Transcript Propulsiometer Instrumented Wheelchair Wheel

Propulsiometer
Instrumented
Wheelchair Wheel
Prepared by:
Seri Mustaza (BME)
Siti Nor Wahida Fauzi (BME)
Ahmad Shahir Ismail (EECE)
Hafizul Anwar Raduan (CompE)
Advisor:
Dr. W Mark Richter (PhD, Director of Research and
Development, MAXmobility)
MAXmobility
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Accessible wheelchair treadmill
Basically, working with ergonomic wheelchair:
 Propulsiometer instrumented wheelchair wheel
 Transfer friendly wheelchair
 Variable Compliance Hand-Rim Prototype (VCHP)
 Effective ways to propel the wheel
Propulsiometer
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Located on tubular hoop that can be mounted on
different sizes of wheelchair’s wheel.
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To access the load applied by manual wheelchair user.
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Consist of DAQ, load cell, wireless transmitter, battery,
DC/DC converter, sensor.
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Mainly use as research tool in lab. Ex: Calculating
metabolic rate
Propulsiometer
Propulsiometer
Battery
Viasat MiniDAT™
Sensor
Load Cell
DC/DC Converter
Force, Torque &
Wheel Angle
Data collected from propulsiometer to the PC
Load Cell signals
Each of the 6 signals ranges from -5 V to
+5 V
 12 bit A/D converter
 Resolution = range/# of states (10/4096)
 For each step size, would equals to
2.4412mV.
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MiniDAT™
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MiniDAT™
 16-bit resolution
 16 single ended or 8 differential analog inputs
 8 digital I/O lines
 IEEE 802.11 wireless LAN
 Uses 15V DC voltage
 7.9 x 4.2 x 1.42 inches (LWH)
 Weight = 1.5lb
 Cost = $4,625.00
Problem
MiniDAT is no longer available
 Bulky
 Use too much power
 Cost = $4,625.00
 Have to wait about 20 minutes to reboot
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Main GOAL
 Replacing
MiniDAT™
Specific Goals
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Size: 4 x 4 x 0.5 inches (LWH)
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Weight= ~0.25lb
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Cost= less than $1000.00
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Low power consumption
Target Specification
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7 analog channels and 1 digital channel
A/D with 12 bit resolution
1 quadrature encoder input
Wireless capability
Sampling rate of at least 10 kHz
Accepts voltage signal of -5/+5 volts
Power consumption ~5 watts
Small and compact
Circuit Diagram
Circuit Schematic
Components
(Development Kit)
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BASIC Stamp® Discovery Kit
 Basic
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Stamp 2 Module (microcontroller)
Speed = 20MHz
RAM = 32 Bytes
Size = 1.2 x 0.6 x 0.4 inches (LWH)
 Uses
9V to operate
 Manual and software (PBasic)
Components
(A/D converter)
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MAX1270
8
channel single-ended
 12-bit resolution
 Programmable input range
( 10V, 5V, 5V, 0V)
 Sampling rate of 110ksps
 Operates at 5V
Components
(Quadrature Decoder Chip)
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LS7166
 8-bit
tri-state I/O bus
 No external clock required
 Operates at 5V
Components
(Wireless Serial Adapter)
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Socket Cordless Serial Adapter (CSA)
 Uses
RS232 (Serial Port)
 Has a class 2 Bluetooth
 Range up to 10m
 Simple plug, install, and play
Interfacing with the computer
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The BASIC Stamp module is
connected to the computer
wirelessly
BASIC Stamp Windows Editor
version 2.2.5 will be used to
program the module
Programming is performed in the
PBASIC language
Programming: A/D
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Two main portions:
 Retrieving
the 6 readings from the
load cell
 Sending the data to a spreadsheet
file
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Since MAX1270 has only one T/H
circuit, each readings has to be
retrieved separately
Maximum of 18µs to retrieve all
6 readings
Programming: Quadrature Decoder
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Three main parts:
 Initializing the chip
 Reading position and direction
 Sending data to a spreadsheet
file
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The LS7166 chip has to be
properly initialized
Then the position and
direction can be read and
sent to a file
Example code (A/D):
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Main loop:
top:
for channel = 0 to 7
gosub ReadSensorData
gosub SendSensorData
next
pause sleeptime
goto top
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ReadSensorData s/r:
ReadSensorData:
controlbyte = basiccontrol ^
(channel << 4)
bytea = 0
byteb = 0
shiftout outputpin,
clockpin, msb,
[controlbyte \ 8]
…
Current Status
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Finalizing the circuit
layout on the wheel
Finishing the
programming portion
Testing the program