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Hand prosthesis design: Enhancing grasping capabilities through mechanical features

Prosthetic hand devices present the following limitations: low functionality, low cosmetics and low controllability. In order to overcome the main weaknesses generally associated with commercial prostheses the following criteria should be addressed: the prosthetic device should perform a stable power grasp with a wide variety of object with complex shapes; the prosthesis should have the same weight and dimensions of the human hand; and furthermore, the grasping movements should result as natural as possible and finally, the prosthesis should be easy to operate.
This thesis presents two different approaches aiming at solving the listed weaknesses and illustrates the differences in design approaches between active and passive adaptive grasp: the first one is based on the increase of the active degrees of freedom through the adoption of micro-electromagnetic actuators. The second approach is based on the exploitation of underactuated mechanisms that performs a passive adaptive grasping. Underactuated mechanisms allow reproducing most of the grasping behaviors of the human hand without augmenting the mechanical and the control complexity. The complexity of an underactuated finger can be further reduced applying the concept of compliant mechanisms that represents a further reduction of mechanical complexity and a strategic feature for prosthetic hand design.

Mostra/Nascondi contenuto.
Introduction “Is computer control needed to perfectly mimic the human hand, or is a simple mechanical design with approximate adaptive grasp sufficient?” The question, asked by Dechev et al. [25], arises concerning the development of an active prosthesis and summarizes the main differences related to the design strategies of an active prosthesis hand. This work does not intend to give an answer to this question; however it contributes to illustrate the advantages and limitations of both active and passive adaptive grasp by means of the development of prosthetic hand prototypes based on the two approaches. 0.1 Human Hand The hand is the end organ of the upper limb. It is designed for prehension and is ideally situated for the important role it plays in the intake of food from the environment [92]. The human hand has evolved to be a complex and adaptable manipulator. It is able to quickly reconfigure itself to different shapes in order to enable both to softly manipulate objects and also to carry heavy items. It achieves this by a combination of more than 22 degrees of freedom (DOFs) and a complex hierarchical control based on a large number of sensors [56]. 1

Tesi di Dottorato

Dipartimento: Settore di Ingegneria

Autore: Bruno Massa Contatta »

Composta da 100 pagine.

 

Questa tesi ha raggiunto 795 click dal 20/03/2004.

 

Consultata integralmente 3 volte.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.

 

 

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