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Ultrasonic Range-Finding Assistive Device forPersons with Low Vision

Aaron Morelli, Eric Osgood, Francis San Luis, Joseph San Diego, Michael Boyd, and Nathan HelenihiComputer Engineering Program

California Polytechnic State UniversitySan Luis Obispo, CA

{amorelli,eosgood,fsanluis,jsandieg,mjboyd,nhelenih}@calpoly.edu

Abstract—The mission of team Engineering 4 Eyes (E4E) is toconceptualize, design, and implement a device which will aidpersons with low vision in the detection of obstacles and/orhazards. Persons with low vision are unable to detect objectsthat are at or above waist level. Team E4E will create a devicefrom start to finish to solve this problem following certain criteriaobtained from potential users. The device will be discrete and willnot draw attention to the client. The device will not impair theuse of existing equipment used by the client. The device will beencased in an enclosure that would be able to attach to any cane.This will be done by using multiple Maxbotix Ultrasonic RangeFinders with an Arduino Nano board that uses an Atmega328microcontroller.

Index Terms—ATmega328, E4E, Low Vision, Maxbotix, Ultra-sonic

I. INTRODUCTION

The QL+ program [1] is a nonprofit organization created tofoster and generate innovatinos to aid and improve the qualityof life for those injured in the line of duty. By harnessingthe exceptional creative and engineering skills of students andfaculty at Cal Poly, QL+ succeeds in developing innovativesolutions that help our nations heroes to live, to work and toplay. At the state-of-the-art laboratory, teams of students andfaculty work together to identify solutions that will improvethe lives of Americas wounded patriots.

Existing tools for people with low vision community areinsufficient in alerting the user to all hazards and obstacleswhich may threaten their safety, health or independence. Issuesidentified to date include traffic signals, construction zones,bicyclists, and obstacles which may be at or above waistheight. Traffic signals present a computer based, and therefore

predictable, obstacle designed to interact with humans [2]. Adevice which can interpret those signals as a human wouldand prompt the user when it is safe to cross is feasible.Construction zones present an unpredictable obstacle. Oneinterviewee [3] pointed out that yellow caution tape is oftenat waist level, and place very near to a dangerous area, suchas an open hole in the ground. Bicyclists approaching frombehind are not always aware that a person has low vision, andmay expect the person to be aware of their presence. Lowhanging obstacles such as tree branches or bushes, which canbe sharp, threaten to injure a person with low vision who maywalk into them.

The Engineering 4 Eyes team, in collaboration with the QL+program, will develop a device that assists people with lowvision. Initial research was done to determine what deviceswere already on the market targeted towards the low visioncommunity. After reviewing the strengths and weakness ofthe already existing devices, marketing requirements for theE4E device were determined by interviews with multiplemembers of the low vision community. The E4E team beganconstructing engineering requirements based on the needsdesignated by the marketing requirements. These engineeringrequirements gave E4E the inspiration for the intial design ofthe device aimed to assist the low vision community. Testingof the alpha prototype was conducted to gather data on theresponse and effectiveness of the sensors interfaced with theselected microcontroller.

II. RELATED WORK

After conducting research on existing products, we foundseveral devices that were similar towards meeting our same

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project objectives. One patent we found was a locator devicefor the visually impaired [4]. This allowed the user to locatecertain objects by determining the distance and direction to theobject. Another product we found was a Polysensory mobilityaid [5]. The Polysensory mobility aid gave a combination ofaudible and tactile feedback to the user giving info about thelocation, distance, and brightness of whatever was in frontof the user. Perhaps the most radical of the existing productswe researched was a tongue placed tactile output device [6].The device would receive signals from a camera and sendelectronic signals to the tongue which would represent theinput image.

