Design and Development of Autonomous Robotics Wheelchair Using

Embedded System

Pankhuri Singh, Anmol Agarwal, Sharad Rajput, Sapna Katiyar*

A.B.E.S. Institute of Technology, NH-24, Vijay Nagar, Ghaziabad (UP) 201009,

(e-mail:pankhurisingh0@gmail.com, anmol1500@gmail.com, er.sharad786@gmail.com,

sapna.katiyar@abesit.in)

Corresponding Author: sapna.katiyar@abesit.in

ABSTRACT

Today is time of automation. Everything is done automatically. So automatic wheelchair is an important

design for the disabled and elder persons. It will be very useful for these persons to move easily and freely. It

includes various technology such as wireless communication, DIP (digital image processing), obstacle

detection, speed controller and light sensing. On the other we propose a design in which it will provide the

information about the thing around it. The seat of it may be adjust as per as the requirement. It includes

different types of sensor such as light, IR sensors.

Keywords: Wireless communication, Reclining seat, speed adjustment, Obstacle detection, DIP, IR sensor.

I.INTRODUCTION

There are lots of persons who cannot walk very easily

due to problem in their legs. Due to blindness,

paralysis, polio and many other deficiencies,

thousands of people don`t move any step. This

automatic wheelchair is so essential for these people.

The story of wheelchair is not as modern as it is

related to the past. In the past, wheelchair was

powered with human hands but it was difficult to

move hundreds of meter. So automatic wheelchair is

an advanced and modified design of it. This

wheelchair is powered by rechargeable battery and

the time of charging is very less. It is operated and

controlled by microcontroller 8051. Body

temperature, blood pressure, heart beats are measured

by different components of it. It is featured by

automatic speed control, wireless communication,

digital image processing. These all technologies

make it multi-functioning and multi-purpose

wheelchair. There are many advantages over other

existing wheelchairs. These advantages make it

costly but very essential and useful for handicapped,

disabled person, patients, paralyzed persons and

elders. These advantages are as following.

1. Speed- The speed of it is controlled easily as

per as requirement. Speed can be set

digitally. It can acquire maximum speed of

up to 5 KM/hr.

2. Obstacle sensitivity- This wheelchair is

featured with sensors. Obstacle sensor is an

important device in it; it identifies the

obstacle and gives a beep signal. If obstacle

is small (height 2-5 inches) it can rollover it

otherwise turn automatically in the right

direction.

3. Global positioning system- It can traced

very easily by GPRS. Its position is shown

in its screen and the wireless connected

computer. So the person can move it

according to the target location.

4. Digital Image Processing- The main

objective of this work was to create an

interface that allows a person to drive a

wheelchair, using only facial expression in

an easy, practical and robust fashion.

5. Reclining seat- The wheelchair is

adjustable; we can easily change its height.

It can be converted as bed seat.

6. Light sensor- This wheelchair includes light

sensor. These sensors are used to detect the

sun light and after detection it turn-off its

light which are switched on in night to show

the path.

II.DESIGN

The design has been divided into several subsystems to

reduce the complexity of the project. Every subsystem is

designed, tested independently and then integrated in to a

whole wheelchair. That’s why it’s important to study the

description of all subsystems.

The subsystems to be discussed are:

Frame

Reclining Mechanism

Drive Motors Controller system

Software testing

Motor Controller / Microprocessor Interface

Obstacle Detector

Light Sensor Unit

Digital Image Processor Unit

Frame- The purpose of the frame is to provide

comfortable support to the patient and support for the

other on-board subsystems. The frame must be able

to accomplish this goal without any deformation. But

to provide safety to the patient in any situation is the

main purpose of frame.

Reclining mechanism- The patients spend most of

their time lying on the bed, and due to that the

wheelchair must be able to recline much like a

hospital bed(fig1.1). The wheelchair provides the

ability for the back of the seat to move through a

range of positions from 90degree to an acute angle

from horizontal.

