FOREARM PROSTHESIS: NEW DESIGN SOLUTIONS TO INCREASE THE RANGE OF MOTION

Authors:

Burov Gennady Nikolayevich, PhD in Technical sciences, head of the Scientific direction, Albrecht Federal Scientific Centre of Rehabilitation of the Disabled, 50 Bestuzhevskaya Street, 195067 St. Petersburg, Russian Federation, e-mail: zxzy@yandex.ru

Bolshakov Vladimir Alexandrovich, head of the Design department, Albrecht Federal Scientific Centre of Rehabilitation of the Disabled, 50 Bestuzhevskaya Street, 195067 St. Petersburg, Russian Federation, e-mail: pko09_903@mail.ru

Shcherbina Konstantin Konstantinovich, Director of the Institute of Prosthetics and Orthotics, Albrecht Federal Scientific Centre of Rehabilitation of the Disabled, 50 Bestuzhevskaya Street, 195067 St. Petersburg, Russian Federation, + 7-921-916-00-49, e-mail: shcherbina180@mail.ru

Drobakha Alena Sergeevna, junior research associate, Albrecht Federal Scientific Centre of Rehabilitation of the Disabled, 50 Bestuzhevskaya Street, 195067 St. Petersburg, Russian Federation, e-mail: drobaha-alena@mail.ru

Annotation:

Introduction. Purposeful processes (holistic motor acts) performed by a disabled person with the help of technical means of rehabilitation to meet various needs are an organized and ordered set of actions — operations that can be divided into two types: work operations and management operations. A disabled person, equipped with a technical device, performs actions that in some cases are combined in time. The effectiveness of a technical means depends on the quality of the control system and the rationality of its construction, as well as on the rational level of its saturation with means of mechanization.
An active hand prosthesis with any control method should facilitate the performance of basic household and simple labor activities with relatively small adaptive movements of the disabled person.
All motor acts performed by a disabled person can be divided into two main groups: manipulation of a free object and movement with a bound object along a rigid trajectory. When moving a free object, the trajectory of movement is not regulated, in contrast to the associated movement, where the prosthetic limb follows the trajectory, forcibly orienting itself in space. When the object is connected, the rigid connection acts on the operator through the technical means, limiting the mobility within the framework of the forced trajectory.

Aim. The aim of the study is to create a constructive version of the kinematic decoupling, which ensures the implementation of hand movements along a rigid trajectory.
Materials and methods. When developing artificial joints and driving mechanisms of hand prostheses, as a rule, rational amplitudes of mobility are taken into account, which facilitates the design and contributes to the simplification of structures. When designing a compliant wrist joint, of interest are also the permissible values of the forces that must be transmitted through the joint to the end link when performing a motor act.
To implement a complex motor act, for example, a circular movement with a forearm prosthesis with a hand fixed on the handle, it is necessary to have two degrees of mobility in the wrist joint, for example, in the form of rotation joints with mutually perpendicular axes. Two types of devices are of interest here: a structure with an elastic element in the form of a spring or an elastic rod, or a spring-loaded output rod of a spherical hinge can be placed in an elastic, for example, a rubber sleeve. As a result of the design layout, two versions of the artificial wrist joint were developed in the form of separate assembly units, and the corresponding measurements were carried out.

Results. 2 variants of artificial wrist joint are presented. For the manufacture of an experimental sample, the most convenient option for the selection of an elastic element was chosen. The measurements of the external load forces in the transverse and longitudinal directions relative to the artificial traction hand, measurements of the deviations of the artificial hand under load were carried out.

Discussion. Known designs of forearm prostheses for the most part do not solve the problem of a disabled person working with a connected object, especially if he is equipped with a traction prosthesis.

Conclusion. The results of the measurements carried out for the rotary mechanical drive showed that the wrist joint of the prosthesis should be flexible, while the proposed device is capable of transmitting forces, providing voluntary movements of a movable artificial hand.

List of cited literature:

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