P14007: Wheelchair Assist: Detailed Design Review Che-An Lee – Industrial and System Engineer Dan Schuster – Mechanical Engineer Phil Medalie – Mechanical Engineer Tom Elliot – Electrical Engineer

Agenda Project Overview Mechanical System Electrical System Assembly Plan Test Plan Risk Assessment Project Timeline

Project Overview Assist manual wheelchair users on slopes Mechanical system Ratchet system Brake system Electrical system Charging system Expected outcome Functional prototype Engineering design experience Basis for future senior design project

Overview

Total 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 Analysis Shaft Bearing Block Bolts Ratchet Tooth

Shaft Analysis

Shaft Results

Ratchet Tooth Analysis S = psi F = 0.25 in Y = for 72 teeth DP = 24 V  Disregard for low speeds W = 270 lbf of allowable tooth load (will see ~115 lbf)

Bolt Analysis Bolt Shear Sy = 70 ksi Ssy = 40 ksi

Detailed Electrical Generator Design

Bill of Materials DescriptionPart #Cost Cost (1000)QuantityTotalTotal(1000)Link USB Port BLF $0.71$0.381$0.71$ Battery n/a $49.95$39.961$49.95$ Motor Dc Geared 24V 30RPM $37.03$31.922$74.06$ Outdoor Speaker Wire 6 feet needed n/a $0.78$0.601$0.78$ Voltage Regulator $7.00$5.601$7.00$ html#.UqA3IsRDuz6 Bridge Rectifier GBU404 DI-ND $1.37$0.592$2.74$ Custom PCB Board(OSH Park) n/a $ TOTAL$138.31$114.63

Buck-Boost Regulator Circuit 5V with 80% Efficiency *Ordered Premade*

DC Generator Motor 2.7W 24V 30RPM

Battery with Battery Protection 5V Outputs up 2A Draws up to 1A Dimensions: 2.9" x 1" x 4.9" / 72mm x 24mm x 125mm Weight: 300g 80% Efficient

Simulation

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

PCB Board Design

PCB Product Ready to Be Ordered TopBottom

Electrical Energy Harvesting Overview Battery = Average 80% Efficiency Buck-Boost = Average 85% Efficiency Motors = 2.7W each = 5.4W at 30RPM W generation at 30RPM mA generation at 5V, at 30RPM

Benefits to design Easily 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 Materials

Target vs. Actual Targeted CostActual Cost Ratchet$150$182 Brake$100$146 Charging$250$138 Total$500$466

Assembly Plan

Test Plan Test Equipment – Plywood base – Car Jack – Cables – Tape Measure – Scale – Multimeter – Fish hook scale or similar – Circuit simulation software Phase of Testing – Component Ratchet System Circuit Design – System Mechanical System Electrical System Usability Testing

Risk Assessment

Project Future

Comments/Questions?

Updated Engineering Requirements rqmt. # Import ance SourceFunctionEngr. Requirement (metric) Unit of Measure Margin al Value Target Value Ideal ValueComments/Status S193C13 System Operation Current output to battery at 5V when moving 1 mph Amps S203C13 System Operation Current output to battery at 5V when moving 4 mph Amps0.514 S213C5 System Portability Ratchet System Weightlbf S223C5 System Portability Brake System Weightlbf1087 S233C5 System Portability Charging System Weightlbf S249C7 System Operation Rachet System Cost$ Production level costs S259C7 System Operation Brake System Cost$ Production level costs S269C7 System Operation Charging System Cost$ Production level costs S279C1 System Operation Hill Holder Roll back distance in210.5 S283C4 System Operation Wear Item Replacement Time minutes30155 S293C2 System Operation User Input Braking Forcelbf20105