02-02-2012, 11:41 AM
Myoelectrically
[attachment=17038]
PROSTHETIC ARM
Prosthetic arm was first implemented by Reinhold Reiter, a physics student at Munich University in May 1945. The report of Reiter‘s work, in German medical newspaper, described a myoelectric prosthetic arm designed for the amputee factory worker. A prototype was demonstrated at the Honnover export fair in 1945. The research leading to this device was supported by the Bavarian Red Cross and private source. Pudlusky was Reiter‘s business manager for the project. Development of the system was terminated due to the lack of funds after the German currency reform in 1948[1]. The idea behind the control system was to amplify the myoelectric signal from a contracting muscle in order to control a wooden hand, which was modified to be actuated by an electric solenoid. Reiter used single muscle site in the residual limb. Control of opening and closing motion was derived from using two different rhythms of contraction. This scheme of using the signal from a single muscle to control two motions was later to be known as three state controls. Reiter’s work was not alone in being overlooked in the early development of myoelectric control. The myoelectric signal has been used to monitor lookout alertness as early as 1947 and by 1957 to control respirators for polio victims. Indeed, it has been investigated as a possible control source for prosthesis as early as 1949, with encouraging results. In the late 1950s and early 1960s, research again started in myoelectric control system. This work occurred independently and almost simultaneously in the USSR, the United Kingdom, the USA, Europe and Canada. It was aided greatly by the availability of transistors, without which a truly portable myoelectric prosthesis was not practical.
ARTIFICIAL ARM
Artificial arm is a boon for those persons who have lost their hand due to some mishap. One of the main requirements of artificial arm is that it should be as near as possible to the natural arm. There are various designs of artificial arm. These designs fall under the categories of mechanical, electrical and myoelectric arm. Mechanical devices are functional prostheses that use some motion of the body to provide the force necessary to control the prosthetic component. Electrical arms operate the hand by a motor driven by micro-switches and relays. Myoelectric arm is stimulated by muscle signal available from the stump of amputee. Powered hand prostheses are used to replace the function of a lost natural hand. Most of the commercial prosthetic hands in clinical use are controlled by myoelectric signal and are referred to as myoelectric hands. One of the important organs of the body is the hand. We perform 90% of our daily work by hand like eating, lifting, gripping an object, writing, typing, driving etc. Many persons, especially industrial workers carrying out different type of machining tasks in the factory, lose their arm due to accidents. Their lost arm is to be replaced by an artificial arm which fulfils all the criteria of a normal arm so that the amputee may lead the life of a normal person and feels rehabilitated
TYPE OF ARTIFICIAL ARMS
There are mainly four types of artificial arms that have been reported in the literature. They may be categorized as:
(A) MECHANICAL ARM
These devices are functional prostheses that use some motion of the body to exert the force needed to control the prosthetic component. Particularly noteworthy is the Bowden cable for use in the prosthetics field. A Bowden cable consists of an inner core cable that is free to move within a sleeve cable which is fixed in place at either end.
These devices require a harness, to be worn about the shoulders, to which one or more Bowden cables are attached. The conventional below-elbow, body-powered prosthesis has a single control cable that runs from the harness to a terminal device. Terminal device opening and closing is then controlled by shoulder shrug and/or flexion of the residual upper arm. An above-elbow amputee has additional control cable, which is used to switch control of the harness from terminal device opening to elbow flexion by unlocking the elbow. Body-powered prostheses are the most common kind of prosthesis used all over the world, due to the intimate connection of the control cable, which is provided between input and output. It helps the user of a body-powered limb to feel closely connected to the operation of the prosthesis. These prostheses are also lightweight, durable and of relatively low cost. However, body-powered prostheses have a number of shortcomings. The major issues are the uncomfortable harness mechanism, the somewhat ungainly control motions, particularly in the case of above elbow prostheses, restricted range of motion and limited load-lifting capacity.
(B) ELECTRICAL ARM
These are externally powered devices and receive their power from an external electric source to the body. These are relatively new (last 15 to 20 years) addition to the armamentarium of prosthetic devices.
Touch Switches: A pair of touch switches remains in contact with antagonistic wrist muscles flexors and extensors. The wrist flexors activate the =CLOSE ‘switch while extensors operate the =OPEN ‘touch switch.
