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Controlling a Wheelchair According to the Head Movements

Dimutu Upeksha*, Chameera Wijebandara, Chamila Dilshan Wijayarathna, Sameera Nilupul

Wijayarathna,Milinda Fernando, Akila Pemasiri, Suneth Vijaindu Gamage, Madhushi Niluka Bandara

Department of Computer Science and Engineering, University of Moratuwa, Sri Lanka

dimuthu.upeksha2@gmail.com; chameerawijebandara@gmail.com; cdwijayarathna@gmail.com;

sameernilupul@gmail.com; milindasf@gmail.com; akilapemasiri@gmail.com; svijayindu@gmail.com;

madhushib@gmail.com;

+94 -719-084-638

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Table of Contents

Abstract………………………………………………………………………………………………… 03

1.Introduction……………………………………………………………………………………….. 03

2.Materials and Method

2.1 Materials……………………………………………………………………………………….. 03

2.2 Method…………………………………………………………………………………………. 04

2.3 Implementation

2.3.1 Identifying the circuits embedded in the wheelchair……………………………………… 05

2.3.2 Identifying voice commands……………………………………………………………… 05

2.3.3 Controlling the movements of the wheelchair…………………………………………….. 05

2.3.4 Collision Avoider…………………………………………………………………………... 05

3. Results………………………………………………………………………………………………. 08

4. Discussion…………………………………………………………………………………………... 08

5. Conclusion………………………………………………………………………………………….. 09

6. Acknowledgement………………………………………………………………………………….. 09

7. Reference…………………………………………………………………………………………… 09

Appendices …………………………………………………………………………………………… 10

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Abstract - The thirty-year long civil war in our

country left many young and able-bodied men

and women with life-long disabilities. The

soldiers who fought for the defence of our

motherland and civilians caught in the crossfire

have suffered grievous injuries that led them to

be wheelchair-bound for mobility. However, for

some of the most severely injured war heroes,

even a wheelchair cannot provide mobility. The

motivation for this engineering research project

is to invent a wheelchair mobility control system

for an army officer who has lost all motor

control functionality below his neck and is only

able to move his head.

On a visit to the longterm-care facility in which

this officer resides, his only request was to be

able to move his wheelchair unassisted by

another. Our team of engineering undergraduates

set about designing a mobility control system

that is capable of interfacing with head

movements of the officer as that is the only part

of his body that can be moved. Based on a

lightweight harness worn on the head and using

a solid-state gyroscope proving a tilt-sensor

capability.

The mobility control system was then interfaced

to a battery-powered motorized wheelchair by

removing the joystick-based control unit of the

wheelchair and replacing it with our invention.

The prototype was successfully tested for the

complete set of motions that the disabled officer

wishes to make. The next step in this

engineering project is to further research on

providing safety and reliability features for the

mobility control unit.

1. Introduction - As a result of civil war

which existed for three decades there are

many soldiers who have been affected. So

as engineering students we thought that it is

our responsibility to utilize our knowledge

and capabilities in a way that is beneficial to

the country. The motivation behind this

project is to support for such an officer who

has not control below his neck.

At the moment he is staying at Mihindu Seth

Madura. What we noticed was that he

cannot do anything of his own. What he

requested mainly was a way to move his

wheel chair of his own.

So we came with up an idea to carry on a

project which results in making a wheel

chair which can be moved according to the

head movements of the officer’s head.

2. Materials and Method

2.1 Materials

Material Quantity

LYEB103 Wheel

Chair(Electric Wheelchair)

1

Arduino Mega 2560

development board

1

Arduino Compatible Voice

recognition Module

1

ZCT245AN-TTL 2-axis tilt

sensor

1

HC-SR04 Ultra Sonic

range finders

8

PIC 16f876 micro

controller

1

10kΏ surface mounts 40

(for R2R Ladder)

40

330Ώ surface mounts 10

7805 Regulator IC 1

4MHz crystal oscillator 1

4

2.2 Method

The overall logic behind this project can

be illustrated as follow. For further

details refer the state diagram in the

appendices

Power on the

wheelchair

Power In

Wheelchair

Check voice

command is

“Drive”

Start Head

Control

Obstacle is

detected

Stop the movement

towards the obstacle

Check voice

command is

“Stop”

Stop Head

Control

Power off

Yes

Check voice

command is

“Manual”

Recoded user

guidance is played

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2.3 Implementation

2.3.1Identifying the circuits embedded in the

wheelchair

The wheelchair selected was LYEB103.

Dissembled the control unit in the

wheelchair.

We identified that a removal of one

component will even lead the wheelchair to

be locked, to the safety of the user.

Then we identified the inputs and outputs of

the joystick by the means of an oscilloscope

(Figure (a))

We supplied the analog voltages using two

variable resistors and deceived the circuit.

As the prior step was successful we supplied

digital values using digital to analog

converters (Figure (b))

2.3.2 Identifying the head movements.

ZCT245AN-TTL 2-axis tilt sensor was used,

which is connected to the head of the user.

This can measure the angles with reference

to the x axis as well as the y axis of the

horizontal plane(Figure (c)).

Through a serial interface the angle

measured by the tilt sensor is caught by an

Arduino Mega board which contains the

driving program of the wheelchair.

2.3.3 Identifying the voice commands

Arduino compatible, voice recognition

shield was mounted on the Arduino Uno

board.

It can be configured to recognize 15 voice

commands.

It generates and sends a signal to the

Arduino Uno board according to the

command received.

The commands used are “Drive”, “Stop”

and “Manual”.

