Hand redirection, which subtly adjusts a user's hand movements in a virtual environment, can modify perception and movement by providing real-time corrections to motor feedback. In the context of motor learning and rehabilitation, observing replays of movements has been shown to enhance motor function. The application of hand redirection to these replays by making movements appear larger or smaller than they actually are has the potential to improve motor function. However, the detection threshold for hand redirection, specifically in the context of motion replays, remains unclear, as it has primarily been studied in real-time feedback settings. This study aims to determine the threshold at which hand redirection during post-exercise replay sessions becomes detectable. We conducted two psychophysical experiments to evaluate how much discrepancy between replayed and actual movements can go unnoticed by users, both with hand redirection (N=20) and without (N=18). Our findings reveal a tendency for the amount of movement during replay to be underestimated. Furthermore, compared to conventional real-time hand redirection without replay, replay manipulations involving redirection applied during the preceding reaching task resulted in a significantly larger JND. These insights are crucial for leveraging hand redirection techniques in replay-based motor learning applications.

We present Virtual Reality Self Co-embodiment, a new method for post-stroke upper limb rehabilitation. It is inspired by mirror therapy, where the patient's healthy arm is involved in recovering the affected arm's motion. By tracking the user's head, wrists, and fingers' positions, our new approach allows the handicapped arm to control a digital avatar in order to pursue a reaching task. We apply the concept of virtual co-embodiment to use the information from the unaffected arm and complete the affected limb's impaired motion, which is our added unique feature. This requires users to mechanically involve the incapacitated area as much as possible, prioritizing actual movement rather than the sole imagination of it. As a result, subjects will see a seemingly normally functional virtual arm primarily controlled by their handicapped extremity, but with the constant support of their healthy limb's motion. Our experiment compares the task execution performance and embodiment perceived when interacting with both mirror therapy and our proposed technique. We found that our approach's provided sense of ownership is mildly impacted by users' motion planning response times, which mirror therapy does not exhibit. We also observed that mirror therapy's sense of ownership is moderately affected by the subject's proficiency while executing the assigned task, which our new method did not display. The results indicate that our proposed method provides similar embodiment and rehabilitation capabilities to those perceived from existing mirror therapy. This experiment was performed in healthy individuals to have an unbiased comparison of how mirror therapy's and VRSelfCo's task performance and degree of virtual embodiment compare, but future work explores the possibility of applying this new approach to actual post-stroke patients.

Hand redirection is a technique used in virtual reality (VR) to alter the virtual hand position from the real hand position, enabling extended interaction in VR. This technique capitalizes on the visual system’s dominance over proprioception, whereby discrepancies between the virtual hand mapping and the reality below a specific threshold are indiscernible to users. However, these detection thresholds are often minute. In this study, we explore the impact of haptic stimuli known as the ‘hanger reflex’ on the detection threshold of hand redirection, specifically concerning forearm pronation, which involves rotating the user’s palm downward. To achieve this, we conducted a user study that involved manipulating the degree of forearm rotation and measuring detection thresholds in three conditions: Neutral, where no force was applied; Inward, where haptic feedback was provided to match the direction of hand rotation through the hanger reflex; and Outward, where haptic feedback was provided in the opposite direction of hand rotation. The results demonstrate that, in the Neutral condition, the virtual degree of rotation can vary between 0.896 and 1.136 times the actual amount without being perceptible to users. However, under the Inward condition, this range increases to between 0.888 and 1.204 times the actual amount, representing a significant expansion of the detection threshold range. Consequently, our findings contribute to the field of upper limb rehabilitation.

Learning an advanced skill in sports requires a huge amount of practice and players also have to overcome both physical difficulties and the dullness of repetitive training. Returning a fast spin shot in table tennis could be taken as an example, as athletes need to judge the spin type and decide the racket pose within a second, which is difficult for beginners. Therefore, in this paper, we show how to design an intuitive training system to acquire this specific skill using different cues in Virtual Reality (VR). Using VR, we can easily provide visual information, attach haptic devices, and distort the speed of time, however, it is difficult to decide which types of information could benefit the training. In an initial study, by comparing real world training with VR training, we showed the effect of VR training and obtained some insights about augmentation for training spin shots. The training system was then improved by adding three new conditions using different visualizations and temporal distortions, as well as a haptic racket for creating realistic feedback. Finally, we performed a detailed experiment, which suggest a significant improvement of skill for each condition compared to the baseline, while a qualitative evaluation indicates that both users' motivation and their understanding of spin are increased by using our system.

Urushi (Japanese lacquer) is a natural resin paint with electrical insulating capability. We focused on Japanese patterns on an urushi-ware that is a product coated urushi. To make urushi-wares interactive without losing elegance and beauty, we transformed Japanese patterns into near-field communication (NFC) antenna patterns. We developed three types of prototype antennas and confirmed their functionality. In addition, we developed an IC key tag and an interactive lunch box as example applications of interactive urushi-wares.

