This study aims to develop a single mobile robot capable of navigating confined spaces characterized by non-circular cross-sections, embedded obstacles, and bends that are difficult for human access. To this end, we propose the Multi-Flexible Wheel Robot using brushes and elastic springs. The robot can adapt its body shape to the surrounding geometry and rotate along the meridional direction, enabling it to traverse a wide range of complex environments. This paper presents the conceptual design and driving model of the Multi-Flexible Wheel Robot, along with experimental results obtained using an initial prototype in confined space locomotion tests. In the tests, the robot traversed a straight duct with a 250 mm inner diameter and 1000 mm length in 13 s, a similar duct containing obstacles in 23 s, and a duct with varying cross-sectional geometry in 19 s. These results demonstrate the robot can transmit rotational force to multiple brushes via a deformable ring-shaped elastic structure, enabling it to autonomously navigate confined spaces that include non-circular cross-sections, obstacles, and bends.

This study aims to develop an autonomous decentralized motion generation system that adapts to the state of the target material to be mixed and transported within a peristaltic pump designed in a manner analogous to intestinal peristalsis. The authors investigate the discrepancy function, which serves as a control law for modular snake-and amoeba-type robots, and propose a method for achieving autonomous decentralized control by regulating the phases corresponding to the supply and exhaust states within each unit of the peristaltic pump. The application of the local feedback term g(θi) was experimentally verified using a two-unit coupled pump to investigate the transition from in-phase motion to mixed-phase motion. The results showed that the phase difference between the units transitioned from in-phase (0 rad) to anti-phase (π rad), demonstrating that the local feedback term induces a phase delay and enables the desired mixed motion. In addition, by applying a control law based on the discrepancy function to the material whose viscosity decreases as mixing progresses, the pump's motion pattern was observed to transition in response to the mixing state of the material. As a result, the motion pattern shifted from mixing motion to peristaltic motion approximately 230 s after the start of mixing. These findings indicate that the pump autonomously and in a decentralized manner switched its motion pattern in accordance with the internal state of the material.

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.

This study develops an autonomous cleaning robot designed to remove accumulated grease in restaurant kitchen ducts, where human access and manual cleaning are not feasible. Prior studies have developed cleaning mechanisms for round ducts employing planetary gear systems, demonstrating their efficiency in grease removal. However, these systems lack propulsion mechanisms, and cleaning experiments have been limited to short-distance, small-diameter pipes (140 mm, 100A). Therefore, no system has been developed for cleaning grease in long-distance, large-diameter ducts in real-world environments. To address this limitation, we developed a self-propelled cleaning robot integrating a planetary gear-based cleaning mechanism and an inchworm-inspired propulsion mechanism. The design of the propulsion mechanism involved modeling brush rotational torque, gripping torque, and gripping force. Based on this model, a duct inspection and cleaning robot equipped with both propulsion and cleaning mechanisms was developed. Subsequently, the developed robot was tested in a 9 m mock-up duct to evaluate its self-propelled cleaning performance. The robot removed an average of over 85% of the grease under all test conditions while operating autonomously. Finally, a cleaning experiment was conducted in a butcher shop duct, where the robot removed most of the adhered grease. These experiments demonstrated that the developed robot can autonomously clean and inspect ducts in real-world environments where human entry is impractical.

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.

Deep vein thrombosis (DVT) is a disease in which blood clots form in the deep veins of the lower limbs. It is a common condition particularly for wheelchair and bedridden patients due to prolonged sitting and supine positions. Calf compression and ankle exercises can prevent DVT, and current studies aim to combine them. However, existing devices suffer from low user comfort because of their exoskeletal structure, which consists of a rigid frame. In addition, the devices have not been tested in various positions, such as sitting and supine positions. This study introduces a flexible DVT prevention device that combines intermittent pneumatic compression (IPC) with assisted ankle exercises, which can be used in high-risk positions. The developed prototype has an endoskeleton-type structure with soft actuators, enabling natural ankle movements while remaining lightweight. Basic characteristic experiments with the prototype demonstrated that a maximum joint range of motion of approximately 30° could be achieved with a force exceeding 50 N when combining IPC and ankle exercises in both the sitting and supine positions. Blood flow evaluation experiments further showed that the combined therapy of IPC and ankle exercises, regardless of the position, was more likely to prevent DVT than no motion or single-motion modes effectively.

Exoskeleton-type assistive device is worn directly on the person, so it is important to improve coordination. In previous studies, the authors focused on the viscosity characteristics of human joints, proposed a knee joint assist method with a wide tolerance range for misalignment between the human and the device, and confirmed the effectiveness of the method. However, in previous studies, assist torque was output based on device information, which affected the misalignment between the device and the wearer. Therefore, this study examines the assist effectiveness of a viscosity assist method using inertial measurement units (IMU s) that can be directly attached to a person. In the first experiment, we compared measurements taken by an encoder mounted on the knee joint of the device and by IMU directly attached to the person during a squatting motion, and compared the misalignment of the measurements depending on the presence or absence of a command torque to the device. As a result, we confirmed the effectiveness of the IMU in reducing the misalignment between the measurement values of the device and the wearer. In the second experiment, we proposed knee joint viscosity assist method based on IMU angular velocity data during seated movement, and verified the assist effect of the proposed method and the method proposed in the previous study by measuring surface electromyography potentials. As a result, the effectiveness of the proposed method was confirmed.

