In this work, we developed a peristaltic bioreactor with an enhanced crushing capability, inspired by the structure of the avian gizzard. Existing peristaltic bioreactors have limited ability to crush boluses, which makes the fermentation of substances such as agar gel time-consuming. To improve crushing capacity, we focused on bird gizzard. Birds utilize pebbles in their gizzard to aid in food crushing. Our approach replicates this mechanism by incorporating both fixed and freely movable spherical solids, which are compressed during operation, inside the bioreactor. An agar gel crushing experiment demonstrated improved crushing efficiency. Furthermore, in a mixed fermentation experiment using milk agar gel and yogurt, the pH value declined compared with that observed using a conventional device, indicating an increase in lactic acid bacteria. These results confirm that the proposed method effectively enhances fermentation.

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.

Artificial muscles are advantageous owing to dynamic stiffness; however, the drawback of this is their poor controllability. Here, a reinforcement learning-based control system is proposed and exemplified on a realistic artificial muscle-driven robot. The proposed system suppresses the modeling error, and allows to generate dynamic motion patterns that utilize the body structure and variable stiffness characteristics. As an example application, we consider drum playing. We propose a reinforcement learning-based realistic drum-playing robot. We propose a reinforcement learning-based strategy for this realistic robot and confirm its effectiveness through simulations and experiments.

For space rockets, a rotating mixer is used to produce solid fuel. However, mixing with the rotary mixer is subject to high shear forces that limit the equipment drive. In a previous study, the authors developed a new production method using a pneumatically driven peristaltic mixing pump that simulates the intestine and a sensing system with pressure and flow rate sensors. Solid rocket fuel was successfully produced by a small pump unit. In this study, mixing experiments of solid propellant consisting of several types of powders, including metal powder and highly viscous fluids were conducted using a pump unit with a volume size eight times larger than that used in the previous study. In this experiment, mixing was performed with the materials packed in a plastic bag to increase efficiency. This reduces the contact area between the rubber tube and the contents of the device. Because only part of the mixing process is reflected in the behavior of the device, it is difficult to see differences in the sensor values, and it is unknown whether existing methods can be applied. The results of the experiment showed that the existing sensing system could be used to confirm the differences in characteristics due to the mixing process based on the time series data of air pressure and flow rate. By using Gaussian mixture model, which is a type of clustering, the mixing state was roughly binary discrimination from the acquired sensor values. This suggests that it is possible to estimate the mixing degree in large pumps using existing systems.

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 wearable assist devices, the assumed and actual command timings are different. This discrepancy cause problems, such as a decrease in the assist effect. In this study, we focus on viscosity, which is a characteristic of human muscles, and propose viscosity assistance to solve the problems. This method outputs the torque based on the predetermined viscosity coefficient and the actual angular velocity if the torque and angular velocity of the human joints are in opposite directions. The possibility of viscosity assist is demonstrated by analyzing the seated movement, and an assist device using a magnetorheological fluid brake is developed. The assist device is driven using three command inputs: time-based, joint angle-based, and constant viscosity coefficient command inputs. Under conditions based on time and angle, the actual output deviates from the assumed value when the motion is different from the expected motion. In terms of the viscosity command, when only the constant command is used throughout the entire motion section, some subjects showed almost identical results to those expected. Even if a deviation from this assumption is indicated, the degree of agreement can be improved by switching several types of viscosity coefficients during motion.

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.

Many haptic devices are currently being developed for human upper limbs. There are various types of force feedback devices for upper limbs, such as desktop and wearable type. However, the lower limbs absorb most of the force when standing or walking. Therefore, to render the sensation of force to the lower limbs, a device worn like a shoe to enable users to walk and have a wide range of movement and a device that provides a dropping sensation have been developed. However, both wide-area movement and a dropping sensation could not be combined in one device. Therefore, the authors propose the concept of a lower limb force feedback device that allows the user to wear it like a shoe and provides the sensation of dropping while enabling wide-area movement. In addition, as the first stage of device development, the authors evaluated the human sensation of dropping. Consequently, it was found that a relatively high sensation of dropping can be provided to a human even with an acceleration smaller than the gravitational acceleration in real space. Thus, the lower limb force feedback device to be developed in the future will allow the user to experience the sensation of dropping by using an acceleration smaller than the gravitational acceleration in real space.

Busy agricultural seasons involve long-term continuous work and heavy labor. Particularly during overhead work, such as harvesting, gibberellin treatment, and bagging, workers need to consistently raise upper limb weights of approximately 2 to 4 kg with their own muscular strength, resulting in a high work burden. For long-duration work in the field, a passive and robust assist system is advantageous. Therefore, we propose an assistance device named TasKi that uses self-weight compensation mechanisms and horizontal link mechanisms to reduce the burden on a worker's upper limbs during overhead work. TasKi can compensate for upper limb weight by using the force of a spring in various postures of the upper limbs without battery support. In this report, we describe the design of the TasKi mechanisms that achieve the upward work assist in actual agriculture with a simple structure. The mechanism of self-weight compensation and the degree of freedom and parameters of the link mechanism are studied.