In this research, we propose a system that can change the tactile material of the wall surface especially in the VR show house. In order to present multiple types of wall materials, an encounter type tactile sense presentation unit with a plurality of wall materials mounted on a uniaxial robot presents a specific type of wall material according to the movement of the hand of the experiencer. With this encounter type approach, users can experience tactile sensations of multiple kinds of realistic wall materials. We examined the specs necessary for such presentation, constructed the system, and conducted a user study to examine the effect of the proposed system, comparing with visual only and visual + force only conditions.

Urushi (Japanese lacquer) is a natural resin paint with electrical insulating capability. By using it as a base material and coating material for electronic circuits, it is possible to construct a circuit with an elegant appearance and feel. It is also possible to build a multilayered electronic circuit by using urushi as insulation layers. In this study, we investigate techniques to construct touch interfaces using a multilayered electronic circuit (urushi circuit). At first, we fabricated an urushi circuit with a touch electrode consisting of two layers. To improve its appearance, we fabricated urushi circuits in which all touch electrodes are arranged on the top layer and all wires are hidden in the bottom layer. Moreover, as an extension of the touch interface, we built a grid of touch electrodes that realizes two-dimensional touch sensing.

The Hanger Reflex is a phenomenon in which the head rotates unintentionally when it is sandwiched by a wire hanger. The reflex is effectively generated by pressing on specific points, and can be reproduced by pressing with an actuator. We propose the HangerOVER, an HMD-embedded haptic display that can provide both force and motion senses using the Hanger Reflex. In this paper, we designed HangerOVER that HMD-embedded force and motion display using the Hanger Reflex, and developed four VR applications for demonstration.

The Hanger Reflex is a phenomenon in which the head rotates unintentionally when it is sandwiched by a wire hanger. The reflex is effectively generated by pressing on specific points, and can be reproduced by pressing with an actuator. We propose the HangerOVER, an HMD-embedded haptic display that can provide both force and motion senses using the Hanger Reflex. In this paper, we designed a mechanism of controlling the Hanger Reflex using air balloons for HMD embedded haptic display, and confirmed the occurrence of the Hanger Reflex.

We present JOLED, a mid-air display for interactive physical visualization using Janus objects as physical voxels. The Janus objects have special surfaces that have two or more asymmetric physical properties at different areas. In JOLED, they are levitated in mid-air and controllably rotated to reveal their different physical properties. We made voxels by coating the hemispheres of expanded polystyrene beads with different materials, and applied a thin patch of titanium dioxide to induce electrostatic charge on them. Transparent indium tin oxide electrodes are used around the levitation volume to create a tailored electric field to control the orientation of the voxels. We propose a novel method to control the angular position of individual voxels in a grid using electrostatic rotation and their 3D position using acoustic levitation. We present a display in which voxels can be flipped independently, and two mid-air physical games with a voxel as the playable character that moves in 3D across other physical structures and rotates to reflect its status in the games. We demonstrate a voxel update speed of 37.8 ms/flip, which is video-rate.

We developed a bed-style haptic display "Haptic Bed" that provides weight sensation to wide area of the user's body. This system comprises motors, belts, a cushion and a comforter to press and swing the user lying on the bed. Haptic Bed is a type of whole-body haptic interface, characterized by the presentation of low-frequency force with multiple degrees of freedom. The prototype system with two motors can present a weight sensation to approximately five regions of the abdomen. Although a sensation is only presented to the abdomen in this study, Haptic Bed can present a weight sensation to a wider area by increasing the number of motors. The system has the potential to enrich the audio visual experience in several ways, such as by expressing the sensation of a horrific ghost sitting on the user as part of entertainment content, or by presenting the existence of a remote relative as a telecommunication tool. Overall, the system changes a bed into a new medium through which immersive contents are presented in an immersive manner.

The hanger reflex is a strong force illusion that was previously known to occur in the human head. We applied the hanger reflex to the wrist and had expected that "sweet spots" would exist for the hanger reflex at the wrist, similar to the properties of the hanger reflex at the head. By measuring the pressure distribution and the rotation angle when the hanger reflex device was attached to the wrist, we found "sweet spots" that efficiently generate the hanger reflex at the wrist. Based on the pressure distribution obtained, we developed a device to control hanger reflex generation at the wrist. This device reproduces the pressure distribution by pressing on the hanger reflex "sweet spots" using four linear actuators, and thus generates the hanger reflex at the wrist. The results of user testing indicated that the device can produce rotational forces efficiently.

When a wire hanger is placed sideways on the head, and the temporal region is sandwiched by the hanger, the head rotates unexpectedly. This phenomenon has been named the “Hanger Reflex”. Although it is a simple method for producing pseudoforce sensation, the use of the wire hanger in this way has up until now been limited in posistion to the head. Here we report a new finding that when a wrist or waist is equipped with a device of a larger circumferance the arm or the body rotates involuntarily. This fact suggests that the Hanger Reflex principle might be applicable to parts of the body other than the head, leading to the possible compact whole-body force display. This paper documents the development and testing of the devices and, suggesting stable presentation of the rotational force.