P14007: Wheelchair Assit

P14007: Wheelchair Assist: Detailed Design ReviewChe-An Lee Industrial and System EngineerDan Schuster Mechanical EngineerPhil Medalie Mechanical EngineerTom Elliot Electrical EngineerAgendaProject OverviewMechanical SystemElectrical SystemAssembly PlanTest PlanRisk AssessmentProject TimelineProject OverviewAssist manual wheelchair users on slopesMechanical systemRatchet systemBrake systemElectrical systemCharging systemExpected outcomeFunctional prototypeEngineering design experienceBasis for future senior design project

OverviewTotal System

Brake Disc w/Shaft

Chair Mount

Pawl Mount

Ratchet and Pawl Interaction

System w/ Washer

System w/ End Plate

Shaft

Electrical Components

Attachment to Shaft

Critical Component AnalysisShaftBearing Block BoltsRatchet ToothShaft Analysis

Shaft Results

Ratchet Tooth Analysis

S = 60200 psiF = 0.25 inY = 0.431 for 72 teethDP = 24V Disregard for low speeds

W = 270 lbf of allowable tooth load (will see ~115 lbf)Bolt AnalysisBolt ShearSy = 70 ksiSsy = 40 ksi

Detailed Electrical Generator Design

Bill of MaterialsDescriptionPart #CostCost (1000)QuantityTotalTotal(1000)LinkUSB Port87520-0010BLF$0.71$0.381$0.71$0.38http://www.mouser.com/ProductDetail/FCI/87520-0010BLF/?qs=x6EjVpvqMVP/2to87x7cdQ==Batteryn/a$49.95$39.961$49.95$39.96http://www.adafruit.com/products/1566#DescriptionMotor Dc Geared 24V 30RPM30573$37.03$31.922$74.06$63.84http://www.digikey.com/product-detail/en/30573/CRA206-ND/186746Outdoor Speaker Wire 6 feet neededn/a$0.78$0.601$0.78$0.60http://www.amazon.com/Cables-Waterproof-Speaker-sequential-markings/dp/B008J4XCB8/ref=pd_sim_sbs_e_1Voltage Regulator90400$7.00$5.601$7.00$5.60http://www.prodctodc.com/dc-35v30v-to-40v30v-converter-auto-boost-buck-voltage-regulators-power-supply-module-p-67.html#.UqA3IsRDuz6Bridge RectifierGBU404DI-ND$1.37$0.592$2.74$1.18http://www.digikey.com/product-detail/en/GBU404/GBU404DI-ND/278605Custom PCB Board(OSH Park)n/a$3.07$3.071$3.07$3.07http://oshpark.com/orders/new/78avpdqgTOTAL$138.31$114.63Buck-Boost Regulator Circuit 5V with 80% Efficiency*Ordered Premade*

DC GeneratorMotor 2.7W24V30RPM

Battery with Battery Protection 10,000mAh @ 5V Outputs up 2ADraws up to 1ADimensions: 2.9" x 1" x 4.9" / 72mm x 24mm x 125mmWeight: 300g80% Efficient

Simulation

Breadboard Proof of ConceptUsed a Linear Regulator which is less then 50% efficient Used a Hand Crank motorUsed a 3.4V Battery

PCB Board Design

PCB Product Ready to Be Ordered

TopBottomElectrical Energy Harvesting OverviewBattery = Average 80% EfficiencyBuck-Boost = Average 85% EfficiencyMotors = 2.7W each = 5.4W at 30RPM3.456 W generation at 30RPM691.2 mA generation at 5V, at 30RPM

Benefits to designEasily can covert to AC Motor if Needed.PCB Fits on top of the Buck-Boost Regulator therefore saving space.Battery can be charged by a wall charger too.Arduino boards and other electronics can also be power by battery therefore opening up further applications and not limiting it to phone charging.Cable System

