Instrumented Wheel For Wheelchair Propulsion Assessment. Jacob Connelly Andrew Cramer John Labiak

Dr. Mark Richter – Project Advisor  Owner and Director of R&D  Stanford Graduate  Wheelchair Propulsion Research Handrim Biomechanics – Flexrim  Product design to maximize the mobility of inidividuals with disability.

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 $5-6K  SmartWheel (3rivers) ~ $25K  Load cell propulsiometer > $10K

Market Outlook Spinal Cord Injury Hospitals and Rehabilitation Centers: 50 – 60 in U.S. Seating and Training Clinics: 50 – Research Labs: ~50 Product will be sold as a pair of wheels  Only 1 wheel will be instrumented.  Same size diameter and same inertial effects. Construction Cost: Below $2K Price of Pair: $5K

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.

Initial 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 Initial prototype completed.  Strain gauges attached and wired to DAQ.  Power supply active.  Connections Insulated in rubber coating. Data recorded in LabVIEW.  Low CMRR. 10 mV noise > signal  Low Pass Filter ineffective.

Current Work Adapt current prototype.  Decrease from 6 attachements to 3.  Hope the handrim will not be as rigid as before. Determine and order parts for new circuits.

5.0 V DAQ TENSION COMPRESSION 5.0 V

Future Work If no mechanical or physical change help  new circuit design including amplifiers  Order circuit parts to test them and ensure we are obtaining accurate results  Have circuit board printed and order the remaining parts Clean up all of the wiring on second prototype.  Run all of the wiring prior to strain gauge attachment.

Future Work Obtain acceptable change in voltage data Analyze trends in the strain data Calibrate the strain data to form a resultant force curve Incorporate other possible tab designs Design the hub to house the electronics of the wheel