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eye-Pod 1.0

The eye that vibrates

ME 102 Design Project

Team 20Shuo-Hsiu Chang

Simon CheungGeorge DatskosAndrew Favor

Tim Wong

Team 20—Spring 2007

Eye-Pod 1.0

Abstract – The eye-Pod was developed to help blind and visually impaired

individuals navigate their environment. Simplicity, ease-of-use, and intuitive

design were the three key pillars upon which the device was based. The eye-Pod

was designed with two goggle-mounted ultrasonic sensors to detect obstacles and

three belt-encased vibrating motors to indicate the presence of those obstacles to

the user.

Keywords: Vision Assistance, Obstacle Detection, DSP

I. Introduction

The theme for Mechanical Engineering

102—the senior design class—was assistive

mobility. As part of the course, each team was

instructed to design and build a prototype of a

device to aid differently abled individuals in

some facet of their life. Team 20, in an

attempt to simultaneously satisfy the theme

and to develop a novel device, settled on a

product to support the visually impaired. We

branded it the eye-Pod 1.0.

Currently, the blind and visually impaired

rely on guard dogs and canes to navigate their

environments. Our design sought not to

supplant the cane but to supplement it. In

order to do this, a vision assistance device

must provide intuitive and responsive obstacle

detection. Where one can avoid ground-based

objects with a cane, one can—with the eye-

Pod—also avoid air-based objects such as tree

limbs or other overhanging obstacles. A grasp

of one’s environment is critical if one is to feel

safe, secure, and independent [1]. Studies by

Spencer et al have demonstrated that humans


are generally unable to mentally envision their

environment from just their movement [2].

That is, humans have a hard time

“constructing an accurate and spatially

integrated mental representation of their

environment” with touch, hearing, and smell

[1]. Therefore, it was essential to complement

these senses with visually-obtained

information.

With sensors and a vibration feedback

system, blind people would be able to detect

potentially dangerous objects. Ultrasonic

sensors were integrated with vibration motors

to allow blind people to detect objects up to 8

feet away. Although competing visual

assistance devices have existed for many

years, the device created as part of this project

provides a cost-effective solution [3].

Previously, devices have focused on vast (and

expensive) arrays of sensors; while these

devices are prohibitively expensive, the eye-

Pod was designed to function with two

ultrasonic sensors effectively performing as

three. In this manner, the system was able to

detect objects to the left, right, and straight

ahead. Upon detection and processing, the

control system that was created relayed the

results to the wearer through vibro-tactile

feedback. The vibratory intensity of an array

of three vibration motors on the user’s belt

changed as the user got closer to (or further

from) obstacles.

II. Equipment

Mechanical and control equipment were

used in concert with two sensors to analyze the

environment and relay the results to the user.

II.1. Sensors

Due to their superior range, ultrasonic

sensors were chosen over infrared sensors.

Two of these sensors were used in the device.

Each sensor, depicted in Figure 2.1, contained

an ultrasonic emitter and an ultrasonic

receiver. The ultrasonic emitter sent out a

pulse every 50 milliseconds. The pulse was

reflected back to the sensor if there was an

object in front of it. The sensor chip and

sensor electronics output the distance to the

object by calculating the time delay between


emission and reception and multiplying that by

the (known) velocity of the emitted pulse.

Figure 2.1 MaxSonar-EZ1 Ultrasonic Sensor

The ultrasonic sensor could detect objects at

distances between 6 inches and 18 feet. Each

sensor had a 60 degree field of vision.

II.2. Goggles

A pair of laboratory goggles were modified

so that the two ultrasonic sensors could be

placed on them and rotated at our discretion.

Mounting the sensors while permitting

rotation was a challenge that the team

overcame by cutting a secondary pair of

glasses; the hinges from those glasses were

attached to the primary glasses shown in

Figure 2.2.

Figure 2.2 Modified Goggles to Hold Sensors

After the hinges were attached, the resulting

goggles looked as they do on the cover page.

By rotating the red components, the sensors

move along the blue goggles. The ability to

adjust their position is a significant advantage

eye-Pod has over its competitors.

II.3. Motors

Three vibrating motors were used to

create the tactile output to the user. These

Nakimi micro pager motors, shown in

Figure 2.3, vibrated at varying intensities.

Figure 2.3 Nakimi micro pager motor


The intensity of the vibratory output was

proportional to the distance of objects in the

proximity of the sensors.

