ENGR 107: Engineering Fundamentals Lecture 4: The Engineering Design Process: The Engineering Method...

ENGR 107: Engineering ENGR 107: Engineering FundamentalsFundamentals

Lecture 4:

The Engineering Design Process:

The Engineering Method and Problem Solving Process

C. Schaefer

September 15, 2003

September 15, 2003 Egnineering Fundamentals 107 2

AssignmentAssignment

Read Chapter 2 of the textbook.Group Cost ROM’s, Bills of Material, and

list of required tools are due today to the Systems Engineering Group.

Systems Engineering group: preliminary schedule and budget due on Wednesday.

Groups: review hull and keel construction.


The Engineering MethodThe Engineering Method

A process within a process.– Systems engineering process.

Engineering method.

The engineering method is the formal approach an engineer takes to solve a particular problem.

The engineering method is a “thought process” or approach similar to, though not identical to, the scientific method.


The Engineering MethodThe Engineering Method11

1. Identification of problem.

2. Analysis.

3. Transformation.

4. Alternative solutions.

5. Modeling.

6. Information gathering.

7. Experimentation.

8. Synthesis.

9. Evaluation and testing.

10. Presentation of solution.

1Engineering: An Introduction to a Creative Profession,G.C. Beakley, D.L. Evans, J.B. Keats



Recognize and Understand the Problem.Accumulate Data and Verify Accuracy.Select the Appropriate Theory or Principle.Make Necessary Assumptions.Solve the Problem.Verify and Check Results.

2Engineering Fundamentals and Problem Solving,A.R. Eide, R.D. Jenison, L.H. Mashaw, L.L. Northrup



Identify and define the problem. Research the problem

– Accumulate data.– Relevant theory.– Previous solutions and approaches.

Solve the problem– Develop alternatives.– Modeling/simulation.– Experimentation– Synthesis

Testing and verification. Presentation.

3 My general method of solvingengineering problems. The “Schaefer Method”.

The engineering methodis a continuous feedbackloop.


The Problem With These The Problem With These Approaches?Approaches?

They are predominantly analytical with no explicit creative process.

Problem solving consists of two elements;– Creative– Analytic

Much emphasis in academia and industry on analytical methods almost at the exclusion of creative processes.


Analytic Analytic andand Creative Problem Solving Creative Problem Solving11

Identify the problem. Define the working criteria or goals. Research and gather data. Brainstorm for creative ideas. Analyze. Develop models and test. Make the decision. Communicate and specify. Implement and commercialize. Prepare post-implementation review and assessment.

1Oakes, et al


Contrast with Scientific MethodContrast with Scientific MethodDefine the problem.Gather the facts.Develop a hypothesis.Perform a test.Evaluate the results.

Notice that science is not overly concerned with implementation, only knowledge gathering.


Let’s Look at an ExampleLet’s Look at an Example

Simplified “real world” example; SUV anti-lock braking system (ABS).

Sport Utility Vehicle (SUV) Sport Utility Vehicle (SUV) Anti-Lock Braking System (ABS)Anti-Lock Braking System (ABS)


Identification of ProblemIdentification of Problem

What is required? What must be done and why? Scope of problem – define problem

boundaries. Example – Anti-lock Braking System

– Is it possible to successfully retrofit an ABS developed for compact cars to heavier, sports utility vehicles?


Research the ProblemResearch the ProblemCan we decompose the problem into easily

managed subproblems?This step defines, for example;

– Literature review for similar problems and solutions to those problems.

– Relevant analytical and modeling techniques.– Testing requirements.– Design constraints.– Resource requirements and allocation.– Project schedule.


Research – ABS ExampleResearch – ABS Example Literature search; Internet search on ABS. Constraints (example);

– Retain compact car ABS system architecture.– SUV ABS costs cannot exceed 110% of current compact

car ABS system cost.– Time to market – 3 months.– Performance criteria;

SUV Total Time to Stop 15% increase over compact car. SUV Wheel Lock Skid Time 10% increase over compact car.

Approach:– Develop MATLAB model of ABS system.– Parametric analysis using model.– Modify system constants.


