Lecture 02 Engineering Design and Systems Engineering ... · Engineering Design Systems Engineering...

Engineering DesignSystems Engineering

Lecture 02Engineering Design and Systems Engineering

Through the Lens of Decision Making

Jitesh H. Panchal

ME 597: Decision Making for Engineering Systems Design

Design Engineering Lab @ Purdue (DELP)School of Mechanical Engineering

Purdue University, West Lafayette, INhttp://engineering.purdue.edu/delp

August 27, 2019ME 597: Fall 2019 Lecture 02 1 / 46

http://engineering.purdue.edu/delp


Objectives for Today

1 To provide an overview of the engineering design and systemsengineering processes.

2 To identify the decisions made within systematic engineering designprocesses.

3 To understand the nature of design decisions.

ME 597: Fall 2019 Lecture 02 2 / 46


Recall: Basic Elements of a Decision

Decision

A1

A2

An

O11

O12

O1k

O21

O22

O2k

On1

On2

Onk

U(O11)

U(O12)

U(O1k)

U(O21)

U(O22)

U(O2k)

U(On1)

U(On2)

U(Onk)

Select Ai

p11

p1k

p21

p1k

pn1

pnk

Alternatives Outcomes Preferences Choice

ME 597: Fall 2019 Lecture 02 3 / 46


Example: A Lottery

Cost: $2Odds of winning the jackpot: 1 in

259 Million!

What are the

alternatives?

outcomes?

preferences?

information?

choice?

ME 597: Fall 2019 Lecture 02 4 / 46


a. Pahl and Beitz Systematic Design Methodb. Four Phases of Pahl and Beitz Approach

Design as Decision Making

Let us start with a simple decision-based view of design.

??? Design = Choosing the best alternative (solution) ???

Decision

A1

A2

An

O11

O12

O1k

O21

O22

O2k

On1

On2

Onk

U(O11)

U(O12)

U(O1k)

U(O21)

U(O22)

U(O2k)

U(On1)

U(On2)

U(Onk)

Select Ai

p11

p1k

p21

p1k

pn1

pnk


Is this an accurate (complete) view of design? Why / Why Not?

...

...

...

ME 597: Fall 2019 Lecture 02 5 / 46



Design as a Decision-making Process

Is this an accurate (complete) view of design? Why / Why Not?

Design is typically not a single decision. It is a network of decisions.

Outcomes are only clear at the end of the process.

Not all alternatives are available. Need to generate alternatives.

Not all information is available. Need to generate information.

Not all information about preferences is directly available. Need tounderstand preferences (gradually).

Resources are always limited.

There may be multiple decision makers involved in the design process.

...

Design methods provide guidance in navigating these decisions.

ME 597: Fall 2019 Lecture 02 6 / 46



The Process of Design Thinking

Design thinking is a process by which designers approach problem solving.

Image Source:https://i.pinimg.com/originals/bb/19/c2bb19c2522081dad7f682c10d99a07903.jpg

ME 597: Fall 2019 Lecture 02 7 / 46



(Some) Principles of Design Thinking

Empathize and understand what users need; Find the latent needs

Prototype early, and prototype often

Work quickly: do not wait for the final design

Test ASAP; Launch Beta

Iterate, Iterate, Iterate

“Fail fast to succeed sooner” - David Kelley

ME 597: Fall 2019 Lecture 02 8 / 46



A systematic engineering design process

Consider an example of a systematic design process.

ME 597: Fall 2019 Lecture 02 9 / 46



The Pahl and Beitz Systematic Design Method

Concept

Preliminary Layout

Definitive Layout

Documentation

Specification

Clarification of Task

Conceptual Design

Embodiment Design

Detail Design

Phase 0 - Start

Upg

rade

and

Impr

ove

Solution

Customer

ME 597: Fall 2019 Lecture 02 10 / 46



Phase 1: Clarifying the Task

An engineer’s first problem in any design situation is to discover what theproblem really is.

