In this work, the load carrying capacity of journal bearing that supporting an overhang load was experimentally investigated with custom-made bearing test rig. In the experiments, the load carrying capacity was defined as transition load that lubrication regime changed from a hydrodynamic to a mixed lubrication. To evaluate the effect of bearing type on the load carrying capacity, two type bearings, circular and two-lobe bearings, were adopted and compared in terms of the load carrying capacity. As a result, the load carrying capacity of two-lobe bearing was changed by preload factor that is a geometrical parameter of two-lobe bearing. When the preload factor was suitable value, the load carrying capacity of two-lobe bearing increased 30% rather than circular bearing. Numerical verification was also conducted, and the tendency of numerical results based on the Reynolds equation were consistent qualitatively with those of experiment.

Tilting pad journal bearings are widely used in High-speed rotating machinery such as turbine generators to support rotating shaft stably. However, reduction of the bearing loss is required for increasing generator efficiency because the bearing loss accounts for approx. 10 % of the total loss in the generator. Generally, the bearing loss is caused by shear resistance of oil around rotating shaft and increases in proportion to amount of lubrication oil. In recent years, the reduction of the supply oil flow rate has been promoted in order to reduce the bearing loss. However, if the oil supplied to the gap (oil film) between the rotating shaft and the pad are insufficient, oil film pressure is decreased due to insufficient lubrication, which may increase the Sub-synchronous vibration of the rotating shaft and the pad. In this study, the developed method for predicting increased the Sub-synchronous vibration caused by insufficient lubrication and the developed method for reducing the Sub-synchronous vibration with a minimum amount of oil supply are shown. Furthermore, the effects of reducing the Sub-synchronous vibration and the bearing loss are shown by testing using the developed method for actual products.

Rotating machineries supported in journal bearings are stably operated at a rotational speed between the one where the minimum oil film thickness is ensured to prevent direct contact of journal and bearing surfaces and the one where self-excited vibration occurs, while avoiding the critical speed of the rotor-bearing system. When a rotating shaft is supported in a cylindrical journal bearing, which has the simplest structure among journal bearings, the upper operational speed will be approximately twice the critical speed. In the present report, focusing on a rotating shaft supported in the bearing with slip regions on part of the bearing surface, those speeds are numerically calculated by applying a hydrodynamic lubrication theory, then the effects of the slip region on the range of stable operation are evaluated. It is found that the range of the stable operation of rotating shaft can be significantly extended simply by creating slip regions on a part of the bearing surface, without replacing complicated journal bearings or employing stabilization method such as adjusting the amount of oil supplied.

Microbubbles have attracted attention as a new friction reduction method for journal bearings. Microbubbles are bubbles with a diameter of 100 μm or less that deform and rotate within the bearing clearance, suggesting that they contribute to friction reduction. Therefore, we used a photochromism visualization technique that uses an oil film that changes color when irradiated with ultraviolet light as a tracer to observe the behavior of the oil film around the microbubbles in journal bearings. As a result, we succeeded in observing a linear flow in front of the microbubbles, but the mechanism of its generation is unknown. Therefore, we changed the method of photographing at high magnification and coloring on the bubbles. As a result, we discovered an unprecedented oil film behavior that suggests that the bubbles are rotating.

Recently, Aerostatic bearings have been attracting attention, and an axial type of slot restrictor Aerostatic bearing has been devised to further increase load capacity. However, the design parameters of these bearings, such as slot restrictor size, clearance, and supply pressure, are numerous, and the effects of these parameters on load capacity and flow rate have not been comprehensively investigated. In this study, the effects of the slot length and supply pressure on the load capacity and flow rate of an axial type of slot restrictor Aerostatic bearing were investigated by CAE analysis. It was found that increasing the slot length causes a large pressure drop in the slot area, resulting in a large decrease in flow rate, but the load capacity also decreases, so the air supply pressure must be increased.

In the fundamental performance of linear motion ball guides, high accuracy, high stiffness, and long life are required. The eight-grooved linear motion ball guide (8-grooved LMBG) with maximized these performances has already been developed and launched. Although the 8-grooved LMBG has almost satisfied customers regarding these performances, it is not compatible with ordinary LMBGs because it does not conform to the dimensions of LMGB in the ISO standard. Therefore, a newly 8-grooved LMBG based on the ISO standard has been developed.

In recent years, due to the demand for energy conservation, rolling guides that can be driven with less force are being replaced. Among these, a mechanical element called a linear guide is used for linear motion guidance. This linear guide has a short history compared to rolling bearings used for rotational guides, and much remains unknown. Future research is expected. In this study, we applied voltages of 0.1 A, 0.5 A, and 1.0 A to the rail side of the linear guide and positive voltage to the carriage side, respectively, and operated for 1000 h. As a result, under all current conditions, there were no discharge marks on the rail, discharge marks were formed on the rolling surface on the carriage side, and discharge marks were formed all around the ball. Furthermore, the area where discharge marks are formed on the carriage side becomes wider as the applied current increases, and at an applied current of 0.5 A, discharge marks with a striped pattern at the pitch of the rolling elements were formed.

