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.
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