Development of a wearable cybernic glove that enables object grasping and gripping force measurement with open finger pad

Patients with hand paralysis have motor and sensory dysfunction of their hands. They can neither flex/extend their fingers nor feel the gripping force. To enable the gripping motion with sensory information, sensory information has to be acquired simultaneously as the fingers are assisted. Since the skin plays a role in increasing friction with the grasped object in addition to acquiring sensory information, it is important for the skin to be in direct contact with the object. Therefore, it is necessary to enable gripping motion and measure the gripping force with an open finger pad. In this study, a wearable system was developed to enable gripping motion and gripping force measurements with an open finger pad. A tendon-driven finger-assist glove assisted the flexion/extension of the fingers and adduction/abduction of the thumb; moreover, a sensor was developed to estimate the fingertip force by measuring the lateral expansion force of the finger tissue. We conducted an evaluation experiment for the developed sensor and object grasping experiments for the developed wearable system with the sensor. The root mean square error (RMSE) in force estimation was approximately 0.2 N. In addition, the system could assist the motions of the thumb/index/middle finger in grasping objects.