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Name : Rajendra B Khatri
Class : CSCI-303
Professor : Dr. R. Daniel Creider
PROSTHETIC ARM
Abstract: This project focuses on the design of a myogenic prosthetic arm to mimic the
movement of the human arm. The number of patients having upper limb amputations has been
increased due to large number of accidents. The initial designs of prosthetic hands have minimal
usability and are costly. This paper provides the source for a prosthetic limb by examining
alternative mechanisms for acquiring and transmitting data.
The prosthetic arm is designed to provide the tactile perceptions experienced by the human body
by integrating a network of sensors into the nervous system. Arm operates based on feedback
received from these sensors. Coordinate reference systems are used for the transformation of
input signals into the desired output. Many models have been proposed that work using
electromyogenic (EMG) signals generated by muscle contractions. All the designs proposed have
some flaws, but they have improved. EMG based prosthetic arm exhibits a full range of motion
required to grab an object. It has also increased the degree of freedom and the number of grip
patterns. In addition to driven thumb roll articulation, which is not seen in commercial products,
it includes five independently actuated fingers.
INTRODUCTION
The prosthesis is a medical device that structurally and functionally replaces an
arm. The hand is a complex part of the human body. There are many people who have lost limbs
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through accidents or by birth and face a lot of problems in performing the normal activities of
life. Due to advances in engineering and computer science technology, prosthetic limbs are
designed as a substitute so that amputees can perform normal activities easily. The previously
designed prosthetic hands are very costly and are not affordable for many individuals. Our main
goal is to develop a cost-effective prosthetic hand that would be easy to manufacture and
maintain. Furthermore, it must be able to carry out daily life activities (Gargiulo et al., 2013).
There are four types of prostheses depending on missing part. Our design is used particularly for
trans-radial amputation. A trans-radial prosthesis replaces an arm below the elbow ("Prostheses Prosthetics: Artificial Limb Information", 2019). The hand must use sensor to read the muscle
activities to cause movements. The data obtained from sensors is used for interpreting muscle
movements. Many experimental hands use the EMG signal pattern recognition system to discern
the motion or gesture of the hand. This approach is difficult to implement because of the limited
hardware memory in the microcontroller. Researchers are trying to improve the previously
designed prosthetic arms but despite these technological advances, they are still limited in terms
of the sensory feedback received, degrees of freedom and methods of distinguishing various grip
patterns of human hands. Most amputees expressed a desire for improved mobility, higher
grasping speeds and powers, natural movement and object contact and enhanced cosmetic
appearance. Some improvements have been made to increase the degrees of freedom and reduce
the weight of the prosthetic arm, for example, many prosthetic hands are using underactuated
mechanisms and shape memory alloy actuators. The upper limb prostheses still have enough
room for improvement. This paper describes the improvements in the design of prosthetic arms
due to advances in computer science technologies.
LITERATURE REVIEW
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The prosthetic counterparts of the hands have undergone significant evolution and
practical advances due to its crucial role in controlling and handling of an object. Many
institutions have done research on the design and construction of the robotic arm. The previously
designed prosthetics were either functional or cosmetically appealing and their focus was on the
mechanical problems that are functioning and designing. There are basically three types of
prosthetics that are cosmetic prosthetics, body-powered prosthetics and myogenic prosthetics
(2019).
Cosmetic Prosthesis
They are intended for those people who need them to carry out only the major functions
of the body. They are inexpensive but can only be used for holding light objects as they offer
limited degrees of motion (2019).
Body-powered prosthesis
Body-powered prosthetics are the most widely used, simplest and most commercially
available prostheses that allow for a greater degree of freedom using cables that operate the
prosthetic arm through muscles relative to the region. Body-powered hooks were functionally
capable, but they did not imitate the human hand's size or shape. It is powered by a cable and
harness system ("Hanger Clinic", 2019). Exaggerated movement of the body pulls a hook or
hand opening cord. Relaxing the tension on the cable close the hook or hand. A lot of energy is
required to operate the prosthesis thus producing more strain on the amputee's body which can
cause shoulder problems and unbalance the anterior muscles (Salem, Mohamed, Mohamed & El
Gehani, 2013) (Lake & Dodson, 2006).