This study proposed a peristaltic motion-type inspection robot equipped with a "linear antagonistic mechanism using artificial muscles with an endoskeletal structure" to amplify propulsion and traction. We sought to develop an in-pipe inspection robot for long, narrow, and complex pipes requiring large propulsion, traction, and flexibility. In a previous study, we proposed a linear antagonistic mechanism allowing the inspection robot to generate both high propulsion and traction along with flexibility in narrow pipes. The proposed mechanism consisted of two extension actuators and a gripping actuator sandwiched between these extension actuators. The large extension force by the extension actuators is distributed to both propulsion and traction. However, owing to the piston-shaped configuration of the extension actuators, the generated force decreased in a manner dependent on the cross-sectional area within narrow pipelines. Therefore, the in-pipe inspection robot took time to move in long-distance, small-diameter pipes with multiple bends. This paper describes a "linear antagonistic mechanism using artificial muscles with an endoskeletal structure" that amplifies propulsion and traction by inserting a tension spring (skeleton) inside the contraction actuators (artificial muscles) and utilizing the action force generated by the actuator and transmitted by the tension spring. In this study, the developed robot with an endoskeleton exhibited maximum propulsion of 60.2 N, surpassing its non-endoskeleton counterpart by a factor of 1.61. Furthermore, the robot equipped with the endoskeleton passed through an elbow pipe 1.29 times faster than that without the endoskeleton, reducing the time from 741 to 576 s. The function value that compares the propulsion and traction considering the effects of the applied pressure and pipe diameter required for long-distance inspection was more than 1.13 times that of the previous study. In addition, the non-dimensionalized traction was 1.55 times greater than that of any other pipe inspection robot, and the propulsion was large enough to pass through a bending pipe. This result indicates the feasibility of the developed robot for inspecting long, narrow, and complex pipes.

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 recent years, the sea ice in the Arctic Ocean has been decreasing due to climate change caused by greenhouse gases. Therefore, the phenomena under the sea ice must be investigated. The existing method of autonomous underwater vehicle (AUV) exploration is limited by its narrow communication and acoustic triangulation range. Therefore, digging a hole through the ice sheet is proposed to secure a communication relay system under the ice sheet. The objective of this study is to develop a robot using peristaltic motion as a system for drilling holes in sea ice. In the previous study, we determined the required specifications for the sea ice drilling robot. In this study, the excavation unit and the propulsion unit of the sea ice drilling robot are developed according to this specification. The basic characteristics of each mechanism were evaluated, and the digging performance of the excavation unit and the gripping performance of the propulsion unit were confirmed.

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 this paper, we describe the development of short-fiber oriented rubber and its application to elongation-type actuators. Short-fiber oriented rubber, i.e., rubber containing oriented short fibers with lengths of 3 mm, has anisotropy in the direction of fiber orientation. In a previous study, it was shown that short fiber-reinforced artificial muscles made of short-fiber oriented rubber can achieve up to 17% shrinkage. However, in that study, characteristics other than the amount of shrinkage were not measured, the basic characteristics of the developed artificial muscle were unclear, and the shrinkage ratio was smaller than that for existing straight-fiber-type artificial muscle. In the present study, we developed a new method for fabricating short-fiber oriented rubber and measured the tensile characteristics in the direction of fiber orientation and vertical to the orientation direction. Moreover, we developed an elongation-type artificial muscle from the rubber sheet and measured its elongation characteristics. Test results indicated that the fabricated rubber sheet had anisotropy. They also indicated that the anisotropy increased with the fiber concentration and that the fiber restraint acted not only in the orientation direction but also in the vertical direction. Furthermore, the developed elongation-type artificial muscle was three times more anisotropic in the ratio of axial changes to diametral changes. On the basis of these results, we expect to develop an automated production method for soft actuators.

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.

There is an urgent requirement to solve the problem of global warming. The sea ice beneath the Arctic Ocean strongly affects the global climate. However, it has not been fully explored. The range of Autonomous Underwater Vehicles (AUV) used for under-ice exploration is limited owing to their short communication range. To solve this problem, we propose a communication relay system that uses a sea ice drilling robot. We conducted excavation and gripping experiments on actual sea ice to study the parameters and control methods required to design a sea ice drilling robot. The required specifications of excavation and propulsion units were obtained from the experimental results, and a recovery method was developed to address drilling failure.

An anchoring mechanism was designed for an earthworm-type robot that can inspect without slipping in sewage or oil pipes. A conventional robot moves through pipes making use of the friction between its surface and the inner surfaces of the pipes. It is difficult for the robot to inspect in pipes where viscous liquid remains. Therefore, a mechanism for inspecting in slippery pipes was developed. A mixture of rubber dough and antislip material was used to produce enhanced frictional force. Three types of antislip were compered based on measurements of the coefficient of friction. The highest frictional coefficient was generated by the material mixed with the largest blast material. The developed anchoring mechanism applying the material increased the frictional coefficient by 3.59 times compared with conventional anchoring mechanisms. These results provide innovative insights into the development of inspection robots in challenging environments, such as those in which anchoring is difficult.

