DESIGN OF A PROSTHETIC ARM USING FLEX SENSOR

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International Journal of Electronics and Communication Engineering and Technology
(IJECET)
Volume 8, Issue 2, March - April 2017, pp. 01–06, Article ID: IJECET_08_02_001
Available online at
http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=8&IType=2
ISSN Print: 0976-6464 and ISSN Online: 0976-6472
© IAEME Publication
DESIGN OF A PROSTHETIC ARM USING FLEX
SENSOR
Dr. V.M. Vyawahare
Assistant Professor & Project Supervisor, EN Department, P.C.E. Nagpur (MS), India
Dipali Pardhi
Student, B.E Final Year, EN Department, P.C.E. Nagpur (MS), India
ABSTRACT
Prosthesis is an artificial device that replaces a missing body part. In medicine,
prosthesis is an artificial device that replaces a missing body part, which may be lost
through trauma, disease, or congenital conditions. Prosthetic amputee rehabilitation
is primarily coordinated by a prosthetist and an inter-disciplinary team of health care
professionals including psychiatrists, surgeons, physical therapists, and occupational
therapists. A person's prosthetics should be designed and assembled according to the
patient's appearance and functional needs.
For instance, a patient may need transradial prosthesis, but need to choose
between an aesthetic functional device, a myoelectric device, a body-powered device,
and an activity specific device. The patient's future goals and economical capabilities
may help them choose between one or more devices.
Key words: Prosthesis, Flex sensor, Data glove, Robotic arm, human hand replica.
Cite this Article: Dr. V.M. Vyawahare and Dipali Pardhi, Design of a Prosthetic
ARM Using Flex Sensor, International Journal of Electronics and Communication
Engineering and Technology, 8(2), 2017, pp. 01–06.
http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=8&IType=2
1. INTRODUCTION
Many people incur an illness or experience an accident that results in the loss of a limb. They
may also have been born with a congenital condition in which one or more of their limbs are
missing. Fortunately, there are artificial limbs that enable those people to still do things such
as run, walk, reach, and grip. These apparatuses are known as prosthetics. A robotic arm is a
robot device, which can perform similar functions to a human arm. Robotic arms are the
important part of almost all the industries. In industries, a robotic arm performs various
different works such as welding, trimming, picking and placing etc. Moreover the biggest
advantage of these arms is that it can work in hazardous areas and also in the areas which
cannot be performed by human. The main objective of this research work was to design and
construct a prosthesis that will be strong and can perform assigned task. The hand is the one
of the most complex and load bearing part of our human body which act as an input and

Dr. V.M. Vyawahare and Dipali Pardhi
output device to human. These goals where targeted by using flex sensor. A sensor a device
which detects or measures a physical property and records, indicates, or otherwise responds to
it , and sensing plays an important role in robotics. Robotic arm manipulators can have
different configurations. Few of these constraints can be effectively mapped from the human
arm domain to the robot’s restricted joint space. In this paper a general method of mapping
human motions to the robotic arm domain has been demonstrated. The arm moment is
reciprocated almost exactly by the robotic arm. Any human arm moment can be mapped on to
any of the robotic arm manipulator.
2. ROBOTIC ARM USING FLEX SENSOR AND
MICROCONTROLLER:
The block diagram consists of sensor, microcontroller, instrumentation amplifier, servomotor,
IC regulator, LCD.
Figure 1 Flex sensor based robotic arm using microcontroller.
2.1. Flex Sensors
A flex sensor or bend sensor is a sensor that measures the amount of deflection or bending.
Usually the sensor is stuck to the surface, and resistance of sensor element is varied by
bending the surface. Flex sensor are analog resistors. They work as an analog voltage divider.
Inside the flex sensor are carbon resistive elements with thin flexible substrate. More carbon
means less resistance. When the substrate is bent the sensor produces resistance output
relative to the bend radius. The flex sensor achieves great form-factor on a thin flexible
substrate. When the substrate is bent, the sensor produces a resistance output correlated to the
bend radius as shown in Figure 2. The variation in deflection or bending of flex sensor results
in variation of resistance itself. The signal conditioning circuit is used to read these resistance
changes and it is given to ADC. ADC converts these values into equivalent digital values

