Download Figure 2 - Research - Vanderbilt University

Propulsiometer Instrumented Wheelchair Wheel
Ahmad Shahir
1
1
Ismail ,Hafizul
Anwar
1
Raduan ,
Seri
2
Mustaza ,
Siti
2
Fauzi
OVERALL REPRESENTATION
OBJECTIVE
MARKETIBILITY
• Continue the electronic and instrumentation development of an innovative
propulsiometer design at an affordable cost.
• 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
• 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
BACKGROUND
• 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
•High incidence of upper extremity injuries occurs among users after
prolonged use of the wheelchair
Figure 1: Overall circuit representation
•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
FINAL CIRCUIT DESIGN
• 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
• 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™)
•It consists of a data acquisition (DAQ) system,
load cell, wireless transmitter,battery, DC/DC
converter and a sensor
TARGET SPECIFICATIONS
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
SAFETY FACTORS
LEVEL OF ACCOMPLISHMENT
•Propulsiometer is an instrument used to access
the characteristic of forces applied to the hand
rim during propulsion
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Group 22
Electrical & Computer Engineering, 2Biomedical Engineering, Vanderbilt University, Nashville TN
CONCLUSION
Figure 2: Schematic diagram of the connection for load cell to A/D converter
and optical encoder to quadrature decoder chip onto the Basic Stamp 2 Module
A/D DATA ANALYSIS
METHODOLOGY
Figure 3: Snapshot of the finalized and
soldered circuit design
QUADRATURE DATA ANALYSIS
Voltage vs Time of Each Channel
• 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
Angle of rotation
4.93
• In conclusion, our design has met about 85% of the requirement
400
CH 0
4.928
CH 3
Voltage, V
4.922
4.92
4.918
4.916
4.914
• Programming the microcontroller and interface, using Microsoft® EXCEL
• Testing the prototype
• Finalized our design, soldered on proto-board (Figure 3)
250
200
Angle of rotation
150
0
3:32:24
3:32:33
3:32:37
3:32:41
3:32:46
Real Time
Figure 4: Graph of voltage vs time from the A/D converter of
each of the six channels at a constant voltage of 5V
ACKNOWLEDGEMENT
100
50
4.912
4.91
3:32:28
300
CH 4
CH 5
• Designing the circuit (Figure 2) and putting all the components together
• We were unavailable to finish the wireless portion due to unavailability of
the wireless device at the present time.
CH 2
4.926
4.924
• Listing all the chips that needed in duplicating the data acquisition system
350
Angular Position, degree
• Do research on pre-packaged products that met the needed specifications
CH 1
3:32:28
3:32:33
3:32:37
3:32:41
3:32:46
3:32:50
-50
Real Time
Figure 5: Graph of angle of rotation of the wheel vs time
collected from the optical quadrature encoder
• 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)