Ultrasound-Driven Wearable Haptic Display for Rendering Edges and Curved Surfaces

Haptic local features such as edge and surface curvature are fundamental components that form haptic experiences. Noncontact haptic displays using focused ultrasound can render such local features by precisely controlling the focus position on the finger pad. However, the workspace has been limited to the vicinity of the phased array to secure the small focus on the finger and reproduce local shapes such as edges. In this study, to expand the workspace, we propose amplifying radiation force and enhancing local shape expression using a passive wearable attachment device based on a lever mechanism. The ultrasonic focus controls the contact position between the finger pad and the attachment device according to the finger's movement in real time, allowing the user to experience the amplified and enhanced sensation of stroking edges and curved surfaces. The results of the psychophysical experiment demonstrated that a curved surface with a curvature radius of 26.7 mm and an edge with an angle of 119.7 deg were presented at a position 500 mm away from the phased array with a long side of 384 mm.