In this study, the erosion of the polishing machine parts was evaluated by Micro slurry-jet Erosion (MSE) method using spherical alumina particles with a diameter of 300 μm. The erosion surface of the polishing machine parts and polyvinyl chloride (PVC) material by MSE method were found to show similar in. Also, the difference of evaluated on the outside and inside of PVC specimen, which is the result that the inside is superior to the outside in erosion resistance during injecting a great number of particles. These results suggest that the MSE method using spherical particles with a diameter of 300 μm is the one of the effective tools for evaluating erosion on polishing machine due to injecting particles.

This study investigates the relationship between the occurrence of wavy wrinkles due to web width shrinkage caused by web tension and conveyance effects and fiber density through conveyance experiments. Non-woven products are generally mass-produced continuously using roll-to-roll production methods employing web handling techniques, where defects can lead to significant economic losses. Focusing on wavy wrinkles, a prominent defect during conveyance in roll-to-roll production, this research employs image analysis to reveal disparities in fiber density within the non-woven surface. Additionally, it evaluates the relationship between widthwise shrinkage due to differences in roller friction and conveyance through experiments. Results confirm that web width shrinks due to web tension and further during conveyance. Furthermore, it is observed that rubber rollers result in less web width shrinkage compared to steel rollers post-conveyance. Moreover, wavy wrinkles formation is linked to both disparities in fiber density and widthwise shrinkage caused by web tension on the non-woven fabric.

In this study, we investigated the application of silicone coating to suppress adhesion of coagulated blood on the tip of an electrocautery and to suppress surgical smoke generation. The actual discharge was observed, and it was noted that when the electrode had silicone coating, small bubbles occurred near the tip during discharge. In contrast, with commercially available electrodes without coating, bubbles grew significantly, leading to the occurrence of sparks. Additionally, we simulated the electric field strength at the electrode tip, temperature increase in blood due to Joule heating, and blood flow, and calculated the position of the electric field strength with and without silicone coating. From the results of electric field strength and temperature calculations, it was suggested that the highest point of the electric field strength, when including an air layer, occurs at the interface between air and blood which is close to the electrode surface, potentially serving as a cause for spark generation.

Wettability is one of the important surface properties in various industrial systems. The wettability on the surface is usually evaluated by an equilibrium contact angle, although it is insufficient to evaluate the droplet removability on solid surfaces. This study focuses on the dynamic characteristics of the contact line to clarify the dynamic behavior of droplets on a solid surface. In our previous study, the dynamic wetting and dewetting of a water droplet on a hydrophobic solid surface with an equilibrium contact angle of approximately 100o was investigated both experimentally and theoretically. We proposed a theoretical model of the extension–contraction experiment and numerically calculated the radius of the contact line circle of a liquid droplet, contact line velocity, and dynamic contact angle. The calculation results were in quantitative agreement with our previous experimental results, indicating that our constructed model was appropriate. However, its theoretical model was constructed based on the approximation that the equilibrium contact angle is nearly equal to 90°, which makes it difficult to apply on many surfaces. Therefore, in this study, we numerically solved the differential equation of the radius of the contact line circle with no approximation regarding the equilibrium contact angle and discussed the effects of the equilibrium contact angle on the contact line radius.

In an environment where glycol-based hydraulic fluid flows at high speed through a hydraulic circuit, the seat of a linear solenoid valve wears due to the synergistic effects of cavitation erosion and corrosion of the metal surface caused by the hydraulic fluid. The wear of the seat of a linear solenoid valve causes leakage of hydraulic fluid in the circuit, so there is a need to elucidate the wear factors and to reduce the wear. Focusing on the additives in the hydraulic fluid, tests were conducted in which hydraulic fluid containing different additives flowed in a hydraulic circuit. As a result, it became clear that different additives contained in the hydraulic fluid affected the amount of wear on the surface of the seat after the test. It was also found that the benzothiazole-based copper corrosion inhibitor promoted wear, but when used in combination with a different type of copper corrosion inhibitor, wear was suppressed.

An electro-pneumatic hybrid actuator, which consists of an electric linear motor for position control and a pneumatic actuator for force control has been developed. The pneumatic actuator with pressure-resistant thin metal bellows realizes force-thrust conversion without friction loss and hysteresis since it has no sliding parts. The electric linear motor reduces compressed air consumption during position control in long stroke. The hybrid actuator selectively utilizes the advantages of electrical precise position control and direct force control by air pressure control. This paper presents the significance of proposing the hybrid actuator, its power saving, and position and force controllability.

