Instrumented WheelFor Wheelchair Propulsion

Assessment.

Jacob Connelly

Andrew Cramer

John Labiak

Problem Statement

Manual wheelchair users are at considerable risk of developing upper extremity overuse injuries. Upper extremities are primary means of mobility. Extensive upper extremity use in seating transfer. Upper extremity function is injury level dependent.

Need to quantify effect of propulsion biomechanics. Propulsion assessment. Properly seat user. Train user.

Project Goals

Develop an inexpensive instrument capable of measuring applied resultant force in order to analyze propulsion techniques of manual wheelchair users.

Lower instrument cost < $5K SmartWheel (3rivers) ~ $25K Load cell propulsiometer > $10K

Solution Strain gauges used to measure resultant force.

ΔV calculate strain calculate resultant force. Create ΔV vs. Force standard curve.

6 push-rim attachments. This is variable.

Solution

Voltage divider circuit. 1mV change with a 4V offset

result in 1.25mV sensitivity. Contingencies involve

instrumentation amplifier design.

8-Pin DAQ unit. Bluetooth wireless transceiver

(USB compatible)

T

C

Completed Work Instrumented wheel design complete – opposing strain

gauges per push-rim attachment. Circuit design complete – voltage divider config. with offset

voltage compensation designed. Backup circuit design of differential operational amplifier config.

designed All experimental elements ordered and received.

Had delays waiting for several parts.

Gauges attached to instrumented wheel.

12 gauges, 2 on each of the 6 tabs.

Completed Work All connection wires

attached to strain gaugesWires arranged in

voltage divider design.Wires ready for

connection to DAQ and power supply.

Mounting board constructed and attached to wheel. Battery holder attached to

board.

Current Work

Mount the DAQ card. Set-up Bluetooth wireless

transmitter and receiver. Wire gauges to power supply

and DAQ card. Insulate any bare wire

connections with the strain gauges. Still brainstorming best

approach to accomplish insulation. Possible use of “Plasti-Dip”.

Future Work Manipulate the LabVIEW program used for the

propulsiometer for our application. Meet with Dr. Richter to review the work before

testing. Begin recording change in voltage data.

Hang weights and/or attach wheel to chair and push. Hopefully, by the end of next week.

Relate change in voltage to obtain strain data.Resultant Force vs. Voltage

0

100000

200000

300000

400000

500000

600000

0 10 20 30 40 50 60 70 80

Voltage (mv)

Res

ult

ant

Fo

rce

(N)

Future Work

Analyze trends in the strain data. Calibrate the strain data to form a resultant

force curve. Gauge success/need to reevaluate

system.Possible bridge circuit with amplifiers.

Future Work Design of future prototypes. Design the center hub to

house the power supply and DAQ card. Eliminate the mounting board.

Clean up the wiring. Through push rim or wheel.

Possible creation of different geometric pushrim tab designs.