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PROSTHETIC ARM
Abstract: This project focuses on the design of a myogenic prosthetic arm to mimic the movement of human arm. A huge increase has occurred in the prostheses for patients with upper limb amputations in recent years. Current prosthetic hands have minimal usability and are costly. Our goal was to design a cost-effective prosthetic hand model. 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 and operating the arm on the basis of feedback received from these sensors. Coordinate reference systems are used for the transformation of input signals into the desired output. Our proposed model works using electromyogenic (EMG) signals generated by muscle contractions. Our design has increased degree of freedom and the number of grip patterns. In addition to driven thumb roll articulation, which is not seen in commercial products, the novel model includes five independently actuated fingers. Besides that, it exhibits the full range of motion required to grab an object.
INTRODUCTION
Prosthesis is a medical device that structurally and functionally replaces an arm. The hand is a complex part of human body. There are many people who have lost limbs through accidents or by birth and have to 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 the 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 [1]. There are four types of prosthesis depending on missing part. Our design is used particularly for transradial amputation. A transradial prosthesis replaces an arm below the elbow [2]. The hand must use sensor to read the muscle activities to cause movements. Electromyography (EMG) sensor 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,. In this design, the simple algorithm is built using the EMG signal to drive multiple grip patterns. Researchers are trying to improve the previously designed prosthetic arms but despite these technological advances, they are still limited in terms of their amount of 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 such as the use of under actuated mechanisms and shape memory alloy actuators. The high degree of flexibility and mobility of the hand and more robust control schemes are needed. The upper limb prostheses still have sufficient room for improvement. [3]
LITERATURE REVIEW
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. A large number of institutions have done research on the design and construction of robotic arm. The main focus of the previously designed robotic hand designs was on the mechanical problems that is functioning and designing. Different methods of actuation were used. 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 the human arm's muscles that are directly connected to the ' bones' . They have also used wires made up of SMA alloys to provide strength and to transmit motion. When heated, these wires contract and return when cooled to their initial shape. Most prostheses are controlled using non-intuitive methods. No research has been found investigating prosthesis control directly from the neural network of the body. Large number of prosthetic hand models have benn designed. Some of them are are Be-bionic, e-Nable and Michelangelo hand, The Be-bionic hand is a myoelectrically 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 functions by the amputee flexing their muscles in the stump. Michelangelo hand also works on the basis of EMG signal with actively driven index finger, middle finger and thumb while the other fingers are passively followed by the ring and pink finger [4]. The arm has 7 styles of grip. 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 [5].
OUR DESIGNED MODEL
The prosthetic limb consists of three main components i.e., biosensors, controller and activator. Biosensors are necessary to detect track neural activity. Controller acts as the key interface between the biosensors and the actuator, so that the data is obtained from the biosensors and this information is fed back to the actuator. Actuator is the end unit that collects controller data and imitates a muscle's movement [6].
Prosthetic limb research is wide-ranging and complex. We have designed a prosthetic hand in such a way that it should be light in weight to allow better movement.
STRUCTURE
The prototype of our model consists of a network of four fingers and a thumb attached to palm of a hand. The hand holds a micro-controller and a battery. A servo motors are used to provide actuation through a series of pulleys. They are basically used to actuate the fingers. These motors have built in encoders that helps motor can to rotate to a specific angle using pulse width modulation. Many options are provided for signal input and control algorithms. The fingers are connected to the DC motor using a copper wire with one end attached to the fingertips and using the program written in ATmega 32 controller. The prototype model is designed in AutoCAD and is 3D printed [7].
WORKING
We have designed a prosthetic arm that works on the basis of Myoelectric signals generated from biosensors. The actuators are attached to the residual part to allow the movement of a prosthetic limb, which will provide input signal produced by the biosensors. The actuators are also attached to a controller device that initiates sensory feedback to the actuators.