A compact jumping robot is expected to have high mobility in the low gravity environment of the Moon. We have developed the compact jumping robot with a thin plate leg for lunar exploration. However, the performance of the robot was insufficient, so we needed to check the shape of its legs. If the robot falls over after jumping, it will be difficult to jump again. The leg shape is one of the most important factors affecting the posture after landing in the jumping motion. In this study, we investigated the leg shape of a jumping robot and fabricated the prototype of a sphere-based leg. The spherical leg was designed to overcome the problems of strain and vibration that have been experienced with the thin plate leg. It was also found that the center of gravity of the device was placed close to the spike for kicking the sand surface, and that the spike was securely placed on a desk, and that the device rotated by inertia to compensate for its own posture. The evaluation tests were carried out on sand: a drop test and an energization test. In the drop test, the device was dropped onto a sand surface with the old and new legs and the ground contact rate of the legs was calculated. In the energization test, the device was found to be able to stand up to 43 degrees even when stationary on the sand, focusing on the fact that the center of gravity was changed by the electric current.

A disk-type mechanism using magnetorheological fluid that works smoothly and quietly has been proposed as a rotational power transmission mechanism with a torque fuse function for actuator drive. This mechanism has a characteristic that there is a limit value of transmission torque, and torque exceeding this limit value is not transmitted. In this study, the maximum transmission torque was increased by increasing the number of discs, and by using a planetary reduction mechanism consisting of discs that hold a magnetorheological fluid.

In this study, we have developed actuators that enable fine force control using magnetorheological (MR) fluids. For the various MR fluids used in these actuators, we proposed a method for measuring short- and long-term torque characteristics for haptic devices. The constant-current test to evaluate filling performance was conducted as a short-term test. The repetition test to evaluate reproducibility based on the coefficient of variation was conducted as a long-term test. These tests were conducted using a small, multi-layered disk-shaped MR fluid clutch. In this paper, we used a new MR fluid with different sizes of ferromagnetic particles contained in the MR fluid and measured the flow characteristics of the two different types of MR fluids. Based on the proposed measurement method, evaluation tests of the torque characteristics of the device were conducted. According to the long-term test, all the coefficient of variations were from 1.0 to 1.2 % within our experiments.

In this study, we have developed a finger and wrist motion support device to prevent joint contracture using a sliding stand and a pneumatic soft actuator that adapts to the size of the user's hand. Joint contracture is a condition in which joints become stiff due to an inability to move as results of an accident, illness, or ageing. A user test was carried out to confirm that the prototype device worked. The device uses an actuator whose length changes with the position of the sliding stand, and the angle of movement was measured and compared at each position. The results showed that the operating angle was greatest in the initial position, indicating that the device was working as designed. The percentages of the pre-test measured angles were 57.3% for wrist extension, 77.8% for MP joint extension, 87.3% for MP joint extension and 92.3% for wrist extension. The performance of the wrist extension movement was lower than the other movements, suggesting that the wrist extension and fixation actuators need to be improved.

The telepresence robotic avatar designed for use in crowded exhibition halls requires a high level of safety. The purpose of our work is to develop a telepresence robotic avatar featuring a soft arm tailored for exhibition purposes. This paper details the structural composition and fundamental characteristics evaluation of the proposed soft arm, which operates using pneumatic actuators and tension springs. Motion analysis experiments revealed that the arm exhibits drooping tendencies during forward extension in both medial and lateral movements. In addition, upward motion showed a limited range compared to other motions, while downward motion showed the greatest displacement from the tip of the arm. The arm's range of motion in both directions was influenced by its weight. Safety evaluation tests indicated that all movements were below standard safety thresholds, confirming the suitability of the arm for human interaction.

Research and development have been carried out on small mobility robot vehicles called personal mobility vehicles (PMV) that use cutting-edge technologies such as robot posture control technology. In this research a new type of small robot vehicle using an omni-directional actuator and a tripod parallel mechanism has been proposed and designed. For the tripod parallel mechanism three actuators independently move to realize a cabin with a six degree-of-freedom motion platform. The ball driving type of the omni-directional actuator for the new type of the small robot vehicle has been proposed and developed. A three-tenths scale prototype model of the robot vehicle has been designed and prototyped. We investigated functions that keep the crew's posture absolutely horizontal even when the ground slopes during movement, and that allow the cabin posture to change significantly when getting on and off the vehicle. We experimentally verified the validity of four functions: movement, getting on and off, changing posture, and running on slopes.

In this research, we describe an octopus jellyfish soft robot for an aquarium. The purpose of developing the soft robot is to improve water quality in aquariums without disturbing the landscape and can support the filtration machine. The robot mainly consists of a bell with a soft actuator, a battery, and a control circuit box. The battery is also housed within the control circuit box. The soft actuator based on a shape memory alloy wire is used to control the movement of the jellyfish’s bell. The bell part is made of silicone rubber, which reduces the possibility of injury if it comes into contact with an aquatic life. The control is wireless by using a microcontroller and radio communication. We investigated the effects of water temperature and drive current on bell movement.

