Fall 2008Grand Valley State University

Eric DomkeDrew Pretzer

Brandon RoodKarl Hiedemann

Powered Wheelchair Trainer Design ProjectFall Semester - 2008

“The ability to move is the first foundation stone in building personal dignity.”

- D. Linda Bidabe

Fall 2008Grand Valley State University

IntroductionIntroduction

● Project DescriptionProject Description● Customer NeedsCustomer Needs● SpecificationsSpecifications● Design EvolutionDesign Evolution● Demonstration & Evaluation of PrototypeDemonstration & Evaluation of Prototype● RecommendationsRecommendations

Fall 2008Grand Valley State University

Problem DescriptionProblem Description

● Must pass test to get Must pass test to get money from insurance money from insurance companycompany

● Not enough practiceNot enough practice● Powered chairs are Powered chairs are

expensiveexpensive● Goal: Build Goal: Build

"inexpensive" device "inexpensive" device which attaches to which attaches to manual wheelchairs.manual wheelchairs.

Fall 2008Grand Valley State University

Target MarketTarget Market

Fall 2008Grand Valley State University

Customer Needs - InterviewsCustomer Needs - Interviews

● Fit through a standard doorFit through a standard door● Change between different wheelchairs quicklyChange between different wheelchairs quickly● Easily transportable between different buildings.Easily transportable between different buildings.● Good battery life.Good battery life.

Fall 2008Grand Valley State University

Product SpecificationsProduct Specifications

● Switch Users in Under 5 MinutesSwitch Users in Under 5 Minutes● Accommodate Different Sized WheelchairsAccommodate Different Sized Wheelchairs

● Widths of 20-25 inchesWidths of 20-25 inches● Lengths of 32-50 inchesLengths of 32-50 inches● Wheelbase of 16-32 inchesWheelbase of 16-32 inches

● Fit Through a Standard DoorFit Through a Standard Door● Width is under 32 inchesWidth is under 32 inches

● Mimic a Powered WheelchairMimic a Powered Wheelchair

Fall 2008Grand Valley State University

Revision ARevision A

● Motor CalculationsMotor Calculations

● Support Bar CalculationsSupport Bar Calculations● 0.065" Wall Thickness for Steel Tube0.065" Wall Thickness for Steel Tube

● Force to Load CalculationForce to Load Calculation● 170 lbs170 lbs

● Tipping CalculationTipping Calculation● Need to move > 9.33" off centerNeed to move > 9.33" off center

Torque (Driving)

480.98 In-lb 54.31 N-m

Torque (Steering)

209.49 In-lb 23.65 N-m

Fall 2008Grand Valley State University

Revision BRevision B

Front of Trainer

1 2 3

Fall 2008Grand Valley State University

Revision CRevision C● Motor TestingMotor Testing

● Cordless motors possible, but Cordless motors possible, but durability and brake concernsdurability and brake concerns

● Frictional Force ExperimentFrictional Force Experiment● Approx. 300 lbf to get a 4" Approx. 300 lbf to get a 4"

dia. wheel over a 0.75" ledgedia. wheel over a 0.75" ledge

Fall 2008Grand Valley State University

Revision DRevision D● Finite Element AnalysisFinite Element Analysis

● Need multiple gussets to Need multiple gussets to minimize deflectionminimize deflection

● Frame Design AnalysisFrame Design Analysis● Tube frame is stronger and Tube frame is stronger and

more cost effectivemore cost effective

Fall 2008Grand Valley State University

Revision ERevision E● Site Visit to LDC #2Site Visit to LDC #2

● Motors cannot go between Motors cannot go between wheelchair wheels.wheelchair wheels.

● Traction AnalysisTraction Analysis● Issues with traction, Issues with traction,

especially on carpet.especially on carpet.

