1. Propulsiometer Instrumented Wheelchair Wheel
1 Electrical & Computer Engineering, 2Biomedical Engineering, Vanderbilt University, Nashville TN
• 6 analog channels and 4 digital channel
• A/D with 12 bit resolution
• Wireless capability
• Sampling rate of at least 200 Hz
• Accepts voltage signal of -5/+5 volts
• Power consumption ~5 watts
• Small and compact
•High incidence of upper extremity injuries occurs among users after
prolonged use of the wheelchair
•Propulsion biomechanical studies have been used to assess what
attributes of propulsion might be contributing to the development of injuries
and what strategies wheelchair users can adopt to reduce the likelihood of
developing injuries
•Propulsiometer is an instrument used to access
the characteristic of forces applied to the hand
rim during propulsion
•It consists of a data acquisition (DAQ) system,
load cell, wireless transmitter,battery, DC/DC
converter and a sensor
OBJECTIVE
BACKGROUND
METHODOLOGY
FINAL CIRCUIT DESIGN
ACKNOWLEDGEMENT
CONCLUSION
• Dr. W Mark Richter (PhD, Director of Research and Development,
MAXmobility)
• Prof. Paul H King (PhD, PE, Associate Professor of Biomedical
Engineering)
• Prof. Tim Holman (PhD, Research Associate Professor of Electrical
Engineering)
• In conclusion, our design has met about 85% of the requirement
• The conversion of analog signals from the load cell to digital using an A/D
converter has been completed using the MAX1270 chip
• The data collected from quadrature encoder was done using a decoder
chip LS7166
• We were unavailable to finish the wireless portion due to unavailability of
the wireless device at the present time.
• Do research on pre-packaged products that met the needed specifications
• Listing all the chips that needed in duplicating the data acquisition system
• Designing the circuit (Figure 2) and putting all the components together
• Programming the microcontroller and interface, using Microsoft® EXCEL
• Testing the prototype
• Finalized our design, soldered on proto-board (Figure 3)
OVERALL REPRESENTATION
A/D DATA ANALYSIS QUADRATURE DATA
ANALYSIS
MARKETIBILITY
LEVEL OF ACCOMPLISHMENT
TARGET SPECIFICATIONS
• Continue the electronic and instrumentation development of an innovative
propulsiometer design at an affordable cost.
• Replacing the MiniDAT™ (DAQ system) and redesigning the
propulsiometer so that we can decrease the size, weight, cost and power
consumption relative to the current design
Ahmad Shahir Ismail1
,Hafizul Anwar Raduan1
, Seri Mustaza2
, Siti Fauzi2
Angle of rotation
-50
0
50
100
150
200
250
300
350
400
3:32:24 3:32:28 3:32:33 3:32:37 3:32:41 3:32:46 3:32:50
Real Time
AngularPosition,degree
Angle of rotation
Figure 5:Figure 5: Graph of angle of rotation of the wheel vs timeGraph of angle of rotation of the wheel vs time
collected from the optical quadrature encodercollected from the optical quadrature encoder
Figure 1:Figure 1: Overall circuit representationOverall circuit representation
Figure 4:Figure 4: Graph of voltage vs time from the A/D converter ofGraph of voltage vs time from the A/D converter of
each of the six channels at a constant voltage of 5Veach of the six channels at a constant voltage of 5V
Voltage vs Time of Each Channel
4.91
4.912
4.914
4.916
4.918
4.92
4.922
4.924
4.926
4.928
4.93
3:32:28 3:32:33 3:32:37 3:32:41 3:32:46
Real Time
Voltage,V
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
Figure 2:Figure 2: Schematic diagram of the connection for load cell to A/D converterSchematic diagram of the connection for load cell to A/D converter
and optical encoder to quadrature decoder chip onto the Basic Stamp 2 Moduleand optical encoder to quadrature decoder chip onto the Basic Stamp 2 Module
• We successfully transferred the data from both load cell and quadrature
encoder to the computer using MAX1270 and LS7166
• MAX1270 is able to accept voltage signals of ±5 volts and has a
resolution of 12-bits
• Reading the quadrature encoder signal was done through using a
quadrature decoder chip, LS7166, which has a 24-bit counter.
• We successfully interface the plots of output data from both load cell and
optical encoder to computer using EXCEL (Figure 4 and figure 5)
• Our system works at about 100 Hz
• This design is also small and low in cost relative to the previous design
(MiniDAT™)
Figure 3:Figure 3: Snapshot of the finalized andSnapshot of the finalized and
soldered circuit designsoldered circuit design
SAFETY FACTORS
• The total cost is $197.00
• Our product can be use in
research lab, i.e. calculating
metabolic rate, determining which
type of tire is the most suitable in
minimizing the occurring of upper
extremity injuries
• Since the cost is fairly low
compared to other solution that is
out there, we hope that our
product can be improved and
commercially marketed
• No suspend wires, so that it will
not interfere with the movement
of the tire
• The circuitry needs to be
checked at the beginning of
each experiment to prevent any
potential problems, ie. short
circuit
• Our product is also easy to
store, if decided not to use the
propulsiometer, can just take
off the tubular hoop
Group 22