II.4. Digital Signal Processing Board

A Texas Instruments TMS320LF Digital

Signal Processing board was used to acquire

input signals from the sensors, to perform

calculations, and to output the results to the

vibrating motors. Digital Signal Processing

(DSP) is a set of techniques permitting the

processing of digital and analog signals.

Analog signals must first be converted to

digital using analog to digital converters. DSP

technology was incorporated into the Texas

Instruments (TI) board used for this project.

The board is indicated in Figure 2.4. The

green object was the actual TI DSP board. On

the green board were all the logic circuits,

input and output pins, and a serial connector

cable input to connect to a desktop computer.

The serial connector is pictured in the upper

right hand corner of Figure 2.4. A computer

program—written in C—read the inputs to the

DSP board (the ultrasonic sensors, in this

case), determined the location of obstacles,

and sent a signal to the outputs (the vibrating

motors, in this case). The program was

downloaded to the board through the serial

connector cable.

Figure2.4 DSP Board

The board—essentially a microprocessor—

was instrumental in creating the eye-Pod, as it

acted as a sort of brain for the device. If the

board was the brain, the sensors were the eyes

and the vibrating motors were the nerve

endings. When the sensors (or eyes) detected

some manner of obstacle along the user’s

trajectory, the board (or brain) processed the

signal from the sensors and sent this

information to the vibrating motors (or the

nerve endings) which alerted the user to the

fact that an obstacle was near.


II.5. H-Bridge

An H-Bridge, pictured in Figure 2.5, was an

electronic device that allowed an input voltage

value to be scaled up to a higher voltage value.

Figure 2.5 H-Bridge

The H-Bridge took in two voltage values—an

input voltage and a source voltage—and

output a third voltage value—the output

voltage. The input voltage was a value

between 0 and 3.3 Volts. The closer the input

voltage was to the maximum value of 3.3

Volts, the closer the output voltage was to the

source voltage. This can be summed up in the

following equation:

(2.1)

As Equation 2.1 demonstrates, the input

voltage was essentially being scaled up to a

value between 0 and the source voltage. As an

example, if the input voltage was 1.65 Volts

and the source voltage was 12 Volts, the

output voltage would be 6 volts.

II.6. Case

A protective case was fabricated in the

machine shop to secure the DSP board, battery

packs, and electronics.

Figure 2.6 Protective Casing

The case was made out of acrylic plastic

scrap from the machine shop. Holes were

drilled into the plastic to allow entrance wires

connecting the DSP board to the sensors and

the DSP board to the vibrating motors. Velcro

was placed inside the case to secure the battery

packs which power the DSP board, the

sensors, and the motors.

II.7. Belt

A belt, pictured in Figure 2.7, was created


out of elastic fabric and Velcro. The belt was

designed to accommodate users with waist

sizes between 30 inches and 48 inches. This

was accomplished by using 10 inches of

elastic fabric flanked by 20 inches of Velcro

on each side. If an individual with a 30 inch

waist were to wear the belt, for instance, the

two Velcro straps would overlap entirely. If a

larger person were to wear it, the Velcro straps

would overlap less.

Figure 2.7 Belt

In this way, the eye-Pod can accommodate

both adults and children with a one-size-fits-

all philosophy. The three vibrating motors

were housed within the elastic portion of the

belt. They were spread evenly with

approximately 4 inches between them—

enough to insure that sensors’ vibratory zones

do not interfere.

III. Theoretical Considerations

The aforementioned sections have dealt with

the intended cost-effectiveness of our solution.

Instead of using there ultrasonic sensors, two

were used with the same functionality. By

angling the sensors (through the hinges

discussed in 2.2), left, right, and the center

areas were detected. The schematic in Figure

3.1 illustrates this principle.

Figure 3.1 Sensor Synthesis

1 2 3


The sensors indicated the distance to an

object by outputting a voltage value between 0

and 3 Volts. Higher voltage values

corresponded to farther objects. If sensor 1

had a high voltage value and sensor 2 had a

very low voltage value, for instance, there was

an object far to the left and another object

close to the right. However, if both sensors

had medium voltage values (in the 3 range

indicated in Figure 3.1) then there was an

object in the center. As demonstrated in this

section, then, only two sensors were necessary.

The flowchart in Figure 3.2 demonstrates the

flow and the processing of signals from the

left and right sensors to the DSP processing

board and finally to the motors.

Both voltages in range?

Activate Right Motor

Left Sensor Data

Right Sensor Data

Activate Center Motor

Activate Left Motor

Process Process

Yes

Figure 3.2 Sensor to DSP to Motor Flwochart


IV. Results and Discussion

A carrying bag kept the cased unit

comfortably tied to the user. A set of

adjustable straps were used for comfort.

