STEVI: Sensory Technology Enhancement for the Visually Impaired

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

SDP Presentation 2Electrical and Computer Engineering

The Problem

The visually impaired can not navigate without assistance.

•Cane

•People

•The Guide Dog

Solution - STEVI

3Electrical and Computer Engineering SDP Presentation

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

SDP Presentation 5Electrical and Computer Engineering

Previously Proposed FDR - Block Diagram

SDP Presentation 6Electrical and Computer Engineering

FDR Proposed Deliverables – Block Diagram

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.

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.

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.

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

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

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

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

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

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

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

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

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

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

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.

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

=

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

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%

SDP Presentation 24Electrical and Computer Engineering

Updated Gantt Chart

SDP Presentation 25Electrical and Computer Engineering

SDP Presentation 26Electrical and Computer Engineering

UDS Prototype

Control Circuitry Detection/Feedback System

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