What objectives must the intended solution satisfy?What properties must it have?What properties must it not have?

Clarifying the Task

Analyze market / company Find and select product ideas Formulate a product proposal

Task

Specification

Clarify the task Elaborate a requirements list

Product Proposal

Phase 1

Product Planning

ME 597: Fall 2019 Lecture 02 11 / 46



Need for Planning and Clarification of Task

what the customer said

what marketing understood

what engineering designed

what manufacturing realized

what the customer really wanted

how customer service solved the problem

ME 597: Fall 2019 Lecture 02 12 / 46



Clarification of Task

What is the problem really about?

What implicit wishes and expectations are involved?

Do the specified constraints actually exist?Avoid

fixed solution ideas / solution-specific considerationsfictional constraints and concrete implications

The outcome is a requirements list.

ME 597: Fall 2019 Lecture 02 13 / 46



Example Requirements List

Problem Statement:

Develop a device that, upon demand, conveniently provides cool, clean water for human consumption. The device must fit in a particular building space (see schematic) and function appropriately in an office environment.

Requirements List for Water-Dispensing Device Page: 1

Requirements Changes DW Responsibility

Schematic:

* Modified

8/2/00

D D D D

1. Water Characteristics Flow rate should be < 35 mL/s Flow velocity should be 20 - 40 cm/s Water temperature (dispensed) should be 5 - 8 ºC Water quality (dispensed) must meet EPA guidelines, e.g.,

Contaminant Threshold Arsenic < 0.05 mg/L Fluoride < 4.0 mg/L Lead < 0.015 mg/L Copper < 1.3 mg/L Mercury < 0.002 mg/L

as specified in Safe Drinking Water Act (1996)

Design Team Members

ME 597: Fall 2019 Lecture 02 14 / 46



Example Requirements List (cont.)

Requirements List for Water-Dispensing Device Page: 2

Requirements Changes DW Responsibility

* Adjusted 8/2/00

* Added 8/2/00

D D D W D D W D D D W D

2. Ergonomics Must be easy to use Must be accessible to all (esp. those in wheelchairs) Must be attractive Should be free of splattering Must be safe Must be quiet Must remain sanitary 3. Cost Total cost (installed) < $450 US Operating cost < $200 per year 4. Production, Installation, & Maintenance Must be manufactured from standard parts/assemblies Should be installed < 35 minutes by 2 skilled laborers Must be easily maintained over 12 week service intervals

Design Team Members

ME 597: Fall 2019 Lecture 02 15 / 46



Outcome of the Clarification of Task Phase

A decision to proceed to Phase 2 is predicated on answers in the affirmativeto the following questions:

Has the task been clarified sufficiently to allow development of a solutionin the form of a design?

Must further information about the task be acquired?

ME 597: Fall 2019 Lecture 02 16 / 46



What is the nature of these decisions?

Decision

A1

A2

An

O11

O12

O1k

O21

O22

O2k

On1

On2

Onk

U(O11)

U(O12)

U(O1k)

U(O21)

U(O22)

U(O2k)

U(On1)

U(On2)

U(Onk)

Select Ai

p11

p1k

p21

p1k

pn1

pnk


ME 597: Fall 2019 Lecture 02 17 / 46



Phase 2: Conceptual Design

In conceptual design the basicsolution path is laid down in the formof a solution principle, through thefollowing steps:

1 identification of the essentialproblems through abstraction,

2 establishment of functionstructures, and

3 search for appropriate workingprinciples and their combination.

Specification

Abstract to identify essential problems

Establish function structures

Search for working principles

Combine working principles into working structures

Select suitable combinations

Firm up into principle solution variants

Concept

Evaluate against technical and economic criteria

ME 597: Fall 2019 Lecture 02 18 / 46



Abstraction of Requirements

Abstraction is

ignoring what is particular or incidental and emphasizing what is general,and

identifying fictitious constraints and eliminating all but genuinerestrictions.

