Propulsiometer Instrumented Wheelchair Wheel Prepared by: Seri Mustaza (BME) Siti Nor Wahida Fauzi...
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Transcript of Propulsiometer Instrumented Wheelchair Wheel Prepared by: Seri Mustaza (BME) Siti Nor Wahida Fauzi...
Propulsiometer Instrumented
Wheelchair WheelPrepared 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 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 Located on tubular hoop that can be mounted on
different sizes of wheelchair’s wheel.
To access the load applied by manual wheelchair user.
Consist of DAQ, load cell, wireless transmitter, battery, DC/DC converter, sensor.
Mainly use as research tool in lab. Ex: Calculating metabolic rate
Propulsiometer
Propulsiometer
Viasat MiniDAT™
Battery
Sensor
Load Cell DC/DC Converter
Data collected from propulsiometer to the PC
Force, Torque & Wheel Angle
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.
MiniDAT™
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
Main GOAL
Replacing MiniDAT™
Specific Goals
Size: 4 x 4 x 0.5 inches (LWH)
Weight= ~0.25lb
Cost= less than $1000.00
Low power consumption
Target Specification 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)
BASIC Stamp® Discovery Kit Basic 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)
MAX12708 channel single-ended12-bit resolution Programmable input range ( 10V, 5V, 5V, 0V)Sampling rate of 110kspsOperates at 5V
Components (Quadrature Decoder Chip)
LS71668-bit tri-state I/O bus No external clock requiredOperates at 5V
Components (Wireless Serial Adapter)
Socket Cordless Serial Adapter (CSA)Uses RS232 (Serial Port)Has a class 2 BluetoothRange up to 10m Simple plug, install, and play
Interfacing with the computer 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
Two main portions: Retrieving the 6 readings from
the load cell Sending the data to a
spreadsheet file 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 Three main parts:
Initializing the chip Reading position and
direction Sending data to a
spreadsheet file 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):
ReadSensorData s/r:
ReadSensorData:
controlbyte = basiccontrol ^ (channel << 4)
bytea = 0
byteb = 0
shiftout outputpin, clockpin, msb, [controlbyte \ 8]
…
Main loop:top:
for channel = 0 to 7 gosub ReadSensorData gosub SendSensorData
next
pause sleeptime
goto top
Current Status
Finalizing the circuit layout on the wheel
Finishing the programming portion
Testing the program