Evaluation of effects caused by individual differences in human shape that affect the safe utilization of wearable robots

Abstract

When using a wearable robot, the interaction force applied to the area of contact may cause skin injuries over time. Therefore, validating the contact safety of wearable robots is important for their practical application. Because previous studies indicated that the repetitive share stress of the wearable robots increased the risk of blister generation, analysis of stress distribution, which is affected by the contact state, was viewed as very important. However, the effect of variability of the shape of the human body on the shear stress applied to the contact area is rarely analyzed, even though uneven contact between human tissue and the robotic cuff can cause stress concentration. In this study, a system for safety verification and validation of the robotic cuff was developed, and the interaction force exerted on the contact area of a variably shaped human tissue dummy when rubbed by a robotic cuff was measured. As a result, the maximum interaction force occurred when the robotic cuff moved over the convex part of the surface. Furthermore, the magnitude of the interaction force corresponded to the gradient. Thus, the shear stress increased by approximately 10% as the height of the iliac spine, which originally mimicked the anterior superior iliac spine, changed by 1 mm. This variability suggests that the stress concentration caused by the unevenness of human tissue plays an important role in the risk of blister.