This paper describes a pseudo multi-DOF sea anemone soft gripper driven by a single pneumatic input. When grasping multiple objects, an optimal gripper should have a different posture for each object, meaning that grasping with a single gripper requires complex control and adaptation to various size and shapes. Therefore, we developed a soft gripper that mimics the sea anemone which use their many tentacles to capture prey of various size and shapes. Pneumatically driven soft fingers with double-helix reinforced fibers were developed for the gripper, and 1-DOF curvature was confirmed by pressurization. A soft gripper equipped with 18 fingers, and all fingers can be driven by a single pneumatic input. Grasping experiments confirmed that the soft gripper equipped with 18 fingers of 7 mm diameter could grasp 7 types of objects with different shapes.

Flexible tactile sensors are important for robots that are used in environments with humans, as they have little physical impact when they contact with people or objects. Most conventional flexible tactile sensors, such as PVDF or strain gages, are based on electrical characteristics. However, these sensors are susceptible to electromagnetic noise, which may reduce the accuracy of measurement. Herein, we developed and evaluated the performance of a tactile sensor using a Fiber Bragg Grating sensor, which is flexible and highly resistant to electromagnetic noise. To discriminating objects with different roughness, we constructed a tactile sensor with optical fiber in which FBG were introduced and fixed in a semicircular shape, and a measurement system that mimics human tactile motion. Vibrations were measured when tracing the surface of seven different aluminum plates with different roughness. Furthermore, we constructed a multi-layer perceptron classification model based on a neural network and calculated the classification accuracy of the vibration information acquired by the sensor. The constructed model has 500-dimensional input layers, 7-dimensional output layers, and 3 hidden layers, and was confirmed to be able to discriminate samples with different roughness with an accuracy of 95.7%.

In a noncircular gear mechanism, the contact surfaces of the tooth are interchanged during its rotational motion because of its unequal speeds. The loads acting on the tooth of noncircular gears include impact loads, so this mechanism is more easily damaged than that of circular gears. Therefore, it is necessary to detect damage to gear tooth at an early stage and take appropriate preventive actions before the entire machine or equipment is damaged. This study describes an attempt to diagnose the type of damage by machine learning using the data mining tool Weka, based on tooth surface images of super duralumin (A7075) noncircular gears taken by a camera, in order to detect tooth surface damage caused by excessive tooth surface contact.

The drive motors of electric vehicles are becoming smaller and faster in order to improve the electricity consumption. However, there are many unknowns in the tooth friction coefficient in the fluid lubrication area, where the oil film becomes thicker due to high-speed rotation. High-speed operation of the testing machine is also necessary for this evaluation, but there are difficulties such as dynamic loading. Therefore, this study attempts to increase the oil film thickness by increasing the pressure angle of the test gear. In addition, the roughness of the tooth surface is reduced by mirror polishing. The objective of this study is to evaluate the tooth friction coefficient over a wide lubrication range using these test gears.

High-torque micromotors are essential to drive microrobots for applications such as minimally invasive medicine and pipe inside inspection. However, a reduction in torque is physically unavoidable as motors become smaller. In this study, we build a micro reduction gear to be mounted on a micro ultrasonic motor of approximately 2 mm in size. The gear components are fabricated using a 3D printer that uses ultraviolet light and MEMS mirrors to achieve miniaturization and high resolution. A prototype gear unit was fabricated, and the transmission efficiency, strength, and improvement methods were investigated, and the results were verified using the finite element method.

Gear pumps have a simple and sturdy structure, are relatively small, can obtain high head, and can transport fluids with a wide range of viscosities. However, it is said that gear pumps have a problem of noise matter. Therefore, in order to reduce the noise of spur gear pumps, the study was started. Firstly, the parts that were the sources of noise were identified in past reports. Then, a suitable design for the tooth profile modification shape of the gear was carried out. In this report, the test gear with tooth profile modification was installed in a gear pump and conducted an operational test to examine how the noise characteristics change due to tooth profile modification. As a result of driving test, it was found that the noise level was significantly reduced when the meshing vibration and natural vibration resonated.

Colonoscopy is the most useful method for detecting the colorectal cancer, however, it takes time to learn how to insert into colon deeply without pain for patients. Therefore, many researchers proposed self-propelled colonoscopy robots. In previous study, we developed a self-propelled colonoscopy robot with a worm gear mechanism. However, hard gears can damage the colon wall. Therefore, we focused on a compliant mechanism, and developed soft gears with elastic deformation. Soft Gears have a variety of potential applications, including a torque limiter. In this study, we propose a design parameter optimization method using a gear design software and a nonlinear modeling method using a finite element analysis (FEA) software, and report on their evaluation results.

