Instrumented Wheel

1
Instrumented Wheel

• For Wheelchair Propulsion Assessment.

Jacob Connelly Andrew Cramer John Labiak
2

• Dr. Mark Richter Project Advisor
• Owner and Director of RD
• Stanford Graduate
• Wheelchair Propulsion Research
• Handrim Biomechanics Flexrim
• Product design to maximize the mobility of
  inidividuals with disability.

3
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.

4
Project Goals

• Develop an inexpensive instrument capable of
  measuring applied resultant force in order to
  analyze propulsion techniques of manual
  wheelchair users.
• Costs less than alternatives 5-6K
• SmartWheel (3rivers) 25K
• Load cell propulsiometer gt 10K

5
Market Outlook

• Spinal Cord Injury Hospitals and Rehabilitation
  Centers 30 50 in U.S.
• Seating and Training Clinics 50 100
• http//www.sci-info-pages.com/rehabs.html
• 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

6
Solution

• Strain gauges used to measure resultant force.
• ?V ? calculate strain ? calculate resultant
  force.
• Create ?V vs. Force standard curve.
• 6 push-rim attachments. This is variable.

7
Initial Solution 1st Prototype

• 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)

8
Completed Work

• 1st 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 gt signal
• Low Pass Filter ineffective.

9
Completed Work

• Adapt 1st Prototype.
• Decreased from 6 attachments to 3.
• Handrim still too rigid no noticable difference.
• Decided to redesign attachments and implement new
  bridge circuit.

10
Completed Work

• Designed 1st Prototype
• pushrim in SolidWorks.
• Ran force simulation in SolidWorks.
• Calculated Safety Factor.
• 40 lb force SF 5.335
• 25 lb force SF 8.54
• 10 lb force SF 21.34

11
Completed Work

• Designed new attachments.

12
Completed Work
13
Completed Work
Force Simulation in SolidWorks 40 lb force SF
1.95 20 lb force SF 3.13 10 lb
force SF 7.81
14
Completed Work.

• Cut out 2 new tabs at 2 different thicknesses
  (0.09 in. and 1/16th in.)
• Attached strain gauges to top and bottom of each.
• Solder into a simple bridge circuit with
  resistors and power supply.
• Applied stress and measured voltage with
  multimeter.
• 1/16th inch too weak.
• 0.09 inch gave 10mV changes in voltage.

15
Current Work
5.0 V
TENSION
DAQ
COMPRESSION

• Meeting with Dr. Baudenbacher to confirm circuit
  design and help with getting components.

16
Current Work

• Work on 2nd prototype
• Drill holes near push rim attachments to run
  wiring through wheel.
• Clean up appearance of wheel.
• User cannot touch wiring when pushing.
• Better organization.
• Run all of the wiring for
• the gauges before the
• push rim is attached.
• Wont break any leads.

17
Future Work

• Cut out 3 new push rim attachments (0.09
  thickness)
• Have Russell weld tabs to push rim.
• Attach strain gauges to tabs.
• Connect wiring to gauges, power supply, and DAQ.
• Test 2nd Prototype with LabView.

18
Future Work

• Obtain acceptable change in voltage data
• Analyze trends in the strain data
• Calibrate the strain data to form a resultant
  force curve
• Design the hub to house the electronics of the
  wheel