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SDP Presentation 1
STEVI: Sensory Technology Enhancement
for the Visually Impaired
10/20/2009
Preliminary Design Review
Alex Starosielski Signal Processing Web-Developer
Brendan Gavin Sensors / Integration Treasurer
Charbel Kobrianos Sensors / Integration Team Administrator
Yi Lin Feedback / Integration Slide Developments
Team Vouvakis
Electrical and Computer Engineering
SDP Presentation 2Electrical and Computer Engineering
The Problem
The visually impaired can not navigate without assistance.
•Cane
•People
•The Guide Dog
SDP Presentation 3Electrical and Computer Engineering
Long Cane
• Common Solution
•Simple, cheap, robust and reliable
• Limited range
• Problems with obstacles above waist.
SDP Presentation 4Electrical and Computer Engineering
Electronic SolutionsElectronic Travel Aids (ETAs) • Detect obstacles with sensors
•Typically ultrasonic
• Indicate obstructions to user
•Feedback often auditory or tactile
SDP Presentation 5Electrical and Computer Engineering
Limitations of Existing Electronic Aids
•Expensive! $400 to $1000
•Trouble with stairs and slopes
•Insufficient directivity
•Problems with reflections indoors
•Problems with absorbing objects
Requirement Specifications
SDP Presentation 6Electrical and Computer Engineering
Society Needs Engineering Constraints Project Specs
Form Factor Handheld Size 5in x 5in x 2in (handheld)
Detection Range
0 – infinity Power and price 0.5-4m
Detection Angle
0 – 180° User interface and signal processing 20°
Obstacle sizes
All sizes Limitations of sensors > 3in x 3in
Cost Free Part, manufacturing and labor costs < $400
Battery Life Infinite Size, power consumption > 7 hours
Weight Negligible Hardware mass < 3 lbs
SDP Presentation 8Electrical and Computer Engineering
Proposed Solution - STEVI
Sensor Fusion!
Auditory & Tactile Feedback
Ultrasound Laser Infrared
Small Objects X
Slanted Surfaces X X
Directionality X
Reflections Signal Processing
Absorbent Objects Signal Processing
SDP Presentation 12Electrical and Computer Engineering
Ultrasonic Sensors2 x Maxbotix UT
• Average time of flight to calculate distance
• Angle calculated from difference in signal return times
c = speed of sound in air = 343 m/s
www.sparkfun.com
SDP Presentation 13Electrical and Computer Engineering
Laser
• Detect distances with triangulation
• Used for handling stairs, curbs, angled walls and smaller objects
•(1/3-inch Sony Supper HAD Color CCD Wired Mini Pinhole Camera
Camera view:
Setup:Sony Supper HAD
www.lightinthebox.com
Infra Red
• Detect closer objects
• Prevents user from hitting objects while sweeping left and right
www.sparkfun.com
• Has a viewing angle of 40 deg.
14SDP PresentationElectrical and Computer Engineering
SDP Presentation 15Electrical and Computer Engineering
Microcontroller
• 3 x 28 pin ATMega88PA• Features: • 8kB Program Space • 20 MIPs at 20 MHz
• 23 I/O Lines, 6-channel 10 bit ADC• In-circuit programming - JTAG
www.digikey.com
SDP Presentation 16Electrical and Computer Engineering
User Feedback
3 x ROB-08449 Vibrating Motor
• Closer obstacle - stronger vibrations• Vibrating pad location - obstacle direction• Alternative Feedback - Audio Jack
www.sparkfun.com
SDP Presentation 17Electrical and Computer Engineering
Prices
Component Cost
Microcontrollers (3)www.digikey.com
$8
Vibrating Motors (3)www.sparkfun.com
$15
IR Emitter/Detector (2)www.sparkfun.com
$4
Ultrasonic Transducers (2)www.sparkfun.com
$10
Laser/Camera Assemblywww.allelectronics.com
$140
PCB Fabrication $100
Total Cost $277
Initial Balance $500
Net Savings $223
SDP Presentation 18Electrical and Computer Engineering
Proposed MDR Deliverables
Demonstration of Ultrasonic Detection• Block Diagram 2 • Ultrasonic Transducers• Transducer Microcontroller• Vibrating Motor Array
Principles of Laser Detection• Laser and Camera• Computer Processing