Rotational Skin-Stretch Distribution Creates Directional Force Sensation on the Wrist

This study aims to develop a compact, palm-free wearable system for mixed-reality (MR) environments that does not interfere with interactions with real objects. We propose a novel wearable system that presents the direction of force through a rotational skin-stretch distribution to the wrist by utilizing four independently controlled rotating tactors. Two control rules, local and global, are proposed to dictate the stimulus distribution. The local stimulus distribution produces a local distortion distribution by combining the rotation of two specific tactors and suggests a direction. The global control rule aims to present the overall direction of the force by combining the directional forces presented on both the palm and back of the hand. The capability of the system to present the perceptual intensity and directional stimuli was confirmed through two experiments. The first experiment confirmed that the proposed system could present perceived intensity. The second experiment showed that the global control law could present stimuli in the front-back direction, whereas the local control law could present stimuli in other directions except for upwards. These findings suggest that proposed system has potential to enhance MR experience by simulating static force sensations, such as the weight of virtual objects.