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.

Using a head-mounted display, users can immerse themselves in virtual reality space and users can via the visual recognition of virtual objects. However, users do not experience the same haptic perception when they interact with these objects, that they do with actual objects. Force feedback devices can render haptic perception. They are classified into desktop and wearable types. A wearable 1 degree of freedom force feedback device using magnetorheological fluid brake, magnetorheological clutches, and pneumatic artificial muscles has been previously developed and it was confirmed that the device can render elasticity, friction, and viscosity. In addition, a wearable 4 degrees of freedom force feedback device using magnetorheological fluid clutches and pneumatic artificial muscles that can render elasticity was also previously developed. However, it was not established that the device could render friction, and viscosity using magnetorheological fluid clutches and pneumatic artificial muscles. In this report, it is confirmed that such a device can render friction and viscosity using magnetorheological fluid clutches and pneumatic artificial muscles without the need for magnetorheological fluid brake.

The cleaning of residential ventilation ducts is necessary to prevent damage to health. However, since residential ventilation ducts are usually thin and curved, cleaning them is difficult. It is also difficult to obtain thrust within the duct using a wheel or a snake type robot because it is hard to obtain an appropriate reaction force in a deformed pipe. Therefore, the pipe must be gripped stably even if it is flexible so that thrust can be generated to run the cleaning robot through the pipe. In this paper, we modeled a cleaning robot that uses peristaltic motion running through a flexible duct with an inner diameter of 50 mm. Then, the validity of the model was verified by experiment. Finally, a cleaning experiment was conducted and the cleaning rate was 98.7 %.

Recently, in the search for alternatives to conventional robots, various types of soft actuators and their applications have been studied. In particular, pneumatic soft actuators have the advantage of being lightweight and high power. One of the uses of these soft actuators is as a substitute for an electric motor to actuate the joint of a structure, such as a link mechanism. Another use involves their fusion with a flexible structure. The features of this concept are a simplified system, in which almost all interfaces can be configured as flexible structures. However, because these actuatable flexible structures are made with rubber, silicone, or flexible resin, it is difficult for them to support their own weight owing to the effect of the square-cube law in the case of increasing size. Hence, these structures are limited to a size of approximately 1 × 10-21 × 10-1m. If an actuatable flexible structure with a size of 1 × 100m can be realized, the concept of soft actuator-flexible structure fusion is expected to provide novel solutions and applications. Herein, as a feasibility study, large actuatable flexible structures were developed. The proposed structure, LayerCAKE, is a laminated open-cell and closed-cell foam structure; cell foam is a lightweight and flexible material that can be used to realize large actuatable flexible structures. LayerCAKE is actuated by using the concept that openand closed-cell foams contract differently when they are vacuumed. The bending-motion model and was experimentally verified, and different types of LayerCAKE models that could exhibit various types of motion were developed and tested. Furthermore, a complex-shaped LayerCAKE model (in the shape of a human hand) was developed. A large actuatable flexible structure of approximately 900 mm was realized. Furthermore, it was confirmed that the bending motion could be controlled by pressure.

Currently, serious accidents are caused frequently by the aging of sewer pipes. Therefore, to inspect sewer pipes, we developed a peristaltic crawling robot that reproduces the locomotion of an earthworm. This robot can drive for more than 100m, and it can be used for the maintenance of sewer pipes (100A pipes). However, the speed of the robot is low. There are two causes. First, the units of the previous robot have steps of artificial muscle fastening. These steps increase the diameter of the artificial muscles. A smaller diameter of the artificial muscles is advantageous for the speed of the robot inside the pipes. Second, the previous robot has slow air response. In this study, we used large-sized solenoid valves to overcome this drawback.

For unmanned rescue, observation, and/or research, vehicles with high terrain adaptability, high speed, and high reliability are needed to reach hard-to-reach-locations. In order to extend the areas that can be explored, we propose a method and a robot capable of running on the surface of water without having to bypass the puddles and streams that exist on uneven terrain. The method that enables the robot to run on the water surface is bio-inspired by the basilisk lizard that can walk on the surface of water. We developed a blade-type crawler robot with a simple and reliable mechanism, capable of traversing uneven terrain at high speed. The robot with the method was tested on a real water surface and the result confirmed the ability of the robot to run on the water surface.