The purpose of this study was to simplify the design of the tooth surface of face gear and to clarify the optimization method of the specification setting. Face gears have long been used in fishing spinning reels as a speed-increasing gear. Recently, face gears have also been adapted to geared motors for orthogonal reduction gears. However, the design method of the face gear is not supported by a standard theory, and its application is not common. To clarify the meshing of the face gear, the author introduced the idea that the meshing contact progresses along a straight line of action. The meshing point between the involute helical and face gear proceeds at a constant speed along the straight line of action. In this report, the meshing between the pinion and face gear was investigated in a cross section where the meshing contact line of action exists. Then, the contact ratio was determined from a normalized graph in which the effective meshing contact surface of action was flattened.

Metal-belt CVTs are effective in improving fuel efficiency in automobiles，but their own mechanical efficiency is low．Since power transmission is performed by friction between the belt and pulley，it is necessary to clamp the belt with the pulley．Currently，excess clamping force is applied to prevent total slippage，resulting in various power losses. A possible way to reduce these losses is to reduce the clamping force by determining the coefficient of friction in the circumferential direction of the elements．In this study，the circumferential friction coefficients are calculated from the clamping force measured by a push force sensor between elements．The results are compared with theoretical calculations．

Miniature screws are a standard for screws with a nominal diameter of 0.3 mm to 1.4 mm, and are used in watches, optical equipment, electrical equipment, measuring equipment, etc. Machining female threads with a fluteless tap is a plastic working process that does not produce chips and has a long tool life, but it is often used for small diameter machining and is prone to tool breakage. The authors attempted to reduce the machining torque by using ultrasonic vibration for machining internal threads of miniature screws. Two types of ultrasonic vibrations, 28kHz and 40kHz, were applied to investigate the relationship between vibration frequency and machining torque. The tap used this time is a fluteless tap with a nominal diameter of 0.5 mm, which is the smallest diameter tap available on the market. Experimental conditions were investigated with and without tapping paste. As a result, the effect of ultrasonic vibration was higher when tapping paste was used.

Graphene oxide (GO) and reduced graphene oxide (rGO) produced from graphite by the Hammer's method are known to exhibit low friction when dispersed in water or oil, but the mechanism is not yet fully understood. So, in this study, friction tests were conducted using water dispersions containing eight different specifications of GO and rGO with different structures, functional group states, and secondary particle size. the bonding state of carbon by XPS analysis, and the secondary particle size by dynamic light scattering were measured to clarify the effects of these factors on the dispersibility of GO and rGO and on the friction coefficient. The results revealed a trend toward lower friction coefficients with smaller secondary particle size and with higher ratios of -C-O and -C-OOH bonds coordinating to GO and rGO.

This study newly developed a hybrid system based on surface plasmon resonance (SPR) and optical interference microscopy, and investigates its suitability and limitations for measuring oil film pressure under elastohydrodynamic lubrication (EHL) sliding conditions. Specific optical setting conditions such as the incident angle and thickness of each film layer for surface plasmon excitations and for oil film pressure measurements were designed based on numerical calculations and demonstration experiments. Through some experiments, the advantages of SPR microscopy, i.e., the high spatial and temporal resolution, were demonstrated. Furthermore, by clarifying the limitations of SPR microscopy, its potential applicability for optical EHL observation systems was verified.

A typical anti-wear additive, zinc dialkyldithiophosphate (ZDDP), has been utilized for many types of lubricants. ZDDP is known to form reaction film by direct contact between sliding two substrates and protects adhesion wear. Especially, the alkyl chain type of ZDDP is important for lubricant design to adjust the anti-wear properties, but there are few reports about the reactivities of ZDDPs with different alkyl chain types using in-situ observation of tribofilm formation. In this study, we conducted in-situ AFM on friction interfaces and investigated the reactivities of ZDDPs possessing different alkyl chain types using a stress-activated Arrhenius model. As experimental results, we found that the growth rate of tribofilm and friction coefficient in primary-ZDDP solution was lower than those in secondary-ZDDP solution. In addition, using a stress-activated Arrhenius model, we estimated the activation energy of primary-ZDDP and secondary-ZDDP, which are 148 and 99 kJ/mol, respectively. The tribofilm formation is known to be influenced by the shear stress value, therefore, we considered that low friction properties of primary-ZDDP influenced the low growth rate of tribofilms.

