A 4-DoF wearable hand device for haptic rendering of surfaces and edges

We present a 4-degrees-of-freedom (4-DoF) wearable haptic device for the palm, able to provide the sensation of interacting with slanted surfaces and edges. It is composed of a static upper body, secured to the back of the hand, and a mobile end-effector, placed in contact with the palm. They are connected by two articulated arms, actuated by four servo motors housed on the upper body and along the arms. The end-effector is a foldable flat surface that can make/break contact with the palm to provide pressure feedback, move sideways to provide skin stretch and tangential motion feedback, and fold to elicit the sensation of interacting with different curvatures. The paper presents the design of the wearable haptic device, together with its mobility, statics, and manipulability, as well as direct, inverse, and differential kinematics. We also present a position control scheme for the device, which is then quantitatively evaluated.