Steps in abstraction:

1 Eliminate personal preferences from the requirements list.2 Consider only requirements that affect function and essential constraints.3 Transform quantitative into qualitative data, reducing them to essential

ideas.4 Broaden essential ideas systematically (generalize).5 Formulate the design problem in solution-neutral terms.

ME 597: Fall 2019 Lecture 02 19 / 46



Abstraction: Example of Motor Vehicle Fuel Gauge

Eliminate personal preferences.

Consider only requirements that affect function and essential constraints

Transform quantitative into qualitative data

Broaden essential ideas systematically

Formulate in solution-neutral terms as an overall function

ME 597: Fall 2019 Lecture 02 20 / 46



Phase 2: Function Structures

A function

specifies the relationship between inputs and outputs in terms of energy,material (matter), signal (information).

ME 597: Fall 2019 Lecture 02 21 / 46



Function Structure – Example

Develop a device that, upon demand, conveniently provides

cool, clean water for human consumption.

Control Delivery

Deliver Water

Deliver Water

Purify Water

Cool Water

Dispose Water

Hold Liquid

Dispense Liquid

Function structures allow clear definition of existing or necessary subsystemsso that they can be dealt with separately (reducing complexity!).

ME 597: Fall 2019 Lecture 02 22 / 46



Search for Solution Principles

Solution (working) principles represent a physical effect and preliminaryembodiment (e.g., “cartoon” sketch). Use ideation techniques, searches, andanalysis of known or existing systems to determine solution principles. Foreach subfunction, identify as many working principles as possible.

Morphological matrix:

Force Cycle

Change Signal

Display Time

Store Energy

Principal Solution Alternatives

Sub-Functions

Oscillating crystal

Stroke magnet Electrical motor Meter

ME 597: Fall 2019 Lecture 02 23 / 46



Combine Solution Principles into Working Structures

Select a working structure.

ME 597: Fall 2019 Lecture 02 24 / 46



What is the nature of concept selection decisions?

Decision

A1

A2

An

O11

O12

O1k

O21

O22

O2k

On1

On2

Onk

U(O11)

U(O12)

U(O1k)

U(O21)

U(O22)

U(O2k)

U(On1)

U(On2)

U(Onk)

Select Ai

p11

p1k

p21

p1k

pn1

pnk


ME 597: Fall 2019 Lecture 02 25 / 46



Phase 3: Embodiment Design

Concept

Develop preliminary layouts and form designs

Refine and evaluate against technical and economic criteria

Select best preliminary layouts

Preliminary Layout

Eliminate weak spots

Check for errors & cost effectiveness

Prepare preliminary parts list and production documents

Definitive Layout

Complexity!! Many simultaneous,interdependent activities!

Analysis and synthesis alternateand complement each other!Optimization and error ID +solution search and evaluation.

Proceed from qualitative toquantitative, from abstract toconcrete, from rough to detailed,with provisions for checks andcorrections (i.e., iterations!).

Outcome of Phase 3

A definitive layout for which production documents can be prepared withminimal detail design.

ME 597: Fall 2019 Lecture 02 26 / 46



Examples of Preliminary and Definitive Layout

Definite layout

Principal Solution

Preliminary layout

8 working elements 20 form elements (0.04%)

50 working elements 2000 form elements (4%)

280 working elements 50000 form elements (100%)

Adapted from Prof. H. Birkhofer’s lecture “Produktentwicklung”, TU-Darmstadt, 2004.

ME 597: Fall 2019 Lecture 02 27 / 46




Decision

A1

A2

An

O11

O12

O1k

O21

O22

O2k

On1

On2

Onk

U(O11)

U(O12)

U(O1k)

U(O21)

U(O22)

U(O2k)

U(On1)

U(On2)

U(Onk)

Select Ai

p11

p1k

p21

p1k

pn1

pnk


ME 597: Fall 2019 Lecture 02 28 / 46



Phase 4: Detail Design

Solution

Documentation

Definitive Layout

Finalize details

Complete all documents

Check all documents

Finalize detailed drawings ofcomponents, detailedoptimization of shapes, materials,surfaces, tolerances and fits.

