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

Recently, the number of older people and the reduc-tion 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 so-ciety, a welfare pneumatic device to rehabilitate the temporally injured elderly and the disabled has been actively researched and developed. However, the de-veloped 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 rehabil-itation 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 pneu-matic 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 mea-sured. To predict the bending angle of FPSA, a simpli-fied shape analytical model of it is proposed. It can be confirmed that a calculated bending angle of FPSA us-ing 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 de-vice. And it can be confirmed that a range of motion ("ROM" for short) is satisfied in an inversion and ever-sion driven by operating one or another FPSA on the device.