In recent years in Japan, over half of all workers suffered from lower back pain. This has become a social problem that needs to be addressed. To reduce its occurrence, we developed a flexible, high-output waist assist suit called “AB-Wear” in a previous study. The AB-Wear suit can assist human motion and reduce muscular fatigue of the waist. However, the assistive forces of the device generate compressive forces on the backbone, which have adverse effects on the body. Hence, in this study, we propose an exoskeleton-type AB-Wear equipped with a compressive force reduction mechanism, called “semi-endoskeleton-type AB-Wear”. This device has a reduction mechanism similar to a flexible flat spring behind the upper body. Because of this structure, this device can generate an effective assistive force. First, we explain the difference between the semi-endoskeleton-type AB-Wear and the previous device. Then, we model the semi-endoskeleton-type AB-Wear because the model is used for its operation. Moreover, its effectiveness is confirmed using musculoskeletal simulation. Finally it is evaluated by measuring surface electromyography (EMG) on a subject's body to confirm its effectiveness with a real body. The EMGs of the wearer with and without the suit are compared. The usefulness of the AB-Wear is confirmed by simulation and experiment.

Unmanned rescue, observation, and/or research vehicles with high terrain adaptability, high speed, and high reliability are needed in difficult-to-reach locations. However, for most vehicles, high performance over rough terrain reduces the travel speed and/or requires complex mechanisms. We have developed a blade-type crawler robot with a very simple and reliable mechanism, which traverses uneven terrain at high speed. Moreover, the gyro wheel design stabilizes the success of this approach in improving the motion, ensuring robust traversal. The improvement in traveling speed and robustness over uneven terrain by our approach was confirmed by experiment.

In this study, a variable viscoelastic joint system comprising antagonized artificial muscles and magneto-rheological fluid brakes is proposed. This system enables human assisting devices such as robotic exoskeletons to retain structural softness when compared with the existing devices driven by motors and reduction gears, which can only achieve superficial softness. The authors had proposed the system and showed its effectiveness via experiments using a prototype with one degree of freedom in their previous works. In this study, as the next step in designing the human assisting device, a lower body assistive prototype “Airsist” is introduced. In addition, a control method that can cooperate with the wearer without the need for an additional operation is proposed.

A range of pneumatically-driven devices have been developed. However, these require a large air compressor, making them heavy, bulky, and therefore inappropriate for use in portable devices. In this study, we proposed and tested a portable pneumatic power source using the chemical reaction between sodium bicarbonate and citric acid. The carbon dioxide generated in the reaction was used as a pneumatic power source. The chemicals used are inexpensive, nontoxic, and readily available. From the result of basic experiment demonstrated in this paper, we conclude that the method can provide enough high pressure (more than 1 MPa) for activating pneumatic actuators and the chemical reaction is safe since it is endothermic reaction. We also demonstrated a novel system that provides continuous mixing of the reagents, using a pressure booster. The system keeps a pressure inside of a tank moderate, and tank can become light weight because it doesn't need to endure high pressure.

Sub-seafloor exploration is an important area of biological and geological research, and often requires samples of seafloor mud to be recovered. The minerals and marine sediments trapped in this mud are also potentially valuable resources. However, seabed exploration has been limited by the complexity and cost of the traditional equipment used. Wide area exploration can be made possible by deploying multiple robots to autonomously search beneath the ocean floor. In this study, we prototyped a sub-seafloor excavation robot for use in seabed exploration. The key system comprised a propulsion unit and an excavation unit that allow the robot to move freely within the seabed. We experimentally demonstrated the ability of the excavation robot to produce curved boreholes with a diameter of 160 mm, a turning radius of 1.67 m, and a depth of 613 mm. Our experimental results confirm that nonlinear excavation is possible using the excavation robot developed.

Lower back pain is a major health concern worldwide. One cause of lower back pain is the burden on the lumbar region caused by the handling of heavy objects. To reduce this burden, the Ministry of Health, Labour and Welfare in Japan has recommended “squat lifting.” However, this technique, which supports a large force on lower limbs, is not very popular. Therefore, we aimed to develop a power assist suit for squat lifting. In this paper, we propose a gastrocnemius-reinforcing mechanism. Next, we discuss estimation of joint torque from motion analysis of squat lifting in order to construct a prototype. Finally, we describe the performance of the prototype mounted on a human body. The %MVC of the gastrocnemius while performing squat lifting was reduced by 40% using the prototype assist suit compared with the value without using the suit.

In this paper, permissible resistant torque considering back-drivability is verified to develop a wearable assist suit (WAS). The WAS has a clutch and a variable viscoelasticity joint. In this paper, permissible resistant torque is defined as torque that is acceptable in daily use. As first stage of the WAS development, the paper discusses the relationship between the resistant torque to the knee and the degree of discomfort experienced by the wearer as evaluated through a survey questionnaire experiment. In addition, the influence of the resistant torque on a muscle of the knee extension is considered and confirmed by measuring surface electromyography (surface-EMG).

Low back pain of workers is increased in workplaces that involve hard work. It is caused by excessive loading of the waist joint and muscle fatigue. Therefore, power-assist suits have been developed to decrease the load on the waist joint. However, previous power-assist suits have had problems such as low output or heaviness. Thus, we have developed an assist suit that is lightweight and exerts a large force. A balloon actuator and pneumatic artificial muscles are attached to assist suit as the actuators. The assist suit has various desirable features: lightweight, flexibility, and high output. First, human motion is analyzed for the development of the assist suit. The assist suit is developed to assist the waist joint torque. The assist suit is modeled, and the theoretical values of its generation force are estimated using an assist-suit model. Finally, the assist suit is evaluated by measuring the surface electromyography (EMG). The EMG of the wearer is compared with that without the suit. The effectiveness of the assist suit is confirmed by a decrease in EMG.