Integrate individual componentsinto assemblies and assembliesinto overall product. Includeassembly drawings, part lists.

Complete production documents(manufacturing, assembly,transport, operating instructions).

Outcome of Phase 4

Final production documents (tolerances, assembly processes, materials,tooling, etc.)

ME 597: Fall 2019 Lecture 02 29 / 46




Decision

A1

A2

An

O11

O12

O1k

O21

O22

O2k

On1

On2

Onk

U(O11)

U(O12)

U(O1k)

U(O21)

U(O22)

U(O2k)

U(On1)

U(On2)

U(Onk)

Select Ai

p11

p1k

p21

p1k

pn1

pnk


ME 597: Fall 2019 Lecture 02 30 / 46



In Summary: Nature of Engineering Design Decisions

ME 597: Fall 2019 Lecture 02 31 / 46


a. What is Systems Engineering?b. Systems Engineering Processes

Systems and Systems Engineering

System

a collection of hardware, software, people, facilities, and proceduresorganized to accomplish some common objectives.

a collection of components organized to accomplish a specific functionor set of functions. (IEEE STD 610.12)

Systems Engineering

An interdisciplinary approach and means to enable the realization ofsuccessful systems. (INCOSE, 1999)

The application of the system analysis and design process and theintegration and verification process to the logical sequence of thetechnical aspect of the product life cycle. (Forsberg and Mooz, 1992)

ME 597: Fall 2019 Lecture 02 32 / 46



Example of a Human Designed System

(Adapted from Wertz and Larson, 1999)

Subject of Study

Orbit and Constellation

Command, Control and Communications

Payload

Spacecraft Bus

Launch Element

Ground Element

Mission Operations

ME 597: Fall 2019 Lecture 02 33 / 46



Systems Engineering goes Beyond the Product

WeightStress

Hydraulics

Engine

Wings

Empennage

Fuselage

Armament

Lof t

Service

Production

Equipment

STRUCTUREGROUP

PROPULSIONGROUP

CONTROLGROUP

MANUFACTUREGROUP

PAYLOADGROUP

Cabling

Electronics

AEROGROUP Streamline

System Organization

Hierarchy is an effective way of managing complexity! The driving principle isnear-decomposability (Simon, 1961).

ME 597: Fall 2019 Lecture 02 34 / 46



The VEE model of Systems Engineering

Understand User Requirements, Develop

System Concept and Validation Plan

Develop System Performance Specification and System Validation Plan

Expand Performance Specifications into CI

“Design-to” Specs and CI Verification Plan

Fab, Assemble and Code to “Build-to” Documentation

Evolve “Design-to” Specifications into “Build-

to” Documentation and Inspection Plan

Inspect to “Build-to”

Documentation

Assemble CIs and Perform CI Verification

to CI “Design-to” Specifications

Integrate System and Perform System Verification to

Performance Specifications

Demonstrate and Validate System to User Validation Plan

Inte

grat

ion

and

Qualif

icatio

n Decom

position

and Definition

Systems Engineers

Domain Engineers

Time

ME 597: Fall 2019 Lecture 02 35 / 46



Examples of Decisions in Systems Engineering (1)

DevelopmentPhase

Examples of Decisions in Systems Engineering

1. ConceptualDesign

* Should a conceptual design effort be undertaken?* Which system concept (usually a mixture of technolo-gies) should be the basis of the design?* Which technology for a given subsystem should be cho-sen?* What existing hardware and software can be used?* Is the envisioned concept technically feasible, based oncost, schedule and performance requirements?* Should additional research be conducted before a deci-sion is made?