However, these products had several limitations that we planon improving on. This included detecting objects in the rangefrom approximately right below the user’s waist to directly infront of the user’s head. In addition, differentiating betweenstatic and moving objects and providing feedback throughmultiple mediums including vibration and audio. One of theproducts that we felt could be most improved on was theK-Sonar [7]. This product was our initial inspiration for ourdesign, but our design has rectified some of the weaknessesthe K-Sonar exhibited. All these devices were very expensiveranging from approximately $800-$1500. Our price will besubstantially less and more affordable for persons with lowvision.

III. THEORY

The development of our design began after the researchphase. This research phase contained several areas includingengineering and marketing requirements, design objectives,researching related projects, and interviewing potential clients.

The engineering and marketing requirements provided a setof standards on which to adhere and guide the conceptualdevelopment. These guidelines and specifications are displayedin tables I & II:

TABLE IMARKETING REQUIREMENTS

MarketingNumber

Marketing Requirement

1. The device is cost-effective.2. The device has a standalone solution that does not

require regular updates or servicing (upkeep).3. The device is highly pre-emptive and can give a

early warning for future obstacles.4. The end product is very presentable which is good

for investors and important clients.5. The system is reliable.6. The device is discrete and bystanders will not be

affected by or aware of the system.7. System must be compatible with existing assistive

devices such as canes, guide dogs, etc.

We conducted several interviews with potential clients,project supervisors, and other professors and specialists re-garding our project objectives. Each interviewee provided ourteam with the necessary knowledge to help address differentpreferences and design implementations during our conceptgeneration phase. Laura Weiss, a potential user with lowvision, gave us the following functionality ideas, interfacemediums, and personal preferences [2]:

TABLE IIENGINEERING REQUIREMENTS1

MarketingNumber

EngineeringRequirement

Justification

2 1.System will be loadedwith static range values(1-10ft) available for userselection using arrow but-tons 2.Sys- tem will notbe dependent on existingdata, only real-time pro-cessing 3. The softwaremust be less than 50mbsof memory.

The user should not haveto update the sys- tem inany way. Lack of data de-pendency en- sures thatsystem will not requireupdates of any kind. Thesoftware must be robustso that it doesnt need tobe patched.

1 1.System must cost lessthan $500 while fulfillingall requirements.

The product must be ef-fective and affordable sothat it is a realistic com-modity for the averagepopulation.

3,5 1.System will detect 95%obstacles in a 10 ft ra-dius 2.System must havean error rate of ≤ 1% 3.System should warn userwithin 1 second of obsta-cle detection

The system must be ableto explain to users wherenear obstacles stand toprevent possible injuries.The users safety is highpriority and therefore thesystem must not error of-ten.

6 1.System will provideoutput only to userthrough Bluetooth eardevice 2.System willonly take input from userthrough voice activationenabling button/trigger3.System must weighless than 10 ounces.

The system must onlycommunicate with thespecific user. Outsidercommunication must notbe viable because it willcause system problems.The system must be lightand unobtrusive so thatsurrounding populationis not aware.

4 1.Unused ports andcomponents will becovered with thin rubberplugs/tabs 2.Primaryfunctional system will be2 x 5 x 5.

Open/Visible componentsare not appealing to theeye. A smaller, compactsystem is more aesthet-ically pleasing than abulky system.

6 Provide audio feedbackthrough headphones ev-ery 5 seconds. Deacti-vate with status button onpackage.

Maintains reliability andefficiency.

5 It will have a casing thatcan withstand a 3ft drop.

Will need a protectioncase to protect the devicefrom shock.

5 Battery must be strongenough to provide 15 hrsof runtime.

Long battery life is cru-cial for reliability.

2,5 System must make an au-dible warning of 65dBwhen obstacle is detected.

Must be able to warn userif user is not wearing aheadset.

1 ”This specification exists primarily to identify the type of constraintswhich should be imposed on the design. As such, the specific valuessupplied are estimations and do not represent immutable constraints.”

