Analysis of Finger Motions for Assisting Spoon Scooping with Soft Actuators

Assistance with eating for patients with hand muscle weakness and limited wrist mobility is important. There have been devices developed for feeding assistance, though most have not used the residual hand function of patients, which may increase the risk of disuse syndrome and loss of joy in life. In addition, soft gloves have been recently used as a way for providing assistance for patients with hand mobility. In particular, one previous study achieved spoon grasping using a soft glove on the hand, which opens the possibility of assist-as-needed. However, scooping and transporting that are required for eating with a spoon have not been investigated in the study. Our ultimate goal is to realize soft actuator assisted self-feeding for the persons with partial hand function impairment. In this study, we analyze the finger-driven spoon-scooping motion for determining significantly associated finger joints and how to control them for assisting the spoon-scooping. The reason for not including wrist-involved scooping is the force and bidirectional control it needs, which might increase the complexity of devices and risk of assisting. The finger-driving spoon scooping motion was measured by motion tracking and inertial measurement units, after that, an assumption about multiple types of finger-driving was made and verified with experiments on soft-actuators assisted finger driven scooping with a dummy hand. As a result, the scooping angle achieved by our device was found to be a maximum of 63.6 degrees, exceeding 52 degrees, the scooping angle required. The results demonstrate the possibility of assistance with scooping with soft actuators. This study is an important step towards our ultimate goal.