Development of Ankle-Joint Rehabilitation Device for Bedridden Patient Using Fan-Shaped Pneumatic Soft Actuator Driven at Low Pressure

Abstract

Recently, the number of older people and the reduction in infant birth rates in Japan have increased. Elderly against the younger increased to more than 28.9% in 2020. According to the Japanese aging society, a welfare pneumatic device to rehabilitate the temporally injured elderly and the disabled has been actively researched and developed. However, the developed rehabilitation device is almost always used for a patient who is not bedridden. Therefore, the joint of a bedridden patient is given only a passive exercise, by a physical therapist (PT). In this study, in order to reduce the burden of PTs, we aim to develop a rehabilitation device that can be used by anyone assisting the bedridden patient. The target joint was decided to be an ankle-joint because it is difficult for patients with contractions to walk. Therefore, a fan-shaped pneumatic soft actuator (FPSA) using a no-stretch hose with weaved bellows and silicone rubber string was proposed and tested. In addition, the characteristics of FPSA with different pitches and lengths are measured. To predict the bending angle of FPSA, a simplified shape analytical model of it is proposed. It can be confirmed that a calculated bending angle of FPSA using the model generally agrees with the experimental result. The proposed analytical model is a first-stage model that does not include the influence of external forces on FPSA. The ankle-joint rehabilitation device using FPSAs is proposed and tested, where an ankle-joint is changed from a plantarflexion to a dorsiflexion motion by pressurizing both FPSAs on the tested device. And it can be confirmed that a range of motion (“ROM” for short) is satisfied in an inversion and eversion driven by operating one or another FPSA on the device.