In this study, a variable viscoelastic joint system with a clutch for a human assistance was proposed. The variable viscoelastic joint system comprised antagonized artificial muscles and magneto-rheological fluid brake (MR-brake). This system enabled the human assisting device such as exoskeletons to retain structural softness when compared with the existing devices driven by motor and reduction gear, which could only achieve superficial softness. In addition, a clutch system that provided high back-drivability to the wearer by structurally separating the device from the wearer was proposed. As an initial step in designing the human assisting device, a prototype with the proposed variable viscoelastic joint system for knee assistance is developed. Also, its control method were developed. Furthermore, experiments were conducted to confirm the influence of the proposed viscoelastic joint system on the wearer and the effectiveness of the clutch system.

A desktop force feedback device is able to render reaction force of virtual objects. However, the desktop type limits operator's motion. In contrast, a wearable force feedback device allows us to interact with virtual objects while moving in virtual space. In this study, we have developed a 1-DOF wearable force feedback device with MR brake and pneumatic artificial muscles. These actuators are lightweight, have a high power density, and are controlled by feed-forward control. This device is equipped with the operator's arm and renders various forces, such as friction, elasticity, and viscosity. In this paper, we improve the device to solve existing problems from previous studies. The proposed device is tested to confirm its basic properties. It is applied to augmented reality space and comparisons of subjective evaluations between virtual objects and actual objects.

Lower back pain accounts for more than half of all reported on-the-job ailments, escalating from a personal challenge to a broader societal challenge. Researchers have developed a power assist suit intended prototype to reduce the incidence of lower back pain in the workplace when process automation is not possible. Equipped with two pneumatic actuators, the prototype suit is lightweight, flexible, and efficient. The prototype suit can assist human motion using passive and active forces. In this study, researchers confirmed the effectiveness of passive assistive force. Two types of motion were considered: lifting and unloading in a crouching position and carrying. Researchers first analyzed the subject motions using video analysis software. Waist joint loads were estimated using motion analysis results and a human link model. Second, researchers determined the power assist suit's operational parameters and developed a power assist suit model. Lastly, researchers confirmed the passive force prototype suit's effectiveness based on measured changes in generated force and electromyography.

Recently, force feedback devices that intuitively achieve excellent operation have attracted attention in a wide range of fields such as remote operation, virtual reality, and medical training systems. However, it is difficult for conventional devices to widely display soft and hard objects because of driving motors. Moreover, they are likely to be hazardous in the event of delayed response to an unexpected external force. To solve these problems, we previously developed a force feedback device using pneumatic artificial muscles, which are structurally flexible and have wide a range of stiffness, and magnetorheological clutches. Furthermore, we confirmed that any three-dimensional virtual object can be displayed using the developed device. However, when the operation part of the force feedback device is moved away from the virtual object, it remains stuck to the virtual object. In this study, we propose a system to reduce the sticking phenomenon and experimentally confirm the reduction rate (85%). Moreover, we displayed viscous torque as a new application of the feedback device.

Bipedal robots capable of various dynamic motions such as walking, running, and jumping have been developed in recent years. In particular, these dynamic motions require the use of high power in a short time when the robot kicks off the ground. Furthermore, it is necessary to decrease the impact force that a robot is subjected to when landing during these motions. Unfortunately, rigid actuators tend to become heavier as their output increases. Therefore, we focus on the method for obtaining a high output using elastic energy. However, the use of the elastic element only leads to robot vibration. Therefore, to control the dynamic motion, we adopted the viscosity element to the robot joint. In this study, we focused on a straight-fiber-type artificial muscle for the elastic element and a magnetorheological brake for the viscosity and friction elements, respectively. A previously designed monopedal robot was able to jump 82.5 mm using a sliding rail and counter weights; however, the robot shook upon landing because of the presence of the elastic element in its artificial muscles. In this paper, we first proposed a dynamic model of the previously developed monopedal robot. We then performed vertical jumping simulations of the robot to confirm the model's utility.

Unmanned rescue, observation and/or research vehicles with high terrain adaptability, high speed, and high reliability are needed to reach difficult locations. However, most vehicles achieve improved performance over rough terrain at the expense of low speed and/or complex mechanisms. We developed a blade-type crawler robot with a very simple and reliable mechanism, capable of traversing uneven terrain at high speed, using aerodynamic devices. As these small devices are in the low Reynolds number region, we tested a wing that made use of the ground effect. We experimentally confirmed the success of this approach in improving the traveling speed and ability to traverse uneven terrain. The robot with aerodynamic lift was climbed 1.5 times higher obstacle than without wings.

Lifting heavy objects increases the risk of low back pain. In this study, we calculate the load exerted on the human body during an actual lifting operation. To assist lifting, we propose an endoskeleton-like suit that exerts an assistive force. A prototype of the assist suit is developed in this study. The force is exerted by a straight-fiber-type artificial muscle combined with an amplification mechanism. The notion of assistive force was subjectively evaluated by wearers, and confirmed in on a visual analogue scale. The electromyography signals of wearers were decreased, confirming the subjective assist effect.

