A concept model for a multi-fingered prosthetic hand
Master Thesis
1997
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University of Cape Town
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Abstract
The various attempts by individuals to replace the hand has led to some ingenious and practical designs, but if compared to the real hand these designs are still light years behind. Till recently the most functional prostheses developed were body powered because of the simple, light weight designs. The designs for these hands have not changed must in the last few decades indicating that the design has reached its functional limit. This and the latest technology have initiated designers ' renewed interest in externally powered prostheses. Existing externally powered hands only have one degree of freedom which limits the function of hands considerably whereas practical multi-fingered hands would provide a new dimension to the functionality of prosthetic hands. For this project a concept model for a multi-fingered prosthetic hand was developed using Lego as design medium. The objective was to develop and test mechanisms as well as control strategies which can be used in a real prosthetic hand. A proper study of the human hand was done to determine its basic anatomy as well as its functioning. An extensive literature study on prosthetic and robotic hands was also done to evaluate existing designs and determine the level of existing technology. Special emphasis was laid on the anatomical design of the human hand which led to a model with a unique design. The model incorporates a tendon driven finger mechanism instead of the traditional linkage systems. This design provides an adaptable closing finger trajectory providing better grip. The model also provide actuation to all five fingers contrary to the three fingers of existing hands. This is achieved by a simple differential mechanism driving the last three fingers semi-independently with one actuator. The model also provides abduction of all fingers as well as opposition of the thumb improving the hands versatility. The hand is controlled using a personal computer and two interface boxes. Software was developed in Visual Basic to provide the user with a control analogue to that of a real myoelectric prosthesis.
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Bibliography: p. 137-139.
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Kotze, J. 1997. A concept model for a multi-fingered prosthetic hand. University of Cape Town.