[attachment=17038]
PROSTHETIC ARM
Prosthetic arm was first implemented by Reinhold Reiter, a physics student at Munich University in May 1945. The report of Reiter‘s work, in German medical newspaper, described a myoelectric prosthetic arm designed for the amputee factory worker. A prototype was demonstrated at the Honnover export fair in 1945. The research leading to this device was supported by the Bavarian Red Cross and private source. Pudlusky was Reiter‘s business manager for the project. Development of the system was terminated due to the lack of funds after the German currency reform in 1948[1]. The idea behind the control system was to amplify the myoelectric signal from a contracting muscle in order to control a wooden hand, which was modified to be actuated by an electric solenoid. Reiter used single muscle site in the residual limb. Control of opening and closing motion was derived from using two different rhythms of contraction. This scheme of using the signal from a single muscle to control two motions was later to be known as three state controls. Reiter’s work was not alone in being overlooked in the early development of myoelectric control. The myoelectric signal has been used to monitor lookout alertness as early as 1947 and by 1957 to control respirators for polio victims. Indeed, it has been investigated as a possible control source for prosthesis as early as 1949, with encouraging results. In the late 1950s and early 1960s, research again started in myoelectric control system. This work occurred independently and almost simultaneously in the USSR, the United Kingdom, the USA, Europe and Canada. It was aided greatly by the availability of transistors, without which a truly portable myoelectric prosthesis was not practical.
ARTIFICIAL ARM
Artificial arm is a boon for those persons who have lost their hand due to some mishap. One of the main requirements of artificial arm is that it should be as near as possible to the natural arm. There are various designs of artificial arm. These designs fall under the categories of mechanical, electrical and myoelectric arm. Mechanical devices are functional prostheses that use some motion of the body to provide the force necessary to control the prosthetic component. Electrical arms operate the hand by a motor driven by micro-switches and relays. Myoelectric arm is stimulated by muscle signal available from the stump of amputee. Powered hand prostheses are used to replace the function of a lost natural hand. Most of the commercial prosthetic hands in clinical use are controlled by myoelectric signal and are referred to as myoelectric hands. One of the important organs of the body is the hand. We perform 90% of our daily work by hand like eating, lifting, gripping an object, writing, typing, driving etc. Many persons, especially industrial workers carrying out different type of machining tasks in the factory, lose their arm due to accidents. Their lost arm is to be replaced by an artificial arm which fulfils all the criteria of a normal arm so that the amputee may lead the life of a normal person and feels rehabilitated
TYPE OF ARTIFICIAL ARMS
There are mainly four types of artificial arms that have been reported in the literature. They may be categorized as:
(A) MECHANICAL ARM
These devices are functional prostheses that use some motion of the body to exert the force needed to control the prosthetic component. Particularly noteworthy is the Bowden cable for use in the prosthetics field. A Bowden cable consists of an inner core cable that is free to move within a sleeve cable which is fixed in place at either end.
These devices require a harness, to be worn about the shoulders, to which one or more Bowden cables are attached. The conventional below-elbow, body-powered prosthesis has a single control cable that runs from the harness to a terminal device. Terminal device opening and closing is then controlled by shoulder shrug and/or flexion of the residual upper arm. An above-elbow amputee has additional control cable, which is used to switch control of the harness from terminal device opening to elbow flexion by unlocking the elbow. Body-powered prostheses are the most common kind of prosthesis used all over the world, due to the intimate connection of the control cable, which is provided between input and output. It helps the user of a body-powered limb to feel closely connected to the operation of the prosthesis. These prostheses are also lightweight, durable and of relatively low cost. However, body-powered prostheses have a number of shortcomings. The major issues are the uncomfortable harness mechanism, the somewhat ungainly control motions, particularly in the case of above elbow prostheses, restricted range of motion and limited load-lifting capacity.
(B) ELECTRICAL ARM
These are externally powered devices and receive their power from an external electric source to the body. These are relatively new (last 15 to 20 years) addition to the armamentarium of prosthetic devices.
Touch Switches: A pair of touch switches remains in contact with antagonistic wrist muscles flexors and extensors. The wrist flexors activate the =CLOSE ‘switch while extensors operate the =OPEN ‘touch switch.
