Development of wearable device for measuring joint motion based on parallel wire-driven mechanism

In human rehabilitation, the measurement of joint range of motion (ROM) is essential in evaluating the degree of disability and recovery of patients. In clinical practice, ROM is typically measured with an angle meter, but its accuracy depends on the skill level of the measurer, and the task is burdensome. Recently, measurement methods using image analysis have been proposed for ROM; however, their cost is high because of the requirements of vast space and a large number of cameras. Therefore, this study proposes a wearable device for measuring shoulder joint motion targeting the shoulder joint which has many types of ROM measurements. This device, which uses a parallel wire-driven mechanism and can be worn by humans, is expected to facilitate the measurement of shoulder joint ROM. The mechanism consists of a base, output link, and three wires connecting them. This study proposed a method of measuring shoulder joint motion using the kinematics of the mechanism, and designed and fabricated the device. The validity of the device was confirmed through basic experiments, and its practicality for ROM measurement was verified in clinical practice by having humans wear the device.