Bipedal robots capable of various dynamic motions - such as walking, running, and jumping - have been developed in recent years. In particular, these dynamic motions require high power for short durations of time when the robot kicks off the ground. Furthermore, it is necessary to reduce the impact force that a robot is subjected to when landing during these motions. When humans perform similar motions, they generate an instantaneous high-power force using an elastic element and dampen the impact force using a viscous element in their muscles. Therefore, a robotic leg designed for jumping that relies on these elements has been developed. It uses a straight-fiber-type artificial muscle and a magnetorheological (MR) brake. A previously designed one-legged robot was able to jump 82.5 mm using a sliding rail and counter weights; however, it shook upon landing due to an elastic element in its artificial muscles. Here, therefore, an MR brake to dissipate energy is applied to the robotic leg in order to suppress vibration. Landing experiments performed with the newly designed one-legged robot confirm that the proposed method (i.e., using the MR brake) is able to suppress vibrations.

Sub-seafloor explorations are important for biological and geological research. Sampling mud is one of the major sub-seafloor exploration procedures. The mud-including mineral resources and marine sediments are potentially valuable resources for future studies. Therefore, we propose a peristaltic-crawling-based sub-seafloor excavation robot for deep sea exploration. This robot consists of three units (propulsion, excavation and extraction units), enabling it to move freely through mud. The excavation and propulsion units are fitted with an earth auger and artificial muscles, respectively. In this paper, we verify the propulsion actuator as the first stage of robot development. First, we evaluate the performance of an oil hydraulic artificial muscle under water pressure. Next, we develop an excavation robot by incorporating a pneumatic artificial muscle into a robot and then experimentally evaluate propulsion and excavation of the robot. We confirmed that the artificial muscle appropriately performs as an actuator for the excavation robot.

Sewer pipes play an important role in a city's infrastructure. However, accidents have occurred in recent years due to increasingly old pipes. To prevent such accidents, there is a need to check the internal condition of pipes. Therefore, we focused on the locomotion of a robotic earthworm that is capable of running stably in a narrow space. We developed a peristalsis crawling robot with the goal of traveling 100 m through a 100A pipe. The robot is composed of six unit sections, five joints, and a head section to which the inspection camera is attached. It uses an artificial muscle operated by air pressure. In this study, we developed a new joint to reduce buckling, increase the running speed, and decrease the unit size. Further, we developed a new head section that allowed passage through a 90° elbow pipe. We evaluated the effectiveness of the new robot, and conducted running experiments in horizontal, vertical, and two types of bent pipes.

In recent years, the demand for rocket launching has increased due to the development of space technology. However, using inexpensive rockets is not always possible. Although the cost of solid-propellant rockets is relatively reasonable, safely manufacturing a large amount of solid propellant is difficult, and the manufacturing process is disjointed. Therefore, safe and continues manufacturing of solid propellant is necessary. On the basis of the movements of the intestinal tract, we realized that the movements required for transport and mixing of solid propellants are possible to achieve without the application of a large force. By mimicking these intestinal movements, we can safely and continuously manufacture a large amount of solid propellant. We developed a peristaltic pump, based on bowel peristalsis, using straight-fiber-type artificial muscle, and in this study, we demonstrate the usefulness of this pump for transporting the highly viscous fluids and solid-liquid mixed fluid. We consider that the peristaltic pump can also be effectively used as a mixing device. In this paper, we show that mixing one highly viscous fluid with another is possible by measuring the luminance values. In the manufacturing process, we use glass beads with the same diameter as microparticles and a sodium polyacrylate aqueous solution resembling a high viscosity fluid or hydroxyl-terminated polybutadiene as the raw material in the solid propellant. We then measure the glass beads in the resulting solid-liquid mixed fluid.

Desktop haptic device has been developed in the field of rehabilitation and entertainment. However, the desktop type restrains human's movement. Therefore, it is difficult to receive force sense information, moving to wide range position and posture. In this study, we developed a 1-DOF wearable haptic device with pneumatic artificial muscles and a MR brake. These smart actuators have high power density and change its output force structurally. Therefore, this haptic device can render various force sense such as elasticity, friction and viscosity. In this abstract, we describe two experiments rendering elasticity and friction to evaluate the performance of the device.

Recently, flexible and light actuators that mimic muscle fibers have been actively researched. Here, we focused on an electroactive polymer (EAP) dielectric elastomer. To construct the actuator, the dielectric elastomer is rolled into a tube, and extended by applying a voltage across its electrodes. In this paper, we experimentally obtained a static characteristic model of the electrostrictive rubber actuator, and proposed a control method. We then incorporated the actuator into a 1-DOF manipulator, and constructed a controller from a mechanical equilibrium model of this manipulator. Finally, the constructed controller was tested in a series of experiments. The angle of the arm fell below the desired angle because of friction in the joint and the spring characteristics of actuators. However, we confirmed that the controller reduced the influence of the load by torque feedback. We also investigated the influence of joint stiffness.

