EE15N: The Art & Science of Engineering Project Design Lecture 4: Functions & SpecificationsAfter Problem Definition…Functional SpecificationsFunctionsTypes of FunctionsIdentify & Specify FunctionsBlack BoxTransparent BoxObjectives vs. FunctionsDesign SpecificationsThree Forms of Design SpecsPerformance specifications refer to several thingsAttaching numbers to design specs (utility plots)Setting performance levels Select variables within zone of interestInterface Performance SpecsMetrics vs. Performance SpecsRevised Project Statement 1 for the Danbury Arm SupportList of Functions of Project 1Revised Project Statement 2 for the Danbury Arm SupportList of Functions of Project 2Group ExerciseSlide 22EE15N: The Art & Science of Engineering Project DesignLecture 4: Functions & SpecificationsAnnouncements:Due next Wednesday: Notes from Brainstorming Meetings. Objective tree for your project. Design SpecificationsFunctions for the Danbury Arm SupportGroup ExerciseAfter Problem Definition…Product Definition Process includes:Translate and clarify client’s wants.Identify limits – what can’t client have?Order client’s wants.Metrics to measure success.What’s next: Functional SpecificationWhat the designed object must do to realize stated objectives.Functional SpecificationsFunctional Specifications includes:FunctionsSpecificationsMetrics From Product Definition to Functional Specifications:From language of client to language of engineers.FunctionsFunctions are things that designed object must do in order to be successful.Statement of a function usually consists of an action verb and a noun. When describing functions, use verb-noun combination that best describes most general cases.Types of FunctionsBasic functions:Specific work that designed object is intended to accomplish.Secondary functions:Any other function, orThose that result from the basic functions.Required secondary functions: needed for basic functions to be accomplished.Unwanted secondary functions: related to undesired byproducts of either basic or secondary functions.Identify & Specify FunctionsEnumeration:Making a list of functions.Black Box/Transparent Box:Indicating system boundary.Showing all inputs and outputs.Focusing on how a group of inputs are transformed.Function-Means Tree:Several means of accomplishing a function are listed.Subsidiary functions that result from that are listed below the means.Dissection & Reverse Engineering.Black BoxConvert RF Signal ToSound At Desire LevelPowerRF SignalVector ofUser ChoicesHeatSoundStatusIndicationsTransparent BoxPowerRF SignalVector ofUser ChoicesHeatSoundStatusIndicationsConvert Power ToAppropriateVoltagesObjectives vs. FunctionsObjectives describe what object is:Objectives detail attributes.Objectives are usually characterized with “are” & “be”.Functions describe what object does:Functions focus on input-output transformations.Functions are usually characterized by active verbs.Design SpecificationsArticulate the attributes and behaviors of a designProvide a basis for evaluating the design“Specs” are targets of the design processFormalize what the client or user wants in terms suitable for engineering analysis and designThree Forms of Design SpecsPrescriptive Specifications: Specify values for attributes of the designed object (e.g. a safe ladder has a 6 inch step.)Procedural Specifications:Identify procedures for calculating attributes or behavior (e.g. a ladder step is safe if its bending stress =Mc/I does not exceed max)Performance Specifications:Identify performance levels that signify the achieved desired functional behavior (e.g. a safe ladder step supports an 800 lb. Gorilla).Performance specifications refer to several thingsPrescriptive performance specifications give values for attributes of the designed objectA safe ladder step must support an 800 lb gorilla.Interface performance specifications indicate how the artifact must work with other artifacts or systems.A portable electric guitar must have a standard plug Detailed design performance specifications are used to indicate how well a designed artifact is predicted to perform a function.A water fountain will increase water efficiency by 25%.Attaching numbers to design specs (utility plots)Utility(usefulness)Level of variableSaturation PlateauZone of InterestToo low to be usefulcost of materialLightweight (1/w)Straight-LineApproximationSetting performance levelsSelect variables within zone of interestRadio functions: convert RF signal to soundTransform power from wall outletFilter out unwanted frequenciesAmplify signalOutput electrical signal to drive speaker(s)Performance levelsTransform 110V power to 12V.1V with power loss of no more than 3dBmFilter frequencies outside the tuned FM radio band of 30 MHz with a minimum attenuation of –30dB.Amplify signal within a range of 1-10 mW by 10dBOutput electrical signal at 12V .1V.Interface Performance SpecsConvert RF Signal To Sound At Desire LevelPowerRF SignalVector ofUser ChoicesHeatSoundStatusIndicationsWall Outlet InterfaceFM Radio InterfaceUser InterfaceSpeaker InterfaceUser InterfaceDevice InterfaceMetrics vs. Performance SpecsMetrics apply to objectivesAllow designers and clients to assess the extent to which an objective is realized by a particular designPerformance specs apply to functionsSpecify how well functions are realized by a designCan be considered constraints, since designs typically must meet their performance specsRevised Project Statement 1 for the Danbury Arm SupportThe problem presented to the team involves Jessica, a third-grader at Danbury Elementary School. Jessica has recently begun painting, but because she suffers from cerebral palsy, she has difficulty pursuing her new interest. Jessica painting with her left hand, with her elbow held above the rest position, using a combination of arm and torso movement. While painting, Jessica exhibits exaggerated movements, and lack of control of finer movements, in all direction. These problems are amplified when her arm is fully extended. Currently, when Jessica wants to paint, she requires a teacher or staff member to hold her left elbow stable. The staff at Danbury school has asked the team to try to design a device that would decrease the