MotorsBatteries

Fall 2008Grand Valley State University

Final DesignFinal Design

Fall 2008Grand Valley State University

LDC – Final VisitLDC – Final Visit

Fall 2008Grand Valley State University

LoadingLoading

● Improvements: NoneImprovements: None

Goal : "Not Strenuous" Actual : Very Easy PASS

Fall 2008Grand Valley State University

LockingLocking

● Improvements: NoneImprovements: NoneGoal : < 5 minutes Actual : < 1 minutes PASS

Fall 2008Grand Valley State University

ManeuverabilityManeuverability

● Improvements: Tweak the controls algorithms Improvements: Tweak the controls algorithms and deal with traction issues.and deal with traction issues.

Goal : Similar to powered wheelchair

Actual : Some minor deviations

PASS

Fall 2008Grand Valley State University

Fits Through a DoorFits Through a Door

● Improvements: NoneImprovements: None

Goal : Width < 32" Actual : Width = 30" PASS

30"

Fall 2008Grand Valley State University

BatteriesBatteries

● Improvements: Better compromise between Improvements: Better compromise between price, weight, and electrical capacity.price, weight, and electrical capacity.

Goal : Discharge > 16 hr

Charge < 8 hr

Actual : Discharge >20 hr (1.4 A Draw)

Charge > 10 hr

(BORDERLINE) FAIL

Fall 2008Grand Valley State University

TransportationTransportation

● Improvements: Make the trainer "collapsible" Improvements: Make the trainer "collapsible" into two or more pieces.into two or more pieces.● Aluminum FrameAluminum Frame

Goal: Can fit in trunk Actual: Length and height are too large

FAIL

Fall 2008Grand Valley State University

General ConcernsGeneral Concerns

● JoystickJoystick● Loses calibration resulting in unexpected motion of Loses calibration resulting in unexpected motion of

the trainerthe trainer● Looser spring and better mounting systemLooser spring and better mounting system

● TractionTraction: Cannot turn easily on carpet: Cannot turn easily on carpet● Over-HeatingOver-Heating: Look at controls system: Look at controls system● Battery-Level ReadingBattery-Level Reading: Calibration could be off: Calibration could be off

Fall 2008Grand Valley State University

Proposed New FeaturesProposed New Features

● Attendant ControlAttendant Control● "E-Stop" Bumper"E-Stop" Bumper● Joystick: Joystick:

"Backwards "Backwards Mode"Mode"

● Multiple control Multiple control interfacesinterfaces

Fall 2008Grand Valley State University

BudgetBudget

Part Supplier Supplier Number Cost Qty Total Cost

Motor NPC NPC-B81, -B82 $339.00 2 $678.00

Charger McMaster-Carr 7558K68 $299.03 1 $299.03

Batteries Digi-Key 522-1015-ND $82.51 2 $165.02Acrylic for Joystick and Controls

McMaster-Carr 8774K43 $134.82 1 $134.82

Motor Driver Dimension Engineering

Sabertooth 2x25 $124.99 1 $124.99

Subtotal $1,952.89

+20% (Shipping, tax) $390.58Total $2,343.47

Fall 2008Grand Valley State University

RecommendationsRecommendations

● Patentable?Patentable?

● Continue engineering design workContinue engineering design work

● Perform market studiesPerform market studies

Fall 2008Grand Valley State University

Our RoleOur Role

● Troubleshooting existing features and making Troubleshooting existing features and making recommendations on design changesrecommendations on design changes

● Website: Website: http://sites.google.com/site/pwtgvsu/http://sites.google.com/site/pwtgvsu/● E-mail: E-mail: pwt.gvsu@gmail.compwt.gvsu@gmail.com

Fall 2008Grand Valley State University

Special ThanksSpecial Thanks

● D. Linda BidabeD. Linda Bidabe● Founder of Move International Founder of Move International

● Cathy RipmasterCathy Ripmaster● Lincoln Development CenterLincoln Development Center

● Karen GoraKaren Gora● Mary Free Bed Rehabilitation Hospital Mary Free Bed Rehabilitation Hospital

● Engineering Faculty and StaffEngineering Faculty and Staff

Fall 2008Grand Valley State University