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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”.
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