Solve the ProblemSolve the Problem Develop alternatives. For example;

– Hardware and software design alternatives.– List of independent variables to vary in modeling or

simulation.

Modeling– Conceptual models.– Physical models and engineering mockups.– Graphical models.– Mathematical models.– Computer models.


Solve the ProblemSolve the Problem

Experimentation– Computer simulation.– Testing, for example;

Ground tests. Flight testing.

Synthesis– Subproblem solutions are merged.– E.g., manufacturing and engineering resolving

issues associated with manufacturability.


Solve Problem – ABS ExampleSolve Problem – ABS Example

ABS hardware and system architecture fixed with exception of interface to SUV.

Control software can be modified.Matlab simulation.Skid pad testing to verify simulation results.Presentation of results to Product

Development Team.


ABS Braking Simulation ModelABS Braking Simulation Model

ABS Braking Model

Developed by Larry MichaelsThe MathWorks, Inc

Double click torun model andplot the results

mu-slipfriction curve

s

1

WheelSpeed

m*g/4

Weight

1/Rr

Vehicle speed(angular)

s

1

Vehiclespeed

slp

yout

s

1

Stopping distance

STOP

Rr

1.0 - u(1)/(u(2) + (u(2)==0)*eps)

Relative Slip

Mux

100

TB.s+1

Hydraulic Lag

Kf

Force &torque

0.2

Desiredrelative

slip ctrl

s

1

Brakepressure

Bang-bangcontroller

1/I

-1/m

tire torque

brake torque

Ff


Simulation ResultsSimulation Results

0 5 10 150

10

20

30

40

50

60

70

80Vehicle speed and wheel speed

Spe

ed(r

ad/s

ec)

Time(secs)

Vehicle speed (v)

Wheel speed (w

)

Vehicle Weight = 1600lbsHydraulic Lag – 0.01 sec



0 2 4 6 8 10 12 14 16 180

10

20

30

40

50

60

70


Spe

ed(r

ad/s

ec)

Time(secs)

Vehicle speed (v)

Wheel speed (w

)

Vehicle Weight = 2900 lbsHydraulic Lag – 0.01 sec



0 2 4 6 8 10 12 14 16 180

10

20

30

40

50

60

70


Spe

ed(r

ad/s

ec)

Time(secs)

Vehicle speed ( v)

Wheel speed ( w)




0 2 4 6 8 10 12 14 160

10

20

30

40

50

60

70


Spe

ed(r

ad/s

ec)

Time(secs)

Vehicle speed (v)

Wheel speed (w

)



PresentationPresentation

Vehicle Weight

(lbs)

Hydraulic System Time

Constant (sec)

Total Time to

Stop (sec)

Wheel Lock Skid Time (sec)

1600 0.010 14.00 0.252900 0.007 15.80 0.252900 0.010 16.00 0.802900 0.030 16.50 2.00

Anti-Lock Braking System Simulation Results

BaselineBest Solution


Testing - ABSTesting - ABS


PresentationPresentationTTS vs. Hydraulic Time Constant

15.40

15.60

15.80

16.00

16.20

16.40

16.60

0.007 0.010 0.030

Hydraulic System Time Constant (sec)

To

tal T

ime

to

Sto

p (

se

c)

Is this relationship linear ornonlinear?

Wt = 2900 lbs


PresentationPresentationWheel Lock Skid Time vs. Hydraulic

Time Constant

0.00

0.50

1.00

1.50

2.00

2.50

0.007 0.010 0.030

Hydraulic System Time Constant (sec)

Wh

ee

l Lo

ck

Sk

id

Tim

e (

se

c) Wt = 2900 lbs


ResultsResultsPerformance Criteria Satisfied.Total Time to Stop

– Required – 15% increase over compact car.– Actual – 12.8% increase.

Wheel Skid Lock Time– Required – 10% increase over compact car.– Actual – 0% increase over compact car.

Time to market – 1.5 months for S/W revisions.Cost – Less than a 2% increase.

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ENGR 107: Engineering Fundamentals Lecture 4: The Engineering Design Process: The Engineering Method...

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