To clarify the effect of precipitates on low friction, friction tests and in-situ observation of precipitates on the contact points by reflection spectroscopy were conducted. The thickness of the precipitates was observed and estimated from the reflection spectra measured by reflection spectroscopy. From viscosity measurements of lubricants, it was observed that lubricants containing stearic acid become turbid below a certain temperature and their viscosity increases rapidly. It was also found that the viscosity increase point shifted to the lower temperature side as the stearic acid content increased. Friction tests showed that the lubricating effect decreased at temperatures below the melting point of stearic acid. Oil film analysis showed that stearic acid was abundant in the friction area. The thickness of the oil film was increased from the theoretical value, suggesting that the precipitation of stearic acid contributed to the increase in film thickness. As a result, stearic acid precipitation increased the oil film thickness, suppressed direct contact, and reduced friction. It was also found that smaller content of stearic acid achieved more friction reduction. Oil film analysis revealed that the smaller the stearic acid content, the smaller the thickness of the stearic acid layer in the friction zone, suggesting that there is a significant difference in film structure depending on the stearic acid content.

In recent years, environmental pollution and the depletion of energy resources have become problems, and there is a growing demand for high-efficiency technology. Lubricating oil is used in gasoline vehicle transmissions to reduce friction, and ester mixture lubricating oil is used in boundary lubrication conditions where solid contact is severe. Ester mixture lubricants increase oil film thickness and reduce friction by adhering to metal surfaces, but it is known that esters containing unsaturated fatty acids undergo thermal denaturation during friction. In this study, we elucidated the effect of thermal denaturation of esters on friction properties. Friction tests were conducted at 23°C, 40°C, 60°C, and 80°C using lubricating oil containing unsaturated fatty acids (TMPTO) added to base oil (PAO), and oil film thickness was calculated from reflectance obtained simultaneously. The viscosity of the mixed layer of TMPTO and its thermal denaturantion was calculated from the obtained oil film thickness using an original formula. The viscosity was found to be higher than that of TMPTO in bulk form at all temperatures. The viscosity increase can be attributed to the formation of multimolecular films by surface adsorption and thermal denaturation.

In this study, we aimed to establish a method for depositing high-nitrogen-content and high-hardness ta-CNx coatings. The two different nitrogen mixing process to add them in tetrahedral amorphous carbon (ta-C) was conducted. The nitrogen ion introduction methods are the gas introduction method where nitrogen gas is directly introduced to the arc source created near the carbon target as a nitrogen ion introduction, and the nitrogen ion beam irradiation method towards the coating substrate direction. The results showed that in both deposition methods, an increase in the N/C ratio led to a decrease in hardness. In the ion beam method, although the N/C ratio could be increased to about 0.21 at 40 sccm, the coating hardness decreased to approximately 12 GPa. On the other hand, with the gas supply method, at 40 sccm, the N/C ratio was approximately 0.17, lower than the ion beam method, but the hardness achieved approximately 20 GPa. When the deposition was carried out with the specimen temperature rise suppressed to below 60°C, supplying nitrogen gas directly to the arc source to introduce nitrogen into the coating resulted in maintained the hardness even with an increase in N/C ratio from 0.10 to 0.17, maintaining it at about 32 GPa. In contrast, with the ion beam method, an increase in N/C ratio from 0.12 to 0.17 led to a decrease in hardness from approximately 32 GPa to a minimum of about 20 GPa.

Plasma CVD requires the generation of high-density plasma when depositing films on the internal surface of millimeter-size tubes. Hollow cathode discharge (HCD) is one of the plasma generation methods to obtain such high-density plasma in tubes. We have been investigating the difference in the deposition results between impulse and non-impulse discharges in DLC (diamond-like carbon) coating onto the inner surface of a small hole using plasma generation by HCD. The results so far have shown that many arc marks were observed on the DLC film formed by impulse discharge. In this study, we verified whether the arc marks continuously increase as the current increases from the initial stage of the transition from impulse discharge to non-impulse discharge. First, a DLC film was deposited on the inner surface of a small hole (4.4 mm inner diameter and 50 mm length) under conditions of non-impulse discharge with a discharge ON time of 0.09 ms. Next, we confirmed that by slightly increasing the discharge ON time to 0.1 ms, the discharge transitioned to an impulse discharge with a maximum current exceeding 40 A, and under these discharge conditions we similarly deposited a DLC film on the inner surface of the small hole. Comparing the two film formation results, many arc marks were seen in the impulse discharge. It was suggested that during the transition from non-impulse discharge to impulse discharge, arcs begin to occur from the initial stage of the transition, and the number of arc marks increases continuously as the current increases.

In ring-on-disk friction tests, our group observed superlubricity in water with silica nanoparticles loaded on silicon carbide, silicon nitride, Si-DLC, silicon nitride and a-C:H pairs, and found the superiority of silicon nitride and a-C:H pairs. In this report, ring-on-disk friction tests with silicon carbide pairs, Si50wt%-DLC pairs and silicon nitride and a-C:H pairs were conducted at a constant load of 500 N and a sliding speed of 300 mm/s with a sliding distance of 1000 m. The results showed that on the friction surfaces that developed ultra-low friction, the presence of a thin layer, which could be considered a silica film, was observed on the silicon carbide pair and on the silicon nitride and a-C:H pair. It was found that the silicon nitride and a-C:H pair required sufficient blending time compared to the silicon carbide pair. The formation of a silica film inducing ultra-low friction can be expected if sufficient mixing time is ensured in the silicon nitride and a-C:H pair.