Buede, D.M, 2009, The Engineering Design of Systems: Models and Methods, Wiley.ME 597: Fall 2019 Lecture 02 36 / 46




DevelopmentPhase


2. Preliminarydesign

* Should a preliminary design effort be undertaken?* Which specific physical architecture should be chosenfrom several alternatives?* To which physical resource should a particular functionbe allocated?* Should a prototype be developed? If so, to what level ofreality?* How should validation and acceptance testing be struc-tured?





DevelopmentPhase


3. Full-scaledesign

* Should a full-scale design effort be undertaken?* Which configuration items should be bought instead ofmanufactured?* Which detailed design should be chosen for a specificcomponent given that one or more performance require-ments are critical?





DevelopmentPhase


4. Integrationand qualifica-tion

* What is the most cost-effective schedule for implemen-tation activities?* What issues should be tested?* What equipment, people, facilities should be used to testeach issue?* What models of the system should be developed oradapted to enhance the effectiveness of integration?* How much testing should be devoted to each issue?* What adaptive (fallback testing in case of a failure) test-ing should be planned for each issue?





DevelopmentPhase


5. ProductRefinement

* Should a product improvement be introduced at thistime?* Which technology or technologies should be the basis ofthe product improvement?* What redesign is best to meet some clearly defined de-ficiency in the system?* How should the refinement of existing systems be imple-mented given safety, performance and cost criteria?




Hierarchy of Objectives

Start with the fundamental objective (e.g., maximize safety) . . . objectivesthat are important to the system’s stakeholders in a value sense, i.e., thestakeholders would be willing to pay for improved performance.

The fundamental objective can be subdivided into value objectives that moremeaningfully define the fundamental objective, thereby forming afundamental objectives hierarchy or value structure.

Maximize

Safety

Minimize

Loss of Life

Minimize

Serious Injuries

Minimize

Minor Injuries

Adults Children Adults Children

ME 597: Fall 2019 Lecture 02 41 / 46



Example of Objectives Hierarchy with Value Curves

ME 597: Fall 2019 Lecture 02 42 / 46



Issues in Systems Engineering

Multi-disciplinary teams: Different disciplines must work together in anintegrated manner.

Distributed enterprises: need to understand interdependencies in theprocess.

Processes, methods, and tools in the process are highly integrated.Over-the-wall method is no longer efficient.

Engineering decisions must be based on an evaluation of the behavior ofproduct when it is used in the holistic environment (hardware,software, people, production, installation, transportation, maintenance,recycling, etc.)

P. Wiese and P. John, 2003, Engineering Design in the Multi-Discipline Era. A SystemsApproach, Professional Engineering Publishers.

ME 597: Fall 2019 Lecture 02 43 / 46



Interactions Among Design Teams

V-8 Engine Design

ME 597: Fall 2019 Lecture 02 44 / 46



Summary

Objectives for Today:1 To provide an overview of the engineering design and systems

engineering processes.2 To identify the decisions made within systematic engineering design

processes.3 To understand the nature of design decisions.

ME 597: Fall 2019 Lecture 02 45 / 46



References

G. Pahl, W. Beitz, J. Feldhusen, K.H. Grote, 2007, Engineering Design:A Systematic Approach, 3rd Edition, Springer London.

P. Wiese and P. John, 2003, Engineering Design in the Multi-DisciplineEra. A Systems Approach, Professional Engineering Publishers, 2003.

D.M. Buede, 2000, The Engineering Design of Systems: Models andMethods, John Wiley & Sons.

C. Paredis, “Systems Engineering”, ME8813: Modeling and Simulation inDesigns, Lecture 2 Notes, Spring 2004, Georgia Tech, Atlanta

F. Mistree, W. F. Smith, et al., 1990, “Decision-Based Design: AContemporary Paradigm for Ship Design.” Transactions, Society of NavalArchitects and Marine Engineers 98: 565-597.

ME 597: Fall 2019 Lecture 02 46 / 46

Lecture 02 Engineering Design and Systems Engineering ... · Engineering Design Systems Engineering...

Documents

Transcript of Lecture 02 Engineering Design and Systems Engineering ... · Engineering Design Systems Engineering...