Controlling multiple agents in parallel is an important challenge in human-robot interaction, with growing applications in remote collaboration, telepresence, and multi-agent coordination. However, empirical work on distributed embodiment remains limited, particularly in scenarios where independently controlled avatars operate in distinct environments. To address this gap, we propose the concept of Dual Body Sensation (DBS): a novel theoretical construct of distributed embodiment, describing a state in which a single operator simultaneously experiences embodiment for two independent robots in distinct environments during their control. We conducted a within-subject experiment to investigate the cognitive feasibility of DBS using a $2\times 3$ factorial design that varied visual presentation (independent view, superimposed view) and tactile presentation (no tactile, bilateral tactile, unified tactile). The results indicated that DBS emerged across all conditions and was significantly enhanced under the unified tactile condition. The combination of the superimposed view and unified tactile conditions also increased the sense of body ownership and the sense of agency, while the superimposed view condition reduced cybersickness and cognitive load. These findings provide empirical support for DBS and inform the design of future multi-agent interaction systems that support flexible distribution of bodily control and awareness.

Effective development of virtual reality (VR) applications is heavily reliant on the evaluation of user experience (UX). However, traditional methods such as questionnaires have inherent limitations which hinder their ability to capture nuanced behavioral responses and impede the agility of VR content creation: They are time-consuming, burdensome for users, and require significant human effort for interpretation. This study introduces an automated framework aimed at addressing the limitations of questionnaire-based evaluations to assess UX in VR. Our primary focus is to validate the concept of this framework through assessment of the sense of presence (SOP), a crucial psychological perception with significant impact on VR UX. Our proposed framework utilizes a deep neural network (DNN) to analyze patterns in multimodal behavioral cues, including facial expressions, head movements, and hand movements, to predict scores from the Igroup Presence Questionnaire (IPQ). Additionally, we introduce two statistical profiles: the Visual Entropy Profile (VEP), which offers insights into visual complexity by depicting scene entropy, and the Experiential Presence Profile (EPP), which is designed to capture users’ historical SOP levels to enable personalized baseline and sensitivity estimation. The proposed framework achieves a significant correlation between actual and predicted IPQ scores, with a Spearman’s rank correlation coefficient of 0.7303, showcasing the potential of DNNs in analyzing complex behavioral signals and automating SOP assessment. This study represents a pioneering effort in leveraging DNNs for the automatic assessment of SOP and paves the way for future advances in automatically assessing VR UX and unlocking new opportunities in the field.

To capture a remote 3D image, conventional stereo cameras attached to a robot head have been commonly used. However, when the head and cameras rotate, the captured image in buffers is degraded by latency and motion blur, which may cause VR sickness. In the present study, we propose a method named TwinCam in which we use two 360° cameras spaced at the standard interpupillary distance and keep the direction of the lens constant in the world coordinate even when the camera bodies are rotated to reflect the orientation of the observer's head and the position of the eyes. We consider that this method can suppress the image buffer size to send to the observer because each camera captures the omnidirectional image without lens rotation. This paper introduces the mechanical design of our camera system and its potential for visual telepresence through three experiments. Experiment 1 confirmed the requirement of a stereoscopic rather than monoscopic camera for highly accurate depth perception, and Experiments 2 and 3 proved that our mechanical camera setup can reduce motion blur and VR sickness.

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.

With the advantages of small size and light weight, electrical stimulation devices have been investigated for providing haptic feedback in relation to virtual objects. Electrical stimulation devices can directly activate sensory receptors to produce a reaction force or touch sensations. In the current study, we tested a new method of electrically inducing force sensation in the fingertip, presenting haptic feedback designed to alter perceptions of softness, hardness and stickiness. We developed a 3D virtual reality system combined with finger-motion capture and electrical stimulation devices. We conducted two experiments to evaluate our electrical stimulation method and analyzed the effects of electrical stimulation on perception. The first experiment confirmed that participants could distinguish between the directions of the illusory force sensation, reporting whether the stimulation flexed their index finger forward or extended it backward. The second experiment examined the effects of the electric current itself on the intensity of their perception of the softness, hardness and stickiness of a virtual object.

With the advantages of small size and light weight, electrical stimulation devices have been investigated for providing haptic feedback in relation to virtual objects. Electrical stimulation devices can directly activate sensory receptors to produce reaction force or touch sensations. In the current study, we tested a new method for inducing electrical force sensation in the fingertip, presenting haptic feedback designed to alter softness, hardness and stickiness perception. We developed a 3D virtual reality system combined with finger-motion capture and electrical stimulation devices. The system can provide visual feedback and the sensation of illusory force that moved the index finger by forward-flexion or backward-extension using tendon or cathodic stimulation. In the demo, participants can experience the sensation of softness, hardness and stickiness of a virtual object.

We developed “Finger Glove for Augmented Reality” (FinGAR), which combines electrical and mechanical stimulation to selectively stimulate skin sensory mechanoreceptors and provide tactile feedback of virtual objects. A DC motor provides high-frequency vibration and shear deformation to the whole finger, and an array of electrodes provide pressure and low-frequency vibration with high spatial resolution. FinGAR devices are attached to the thumb, index finger and middle finger. It is lightweight, simple in mechanism, easy to wear, and does not disturb the natural movements of the hand. All of these attributes are necessary for a general-purpose virtual reality system. User study was conducted to evaluate its ability to reproduce sensations of four tactile dimensions: macro roughness, friction, fine roughness and hardness. Result indicated that skin deformation and cathodic stimulation affect macro roughness and hardness, whereas high-frequency vibration and anodic stimulation affect friction and fine roughness.

The most common method of presenting tactile stimuli to touch screens has been to directly attach a tactile display to the screens. This requires a transparent tactile display so that the view is not obstructed. In contrast, transparency is not required if the tactile stimuli are presented on the back of the device. However, stimulating the entire palm is not appropriate because touch screens are typically used by only one finger. To overcome these limitations, we propose a new method in which tactile feedback is delivered to a single finger on the back of a touch screen. We used an electro-tactile display because it is small and dense. The tactile display presents touch stimuli as mirror images of the shapes on the touch screen. By comparing cases in which the device was operated by one or two hands, we found that shape discrimination is possible using this method.

Various systems for hand tool skill training have been developed in the domain of haptic displays. These systems typically present force to a learner's palm by directly actuating the tool. However, this approach is sometimes ineffective because learners have difficulty sensing the haptic feedback from the tool when they are holding it tightly. Thus, we propose a different approach (OCHD) that effectively guides the learner's hand by presenting force to the back of his/her hand as if an instructor is holding it. A preliminary experiment showed that OCHD effectively guides users with less actuator drive force than cases where the tool is directly actuated.