stevi: sensory technology enhancement for the visually impaired
DESCRIPTION
STEVI: Sensory Technology Enhancement for the Visually Impaired. 10/20/2009. Comprehensive Design Review. Team Vouvakis. Electrical and Computer Engineering. The Problem. The visually impaired can not navigate without assistance. Cane People The Guide Dog. - PowerPoint PPT PresentationTRANSCRIPT
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SDP Presentation 1
STEVI: Sensory Technology Enhancement
for the Visually Impaired
10/20/2009
Comprehensive Design Review
Alex Starosielski Ultrasonic Sensing Web-Developer
Brendan Gavin Laser Sensing Treasurer
Charbel Kobrianos Laser Sensing Team Administrator
Yi Lin Ultrasonic Sensing Slide Developments
Team Vouvakis
Electrical and Computer Engineering
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SDP Presentation 2Electrical and Computer Engineering
The Problem
The visually impaired can not navigate without assistance.
•Cane
•People
•The Guide Dog
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Solution - STEVI
3Electrical and Computer Engineering SDP Presentation
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SDP Presentation 4Electrical and Computer Engineering
CDR Deliverables
Demonstration of Ultrasonic Detection• Range and Direction up to 4m (Non-Stationary)• Vibrating motors with microcontroller
Demonstration of Laser Detection• Laser and Camera • Microcontroller Processing • Vibrating Motors with microcontroller
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SDP Presentation 5Electrical and Computer Engineering
Previously Proposed FDR - Block Diagram
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SDP Presentation 6Electrical and Computer Engineering
FDR Proposed Deliverables – Block Diagram
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SDP Presentation 7Electrical and Computer Engineering
UDS Design Modifications from MDR
MDR Design: 4x Maxbotix UT
CDR Design: 2x Maxbotix LV-EZ4
Transducers
Reason for Change: • Previously 4 used (2 Transmit, 2 Receive) Currently pre-assembled transducers on chip can both transmit and receive.• On chip microcontrollers compute distance for individual transducers.
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SDP Presentation 8Electrical and Computer Engineering
Microcontroller Operation
• Synchronizes transducer operation.
• Receives distance from transducers & LDS.
• Controls Feedback operation.
• Switched between LDS & UDS mode.
FPR Goals:
• Directionality in UDS module.
• Range of UDS & LDS simultaneously.
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SDP Presentation 9Electrical and Computer Engineering
User Feedback System (Vibrating Motors)
• Tactile feedback controlled by dsPIC.
• Decreasing distance to obstacle increases frequency of vibrating pulses (2/sec at max range, 20/sec at min range.
• FPR Goal: Allow for feedback of direction to obstacle.
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SDP Presentation 10Electrical and Computer Engineering
UDS Test & Analysis: Range Error
•Goal: 15cm – 4m range
•Achieved: 15cm – 4m range
•Limitation: Range error significant for longer distances
•Solution: Modify programming to account for error at long ranges
Range Error (Human Target)
-15-10-505
101520253035
0 100 200 300 400
Measured Distance (cm)
Err
or
(cm
)
Dmin-D
Dmax-D
Range Error (5cm Wide Pole)
-20
-10
0
10
20
30
40
0 100 200 300 400
Measured Distance (cm)
Err
or
(cm
)
Dmin-D
Dmax-D
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SDP Presentation 11Electrical and Computer Engineering
UDS Test & Analysis: Lateral Detection Error
•Goal: Detect obstacles within 20º of direction of travel (5cm wide pole used for tests)
•Achieved: 26º beam angle at 50cm, 17º beam angle at 100cm, 10º beam angle at 200cm, 8º beam angle at 300cm, 5º beam angle at 400cm
•Limitation: Small obstacles difficult to detect at long ranges
Lateral Detection
0
50
100
150
200
250
300
350
400
450
-50 -30 -10 10 30 50
S (cm)D
ista
nce
to
Po
le (
cm)
Detected
No Detection
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SDP Presentation 12Electrical and Computer Engineering
UDS Test & Analysis: Obstacle Size Limitation
Goal:
•Detect object with 25cm2 CSA at all ranges up to 400cm
Achieved:
• 9cm2 object up to 200cm
• 16cm2 object up to 340cm
• 25cm2 object at all ranges
CSA (cm2) Max Range (cm)
9 200
16 340
25 400
36 400
49 400
64 400
81 400
100 400
CSA: Obstacle Cross Sectional Area
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SDP Presentation 13Electrical and Computer Engineering
LDS Algorithm
Algorithm same as from MDR:
• Find brightest pixel in camera’s vision
• Use y-coordinate of pixel to calculate distance
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SDP Presentation 14Electrical and Computer Engineering
LDS Design Modifications from MDR
Reason for Change:
• USB camera excessively difficult to integrate with electronics.
• New camera small enough for device housing.
Camera
MDR Design: Logitech USB 2.0 MP Camera
CDR Design: Camera Mod C3188A-6018
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SDP Presentation 15Electrical and Computer Engineering
LDS Design Modifications from MDR (Cont.)
