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