Design of a Prosthetic ARM Using Flex Sensor
Figure 2 Flex sensor bend proportional to varying degree of resistance
Figure 3 Basic diagram of flex sensor
2.2. Microcontroller
The micro controller is responsible for the controlling the action of robotic arm. It receives
input variation of the flex sensor through ADC, which is given in form of proportional current
variation to the motors attached to robotic arm. It consists of four ports (i.e. A,B,C,D).
Atmega16 is based on enhanced RISC. In this Port A is used for the output. Port B is
connected to LCD, PORT D is connected to servo motor.
Figure 4 Diagram of AT Mega16 microcontroller

3. METHODOLOGY
In this design we will be using flex sensor to sense the motion of our fingers. We will be
using 5 such sensors that will be arranged in a hand glove, which will make the sensors
comfortable to wear. The Other part i.e. mechanical hand will consist of 5 fingers that will be
controlled using 5 servo motors i.e. one motor for each finger. All together it will be one hand
consists of 5 flex sensor one in each finger. Bend of fingers is analysed using AT Mega 16
microcontroller and this data will be send to another port via serial communication, the
microcontroller will generate appropriate PWM signals for controlling servo motors. The
complexity of the project is reduced by properly categorising the whole project into sub
design. It makes it to make a better design and work effectively. The readings of each fingers
where measured in the form of voltage, while the movement of each fingers will be given
with respect to angle. Thus to relate voltage with respect to angle we plot the graph of each
finger and then we get a linear graph. By calculating equation of each line we can relate each
other easily. Then by knowing only one of the value we can calculate another value very
easily. This equation will be then feed to code of microcontroller connected in sensor unit
then it will generate appropriate angle for respective finger. Ones it is done all data will be
formatted in particular packet so that it will be easily handled and send over serial port.
Figure 5 Experimental setup
4. GRAPH REPRESENTATION
To plot graph we took the readings of flex sensor with hands, then bend each finger and move
the servo motors manually to set the desired angle.

Design of a Prosthetic ARM Using Flex Sensor

5. FLOW OF ACTION FOR THE ROBOTIC ARM
• Read values of the sensor
• Micro controller processes the sensor values
• Send values from microcontroller to servomotors
• Pick up the objects
• Place at the required position
• Bring arm at original position
6. CONCLUSION
The paper discusses a hardware and software co design of robotic arm controller using five
servomotors employing micro controller. This Robotic Hand is useful for the society as well
as industrial application and it works successfully at the time of demonstration.
REFERENCE
[1] Chandrasekhar P.Shinde,”design of myoelectric arm”, international journal of advanced
science, engineering and technology. ISSN 2319-5924,Vol 1, Issue 1, 2012, pp 21-25.
[2] “A Survey of robotic hand-arm systems” international journal of computer application
(0975-8887), volume 109-No. 8, January 2015.
[3] “flex sensor based robotic arm controller using microcontroller”, journal of software
engineering and application,2012,5,364-366.
[4] “Design of robotic hand using flex sensor”,International journal of advanced research in
electronics and communication engineering, volume 4, issue 12, December 2015.
[5] Parth Ranjan Singh, Prathishastry, Jagadish D. Kini, Farzadtaheri and T.G.Giri Kumar,
Design and Development of a Data Glove for the Assistance of the Physically Challenged.
International Journal of Electronics and Communication Engineering & Technology
(IJECET).4(4), 2013, pp. 36–41
[6] L. Shrimanth Sudheer, Immanuel J., P. Bhaskar and Parvathi C. S. ARM 7
Microcontroller Based Fuzzy Logic Controller for Liquid Level Control System.
International Journal of Electronics and Communication Engineering & Technology
(IJECET).4(2), 2013, pp. 217–224

DESIGN OF A PROSTHETIC ARM USING FLEX SENSOR

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