Instrumented Wheel For 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 gauges  Wires 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.

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.