Myoelectric Prosthetics
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The myoelectric prosthesis does not require the patient to perform strenuous muscle
contractions instead it exploits the residual muscles of the amputated limb's capacity for
electrical activity. The prothesis amplifies the signal when the action potentials are given and
use the electrical signals to drive the motors operating the corresponding arm part. Myoelectric
prosthesis allows for a much higher degree of freedom as compared to the other types. They are
typically more powerful than the traditional ones ("Myoelectric Prosthesis", 2019).
Electromyography
Electromyography (EMG) is the measure of signals of muscle activity with the help of
electrodes to detect changes in the muscle to control the movement of the hand. The signal is
detected by placing electrodes on the surface of the skin surface. Electrodes and sensors make
electrical contact with the skin, with two of them in a target muscle and the third closer to the
corresponding bone. Because the EMG surface is non-invasive, it is the most common and
effective technique used to program a prosthesis. Electrodes are made of stainless steel and feel
the muscle's movement. The signal obtained is very small, so differential amplifiers are needed
to increase the size of signal. The EMG is decoded to produce a voltage that matches the
corresponding operation of the muscle. The muscle fiber responses activate the sensors of the
electrode; the resulting signals are decoded and processed. One downside is that the signal
strength depends on the performance of the voltage and the contractions of the muscle.
The initial designs of myogenic prosthetic arms have a limited number of degrees of freedoms
and it lacked functionality. The early designs were only able to open and close the hand due to
which amputees preferred body-powered prosthetics instead of using myogenic prosthetics.
Some designs were based on a switch that performs the opening and closing motion of the hand.
The reason behind this was the lack of technology. With the advances in computer sciences
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technology, thousands of amputees can perform daily activities of life that they never dreamed
would be possible again. Patients who are physically challenged can now return to whatever they
want to do. Today’s prosthetics provide improved functionality along with greater degrees of
freedom. Using biosensors, controllers, and actuators, the myoelectric prosthetics can conduct a
wider range of gestures ("An Introduction to the Biomechanics of Prosthetics", 2019). There are
five types of grasps to perform the basic functions namely pinch, lateral, hook, spherical and
cylindrical grasp (Cloutier & Yang, 2013). All these grasps are performed by the electrical
activity of the muscles. The bionic hand uses electrodes to capture weak electrical signals from
the amputee's arm, which after sampling and filtering is passed to a miniature device (Keerthana,
Rubi, Srividhya & Priya, 2019). The final signal obtained is then passed to the servo motors and
on the basis of this signal, the servo motors perform the desired gesture.
The computer's machine learning algorithm interprets the signals and generates the set of
instructions that the prosthetic hand needs. The patient is not only allowed to move in the
direction he wants, but it can also control the speed of the motion. The advantage of using
myoelectric based prosthetics is that it does not require an invasive procedure and the
disadvantage is that the signals must be received from the nervous system by muscle contractions
which can lead to involuntary movements ("Literature Review on Prosthetic Limbs", 2019).
A large number of prosthetic hand models have been designed using different methods of
actuation. Some of them are the Novel Dexterous, Be-bionic, e-Nable and Michelangelo hand.
The Novel Dexterous Hand uses motors to operate the finger joints. These motors are attached
through cables much like the tendons in the human hand. With the help of a series of cables, the
movement of motors is transmitted to the fingers. Some designs, for example, Anthroform Arm
have actuators that directly transmit the power to the joint. It uses pneumatic 'muscles' to imitate
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the human arm's muscles that are directly connected to the bones. They have also used wires
made up of Shape Memory Alloy (SMA) to provide strength and to transmit motion. When
heated, these wires contract and return to their initial shape on cooling. Most prostheses are
controlled using non-intuitive methods. No research has been found investigating prosthesis
control directly from the neural network of the body. The Be-bionic hand is a myoelectrical
operated prosthetic hand in which all fingers are guided. Gears and leadscrews move the fingers
independently with 4 selectable grip settings. The e-Nable hand is available to the public freely.
