Evaluation of Flexibility in Frontal Plane and Improvement of Usability for Dorsiflexion Support Unit

Aging society has recently been a serious social problem in many countries, and the frail elderly are focused on as major targets for human support devices. To support the dorsal flexion of their ankles, we have developed a dorsiflexion support unit (DSU) using elastomer-embedded flexible joints (EEFJ). In this study, we conducted gait analyses on cross-slope surfaces. By considering the results of the cross-walking experiments, the mechanical analyses are conducted with computer simulations. In addition, the usability tests for the DSU with an improved elastomer cap were conducted. The results of the gait analyses show the ankles maintain inversion without returning to their neutral positions in swing phases. This information is useful for designing orthosis, prostheses, and robotic gait aids. The results of the mechanical analyses show the required forces were 5 N for inversion, 7 N for eversion at 10 degrees rotations, and 10 N for inversion, 15 N for eversion at 20 degrees rotations. These asymmetric mechanical properties come from the non-linearity of the EEFJ. We improved the shape of the elastomer cap from a double flange type to a single flange type with a fixing bolt to reduce a burden of wearing. According to the results of usability tests, though the setting time was slightly increased, the rotational motions required for the settings were decreased by half for all participants.