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ENGR 107 Engineering Fundamentals by niusheng11

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									ENGR 107: Engineering
   Fundamentals
          Lecture 4:
The Engineering Design Process:
 The Engineering Method and
  Problem Solving Process

          C. Schaefer
      September 16, 2002
                     Assignment
 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.

September 16, 2002    Egnineering Fundamentals 107   2
         The 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.

September 16, 2002          Egnineering Fundamentals 107   3
            The Engineering Method1
     1.    Identification of                         6.     Information
           problem.                                         gathering.
     2.    Analysis.                                 7.     Experimentation.
     3.    Transformation.                           8.     Synthesis.
     4.    Alternative solutions.                    9.     Evaluation and
     5.    Modeling.                                        testing.
                                                     10.    Presentation of
1Engineering: An
                                                            solution.
                 Introduction to a Creative Profession,
G.C. Beakley, D.L. Evans, J.B. Keats

     September 16, 2002             Egnineering Fundamentals 107               4
         The Engineering Method2
   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

  September 16, 2002       Egnineering Fundamentals 107   5
         The Engineering                              Method3

   Identify and define the problem.
   Research the problem                              The engineering method
     – Accumulate data.                               is a continuous feedback
     – Relevant theory.                               loop.
     – Previous solutions and approaches.
   Solve the problem
     –   Develop alternatives.
     –   Modeling/simulation.              3My general method of solving
     –   Experimentation                   engineering problems. The
     –   Synthesis
                                           “Schaefer Method”.
   Testing and verification.
   Presentation.

September 16, 2002         Egnineering Fundamentals 107                    6
        The Problem With These
             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.

September 16, 2002   Egnineering Fundamentals 107   7
       Analytic and Creative Problem Solving1

    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
   September 16, 2002   Egnineering Fundamentals 107      8
    Contrast with Scientific Method
 Define 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.
September 16, 2002   Egnineering Fundamentals 107   9
        Let’s Look at an Example
   Simplified “real world” example; SUV anti-
    lock braking system (ABS).




September 16, 2002   Egnineering Fundamentals 107   10
   Sport Utility Vehicle (SUV)
Anti-Lock Braking System (ABS)
          Identification 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?

September 16, 2002      Egnineering Fundamentals 107     12
            Research the Problem
 Can 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.
September 16, 2002    Egnineering Fundamentals 107      13
      Research – 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.
September 16, 2002          Egnineering Fundamentals 107              14
                     Solve 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.

September 16, 2002       Egnineering Fundamentals 107         15
                     Solve 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.
September 16, 2002       Egnineering Fundamentals 107   16
    Solve 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.
September 16, 2002   Egnineering Fundamentals 107   17
              ABS Braking Simulation Model
                                                                     ABS Braking Model


                                               100               1                                                               1
  0.2                                                                              Kf                              1/I
                                             TB.s+1              s                          brake torque                         s
Desired                    Bang-bang      Hydraulic Lag          Brake            Force &
relative                                                                                                   tire torque          Wheel
                            controller                          pressure           torque
  slip                                                                                                                          Speed
                  ctrl

                                             m*g/4                                  Rr                                        1/Rr           Mux         yout
                                                          Ff
                                mu-slip       Weight                                          1                           Vehicle speed
                            friction curve                                 -1/m                                             (angular)
                                                                                              s            STOP
                                    slp                                                                                         1
                                                                                             Vehicle
                                                                                              speed                              s
                                                                                                                         Stopping distance

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

                                                                        Relative Slip
        Double click to
        run model and                                                                                                            Developed by Larry Michaels
        plot the results                                                                                                             The MathWorks, Inc




        September 16, 2002                                      Egnineering Fundamentals 107                                                            18
                                  Simulation Results
                                             Vehicle speed and wheel speed
                         80



                         70
                                                Vehicle Weight = 1600lbs
                                                Hydraulic Lag – 0.01 sec
                         60

                                                                   Vehicle speed (wv )
                         50
        Speed(rad/sec)




                         40



                         30



                         20
                                      Wheel speed (ww )

                         10



                         0
                              0          5                                   10          15
                                                      Time(secs)




September 16, 2002                     Egnineering Fundamentals 107                           19
                                   Simulation Results
                                                       Vehicle speed and wheel speed
                          80



                          70                                Vehicle Weight = 2900 lbs
                                                            Hydraulic Lag – 0.01 sec
                          60

                                                                   Vehicle speed (wv )
                          50
         Speed(rad/sec)




                          40



                          30



                          20
                                           Wheel speed (ww )

                          10



                          0
                               0   2   4           6           8          10             12   14   16   18
                                                                Time(secs)




September 16, 2002                            Egnineering Fundamentals 107                                   20
                               Simulation Results
                                                   Vehicle speed and wheel speed
                       80



                       70
                                                           Vehicle Weight = 2900 lbs
                                                           Hydraulic Lag – 0.03 sec
                       60

                                                               Vehicle speed ( w )
                                                                                v
                       50
      Speed(rad/sec)




                       40



                       30



                       20
                                       Wheel speed ( w )
                                                      w
                       10



                       0
                           0   2   4           6           8          10             12   14   16   18
                                                            Time(secs)




September 16, 2002                           Egnineering Fundamentals 107                                21
                               Simulation Results
                                              Vehicle speed and wheel speed
                      80



                      70                              Vehicle Weight = 2900 lbs
                      60
                                                      Hydraulic Lag – 0.007 sec
                                                                   Vehicle speed (wv )
                      50
     Speed(rad/sec)




                      40



                      30



                      20
                                       Wheel speed (ww )

                      10



                      0
                           0   2   4            6              8           10            12   14   16
                                                           Time(secs)




September 16, 2002                        Egnineering Fundamentals 107                                  22
                         Presentation
       Anti-Lock Braking System Simulation Results

                         Hydraulic
                          System           Total
               Vehicle     Time           Time to          Wheel
               Weight    Constant          Stop          Lock Skid
                (lbs)      (sec)           (sec)         Time (sec)

Baseline          1600     0.010            14.00           0.25
                  2900     0.007            15.80           0.25      Best Solution
                  2900     0.010            16.00           0.80
                  2900     0.030            16.50           2.00



  September 16, 2002      Egnineering Fundamentals 107                     23
                     Testing - ABS




September 16, 2002     Egnineering Fundamentals 107   24
                                           Presentation
                                    TTS vs. Hydraulic Time Constant

                                16.60
     Total Time to Stop (sec)




                                16.40   Wt = 2900 lbs
                                16.20
                                16.00
                                15.80
                                                             Is this relationship linear or
                                15.60
                                                             nonlinear?
                                15.40
                                           0.007                 0.010           0.030
                                            Hydraulic System Time Constant (sec)


September 16, 2002                             Egnineering Fundamentals 107                   25
                              Presentation
                      Wheel Lock Skid Time vs. Hydraulic
                               Time Constant

                      2.50
    Wheel Lock Skid




                      2.00   Wt = 2900 lbs
      Time (sec)




                      1.50
                      1.00
                      0.50
                      0.00
                               0.007                0.010       0.030
                             Hydraulic System Time Constant (sec)

September 16, 2002               Egnineering Fundamentals 107           26
                           Results
 Performance 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.

    September 16, 2002   Egnineering Fundamentals 107   27

								
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