• Phone application that could consolidate device function-ality

• Detect objects appearing in walkways. Dangling branchesproblematic

• Prefers not to use the cane so people do not see her as’blind’

• Vibration feedback for obstacle detection• Headset for audio feedback or bluetooth headset• Alert user of when to replace rechargeable battery• Wrist strap (the device similar to a digital camera)

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TABLE IIIDESIGN OBJECTIVES

DesignNumber

Design Objective

1. Design an effective solution. The top solution maynot be the cheapest, but the best system at the bestvalue.

2. Design a standalone solution. Thesoftware/hardware system must not requireregular updates or servicing (upkeep).

3. Design a solution that is highly preemptive innature. The system must be efficient in warningits users of prospective future obstacles.

4. Design a solution that looks presentable. Theproducts will be revealed to important clients andtherefore must be appealing at first encounter.

5. Design a reliable solution. System reliability isvery important when dealing with users who havelow vision.

6. Design two exact solutions simultaneously. Theclient needs to have a completed system on boththe east and west coast for presentation means.

• Minimal damage to the device if walking and tripping(drop test)

• Rubber coating or similar material enclosure for durabil-ity

• Buttons for turning On/Off• Size, shape, texture, and color important characteristics• Use the device with one hand• Buttons are easier interface than talking to device, less

disruptive to environment

John Lee, a rehabilitation specialists, provided a broaderdescription of other particular devices being used by peoplewith low vision. This information reflected how people withlow vision already use several devices in their daily use andwhat types of sensors are utilized for their functionality. Thefollowing information was noted [8]:

• Minimize the amount of devices carried. (Phone apps)• Important to have backup if a device stops working• Vision enhancing devices, magnifying images• Infrared/reflective dot system that moves mouse of a

computer by moving one’s head• Large remotes/keyboards with large buttons• Important to provide buttons that represent their function-

ality through color, shape, and texture

Kevin Taylor, a Kinesiology Professor at Cal Poly, statedhow people with low vision react and feel towards their visionloss. This information conveys how our group can restorepersons’ with low vision independence and freedom [9].

• Large difference between person’s with low vision andblind

• People lost independence with vision loss• Low vision people lost freedom to do things alone

Jennifer Allen-Barker, a specialist at Cal Poly’s DisabilityResource Center (DRC), provided us with the following infor-mation pertaining to walking around campus with low vision[3]:

• Walks at a comfortable speed. Important not to move veryfast.

• Curbs, cracks, low hanging branches, and debris onwalkways need to be detected

• Skateboarders and bicyclists traveling at fast speeds.(Awareness)

• Does not use cane• Detect barriers and poles holding up construction fences• Construction zones and caution tape perimeters problem-

atic• Find a safe path around hazardous and unpredictable

obstacles• Traffic signal beeping for crosswalks helpful audio recog-

nitionScott Monett, Quality for Life Administrator, provided spe-

cific guidelines on which the organization, QL+, funding thisproject had to adhere to. The following information addressedthose needs [10]:

• Obstacle detection device used in addition to the user’scane

• Reliability important• No patching or firmware/software updates. Standalone

device• Build two devices concurrentlyAfter analyzing all the information gathered from the in-

terviews, our group developed a design that incorporated ourproject guidelines and user preferences to give clients a simplestandalone obstacle detection device that would help themsafely navigate around objects while furthering their freedomto remain independent.

IV. APPLICATION

Our team developed an alpha prototype based off theconceptual design described in the previous section. Thisprototype consisted of the following parts:

• 1 Adruino Uno Microcontroller (ATmega328 Processor)[11]

• 2 Maxbotix LV-WR1 High Performance Weather Resis-tant Sonar Range Finder [12]

• 2 Ultrasonic Range Finder Maxbotix LV-WR1 MountingHardware [13]