Recently, a robot's activity has been spreading into the care setting and homes. For these robots to work alongside humans requires them to have the same flexibility as that of the human muscle and ensure safety even if they collide with humans. To satisfy these requirements, we examined pneumatic artificial muscles—which are not only provide high output but are also light, flexible, and safe—as robot actuators. However, the commonly used McKibben-type artificial muscles have several drawbacks. Therefore, we developed straight-fiber-type artificial muscles, which have a contraction ratio and force that surpasses those of McKibben-type artificial muscles. We also developed a 6-DOF manipulator that is actuated by straight-fiber-type artificial muscles. However, since the DOF of this manipulator is less than that of the human arm, it is difficult for the end effector to make detailed movements. To solve this problem, we developed a 7-DOF manipulator, introducing a new mechanism in the joints. In this paper, we introduce a new restraint condition to the inverse kinematic computation of this manipulator and propose the method of redundancy use. Finally, we conduct an experiment following the trajectory and verify the effectiveness of the proposed method.

This paper describes the development of an inspection robot for use in 1-inch gas pipes. These pipes are commonly used in residences and between gas meters and a main pipe that is buried under the road, and they require regular inspection. However, appropriately advanced inspection technologies have not yet been developed. An endoscope, which is the current inspection method, can only be utilized in a limited inspection scenarios. As for robot inspection, current in-pipe robots cannot pass through a 90-degree elbow, which has a radius of curvature equal to its inside diameter (Rc= 1.0 ID). However these elbows are frequently encountered in real-life environments. In this study, to solve these problems, we developed a peristaltic crawling robot with pneumatic artificial muscles for use in 1-inch gas pipes. This robot can pass through a 90-degree elbow (Rc= 1.0 ID) in the horizontal and vertical planes. In addition, this robot can be equipped with an endoscope and take videos inside a pipe. However, has been unable to pass through continuous elbows, which are occasionally encountered. For use in real-life environments, a robot is needed that can pass through continuous elbows. In this paper, we report the development of a robot that can pass through continuous elbows.

Highly rigid actuators such as geared motors or hydraulic actuators are widely used in industrial robots. To obtain high-speed motion, it is necessary to increase the actuator output as the robot weight increases. In contrast, humans perform motions using instantaneous force, such as jumping or throwing, via variable stiffness characteristics. We have developed a one-degree-of-freedom manipulator with a variable rheological joint using a straight-fiber-type artificial muscle and a magnetorheological (MR) brake. With the generation of instantaneous force, the dead and rise times decreased compared to the conventional method. After the generation of an arbitrary instantaneous force, we were able to control the robot's arm position by applying an equilibrium force on the joint. Furthermore, we were able to control the vibrations of the arm by controlling the MR brake using an evaluation function.

Pipe failures resulting from corrosion or other forms of deterioration are a common occurrence. To combat this problem, in-pipe inspections are required Fiberscopes are currently used as industrial endoscopes to inspect pipes for defects. However, because of friction, fiberscopes cannot be inserted into pipes that are more than 15 m long or have complex shapes such as elbows. Therefore, in-pipe inspection robots need to be self-propelling. In this study, we developed two robots that mimic the peristaltic crawling motion of earthworms as a locomotion mechanism. These robots consist of several units. Each unit has an artificial muscle that is driven by pneumatics. Each of the robots has an internal space to hold inspection apparatus. We conducted several experiments with a robot inside a 25A acrylic pipe (diameter: 27 mm). These experiments were conducted to examine the relationship between the locomotion speed and motion patterns. The robot was able to pass through the elbows that were positioned in both horizontal and vertical planes. In addition, we developed a smaller robot for a 15A pipe (diameter: 16 mm) to examine the relationship between the locomotion speed and motion patterns. Our findings exhibited good performance by the robots.

This paper describes the development of an endoscopic robot attached to a large intestine endoscope. Colorectal cancer can be cured completely if they are discovered and treated early with a large intestine endoscope. Conventional endoscope can screen and heal inside of the intestine. But, operation of the endoscope is hard for doctors; the training is needed many times. In addition, even if experienced doctors, it occasionally spends one hour for this operation. In this study, in order to solve these problems, we propose the endoscopic robot using peristaltic crawling with bellows-type artificial rubber muscle. This robot can move forward automatically and pulling up the slack. In addition, because of bellows-type artificial rubber muscle, this robot can also pass bent pipes like splenic flexure. Unlike another endoscopic robot, our robot can be attached the endoscope. Thus we can use various function of the conventional endoscope. In this paper, in order to pass splenic flexure, we describe that we fabricated bellows-type artificial muscle. Next, we experimentally confirmed that the robot can pull up the sigmoid colon of the large intestine of dead swine that is arranged in the human body. In addition, in a large intestine model, we reach a endoscope to the cecum with the robot.