Bill of MaterialsItem#Part DescriptionVendorPart#QuantityCost per UnitTotal Price1WMB R24S6-72 RatchetKaman Industrial TechnologiesWMB R24S6-72 270.76141.522RP-2 PawlKaman Industrial TechnologiesRP-2220.0340.063Brake Handlepark ave bike shopOEM12299248T1554Shifterpark ave bike shopFalco 677062633112.9912.995Rotors and caliperpark ave bike shopBRA332657820256.99113.986Brake Cablepark ave bike shop23.997.987Cable Housingpark ave bike shop31.995.97Bill of MaterialsItem#Part DescriptionVendorQuantity8ShaftRIT29Welded shaft plateRIT210WasherRIT211Outside PlateRIT21292196A556 BoltMcMaster81394804A029 NutMcMaster814Bearing BlockRIT2156384K790 BearingMcMaster416PinRIT417Shoulder BoltRIT218Brake MountRIT21992095A214 BoltMcMaster102092497A300 NutMcMaster102193827A245 NutMcMaster42292185A636 BoltMcMaster42394804A320 NutMcMaster424SpringRIT2Target vs. ActualTargeted CostActual CostRatchet$150$182Brake$100$146Charging$250$138Total$500$466Assembly Plan

Test PlanTest EquipmentPlywood baseCar JackCablesTape MeasureScaleMultimeterFish hook scale or similarCircuit simulation softwarePhase of TestingComponentRatchet SystemCircuit DesignSystemMechanical SystemElectrical SystemUsability Testing

Risk AssessmentIDRisk ItemEffectCauseLSIAction to Minimize RiskOwner1Project Scope too largeTeam not able to deliver all deliverablesProject Improperly scoped236Contact customer to prioritize the deliverablesTeam2Parts are ordered too latePrototype cant be build and tested on scheduleUncertainty in lead time for parts133Order parts before winter break, Assign team member to order the parts during winter breakTeam3Parts needs to send out for machiningUnexpected lead time and increased costsPart design is not producible by in house process122The design has the least specialize tooling and if required, incorporate into the project schedule, make sure the machine shop stay on the schedule with promised delivery timeTeam4Expensive prototypeUnsatisfied Customer, no funds for prototypeToo many features, improper estimates339Include a range for all the parts estimatesTeam5Chair rolls backwards down slopeProject failure, unsafe for useUnreliable stopping system133Multiple failsafes for systemTeam6System does not disengageChair made unfit for normal useImproperly designed system122Include multiple methods of disengagingTeam7System does not engageProject failure, system does not provide assistanceImproperly designed sensing system122Reliable device for activating system with failsafes (including manual activation)TeamIDRisk ItemEffectCauseLSIAction to Minimize RiskOwner8System does not slow down chair on a declineProject failure, User moves faster than is safeImproperly designed system133Reliable device for activating system with failsafes (including manual activation)Team9System breaks/yields earlier than expectedChair is unusableimproper analysis/ improper manufacturing techniques224Inspection of parts and installation, Perform durability tests to match with the desire durability, if system breaks it remains the functionality of a manual wheelchairTeam10Turning radius is too largeSystem is not a good alternative to existing solutionsDrive Wheels only turn one direction111Make sure the wheels can rotate independently.Team11Expensive Manufacturing CostUnsatisfied Customer, no funds for prototypeComplicated Design, High Labor Cost339Streamline Design, Design for ease of manufacturing, design of manufacturing analysisTeam12System SafetyUnsatisfied Customer, Potential for project failureSafety feature fail or not included into system design133Verify safety feature is included into the system design. Develop test plan to test the durability of the safety features.Che-An13The charging system fails to chargeEngineering requirements are not metThe speed of the chair are slow, Motor failure212Feasibility analysis on the charger, if the system fail will not have an effect to the chairTom14Blown motor and/or blown batterySafety and maintainability concernsSpeed of the motor is going to fast due to the gearbox133Install cutoff device and system to disengage the battery from motor or motor from gearbox if the speed exceed the limitTomProject Future

Comments/Questions?Updated Engineering Requirementsrqmt. #ImportanceSourceFunctionEngr. Requirement (metric)Unit of MeasureMarginal ValueTarget ValueIdeal ValueComments/StatusS193C13System OperationCurrent output to battery at 5V when moving 1 mphAmps0.1250.251S203C13System OperationCurrent output to battery at 5V when moving 4 mphAmps0.514S213C5System PortabilityRatchet System Weightlbf151210.5S223C5System PortabilityBrake System Weightlbf1087S233C5System PortabilityCharging System Weightlbf252017.5S249C7System OperationRachet System Cost$30015060Production level costsS259C7System OperationBrake System Cost$20010040Production level costsS269C7System OperationCharging System Cost$500250100Production level costsS279C1System OperationHill Holder Roll back distancein210.5S283C4System OperationWear Item Replacement Timeminutes30155S293C2System OperationUser Input Braking Forcelbf20105