Reason for Choice:
• CPLD can easily take data synchronously from camera
MDR Design: Matlab
CDR Design: CPLD
Camera Data Processing
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SDP Presentation 16Electrical and Computer Engineering
LDS Design Modifications from MDR (Cont.)
Reason for Choice:
• Ease of use for floating point calculations and data transmission
MDR Design: Matlab
CDR Design: ATMEGA32 16PU
Processing Unit
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LDS Test & Analysis: Experimental Data
•Goal: Detect distance to obstacles up to 3 meters
•Achieved: Detection of light-colored obstacles between 0.6 and 2.1 meters
Measured vs. Calculated Error
0
1
2
3
4
5
6
Target Distance (cm)
Err
or
(cm
)
Measured Error
Calculated Error
Ideal vs. Experimental Measurements
0
50
100
150
200
250
Target Distance (cm)
Mea
sure
d D
ista
nce
(cm
)
Ideal
Experimental
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LDS Test & Analysis: Quantization Error
•Goal: Reduce Quantization error
•Solution: Increase laser-camera separation distance (w)
•Limitations: Increases smallest detection distanceCalculated Quantization Error Comparison
0
2
4
6
8
10
12
1.000 13.000 25.000 37.000 49.000 61.000 73.000 85.000 97.000 109.000 121.000 133.000 145.000 157.000 169.000 181.000 193.000
Target Distance (cm)
Err
or
(cm
)
w =2 cm
w =8 cm
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SDP Presentation 19Electrical and Computer Engineering
Laser Safety
• Safety issue: device pointed parallel with ground poses laser hazard
•Plan to use three tilt sensors to account for multiple possible orientations of device
• Currently working on circuit to prevent tilt sensor activation due to shock or suddent movement
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SDP Presentation 20Electrical and Computer Engineering
Updated Power Consumption
Item Voltage (V) Current (I) P (watts)
camera 0.120000
laser 0.000400
cpld 3.300000 0.030000 0.099000
AVR uC 5.000000 0.009000 0.045000
dsPIC uC 5.000000 0.009000 0.045000
motor 1 3.000000 0.075000 0.225000
motor 2 3.000000 0.075000 0.225000
transducer 1 5 0.002 0.010000
transducer 2 5 0.002 0.010000
Total: 0.779400 W
Estimated power consumption reduced, but close to original calculation of 0.8 W.
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SDP Presentation 21Electrical and Computer Engineering
Weight Estimate
Component # of components Weight (g)
Misc 22 51.65
Camera 1 15.2
Battery 1 110
Housing 1 60
Optical Filter 1 5.1
Laser Diode 1 7.3
Total Weight 249.25
STEVI will weigh less than 2 Blackberrys
=
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SDP Presentation 22Electrical and Computer Engineering
Current Budget Update
Date Item QTY Unit Price Total Price
10/27/2009 ATMEGA88PA-PU-ND microcontroller 0 2.69 0.00
Ultrasonic Transducer - Maxbotix UT 2 4.95 9.90
Vibration Motor ROB-08449 2 7.95 15.90
5.0 megapixel webcam 1 7.95 7.95
laser diode 1 7.5 7.50
0.00
11/12/09 laser diode 2 7.5 15.00
11/13/2009 Ultrasonic Transducer - Maxbotix UT 4 4.95 19.80
11/17/2009 bandpass filter 1 37.5 37.50
1/25/2010 serial cmos camera 1 56.95 56.95
2/18/2010 laser diode 2 7.5 15.00
dsPIC30F4011 20E/P 2 5.16 10.32
tilt ball switch 6 2 12.00
Budget: 500.00
Expenditure to date: 207.82
Remaining Funds: 292.18
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SDP Presentation 23Electrical and Computer Engineering
Summary and Look AheadSummary:
• Better ultrasonic sensor detection
• Successful breadboard integration of STEVI prototype
FPR Deliverables:
• Final STEVI prototype
• Sensor fusion algorithm (s) (Implemented in dsPIC)
• PCB + housing + sensors + power system
Range Accuracy
UDS 4 m < 11%
LDS 2 m < 5%
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SDP Presentation 24Electrical and Computer Engineering
Updated Gantt Chart
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SDP Presentation 25Electrical and Computer Engineering
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SDP Presentation 26Electrical and Computer Engineering
UDS Prototype
Control Circuitry Detection/Feedback System
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SDP Presentation 27Electrical and Computer Engineering
LDS Camera-Laser Separation Testing
Pixel Difference: 3 cm vs. 8cm Separation
0
5
10
15
20
25
0.406 0.508 0.61 0.711 0.813 0.914 1.016 1.118 1.219 1.321 1.422 1.524 1.626 1.727 1.829 1.93 2.032 2.134
Target Distance (m)
Pix
el D
iffe
ren
ce
w =8 cm
w =3 cm