We have developed an exclusive planetary sub surface explorer robot with propulsion and excavation units. In this paper, we first explain the concept of our underground explorer robot. Next we develop an excavation unit with a tapered earth auger and a propulsion unit with dual pantograph. Several experiments are performed to demonstrate these features. Finally, we develop a subsurface explorer robot with propulsion and excavation units. Excavation experiments are successfully conducted using the excavator alone and at lighter weights. We show that the excavator can begin boring from a launcher, and in case of excavator of 1/6 of its own weight, it successfully excavates at the same depth as in its own weight. This demonstrates that this novel excavator is expected to accomplish future missions on other planets and the moon.

In this study, we present an omni-directional mobile robot based on the locomotion of a snail. The snail moves by propagating traveling waves from its tail to its head. If it were possible to propagate a traveling wave in several directions, an omni-directional mobile robot could be realized. Since the locomotion mechanism of the snail involves moving a larger area than in the case with other creatures, it is able to move not only on irregular ground such as swamps, but also on walls and ceilings. We have developed an omni-directional mobile robot that makes use of a traveling wave and have derived a kinematical model for locomotion strategy. In experiments, the robot showed good performance, as described in this paper.

The global water shortage has recently been debated at the United Nations. The main cause of this shortage is the excessive use of water resources by humans. Therefore, a positive approach to saving water is needed. Much water is used to flush toilets in homes. Thus, it is necessary to develop a sewage disposal system that saves water. We focused on the bowel peristalsis as a model for a mechanism that can transport sludge with little water. In this paper, we suggest a mechanism that uses such a pump and confirmed its capability. In addition, we fabricated a peristaltic pump of six units, and conducted liquid transportation experiments as an operational check.

A master-slave system has been used to operate a robot. This system is necessary to communicate human intentions to the robot. In this context, we focus on Myo-Electric (ME) potential. In many previous studies, a motor is used as an actuator, and the torque and position are estimated from the ME potential. However joint stiffness, which humans can change, is not considered. It is possible to solve this problem about the actuator by using the artificial muscle that we have studied, because the muscle can adjust joint stiffness. Therefore, it is necessary to estimate the joint stiffness of humans. In this study, we propose a method to estimate the stiffness of a human elbow. Furthermore, we apply our method to the 1-DOF manipulator of the artificial muscle.

A reliable control method is proposed for multiple loop control systems. If a feedback loop fails (e.g., as a result of a sensor breakdown), the control system develops an unstable fluctuation. To cope with this problem, the proposed method uses an equivalent transfer function (ETF) for active redundancy compensation after loop failure. The ETF is used to maintain the transfer function of the entire system the same before and after loop failure. In this study, the characteristics of a reliable control system that uses an ETF were examined experimentally. A position servo system including a disturbance observer is used in the experiment. In case of feedback loop failure, the control system could not be stabilized using the disturbance observer alone; however, the ETF stabilized the control system after feedback loop failure.

Robots have become an integral part of human life, and the relationship between humans and robots has grown closer. Thus, it is desired that robots have characteristics similar to humans. In this context, we paid attention to an artificial muscle actuator. We used straight-fiber-type artificial muscles, derived from the McKibben type, which have excellent characteristics with respect to the contraction rate and force. We developed a 6-DOF manipulator actuated by a straight fiber artificial muscle. Furthermore, we tried to control the manipulator position by considering its characteristics.

An earthworm moves by peristaltic crawling, which propagates a longitudinal wave from the front of the body to the back by varying the thickness and length of its segments. This locomotion mechanism can move while keeping a large area in contact with the ground. Further, the amount of space required by this locomotion mechanism is less than that by other locomotion mechanisms. Therefore, it is desirable to apply this mechanism not only to robots for rescue and limited environment exploration operations but also to locomotive endoscopic robots for medical engineering. In this study, we developed a peristaltic crawling robot that can move not only in a tube but also on a plane surface Furthermore; we propose a peristaltic crawling robot and its locomotion strategy. As a result, the simulation and experimental results showed good performance.

An earthworm moves by peristaltic crawling, which propagates extension and contraction waves along the anteroposterior direction from the anterior to posterior part, by varying the thickness and length of its segments. This locomotion mechanism is in contact with a large area on the ground when the robot moves. Furthermore, the amount of space required is less than that for other locomotion mechanisms. Therefore, this mechanism is suitable for not only rescue robots but also exploration robots in the ground and automatic endoscopic robots. In this study, we developed a peristaltic robot with a flexible feature actuated by servomotors. We proposed different turning patterns. In addition, we confirmed that the robot could move not only on a plane surface but also in a tube. The experiments revealed good performance.

This paper reports on the position and force control of pneumatic artificial muscles reinforced by straight glass fibers. This type of artificial muscle has a greater contraction ratio and power and a longer lifetime than conventional McKibben types. However, these muscles are highly non-linear; hence, it is difficult to use them in a mechanical system. Furthermore, this actuator has a high compliance characteristic. Though this characteristic is useful for human interactions, the position and force of this actuator cannot be easily controlled. In this paper, a mathematical model of this type of artificial muscle is proposed, and the relationship between design parameters and control specifications is realized. In addition, the position and force based on the mathematical model are determined and applied to artificial muscle linearization.