About 15% of the available energy in automobile engine is dissipated as mechanical, mainly frictional loss. In automobile engine, friction coefficient of boundary lubrication mode should be expected to be reduced less than 0.05 under reciprocating sliding parts. Recently, in order to overcome this problem, the synergy effect of specific DLC (Diamond-Like-Carbon) coating doped with various elements and friction modifier as MoDTC are expected under boundary oil lubrication. Therefore we prepared carbonaceous hard coatings doped with Ta and N by a combination coating equipment combined with FCVA (Filtered Cathodic Vacuum Arc) deposition and a gas ion implantation source. And a reciprocation sliding friction tests against SUJ2 roller were conducted under PAO base oil and PAO oil including MoDTC. We have prepared 4 different carbonaceous hard coatings as ta-C, ta-CNx, ta-C:Ta and ta-CNx:Ta and reciprocation sliding test was carried out in various sliding conditions. And normal load was decreased by 0.5 N after each 100 sliding cycle up to 0.5 N. For PAO base oil, all of carbonaceous hard coatings showed high friction coefficient. Minimum average friction coefficient was 0.126 for ta-C. On the other hand, for MoDTC including PAO oil, Nitrogen and Tantalum doping ta-C showed lower friction coefficient.

To enhance the friction reduction characteristics of MoDTC are desired to reduce a friction loss of automobile engines. In this research, we focused on the influence of doped metal of a-C:H coatings, specifically hydrogen-containing DLC coatings, as factors that affect the friction reduction effect of MoDTC. We prepared three types of DLC coatings: a metal-free a-C:H coating, a-C:H coating with Ta doped, and a-C:H coating with Nb doped, both belonging to the fifth group of elements. Friction tests were conducted to evaluate the friction characteristics, and Raman spectroscopy analysis was performed on the tribofilm formed after the friction tests. Among the three DLC coatings, the a-C:H:Nb coating exhibited the lowest friction. Raman spectroscopy analysis revealed clear peaks of MoS₂ in the tribofilm formed on the a-C:H:Nb coating. Based on our findings, we proposed that addition of metals, particularly Nb, to the a-C:H coating contributed more to the reaction of MoDTC, resulting in a larger friction reduction effect of the tribofilms derived from MoDTC.

Laser micro-textured surfaces can be used to control and adjust friction. In general, metal-to-metal friction causes the generation and growth of wear debris in the initial stage (running-in process). The contact state changes drastically when micro-dimples are formed. For undulated surface made by laser micro texturing, it is thought that the micro-uneven surface inhibits the growth of wear particles and suppresses adhesion, and is effective in reducing friction by reducing adhesion and other factors. However, the frictional properties of undulated surfaces by laser micro texturing have not been investigated in detail. In this paper, the friction between DLC film and micro textured surface was investigated. And the effect of sliding motion patterns on the formation of the adhesion and transfer layer were also investigated.

In this research, we develop an artificial rubber muscle capable of force transmission using a belt. Proposed artificial muscle can generate a contraction force by sealing up with attached belt. The artificial muscle is configured by an elliptical rubber tube, a fiber sleeve, and two belt fixing mechanisms. Belt fixing mechanism fixes the artificial muscle by friction between the belt and rubber material. Proposed artificial muscle attached onto the belt can transmit the contraction force through the belt by supplying a compressed air. In this paper, we discuss the structure and principle of operation of the artificial muscle. Thereafter, the rubber material, which is attached in the artificial muscle, to fix the belt in is determined from a comparison of the friction coefficient.

An electro-conjugate fluid（ECF）is a type of functional fluid that flows when a high DC voltage of several kilovolts is applied. In this study, in order to expand the potential of ECF, which is expected to be a power source for microactuators, the shape of the electrode pair is redesigned. Namely, we have divided the triangular prism electrode of the triangular prism and slit electrode pair（TPSE）proposed in a previous study into two parts. To show the effectiveness of the bisected TPSE, the ECF flow was numerically analyzed using a finite element method. The results show that the flow velocity of the bisected TPSE is higher than that of the conventional TPSE. In addition, the velocity distribution of the bisected TPSE confirmed the reduction of flow resistance with the triangular prism electrode.

Cell culture method using ultrasonic atomization of culture medium is a recently proposed method under atmospheric pressure. In contrast to conventional method, this method can prevent cell desiccation, but the appropriate culture conditions are unknown. In order to improve this method, an environment for the proliferation of mouse myoblast cells was established using atomization culture. Initially, a cell culture device using piezoelectric element was fabricated, and experiments were conducted to evaluate the resonant frequency and input voltage. Based on the results of the experiments, the input frequency and input voltage were determined to be 2.04 MHz and 211.9 V, respectively. Subsequently, culture experiments were conducted under two conditions with burst ratios of 0.02 and 0.04. As a result of the experiments, it was confirmed that the cell area increased with burst ratio of 0.02 but decreased with burst ratio of 0.04. Furthermore, the surface of the culture base was divided into 10 areas, and the cell area in each area was compared, and it was confirmed that the area was generally uniform.