2.3.4 Controlling the movements of the

wheelchair

According to the head movements

According to the input signal (which

was generated by tilt sensor),

Arduino Uno board generates the

relevant digital signal.

Those signals are converted to

signals which are analogous to the

output signals of the joy stick and

given to the relevant ports of the

control circuit.

According to the voice commands

The original control circuit uses

inputs from switches to control

power and speed.

According to the input signal (which

was generated by Arduino

compatible, voice recognition),

Arduino Uno board generates the

relevant signal.

The circuit is developed so that the

tasks done by switches take place

according to the generated signals.

2.3.4 Collision Avoider

8 sonar sensors were used to identify the

barriers which are along and on the sides

of the moving wheelchair.

By measuring the distance to the

obstacles from the wheelchair, position

of the obstacle is found.

By using a clock interrupt the obstacles

are checked in regular intervals and the

movement of the wheelchair is

terminated if there is an obstacle in the

relevant direction

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1 2 3 4

8 6 7 5

1. Vref

2. Vcc

3. X

4. Y

5. X

6. Y

7. GND

8. Vref/ Not Connected

Figure (a)

Figure (b)

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Figure (c)

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3. Results - Some quantitative factors were

taken into the accountant to measure the

accuracy and reliability of the system

The response time of the tilt sensor – The

time taken between giving the input and

receiving the output (response time) was

measured

In the final result the response time is 10ms

(approximately) and at the time of stopping the

wheel chair, in first few test sessions a

significant time was taken to slowdown and to

stop. But after few improvements it was reduced

and a sudden stop can be handled now.

The accuracy level of the voice recognition

module – To measure the accuracy level of

the voice recognition module testing was

carried out by giving voice commands and

getting the responses.

4. Discussion - The movement detecting

module of the developed system is very

flexible as it takes relative readings. That

makes it enable for the user to operate the

system having any initial position. The user

can move not only to a limited number of

directions, but he also can move to any

direction that he wishes. Also he can turn,

while moving forward or backward.

The voice recognition and responsible

module works accurately in general

circumstances. But in some practical

situations when there is a very large noise

this module may not be able to recognize the

commands and distinguish between the

commands.

The obstacle avoidance module of the

system works in proper manner. But it needs

a well maintenance because the dust

particles on the sensors may reduce its

detecting ability and the accuracy.

The main benefit of this system is this can

be easy interfaced to any kind of wheelchair

through an appropriate motor controller and

the voice commands can be tailored to the

each user according to their preference.

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25

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75

100

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225

1st 2nd 3rd 4th 5th

Res

po

nse

Tim

e (m

s)

Testing Session

0

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40

50

60

70

80

90

100

1st 2nd 3rd 4th 5th

Acc

ura

cy L

evel

(%

)

Testing Session

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5. Conclusion - The prototype we developed is

fully functional and it provides a very good

solution to the identified problem.

Even though in the short term we aimed

only for this particular army officer, he is

not the only one with this problem. There

are many army soldiers and officers in the

same condition in Sri Lanka.

Moreover considering about the whole

world it has been estimated that there are

more than 50,000 individuals who don’t

have use of their arms and legs

(quadriplegics). Majority of them are war

heroes of developing countries as Sri Lanka.

As this invention is a safe, reliable and

economical for the purpose, these people

would be able to upgrade their living

standard at least for some extent by using

this product.

So our idea is, that by expanding this

product we would be able to support to the

social and economical development as a

whole, while supporting to those suffering

lives.

6. Acknowledgement - First on foremost, we

would like to thank, Head of the Department

of Computer Science and Engineering,

University of Moratuwa, Eng. Lt. Col. Dr.

Chandana Gamage who guided us through

doing this project, provided important

advices, helped us in difficult periods and

provided equipment for our project. His

willingness to motivate us contributed

tremendously to our project. Besides we

would like to thank CSE staff who helped us

by giving advices and providing equipment

which we needed.

Also we would like to convey our gratitude to

Dr. Upali Khomban, President of Computer

Science and Engineering Society, who gave us

necessary information to proceed in project. He

always communicated with us, look at current

progress and motivate us to do the project. We

also thank Lt. Col. Athula Samarasinghe who

motivated us to do this project.

We would also like to convey our special thanks

to “Brandix Apperal Ltd” who donated an

electric wheelchair for this task.

In addition we like to thank Maj. Madugoda of

“Mihindu Seth Madura” and official there, who

helped us to go there and do necessary tastings.

They also helped us in finding a suitable

motored wheelchair for our project.

At last but not in least we would like to thank all

who helped and motivated us.

7. References –

http://arduino.cc/en/Main/ArduinoBoard

Mega/

Data sheet of Arduino Compatible

Voice recognition Module

Data sheet of ZCT245AN-TTL 2-axis

tilt sensor

Data sheet of HC-SR04 Ultra Sonic

range finders

Data sheet of PIC 16f876 micro

controller

Data sheet of 10kΏ surface mounts 40

(for R2R Ladder)

Data sheet of 330Ώ surface mounts

Data sheet of 7805 Regulator IC

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Appendices

The system architecture is depicted below.

Main sensor which

tracks the head

movement

Arduino Board

(PIC) Voice Recognition

Model

R2R

Ladder

Tilt Sensor

Main Circuit

Board of Wheel

Chair

MP3 module

for voice

responses

US4

US3

US2

US1

Module

converting

digital signal

in to analog

To activate the

system by voice

command

Show the current

state

Of the wheelchair

To avoid

obstacles and

for safety

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The state chart of the system is depicted below