Developing a body-powered co-contraction equivalent

Abstract

Myoelectric as well as body-powered hand prostheses, the two commercially available prosthetic control types, have both their specific advantages. Advanced myoelectric prostheses for example have the characteristic of facilitating multiple degrees of freedom due to grip type variation and/or wrist movements. Compared to prosthetic devices with only one degree of freedom (e.g. body-powered ones), the usage of prostheses with multiple degrees of freedom appears more natural and the need for compensatory body movements in everyday life activities is reduced. The accuracy of grasping and the dexterity when conducting complex movements is improved. Furthermore, a more stable grip is achieved especially in case of grasping irregular shaped-objects. On the contrary, body-powered prostheses are e.g. lightweight, robust and cheap. Furthermore, they provide extended proprioceptive feedback, whereas the amputee always knows the prehension state of his/her prosthesis and how much pinch force he/she applies without having to visually monitor the device. Since a prosthesis providing both extended proprioceptive feedback as well as multiple-degrees of freedom would strongly benefit the amputee, a literature review has been conducted to investigate, if attempts have been or are currently undergone to design a body-powered prosthesis with multiple degrees of freedom. This literature review has shown, that less successful attempts have already been conducted on this regard. The approaches to equip body-powered prostheses with multiple degrees of freedom are mentally challenging, counterintuitive or restricted to unilateral amputees. Therefore, they are inadequate solutions. Myoelectric prostheses, on the contrary, solely require a trigger signal, co-contraction or a signal combination to control multiple degrees of freedom. In order to expand the advantages of body-powered prostheses, the aim of this project was to develop a mechanism to cooperate multiple degrees of freedom of a body-powered prosthesis as easily as with the myoelectric control. More precisely, the mechanism should enable to switch between a lateral and an opposition grip of a body-powered hand prosthesis. The thesis was conducted in cooperation with Otto Bock HealtchCare GmbH in Duderstadt, Germany, wherefore the information of this thesis is confidential until November 25th, 2021.