Mobile manipulators, which can move to different locations and perform various tasks at the destination, are attracting attention. In order for mobile manipulators to perform human-like tasks, the mobile platform must be able to move not only in one direction, but also in arbitrary directions. In this study, we have proposed a new multidirectional mobile platform called CRoMop. CRoMop is equipped with three swivel-passive caster wheels and performs multidirectional motion by utilizing rotational motion. Due to the rotation, CRoMop can move indefinitely in any direction while avoiding a singular state. Thus, CRoMop can satisfy the use of ordinary wheels, fewer motors, and multidirectional motion at the same time. To confirm the fundamental effectiveness of the proposed mechanism and locomotion method, experiments were conducted. The result clarified that the CRoMop prototype worked as expected even with feedforward control.

A noble flexible two-finger hand mechanism that can grasp an object with various sizes and locations with easy control is proposed. The hand is a planer 17-bar underactuated mechanism with one driving motor and five prismatic joints with springs. Mechanism dimensions are designed to set angular velocities of phalanxes to 0 when the hand has just grasped the object, and are optimized by maximizing the difference of relative angles between phalanxes while transmissibility is taken into account. In order to calculate motion of the hand and grasping force, a kinetostatic analysis of the hand that has contact with the object is carried out. The motion of the object is then calculated with the contact forces. Finally, a prototype of the hand mechanism can grasp objects that have different diameters and locations with input rotation of the motor at uniform speed. It is thus confirmed that the proposed underactuated hand mechanism is effective and useful for flexible grasping an object with various sizes and locations.

For patients who suffer from brain stroke severely, it is difficult to extend their fingers. Therefore, we have developed a hand splint which can assist finger extension. This splint has a unique feature that circular Shape Memory Alloy is adopted. In this paper, we introduce basic mechanisms of splint for the thumb in consideration with anatomical structures. Moreover, we explain development of an endurance testing device for the developed thumb splint.

A passive type assistive device for the upper limb using a double parallelogram remote center of motion: RCM mechanism was designed to reduce the burden of lifting and upward work in the work environment. Simple and compact structure that there are no frames on the user’s shoulder was achieved by using the RCM, so that this device can use in narrow aisles in the warehouse and pass the door easily. And also, it was achieved by the RCM, that the rotational center of the linkage corresponds with rotational center of shoulder joint. The gas spring was used as the source of assist force. The placement of the gas spring was determined by examining all possible candidates (11 locations) so that appropriate assistance could be provided according to the angle at which the arm was raised. We built a prototype of the device and confirmed the effectiveness of the device's assistance by electromyographic measurements.

When carrying heavy objects, a person's arms are subjected to a great deal of strain. Therefore, a device is needed to reduce the burden on the arms. Many assist suits with actuators have been developed as devices to reduce the burden on the arms. However, these assist suits have a short operating time because they use batteries. In addition, these assist suits are dangerous to the user when their computer runs out of control. Therefore, we have proposed a mechanical brake to improve the safety and energy consumption of the assist suits. The assist suit with mechanical brakes can use actuators to support the user when lifting heavy objects. When the user continues to hold heavy objects in a raised position, the mechanical brakes are used to support the user. The mechanical brakes do not consume energy because they consist only of passive mechanical elements. Furthermore, if the assist suit’s computer breaks down and unexpected high velocities occur at the suit’s joints, the mechanical brakes turn off the power to the assist suit and stop the assist suit. However, the mechanical brake may malfunction due to resonance with a human gait cycle, etc. This paper proposes a method to design a mechanical brake that does not resonate with a human gait cycle, etc. using frequency response analysis.

Orchard farmers often maintain a standing posture for long periods of time when growing and harvesting fruit. Japanese farmers are aging. Prolonged standing posture puts strain on their knees and hips. In this paper, we describe a design of a standing posture assist suit that requires no power supply using a drum-type mechanical brake (DTMB). This assist suit does not use batteries or motors, but only passive mechanical elements. When the user’s knees are bent after moving down a lever of the assist suit, the assist suit’s knee joints are fixed by the DTMBs to support the user’s body. After that, even if the user does not continue to depress the lever, the knee joints remain fixed by the DTMBs while the user’s body is supported by the assist suit. Fixation of the knee joints are released when the knees are extended. The method to design the DTMB including an analysis of the activation angle of the DTMB is also explained. An experiment using the DTMB developed based on the design method was conducted to compare the theoretical actuation angle with the experimental results. The experimental results were approximately the same as the theoretical value.