(fig1.1)

Drive motor- The Drive motors are basically used to

generate controllable torque. Each rear wheel

requires a drive motor to provide support for steering

the wheelchair and to decrease the torque

requirement per motor. Thus in total two drive

motors are used.

Controller system- It is the “brain” of the

wheelchair as it is responsible for accepting input

signals from the sensors to determine the user’s

commands and then performing the actions.(fig1.2)

The drive motor and the reclining mechanism motor

are controlled by controller system.

fi

Software testing – The heart of the system controller

is the software of the wheelchair.(fig1.3) It performs

necessary computations, determines the output and

then makes decisions so that system controller can

act according to the user. The software responsibility

is to correctly carry out the requests of the user and,

at the same time, prevent any harm to the user. It also

controls the wheel speed by maintaining the feedback

loop.

MAIN PROGRAM COP RESET VECTOR

PERIODIC INTERRUPT

Left Encoder Interrupt Right Encoder Interrupt

(Fig1.3)

Motor controller/microprocessor interface- The

system controller accepts and provides the TTL logic

level signals. The logic outputs are converted into

signals that are compatible with various motors in the

design and the signals from the various sensors are

made compatible with the logic inputs. The

wheelchair design includes motors that are controlled

by the microprocessor in order to provide necessary

capabilities in the design. Two permanent magnet

motors and two smaller DC motors are used to propel

the chair and to release the braking mechanism

respectively. While protecting both the motors and

the microprocessor from damage, the motor

controller is also responsible for coupling the

microprocessor signals to the motors. The signals

provided by the microprocessor are:(table1)

SIGNALS DESCRIPTION

BRAKE Mechanical Brake

ENABLE Enable the drive motors

RIGHT PWM PWM signals for right motor

LEFT PWM PWM signals for left motor

RIGHT BRAKE Right wheel dynamic braking

LEFT BRAKE Left wheel dynamic braking

Left

forward/Recline

on

Enable=1 left wheel direction

Enable=0 controls reclining

mechanism of motor

Right forward/

Recline direction

Enable=1 Right wheel direction

Enable=0 controls reclining

mechanism of motor

UP LIMIT Upper limit of reclining

mechanism

DOWN LIMIT Lower limit of reclining

mechanism

UP COMMAND Raise the seat back

DOWN

COMMAND

Lower the seat back

RIGHT

ENCODER

Pulses from right encoder

LEFT

ENCODER

Pulses from left encoder

(table1)

Obstacle detection unit-

Concept-“Action according to the information”

The four necessary parts for the automatic

wheelchair modulates the information:

Map of the Area: The map contains the

information such as routes, places we can

go, buildings and other obstacles. The view

of the small area is provided by this

information.

START

Initialize Interrupts

and PWM subsystems

suystems

Reset COP timer

Process Recline

Commands

Process Brake

Override switch

Read Pressure sensor

Determine motor set

points

Print diagnostic

information

START

Stop motors

Restart software

START

Record left and right

encoder counts

Zero encoder counts

Compute new PWM for

each wheel: u[n]=u[n-1]

+1.03*e[n]-0.97*e[n-1]

Return

Increment left

encoder counter

Increment right

encoder counter

START START

Return Return

Shortest Route: After retrieving the map

the shortest route can be determined and

evaluated but, the time complexity of it is

O(n3) [8] . So it is efficiently provided by

the other means.

Positioning: The wheelchair needs to know

its current position and location and then

accordingly can decide how to move to the

target entry.

Obstacle Detection: Because our

environment is very dynamic, there must be

some minor obstacles that cannot be listed

on the map. The wheelchair must have some

mechanism to sense these obstacles in order

to avoid accidents. The application of

Obstacle Detection can be completed with

the following procedure:

In server site, by using wireless positioning

technology the position of each node on

roads and target places can be retrieved. And

then the retrieved information is recorded on

the map. After building this map, the server

can compute the shortest route with time

complexity O(n3).