Figure 4.1 Carrying Bag

The eye-Pod, pictured in Figure 4.2, was a

significant success. Indeed, the system was

intuitive and responsive. During the

technology expo on May 4, 2007, many

individuals came by to try out the device while

blindfolded. The results were convincing: the

eye-Pod can be picked up quickly due to its

intelligent design. Initially, the system was set

up to output 0 voltage when there were no

objects in the vicinity and a higher voltage as

objects got closer.

Figure 4.2 Wearable eye-Pod device

However, the team ultimately decided to

reverse its approach. When no objects were in

the vicinity, high voltage was sent to the

motors, making them vibrate at a high

intensity. Therefore, large vibration

essentially meant, “go!.” When an object

(such as a person, in our tests) interfered by

entering the eye-Pod user’s path, the voltage

would begin to decrease; as the object got very

close, the voltage would drop to 0. Although

one may naively dismiss this reversal as


arbitrary, it is indeed quite important for

safety. Whereas the first version had 0

vibrations when there were no obstacles, the

new version had vibrations when there were

no obstacles. This way, if the batteries lose

power or the device malfunctions, the user

will not continue walking: if the batteries stop

powering the device the voltage will drop to 0

indicating that the user should stop. In the

older system, the user would continue to walk

in this scenario with potentially harmful

consequences.

V. Summary and Conclusions

The eye-Pod provided a very inexpensive

and intuitive alternative to other obstacle

detection systems. It was developed entirely

by the 5 members of Team 20 to satisfy the

theme of assistive mobility. Indeed, the goal

appears to have been accomplished as the

project and demonstration were quite

successful. With a total cost under $150, the

system could supplement a visually impaired

person’s cane and allow that person to avoid

airborne obstacles.

References

[1] Espinosa, M.A. “Comparing

Methods for

Introducing Blind and Visually

Impaired People to Unfamiliar Urban

Environments.” Journal of

Environmental Psychology 18, 277–

287 (1998)

[2] Spencer, C., Blades, M. & Morsley,

K._1989.. The Childin the Physical

Environment: the development of spatial

knowledge and cognition. Chichester: Wiley.

[3] Cardin, Sylvain. “A wearable system for

mobility improvement of visually impaired

people.” Visual Computation. 23 109-118

(2007)


Appendix A: Code

/******************************************************************Filename: eyePod.cTeam 20 – Spring 2007******************************************************************//* include header files */#include "f2407_c.h" /* Defines register names and addresses */#include "funlib.h" /* Defines global variables and prototypes for function library */#include <math.h> /* Enables the DSP to do certain math functions */

/* define symbolic constants */#define pwmperiod 2000 /* 20KHz assymmetric PWM with a 40MHz CPUCLK */

void main(void){

/* initialized local variables */static int sensor1in = 0;static int sensor2in = 0;static int pwm1 = 0;static int pwm2 = 0;static int pwm3 = 0;

/* sensor scaling factor */static double s1scale = 1;static double s2scale = 1;

initGen();

initPWM(1, pwmperiod); /* MOTOR1 */ initPWM(3, pwmperiod); /* MOTOR2 */initPWM(9, pwmperiod); /* LED */

initADC();

initClock(3,0);

/* enter infinite while loop */while(1) {

/* sensor 1 */ sensor1in = getADC(0)*s1scale;

/* sensor 2 */sensor2in = getADC(1)*s2scale;

/* pwm1 */


if (sensor1in < 60){

pwm1 = 0;}else if (sensor1in < 100){






pwm1 = 330;}else{

pwm1 = 330;}

/* pwm2 */if (sensor2in < 60){








pwm2 = 330;}else {

pwm2 = 330;}

/* pwm3 */if ((pwm1 == 0) && (pwm2 == 0)){

pwm3 = 1500;}else{

pwm3 = 0;}

setPWM(1, pwm1);

setPWM(3, pwm2);setPWM(9, pwm3);

}

}


Appendix B: Circuit Layout

Ultrasonic Sensors

DSP

ADCIN 1, 2

Voltage Regulator

Op Amp 4342

PWM 1, 3

H - Bridges12V & Ground

Vibration Motors

3.3V & Ground

Voltage Follower(input buffer)

Analog Out

Set PWM

From 8x AA Batteries

Output Buffer 7414

Ground

Out 2Out 1

Vin

Control

6V & Ground

From 4x AA Batteries

Voltage Inverter

From DSP

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