Hiroaki Toyama ^1,2* Hiroaki Kawamoto ^1,2,3 Yoshiyuki Sankai ^1,2,3

• ¹ Center for Cybernics Research, University of Tsukuba, Tsukuba, Ibaraki, Japan
• ² Cyberdyne Inc., Tsukuba, Ibaraki, Japan
• ³ Faculty of Engineering, Information and Systems, University of Tsukuba, Tsukuba, Ibaraki, Japan

A robot hand-arm that can perform various tasks with the unaffected arm could ease the daily lives of patients with a single upper-limb dysfunction. Smooth interaction between the robot and the patient is desirable, as their other arm functions normally. If the robot can move in response to the user’s intentions and cooperate with the unaffected arm, even without detailed operation, it can effectively assist with daily tasks. This study aims to propose and develop a cybernic robot hand-arm with the following features: 1) input of user intention via bioelectrical signals from the paralyzed arm, unaffected arm's motion, and voice; 2) autonomous control of support movements; 3) a control system that integrates voluntary and autonomous control by combining 1) and 2), allowing smooth work support in cooperation with the unaffected arm reflecting intention as a part of the body; and 4) a learning function to provide such work support across various tasks in daily use. Then, we confirmed the feasibility and usefulness of the proposed system through a pilot study involving three patients. The system learns to support new tasks by working with the user through an operating function that doesn’t require the unaffected arm. The system divides the support actions into movement phases and learns the phase-shift conditions from the sensor information on the user's intention. After learning, the system autonomously performs learned support actions through voluntary phase shifts based on input of the user’s intention via the bioelectrical signals, unaffected arm's motion, and voice, enabling smooth collaborative work with the unaffected arm. Experiments with patients demonstrated that the system could learn and smoothly provide work support in cooperation with the unaffected arm, successfully completing the tasks that are difficult for them. Additionally, the questionnaire confirmed that, subjectively, cooperative work according to the user's intention was achieved, and that the work time was within a range feasible for daily life. Furthermore, it was observed that participants who used bioelectrical signal from their paralyzed arm perceived the system as part of their body. In conclusion, we confirmed the feasibility and usefulness of various cooperative work supports using the proposed method.