When an automatic wheelchair enters into

the area, the mobile device built in the

wheelchair will get the map of the area by

automatically communicating with the

server of that small area.

After getting the map of the small area, user

can use various input methods, such as

keyboard, mouse, or even speech

recognition to choose one of the places

listed on the map. And then the request for

the shortest route to the server is send by the

automatic wheelchair.

The server in response sends back the

shortest route. And then according to this

route the automatic wheelchair will go to the

target. While building the map, the route

between nodes on the road is assumed to be

straight. Also, the wireless positioning

system is used by automatic wheelchair to

get the information of current location.

Now the automatic wheelchair can compute

the direction D, according to the following

equation where Pc is the current position

and Pn is the position of next node through

Wheelchair will pass.

Dn = Pn - Pc eq(1)

With wireless positioning devices the

current direction of the automatic

Wheelchair Dc can be iterated by having the

head and tail of wheelchair. The difference

of direction D can be computed as the

following:

eq(2)

D can be expressed as a two dimensional

vector (Xd :Yd). Therefore, the radius θ to

be turned can be computed as the following:

√

√ eq(3)

Light Sensor- To sense the environment or room

lighting conditions, Ambient light sensors are

included in the wheelchair, which allows to adjust the

sensors to glow to comfortable levels for the

patient.(fig1.4). The range of "comfortable levels"

depends on the room's light.

(fig1.4)

Digital Image Processing Unit- The aim DIP used

in this design is to create a prototype of a wheelchair

command interface that do not require hand usage.

Facial expressions are used provide the necessary

visual information for the interface to recognize the

user commands. The digital camera captures the

facial expressions which are interpreted by an

application running on a laptop computer on the

wheelchair. The software includes digital image

processing algorithms for feature detection, such as

color segmentation(fig1.5) and edge detection,

followed by the application of a neural network that

uses these features to detect the desired facial

expressions.

Segmentation Result

(Fig1.5)

Edge detection is used to capture the shapes inside

the face(fig1.6). For this canny operator is used

which extracts the high frequency components.

Edge detection contains three steps: Filtering,

Enhancement and Detection.

1) Filtering: Sometimes images are corrupted by

noise which is the random variations in intensity

values. Some common types of noise are salt and

pepper noise that contains random occurrences of

both black and white intensity values. Other is

impulse noise and Gaussian noise. However, there is

a trade-off between noise reduction and edge

strength.

2) Enhancement: It is necessary to determine

changes in intensity in the neighborhood of a point in

order to facilitate the detection of Enhancement edge.

Emphasizes pixels where there is a significant change

in local intensity values and is usually performed by

computing the gradient magnitude.

3) Detection: Some methods should be used to

determine edge point as many points in an image

have a nonzero value for the gradient, and not all of

these points are edges for a particular application.

Thresholding is one of the criterions used for

detection.

Edge Detection Results

(Fig1.6)

III.CONCLUSION

This paper presents the architecture of Automatic

Wheelchair using embedded system. By using

similar coding environment with PC based solution,

the size and power consumption are minimized.

Features associated with it are Omni-direction

wheeled, goal-seeking, obstacle avoidance, wall-

following, light sensing. The future prospects in

relation to automatic wheelchair are to improve its

mechanical properties, reliability and clinical

feasibility.

IV. REFERENCES

Matt hortman, project leader matt barker and

karl palutke, Mercer University, school of

engineering, October 10,1997,”Critical

design review for the inexpensive

quadriplegic power wheelchair”.

G.Bourhis, O.Horn, A Pruski “An

autonomous vehicle for people with Motor

Disabilities “IEEE Robotics & automation

magazine” ,VOL.8.pp.20-8-2001

The 33rd

Annual conference of the IEEE

industrial Electronics society (IECON) ,5-8-

2007,Taipei,Taiman “Development of

Autonomous Robotic wheelchair controller

using Embedded system”.

Bruno martins, Eduardo volgode, Pedro

faria, and Luis Paulo reis, “Multimedia

interface with an intelligent wheelchair”.