It is entirely operated by the body and operates by the flexing of muscles in the stump region of
an amputee. Michelangelo hand also works based on EMG signal with actively driven index
finger, middle finger and thumb while the other fingers are passively followed by the ring and
pink finger (Herath, Gopura & Lalitharatne, 2018). Although many manufacturing methods are
available for manufacturing prosthetics, 3D printing has become popular in recent years due to
the increase in rate at which prosthetic hands design can be prototyped. From the research, we
also concluded that our model should be able to allow adaptability based on the amputee's needs
depending on what their device should require. Therefore, the prosthetic hand can be modified.
This project is trying to lay the foundation for an arm with an intuitive control method that can
imitate the human arm (Cloutier & Yang, 2013).
CONCLUSIONS
The prosthesis is a major research area that improves the strength and recovers the
amputee's usability. The project has shown effectively the value of hand design as well as design
improvements. By placing electrodes on the skin, we have acquired EMG signals of finger
gripping movements. After this, raw EMG signals obtained were amplified and rectified using an
EMG acquisition circuit. Bio-signals serve as a driving force, thereby transmitting the nerve
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signals to accomplish the mission. A microprocessor controls this form of the prosthesis and DC
motors control the finger motion in turn. Different finger movements are controlled using servo
motors. The myogenic EMG based prosthetic arms have improved the life of amputees by
providing them with an artificial limb with increased functionality and many other features. The
main requirement of this hand is to provide the natural hand's flexibility so that amputees can
also perform daily life activities easily and efficiently.
REFERENCES
An Introduction to the Biomechanics of Prosthetics. (2019). Retrieved 9 October 2019, from
https://www.azorobotics.com/article.aspx?ArticleId=11
Cloutier, A., & Yang, J. (2013). Design, Control, and Sensory Feedback of Externally Powered
Hand Prostheses: A Literature Review. Critical Reviews In Biomedical Engineering, 41(2), 161181. doi: 10.1615/critrevbiomedeng.2013007887
Gargiulo, G., Polisiero, Bifulco, Liccardo, Cesarelli, & Romano et al. (2013). Design and
assessment of a low-cost, electromyographically controlled, prosthetic hand. Medical Devices:
Evidence And Research, 97. doi: 10.2147/mder.s39604
Hanger Clinic. (2019). Retrieved 19 October 2019, from http://www.hangerclinic.com/limbloss/adult-upper-extremity/Pages/Body-Powered-Protheses.aspx
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Herath, H., Gopura, R., & Lalitharatne, T. (2018). An Underactuated Linkage Finger Mechanism
for Hand Prostheses. Modern Mechanical Engineering, 08(02), 121-139. doi:
10.4236/mme.2018.82009
Keerthana, A., Rubi, J., Srividhya, & Priya, S. (2019). Design and Development of Low cost
Prosthetic Hand controlled by Myoelectric Signal. Indian Journal Of Public Health Research &
Development, 10(5), 796. doi: 10.5958/0976-5506.2019.01110.0
Lake, C., & Dodson, R. (2006). Progressive Upper Limb Prosthetics. Physical Medicine And
Rehabilitation Clinics Of North America, 17(1), 49-72. doi: 10.1016/j.pmr.2005.10.004
Literature Review on Prosthetic Limbs. (2019). Retrieved 19 October 2019, from
https://www.ukessays.com/dissertation/full-dissertations/literature-review-prostheticlimbs.php#citethis
Myoelectric Prosthesis. (2019). Retrieved 19 October 2019, from
http://bme240.eng.uci.edu/students/10s/slam5/types.html
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Prostheses - Prosthetics: Artificial Limb Information. (2019). Retrieved 9 October 2019, from
https://www.disabled-world.com/assistivedevices/prostheses/
Salem, F., Mohamed, K., Mohamed, S., & El Gehani, A. (2013). The Development of BodyPowered Prosthetic Hand Controlled by EMG Signals Using DSP Processor with Virtual
Prosthesis Implementation. Conference Papers In Engineering, 2013, 1-8. doi:
10.1155/2013/598945
(2019). Retrieved 19 October 2019, from https://www.llop.com/prosthetics/
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