The human arm has seven DoF. If the human arm were more redundant, it would improve workability. However, intuitive manipulation of redundant arms is difficult due to the complexity of the input system or the limitations of the human arm. In this study, we constructed a system in which multiple operators integrate their bodies to intuitively operate a redundant multi-DoF robotic arm. The robotic arm was assembled by connecting two arms, and the roles of each section –distal arm and proximal arm– were assigned to different operators. First, vibrotactile feedback methods to the users based on the operation movement were investigated to compensate for the recognition of the partner’s movement. Three types of feedback methods —the actions of both oneself and one’s partner, the actions of the partner, and none— were compared in order to improve the body awareness. It was shown that feedback of the movement from the partner who operates the proximal robotic arm significantly enhanced the sense of body ownership. Then, the proposed co-operation of the redundant robotic arm was evaluated in the workability. Two types of manipulation methods —a single-operator system that switched the target robotic arm and a multi-DoF body-integration system used by two people— were compared through an object-manipulation task involving obstacle avoidance. It was shown that the two-person co-operation through body integration system to be faster than the single-person operation.

Teleoperation makes it possible to work in in-accessible environment. To do so safely and effectively, some means of force feedback is necessary. However, force feedback methods that involve a reaction force often require bulky equipment. Instead, our study has utilized force feedback using vibrotactile stimulation. Although the modulation method of force information to vibrotactile stimulation has previously been demonstrated in magnitude (AM) and frequency (FM), we propose a method called AFM that uses amplitude and frequency modulation simultaneously to improve performance. In particular, we adjusted the amplitude using the sensation level and used logarithmized frequency for the AFM. First, the vibrotactile detection threshold of participants was measured to determine the amplitude to be equivalent in the same sensation level among participants. Then, the performance of discrimination was evaluated through stair-case psychophysical experiments. The results showed that our proposal AFM method significantly improved the discrimination sensitivity for the force information as compared with AM and FM methods.

Humans have spatiotemporal limitations. Robotic avatar technology enables the expansion of an individual's innate physical characteristics, physical capabilities, and perceptual and cognitive abilities. Our research group has focused on scalability and co-creativity through co-operation and collaboration between humans, and has developed a system in which two operators are physically integrated into a single robotic arm. In particular, to enable more human-like tasks, such as receiving and delivering, we extended the system to a dual-arm robotic avatar and built a system in which multiple persons can integrate their bodies, with the expectation of further task efficiency and human extension. Specifically, we investigated the workability and operator cognition of the dual-arm robotic avatar when it was operated by one, two, or three individuals. The results showed that stability improved with the three-person operation. Furthermore, it was found that co-operation among multiple persons can overcome the original individual abilities for operation. In the three-person condition, all participants obtained a higher feeling of control than the actual amount of manipulation, which has potential applications in skill transfer. The three-person condition tended to be better, validating the usefulness of multi-person body integration.

Tactile sensation is essential for recognizing mechanical interactions between the human body and its environment; it is generally uniquely experienced by individuals. Haptic sharing technologies enable to share of other person’s (or robot’s) tactile sensations, and it is expected to apply for skill learning, collaborative work, and robot operation. While wearable tactile sensors are useful for tactile measurements, they are affected by differences in physical characteristics between individuals. Therefore, to accurately convey the tactile information felt by others and utilize it for work, it is necessary to remove individual differences due to differences in individual physical characteristics. In this study, based on the frequency based intensity of skin vibration of an individual, the vibration detected by the acceleration sensor affixed to the fingertip was modulated to remove individual differences. To confirm the effectiveness of the proposed method, we investigated both physical and perceptual similarities for skin vibrations collected from three persons with three different fine textures. The results showed that vibrations individually modulated with the proposed method was similar in the intensity and power spectrum density than those using the uniform modulation function, and was perceived similar when presenting those with a vibrator.

Crafting workshops are useful methods for the promotion of products because it can let customers know about the technical and social appeal of the product. In this study, we have developed simple, portable, and active multisensory VR systems of crafting experiences for product promotion. It comprises a video of crafting a wooden object with scent and hand motion synchronized with the video. The result of the product evaluations demonstrated positive effects, wherein the participants were found to be more attracted to the product in the video, where only scent or haptic stimulations were presented. However, the result also indicated that there is a negative synergetic effect when two stimulations were simultaneously presented.