensure consistency

Attainable The solution space should not be a “null” set

Translating Needs into Specifications

•  What are the key specifications that will drive the system’s design and development? –  Assessment Criteria: System requirements

a) have been derived from and are linked to the stakeholder requirements, b) describe what the system shall do, not how, and c) are verifiable and properly written.

1.  What is your proposed system concept? What alternative concepts did you consider and why did you choose the one you proposed? •  Assessment Criteria: Broad range of concepts defined and systematically

analyzed against criteria linked to key stakeholder needs. 2.  How will your proposed concept operate within the larger context to achieve

its intended purpose? •  Assessment Criteria: The external systems with which the system will

interact have been identified, the system boundary has been clearly defined, and the interactions between the system and the external systems have been specified from a black box perspective.

3.  What are the key specifications that will drive the system’s design and development? •  Assessment Criteria: System requirements a) have been derived from

and are linked to the stakeholder requirements, b) describe what the system shall do but not how, and c) are verifiable and properly written.

Creating an Operational Concept Key Questions:

And from last class: Defining the Problem Key Questions:

1.  What operational need or market opportunity is your system intended to address? –  Assessment Criteria: The need for the system is well understood,

fully described in the language of the stakeholders and free of solutions.

2.  Who are the most important stakeholders and what are the key requirements of each? –  Assessment Criteria: The key stakeholders have been identified and

their most important requirements defined, validated and clearly stated.

3.  What are the three to five most important features of your system that distinguish it from those of your competitors? –  Assessment Criteria: Features are specific, quantifiable (or readily

observable), and important to the customer.