Exoskeletal meal assistance system (EMAS II) for patients with progressive muscular disease

Patients with muscle weakness such as muscular dystrophy usually need someone’s assistance in their daily activities. In order to reduce the caregiver burden and to improve quality of life (QOL) of the patients, various robotic technologies have been developed. This paper presents an exoskeletal assistance system EMAS II for the patients, which assists the upper extremity for the purpose of daily activities such as eating, writing, or other desk works. The EMAS II assists four DOF; shoulder flexion-extension, shoulder abduction-adduction, shoulder medial-lateral rotation, and elbow flexion-extension. The EMAS II has three kinds of user interfaces which are operated by residual functions of the patients, because it is important for patients’ health and initiative to use the residual functions. In order to control the four DOFs exoskeleton system using the interfaces with less DOF, the EMAS II simulates upper limb motion patterns of healthy people. The patterns are modeled by extracting correlations between the height of the wrist joint and that of the elbow joint. Therefore, users have only to control the position of their wrist joint to do tasks at a table. Through an experiment with a healthy subject, the feasibility of meal assistance by the EMAS II was confirmed. Furthermore, the system was applied to a spinal muscular atrophy patient in a clinical trial to check the usability. The experimental results indicated that the EMAS II could support the patient’s upper extremity to do tasks at a table.