Deyst, John

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Research Sponsored LAIUnderstanding Riskand UncertaintyApril 10, 2001Growing theLean CommunityAn LAI Plenary ConferencePresented By:John DeystMIT2 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanAdvanced DSM model example550600650700750800850900120130140150160170180       Cost ($k)Schedule (days)Relative ProbabilityJoint PDF of Cost and Schedule for (real) PD processFromBrowning,19983 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanEvolution of Performance700750800850900950100010500 20 40 60 80 100 120 140Project Time (t, days)From Browning,19984 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanValue CreationGraph Created by James Chase5 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanHypothesesâProduct development is an investmentâUncertainty and risk are inherent, tovarying degrees, in all productdevelopmentsâRisk is the probability that the productrequirements will not be achieved, thusimperiling the investment6 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanHypotheses (cont.)âQuantifying uncertainty and risk will enablebetter management of productdevelopmentsâValue in product development is theamount by which risk is reduced per unit ofresource expendedâBalancing risk across all aspects ofproduct development is a significant leanprinciple7 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/lean           Design Parameters vs.            Performance MeasuresDesignParameters(many)itPerformanceMeasures(not so many)ft  Functional Relationshipsti l l ti i(e.g. -               ) (e.g.- Breguet RangeEquation)(e.g. – Range)fwwDL /,,/ 1η8 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/lean    Viewing Product DevelopmentUncertainty Reduction  (initial state)                                             (final state)ProductDevelopmenttl tSmall UncertaintyIn Design Parameters andPerformance Requirements Metll t i tI  i  t  f  i t  tLarge UncertaintyIn Many DesignParameters, HenceLarge Risk toPerformance Measures t i tI   it ,  i  tf  9 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanEvolution of Knowledgeof Performance00.511.522.50 5 10 15 20PerformanceRequirementRisk of Failure!ImmatureDesignMatureDesign10 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanBasic AssumptionsâEffective product developments have thefollowing characteristicsâProcesses are well calibrated so that errorbiases and trends are negligibleâAs new information is generated it is combinedwith old Information according to the relativequalities of new and oldâAll productive activities serve to reduceuncertainty11 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanProduct Development ModelâFrom these assumptions informationtheory yields the following differentialequationâRate of variance reduction is proportionaltoâ effectivenessâ square of varianceupdtdp−=2Rate of changeof uncertaintyvarianceEffectivenessof theexpendedeffortSquare of the variance ofuncertainty 2σ=p( )12 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanUncertainty Reduction Derivedfrom the ModelStandard Deviations of L/D Estimation ErrorsUpper Curve-2 Wk Spending Rate Ramp UpLower Curve-Constant Spending Rate00.20.40.60.811.21.41.60 1 2 3 4 5 6 7 8 9 10Time (wks)Standard Deviation13 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanMulti – Parameter /MultiActivity Product DevelopmentâParameters are an array (n dimensionaldesign vector)âUncertainty is a matrix (n x n covariance)P = -PH UHPTlRate of changeof uncertainty EffectivenessmatrixActivity matrix Uncertainty matrix14 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanModel of a Transport AircraftPreliminary Design StudyâDesign Parameters-(3 dimensional)âLift – to – Drag RatioâOverall EfficiencyâInitial to Final Weight RatioâPerformance Measure-(1 dimensional)âRange > 13,000 kmâProduct Development ActivitiesâAerodynamic designâPropulsion System DesignâStructural DesignDL /( )η( )fww /115 - PD Deyst  - 041001 © 2001 Massachusetts Institute of TechnologyLeanAerospaceInitiativeweb.mit.edu/leanModel of a Transport AircraftPreliminary Design Study (cont.)â Initial design parameter estimates indicaterange>13,000kmâ Uncertainty in these estimates produces a probability of0.4 that the final product will not meet the requirements(unacceptable risk)â Preliminary PD effort will refine the design and reduceuncertainty by a factor of 5â Initial Plan-spend $500K over a 10 week period to refinethe design and reduce uncertainty by the required factor of5â Final Plan- for the same reduction in uncertainty, but bybalancing risk over the three activities, the cost is reducedby 13% (saves $66K)

Growing the Lean Community

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Growing the Lean Community

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