Prosthetic hand ppt

prosthetic descriptions and types

1. PROSTHETIC HAND SUBMITTED TO : DR. SHABNAM SUBMITTED BY : MANOJ PUROHIT 170171720001

2. PROSTHESIS A prosthesis is a device that is designed to replace, as much as possible, the function or appearance of a missing limb or body part. It is a device that is designed to support, supplement, or augment the function of an existing limb or body part.

3. Functional prosthesis generally can be divided into the following two categories 1. Body-powered prosthesis - Cable controlled 2. Externally powered prosthesis – Electrically powered Myo -electric prosthesis Switch-controlled prosthesis

4. Body-powered prosthesis (cables) usually are of moderate cost and weight. They are the most durable prostheses and have higher sensory feedback. A body-powered prosthesis is more often less cosmetically pleasing than a myoelectrically controlled type is, and it requires more gross limb movement. Body Powered Prosthesis

5. Externally Powered Prosthesis Prosthesis powered by electric motors may provide more proximal function and greater grip strength, along with improved cosmesis , but they can be heavy and expensive. Patient-controlled batteries and motors are used to operate these prosthesis.  Currently available designs generally have less sensory feedback and require more maintenance than body-powered prosthesis. Externally powered prosthesis require a control system. The two types of commonly available control systems are myoelectric  and switch control

6. A typical example of a transradial (below-elbow) prosthesis includes a voluntary opening split hook, a friction wrist, a double-walled, plastic-laminate socket, a flexible elbow hinge, a single–control-cable system, a triceps cuff, and a figure-8 harness. TYPICAL COMPONENTS BODY-POWERED PROSTHESIS Socket Suspension Control-cable system Terminal device Components for any interposing joints as needed according to the level of amputation

7. The socket of an upper extremity prosthesis typically has a dual-wall design fabricated from lightweight plastic or graphite composite materials. In this design, a rigid inner socket is fabricated to fit the patient's residual limb and the second, outer wall is added, designed to be the same length and contour as the opposite, sound limb. Comfort and function are directly tied to the fit of the inner socket. An alternative approach parallels the rigid frame, flexible liner approach sometimes used in lower extremity socket fabrication. The inner socket is fabricated from flexible plastic materials to provide appropriate contact and fit. Surrounding the flexible liner, a rigid frame is utilized for structural support and for attaching the necessary cables and joints as needed. The windows in the outer socket allow movement, permit relief over bony prominences, and enhance comfort. Socket

8. The suspension system must hold the prosthesis securely to the residual limb, as well as accommodate and distribute the forces associated with the weight of the prosthesis and any superimposed lifting loads. Suspension systems can be classified as follows: Harnessed-based systems. Self-suspending sockets. Suction sockets. Suspension

9. The major function of the hand that a prosthesis tries to replicate is grip ( prehension ). The 5 different types of grips are as follows Precision grip Tripod grip Lateral grip Hook power grip Spherical grip TERMINAL DEVICE

10. MYOELECTRIC PROSTHESIS A myoelectric prosthesis uses signals or potentials from muscles through electromyography , within a persons stump. The signals are picked up by electrodes on the surface of the skin which activates a battery-driven motor that operates a prosthetic component, like the finger . Control of the motor regulates the extent or speed of the prosthesis, such as elbow flexion or extension , or opening and closing of the fingers of the terminal device

11. ADVANTAGES • Use of natural muscle stimuli. • More accurate control with less energy expenditure. • Eliminates the shoulder harness. • Decreased body movement to control prosthesis. The myoelectric prosthesis provides more mobility, pinch force, and cosmetic appearance than body powered prostheses.

12. DISADVANTAGES • They are very expensive • In the event of a breakdown, it needs very skilled technical backup to repair. Also they need servicing on a regular basis • Component operation is noisy and slow. • The energy source is from a battery, which would have to be recharged regularly . • Lack of proprioceptive feedback as from the harness in body powered systems . • It is heavy , It cannot control fine rhythmic and fast movements. • There is poor control of co-contracting muscles and poor motor control. Myoelectric components get dysfunctional in water or around magnetic or electronic fields. • The cosmetic/protective gloves get dirty very easily

13. BIOMECHTRONIC HAND The objectives of the work of an bio mechtronic is to develop an artificial hand which can be used for functional substitution of the natural hand and for humanoid robotics application. The artificial hand is designed for replicating sensory motor capabilities of human hand. Commercially available prosthetic devices, such as Otto bock sensor hand, as well as multifunctional hand designs are far from providing the grasping capabilities of human hand.

14. In prosthetic hands active bending is restricted to two or three joints which are actuated by single motor drive acting simultaneously on the metacarpo-phalangeal joints of the thumb, of the index and of the middle finger while other joints can bend only passively. This limitation in dexterity is mainly due to the very basic requirement of limited size and weight necessary for prosthetic applications. On the other hand robotics have achieved high level performance in grasping and manipulation, but they make use of large controllers which are not applicable in prosthetics or humanoid robotics where it is necessary to provide the user with wearable artificial hand.

15. BIO MECHATRONIC DESIGN The main requirements to be considered since the very beginning of artificial hand design are the following : natural appearance, controllability, noiselessness, lightness and low energy consumption. These requirements can be fulfilled by implementing an integrated design approach aimed at embedding different functions within a housing closely replicating the shape, size and appearance of human hand. This approach can be synthesized by the term biomechatronic design.

16. ARCHITETECTURE OF THE BIOMECHATRONIC HAND The biomechatronic hand will be equipped with three finger to provide a tripod grasp : two identical finger. The finger actuator system is based on two micro –actuators, which drive the MP and the PIP joints respectively ; for cosmetic reason ,both actuator are fully integrated in the hand structure: the first in the palm and the second within the proximal phalange. The grasping task performed by the biomechatronic hand is divided in the subsequent phases: Reaching and shape-adapting phases; Grasping phase with thumb opposition