Stand-Up Assistive Devices Allowing Patients to Perform Voluntary Movements Within the Safety Movement Tolerance

This paper proposes a novel standing assistance robot, which realizes voluntary movements of the patient within a safety motion range. In previous studies, conventional assistive robots did not require patients to use their own physical strength to stand, which leads to decreased strength in the elderly. Such general assistive robots helped patients by using a fixed motion reference pathway in spite of their original intention, and as a result, these robots failed to use the physical strength of the patients. Therefore, this study proposes a novel method for assisting the patient to stand up safely while using their physical abilities, by determining the range of movements that can be safely performed from the patient's physical condition, and allowing the patient to move freely within this range. The standing motion is a set of different movements: inclining the trunk forward, lifting the trunk and extending the trunk. In this study, the range of movements in which the patient can safely stand in each movement was determined in terms of body stability and the muscle output that the patient can generate. Furthermore, this study proposes a robot control method that allows movements based on the patient's free will if the patient's posture is within the safety tolerance, and corrects the movements when the patient's posture is estimated to fall outside of it. Proposed idea is implemented to our new prototype and its effectiveness is verified by experimental results with elderly subjects who lives in the nursing care house.