In virtual reality (VR) environments, enhancing force feedback is crucial for achieving immersive and natural interactions. Force feedback devices are generally used to present stiffness and resistance, allowing users to perceive physical properties of virtual objects. However, even with force feedback, users may fail to perceive contact despite visual confirmation that the object is being touched. This can be attributed to timing mismatches between visual and haptic cues, which often result from actuator latency or communication delays in the system. To address this issue, we developed a multimodal haptic presentation system that combines force feedback using a magnetorheological (MR) brake with vibrotactile feedback. The integration of vibration aims to complement force feedback, enhancing the sensation of contact. Experiments were conducted to evaluate the effectiveness of the proposed system by comparing four feedback conditions: no feedback, force feedback only, vibrotactile feedback only, and combined feedback. The results indicated that the combination of force and vibrotactile feedback significantly improved contact perception and pressing sensation, especially in upward and forward pressing tasks. Additionally, vibrotactile feedback alone was found to enhance contact sensation compared to force feedback alone, suggesting that vibration effectively compensates for contact perception when force feedback is insufficient. These findings demonstrate that combining force and vibrotactile feedback contributes to more realistic and intuitive haptic experiences in VR, providing valuable insights for designing advanced haptic interfaces.

We present the development of a wearable body support device for LP gas delivery work and evaluation of the device by wearers. This study proposes a method for reducing the physical burden involved in delivering LP gas cylinders, as LP gas cylinders are transported manually. Delivery personnel must navigate stairs and narrow spaces, which make it difficult to use existing methods for reducing physical burden, such as carts. We aim to develop a device that can be used for LP gas delivery. In a previous study, we conducted a field survey. We found that the burden on delivery workers was due not only to carrying the cylinder, but also to lifting. Based on the field survey, this paper describes the development of a lifting support device that reduces the physical burden and facilitates smooth delivery. The subjective evaluations confirmed that the proposed device reduced the physical burden while providing the same ease of lifting as do conventional grasping methods. The device is designed to support lifting during delivery work and greatly supports lifting movements during delivery work.

In this study, a two-step dropping model was proposed to replicate a long-distance fall in a virtual reality (VR) space, while realizing only a short drop distance in reality. In a previous study, a two-step dropping model representing a falling motion was proposed and presented to humans in real space. This concept replicates the sensation of a long-distance fall by presenting the dropping motion to the wearer only at the start and landing of the fall in the VR space. A two-step dropping device was fabricated using an air cylinder. A two-step dropping motion was realized by combining the open/close control of the conduit with a directacting solenoid valve and pressure control with a proportional solenoid valve. In the sensitivity evaluation experiment, participants were presented with a combination of the device's operation and VR images. The evaluation scores for the sense of reality of falling in the two-step dropping condition tended to be higher than those in the other conditions, compared to the condition in which the device was not operated or only one-step dropping was presented. This confirmed that the two-step drop was an effective operation for experiencing a free-fall sensation.

In recent years, force feedback devices have been developed to improve the reality of virtual reality (VR) experiences. However, most of the general force feedback devices target the upper limbs. By realizing force feedback to the lower limbs, it is possible to realize an experience in VR space that cannot be achieved by force feedback to the upper limbs alone. Therefore, in this study, we developed a lower limb force feedback device based on a physical model of the human lower limb. The output torque of the developed device that met the target torque by the experiment was confirmed. The device was then experimented with to determine if it could reproduce an impact force similar to that of a soccer pass as an initial study. The results suggested that even a low torque of 10 Nm could reproduce a soccer pass.

Recently, force feedback devices have been developed to improve the virtual reality (VR) experiences. However, most conventional force feedback devices target the upper limbs. In addition to achieving force feedback to the upper limbs, realizing force feedback to the lower limbs will make it possible to realize an experience in the VR space, which would not be achieved by force feedback to the upper limbs alone. The authors have elucidated the perceptual characteristics of the human dropping sensation to present force feedback to the lower limbs. In this study, we develop a pair of wearable force feedback shoes that can realize the falling sensation in the VR space. The proposed device meets the required specifications for descent height and acceleration to render the falling sensation. Furthermore, we confirm the usefulness of the theoretical equation by measuring the basic characteristics of the developed device.

Because information transmission by force is a vector quantity with magnitude and direction, it can directly affect humans. However, most existing force feedback devices are stationary, and their movement is restricted. On the other hand, wearable force-feedback devices induce a strange feeling, as they must support the reaction force of the presented force at the body fixing part. Therefore, in this paper, we propose a posture guidance method using force feedback provided by air jets. Specifically, for table tennis movement guidance, we developed a prototype with two degrees of freedom using a table tennis racket. We also conducted a hand posture guidance experiment and confirmed that the proposed method can guide the wrist posture without disturbing the wearer's movement.

In this study, we evaluate the dropping sensation for the development of a wearable lower limb force feedback device that can render both dropping and walking sensations. The developed device can render the dropping sensation at a smaller height than in reality by decelerating and stopping descent during the rendering of the drop image. Considering the user will be walking with the device, a smaller device height leads to better safety. The purpose of this study is to clarify the required specifications of the height of the vertical range of motion of the platform part, and the feasibility of the concept of rendering the dropping sensation. For this purpose, the dropping sensation for the difference in human acceleration time and human deceleration acceleration was evaluated. The results showed that the rendering of the dropping sensation required more than 0.41 s of descent at an acceleration of approximately 1377 mm/s2. Moreover, the dropping sensation and sense of reality were not impaired, even when the platform part of the foot was decelerated. This result indicates that the device can be made smaller.