• 2 Battery Holders [14]• 8 AA Batteries• 1 Medical Deluxe Folding Blind Cane• 1 Chameleon Enclosure Black [15]• 4 Vibration Motors [16]• 2 Voltage Regulators -5V [17]• 1 Basic 16x2 Character LCD screen• 1 Breadboard• 2 Push buttonsThe black enclosure contained the power supply (batteries

and battery holders) and the Adruino Uno microcontrollerboard which is attached to the upper fourth part of the cane.The enclosure case is mounted on the bottom of the cane.There are two push buttons located on the outside of theenclosure to turn On/Off the LCD and the system. The two ul-trasonic sensors are mounted on the top of the cane right abovethe black case. Each sonar sensor points in the same directionas the cane, however, each sensor has a different vertical

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orientation. The bottom sensor points below the horizontal(approximately 10 degrees below) detecting objects from themid-waist and below range. The top sensor points above thehorizontal (approximately 15 degrees above) detecting objectsfrom the waist to head range. The LCD is on the outside ofthe case connected to the breadboard and displays readingsfrom the sonar sensors primary for debugging purposes. Thevibration motors are attached to the top part of the cane wherethe user grips the cane to alert the user of an obstacle.

Fig. 1. Alpha Prototype

The system is an attachment to the cane. With power to thesystem from the push button and making sure the sonar sensorspoint in the same direction as the cane, the system is ready foruse. The detection works by relying on the user to sweep thecane from left to right. The sensors begin detecting obstaclesin the desired vertical range once an object is approximatelyeight feet away. The vibration motors receive a pulse signalthat vibrate the motors on and off at a frequency that isrelative to the proximity of an obstacle detected. The frequencycontinues to increase as the obstacle moves closer to the userand reaches is maximum frequency at approximately four feet.The vibration motors will continue to vibrate when an objectis less than four feet away, however, the frequency will notincrease.

In regards to our engineering requirements, the devicecosts approximately $320, weighs approximately 5-8 pounds,and detects obstacles within less than one second. With thisAlpha prototype functioning very accurately and efficiently,our group will be constructing a Beta prototype with the goalsto miniaturize the entire system, reduce cost, and maintain thesame fundamental functionality. The following is a list of goalsfor the next design and a list of new components that will beused to build the Beta prototype:

• (1) Arduino Nano V3 Microcontroller (ATmega328 Pro-cessor)

• (2) LV-MaxSonar -EZ3 High Performance Sonar RangeFinder

• (6) Vibration Motors• (1) 60 inch (5 foot) cane• Custom removable grip enclosure• (1) 8.4V 1400mAh rechargeable Nickel-Metal Hydride

(NiMH) battery pack• Switch Indoor/Outdoor Mode

• 3.5mm Headphone Jack -Audio output (high / low)• Approximately $150 cost• Weight approximately 1 pound• Audio feedback for depicting high and low obstacles

Fig. 2. Beta Prototype

V. TESTING

The project prototype was tested in two stages:• Component Testing.• System Testing.For component testing, each component was tested to make

sure it was both operating to specification and that it wascorrectly interfaced with the rest of the system. Examples ofcomponent testing included:

• Distance measurement capabilities of the ultrasonic sen-sors.

• Correct LCD readout of each measured distances, ininches.

• Vibrational feedback to the user when an object wasdetected.

Once each component was verified to be working, the entiresystem was subsequently tested. Since the goal of this projectis to sense any object in the users path, Engineering 4 Eyesfirst tested the width of the ultrasonic sensors signal widthagainst the sensors data sheet. Table IV shows the results:

TABLE IVULTRASONIC SENSOR SIGNAL WIDTH

Object Distance Signal Width4 feet 1 foot8 feet 2 feet

This data was congruent with the sensors datasheet andoptimal for the project.

