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Optimization: Technical Performance Allocation

EMIS 8340. Systems Engineering Tool—applying tools to engineering systems. Optimization: Technical Performance Allocation. Mark E. Sampson. Requirement Types… Allocatable (Weight, Cost,…) Non-Allocatable (material/process standards that apply to everything) …shall be painted green

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Optimization: Technical Performance Allocation

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  1. EMIS 8340 Systems Engineering Tool—applying tools to engineering systems Optimization: Technical Performance Allocation Mark E. Sampson

  2. Requirement Types… • Allocatable (Weight, Cost,…) • Non-Allocatable (material/process standards that apply to everything) • …shall be painted green • …shall be written in Mil-Std 1750 compliant ADA • …let’s talk about the interesting ones… [DSMC 1986 6.4]

  3. Requirements Allocation…the big picture • Captured requirements… • Linking requirement to functions… • Functions linked to physical alternatives/architectures… • …keep going until realizable • …requirements flow thrusystem & documentedin allocation matrix R R R R R Motor Battery Drive Processor Allocation Matrix R Func1 Battery R Battery R Func2 Motor [SE Handbook 9.2 ] [DSMC 1986 6.4]

  4. Technical Budgets/Targets/Design Constraints • Come from external interfaces, drivers, constraints… • “How much” coming from functions • Allocated/divided up among design alternatives • Quantifiable requirements like: • weight • power • thru-put • cost • error • … • Example allocation flow-down: • System-transmit collected data in real time to remote ground site • Segment-provide wideband data link from spacecraft to relay • Element-provide 10Mhz link at 17Ghz • Sub-system-provide 10Mhz link at 17Ghz with 10W effective radiated power for 20 minutes per orbit revolution [SE Handbook 9.2.2] [Lacy 1992]

  5. Flowing-down Technical Budgets/Constraints… • Tools are an important part of this process... • Math Models • Excel • Tracing tools with extensions… • A few SE tools include integrated budgeting (SLATE, Cradle-SEE,…) • SLATE Technical Budgeting Demo… [SE Handbook 9.2.2] [DSMC 1986 6.4.4]

  6. Costing…Design to Cost, Life Cycle Costing,… • Predicting the cost of your system • Using it as critical parameter for choosing alternatives • Apparently we aren’t very good at predicting how much something will cost…particularly in software: • GAO: “only 2% of software is usable exactly as delivered” • Standish: “53% of projects will cost 189% of estimates” • …either we are poor at executing or we are poor at estimating • Engineered Costing relies on bottom-up rollups of tasks, etc. • Analogs—just like this other one • Rules-of-thumb—test costs 25% of manufacturing • Validated/Modeled rules-of-thumb—Parametric Cost Estimation Models [www.jfc.nasa.gov/bu2/] [DSMC 1986 17]

  7. Costing…Parametric Cost Estimation • Identifies Cost Estimating Relationships (CERs) & “logic” among those relationships to estimate costs. • Cost Estimates are then validated/tested using statistical techniques • A number of hardware/software cost models have been created: • Price-H,-S,… (LMCO) • REVIC • COCOMO • AMCM--missions • SoftCost-R • …and a systems model is under development… • COSYSMO Dr. Barry Boehm (USC) Dr. Richardo Valerdi (MIT/UofA) Present/Demo Unmanned Mission Non-recurring Cost Model [www.jfc.nasa.gov/bu2/]

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