Investigation of the Stresses Exerted by an Exosuit of a Human Arm

Abstract

If a wheelchair could be considered as a better solution than an exoskeleton for the mobility of people suffering from neuromuscular diseases, there is a relevance to use a soft wearable exoskeleton (or exosuit) to assist the upper limbs in order to perform daily tasks such as having a drink, a pencil. It is imperative to limit the stresses generated by the exosuit on human. Numerical tests are proposed to investigate the possible technology choices to design the exoskeleton to limit these stresses. These numerical tests are based on the study of the inverse dynamic model of the human arm and its exosuit. A trajectory of the hand is defined and we deduce the cable tension to track this trajectory. Two decoupled planes are considered for the numerical tests, the sagittal plane where a flexion of the forearm with respect to the upper arm, and the frontal plane where abduction and adduction movements are possible. We assume that the human arm cannot provide any effort. The results show that the position of the anchor points at the shoulder and the orientation of the cable for the abduction movement have an influence to limit the stresses. However, these stresses are important on the shoulder.