Next the system was tested in a dynamic environment byhaving test users use it to navigate around campus. An unusualoccurance began to happen when the full prototype began to betested. The readings for both sensors would suddenly dip downto the minimum distance and slowly climb to the correct value.To solve this, a running average algorithm was implementedto reduce the noise being received on both sensors. This washighly effective, however it lengthened the reaction time ofalerting the user to an obstacle being deteced. Further testing

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was done to bring the reaction time to as quick as possible.During this testing, it was discovered that the proximity ofthe two ultrasonic sensors was the basis of the distance noise.One ultrasonic sensor would occasionally receive a pulse sentby the opposite ultrasonic sensor, creating a false reading.The simple solution was to completely remove the runningaverage algorithm from the readings, then begin alternatingeach ultrasonic sensor on and off. This brought the reactiontime of detecting objects back to a reasonable amount alongwith reducing, if not completely negating, any noise that wasbeing received.

Another problem that was noted while initially testing thealpha prototype was the inefficient usage of the microcontrollerwhile alerting the user with vibrational feedback. When anobject is detected, the program would turn the vibrationalmotors on, wait for half second, then turn the vibrationalmotors off. While the microcontroller is waiting to turn off thevibrational motors, no detection can occur. This would proveto be problematic if there was a rapidly approaching objecttowards the user. Trying to improve the efficiency of the micro-controller while alerting the user through vibrational feedback,a task-oriented programming structure was attempted to beimplemented. However, it was found to be extremely complexand with much memory overhead to be of any use.

After thorough testing of the alpha prototype, it was ableto detect objects up to eight feet away and notify the user oftheir existence, providing safe navigation.

VI. CONCLUSION

Engineering 4 Eyes was designated the task of creating areliable and cost-effective device to assist the low vision com-munity in detecting dangerous obstacles. After determiningthe existing products were both insufficient and over priced,interviews of persons with low vision were conducted tofurther determine the requirements that needed to be met bythe device. Engineering 4 Eyes designed a device that bothcosts less and works better than any currently existing productas per the marketing requirements set forth by the clients.After testing all system components and the integrated system,the prototype was deemed operationally functional. The nextsteps for this project are to create a beta prototype that issignificantly smaller and lighter and continue optimizing thecode.

REFERENCES

[1] Quality of Life Plus, “Ql+,” http://qlplus.org/, 2010.[2] L. Weiss, Nov. 2010.[3] J. Allen-Barker, Oct. 2010.[4] S. N. . Silverman, Hildy S. (4 Lowe Rd., “Identifier/locator device for

visually impaired,” Patent 5 508 699, April, 1996. [Online]. Available:http://www.freepatentsonline.com/5508699.html

[5] I. S. R. H. F. W. I. Moricca, Larry S. (Churubusco, “Polysensorymobility aid,” Patent 3 993 407, November, 1976. [Online]. Available:http://www.freepatentsonline.com/3993407.html

[6] W. K. K. A. M. W. Bach-y rita, Paul (Madison, “Tongue placed tactileoutput device,” Patent 6 430 450, August, 2002. [Online]. Available:http://www.freepatentsonline.com/6430450.html

[7] Bay Advanced Technologies, “The bat k-sonar,”http://www.batforblind.co.nz/, 2006.

[8] J. Lee, Oct. 2010.[9] K. Taylor, Oct. 2010.

[10] S. Monett, Oct. 2010.[11] Sparkfun, “Arduino uno board.” [Online]. Available: http://www.

sparkfun.com/products/9950[12] ——, “Ultrasonic range finder - maxbotix lv-wr1.” [Online]. Available:

http://www.sparkfun.com/products/9009[13] ——, “Ultrasonic range finder - maxbotix lv-wr1 mounting hardware.”

[Online]. Available: http://www.sparkfun.com/products/9010[14] ——, “Battery holder - 4xaa square.” [Online]. Available: http:

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//www.sparkfun.com/products/9682[16] ——, “Vibration motor.” [Online]. Available: http://www.sparkfun.com/

products/8449[17] ——, “Voltage regulator - 5v.” [Online]. Available: http://www.

sparkfun.com/products/107