In this technology, muscles in your residual limb drive the body. These muscles can be contracted to produce electrical signals to move the arm. The disposable surface electrodes are positioned over the appropriate muscles on the body. The voltages created by contracting muscles are captured by these electrodes. A sEMG amplifier consists of three electrodes, two of which are placed over the muscle and the third electrode act as the ground. The three surface electrodes are placed on different muscles at different positions. The amplitude of signal obtained from electrodes varies from 0 to 10 millivolts and the frequency ranges from 50 to 150 Hz
After acquiring EMG data, it is amplified through amplifier which is connected to a PC for data storage. On a computer screen, auditory and visual animated signals are displayed and used to synchronize with the information. The obtained signal is sampled and bandpass filtered. The prosthetic hand includes a microcontroller capable of handling all hand movements [8].
The filtered signal is then passed to the microcontroller which is not able to move the robotic hand alone with the latest driving capabilities. . It involves a driving circuit to move the motors and moving parts in the robotic hand for the microcontroller's signals by mapping the value of the signal with the range of gesture value already stored in the microcontroller. 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.
Finally, the robotic hand imitates a human hand's movements depending on the input signal [7][9][10].
FUTURE WORK
Many areas require more research and development in order to enable the prosthetic to act as part of the neural network of the human body. It is important to investigate the rates of appropriate neuron stimulation without cell damage. It is also necessary to determine the technique of adding the prosthetic to the human nervous system. The acquired data through EMG signals in to produce the desired movement must be defined on the basis of the selected data point. Besides that, you can also incorporate machine learning algorithms to improve its functionality and behavior. Wireless communication can also be established inside it, allowing the user to move in an even more unrestricted manner.
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 signals to accomplish the mission. A microprocessor controls this form of prosthesis and DC motors control the finger motion in turn. Then, we designed our own prototype of arm using Solidworks and AutoCAD. Different finger movements are controlled using servo motors. Hence, amputees can install this myoelectric arm which is very affordable in price as compared to other commercially available prosthetics. As an actuator, motors give the hand a light in weight structure. 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
[1] M. Ariyanto, Munadi, G. D. Haryadi, R. Ismail, J. A. Pakpahan, K. A. Mustaqim, "A low cost anthropomorphic prosthetic hand using DC micro metal gear motor", 2016 3rd International Conference on Information Technology Computer and Electrical Engineering (ICITACEE), pp. 42-46, 2016.
[2] Prostheses - Prosthetics: Artificial Limb Information. (2019). Retrieved 9 October 2019, from https://www.disabled-world.com/assistivedevices/prostheses/
[3] https://web.wpi.edu/Pubs/E-project/Available/Eproject042612145912/unrestricted/MQP_PaulV_Complete_Final_3.pdf
[4] H. M. C. M. Herath, R. A. R.C. Gopura, Munadi, Thiliana D. Lalitharatne, "Prosthetic Hand with a Linkage Finger Mechanism for Power Grasping Applications. "." IEEE n. pag. Print.
[5] Cloutier, Aimee, and James Yang. "CONTROL OF HAND PROSTHESES- A LITERATURE REVIEW." IEEE n. pag. Print.
[6] An Introduction to the Biomechanics of Prosthetics. (2019). Retrieved 9 October 2019, from https://www.azorobotics.com/article.aspx?ArticleId=11
[7] Harvey, David, and Benjamin Longstaff. "THE DEVELOPMENT OF A PROSTHETIC ARM." IEEE n. pag. Print.
[8] P. Priya, E. Priya, "Design and control of prosthetic hand using myoelectric signal", 2017 2nd International Conference on Computing and Communications Technologies (ICCCT), pp. 383-387, 2017
[9] K. Sharmila, T. V. Sarath, K. I. Ramachandran, "EMG Controlled Low Cost Prosthetic Arm", 2016 IEEE Distributed Computing VLSI Electrical Circuits and Robotics (DISCOVER), pp. 169-172, 2016.
[10] M. Gauthaam and S. S. Kumar, "EMG Controlled Bionic Arm", in proceedings of the National Conference on Innovations in Emerging Technology, pp. 111-114, Erode, India, February 2011.
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