Some methods are discussed to improve positioning accuracy and realizing finer positioning resolution using leadscrew mechanisms. Recent trend on current positioning technology is overviewed briefly, and accuracy level imposed on leadscrew mechanisms is clarified. Frictional property in starting and reversing motion is discussed on a sliding leadscrew and a ball screw. It is shown that a ball screw has nonlinear elastic property within microscopic range. Next, a proper control method is discussed for a positioning mechanism using a ball screw with such nonlinear elastic property. And a method of intentionally attaching the elastic property to a sliding leadscrew is proposed. Moreover, a differential ball screw is introduced to realize finer resolution.

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Modeling, control and sensing methods of a redundantly actuated 3-DOF planar parallel robot are discussed in this paper. This mechanism offers a wide range of motion in addition to the existing characteristics that parallel mechanisms provide, namely, rigid mechanisms, high precision, and high speed. The notable link arrangement of the mechanism makes it easy to derive the forward kinematics, which have been difficult to derive the conventional parallel mechanisms. Firstly, kinetostatics and dynamics of the proposed mechanism are derived. Then, impedance control, internal and external forces measurement, and mode change of the robot are proposed. Effectiveness of each application is confirmed by experimental results with specially designed prototyping.

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The intended purpose of small ball bearings is mainly for motors in home electric appliances. The production quantity of small motors is over 12300 million according to the prediction of the year 2013. Assuming that ball bearings are applied for the 70% of them, about 17200 million small ball bearings are necessary. Usage environment of small motors becomes more hostile, and requirement for high speed and low noise is increasing. Furthermore, low cost is also requested. Therefore, bearing manufacturers are pressed for such correspondence. In this paper, some case studies performed so far by the author are described

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This paper describes analysis and synthesis of flexible link mechanisms of a single spring beam which can be manufactured by NC coiling machines. Smooth Curvature Model (SCM) with 3rd order Legendre polynomial curvature functions is applied to calculate large deformation of a curved cantilever beam by taking account of the balance between external forces and internal elastic forces. SCM is then extended to analyze large deformation of a closed-loop curved elastic beam which is composed of multiple curved beams. The sets of coefficients of Legendre polynomials are optimized to design closed-loop flexible link mechanisms which can generate specified output motion due to input force. For example a planar gripper with a single pulling input force is designed and experimentally examined.

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To achieve precise and stable pipe/thin plate bending based on the penetration bending method,a grip-and-feed mechanism was proposed. This mechanism is driven by an actuator and composed of two cam mechanisms and a chain-drive mechanism. One of the cam mechanisms was designed to generate a periodic grip-and-release motion of grippers, which circulate along a track, by a grooved cam mechanism.The other was designed to constrain the grippers'orientation during feeding to achieve a stable gripping. These mechanisms are synchronously driven by an actuator. Thickness of the rubber attached on the gripper was investigated through experiments. The fundamental performance of the proposed feeder was demonstrated by applying it to fabrication of a circular-shaped pipe. The results are shown to support the proposed mechanism.

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This report describes a new self-propelled cleaning robot which cleans floor by a wet rotational brush like a floor polisher. The rotational brush does not only clean floor but also transfer itself. Velocity of the robot is controlled by inclining the rotational axis of the brush. Its moving direction is controlled by direction of the rotational axis and moving speed is controlled by degree of inclination angle of the rotational axis. A cleaning robot which has single rotational brush driven by hydraulic motor and the water passed through the hydraulic motor is used to clean the floor was proposed and designed. An experimental apparatus was fabricated and its moving and cleaning performance was experimentally demonstrated.

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A miniaturized parallel manipulator with 6 degrees of freedom has been developed for manipulating small-scale mechanical parts. A hand-operated hexapod-type mechanism remotely actuates another hexapod mechanism through six steel wires. This report firstly describes the design for the link configuration to the same motions between the master and slave manipulators. Secondly,the master-slave manipulator system consisting of fixed-length links and magnet spherical joints was manufactured. In the experiment,non-contact laser displacement sensors measured positioning error and motion errors of the slave's end-effector when the moving platform of the master was moved in ±3mm. As a result,submillimeter-order lost motion and hysteresis were observed during the positioning.

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The authors have developed a penetration pipe bending model which can accurately predict the shape of a bent pipe. In this model, the centerline of the pipe which contacts the movable-die was calculated by considering the springback of the pipe and the clearance between the pipe and fixed-die. Using the model,the distribution of the resulting radii within the workspace of the movable-die drive mechanism was calculated in order to determine the optimal position and orientation of the movable die for achieving precise bending. Throughout several experiments,the precise pipe bending was successfully performed to demonstrate the effectiveness of the proposed methods.

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It is important to give a cardiomycyte mechanical load for developing cardiomyocite physiology study. Therefore a gripper which grasps an isolated cardiomyocyte is required. However at present, there is no device grasping the cell easily without electrical and magnetical noises. In our previous research,a pneumatic gripper which has a fluid chamber and composed of polymer materials has been developed. Gripper's drive properties were clarified by the last year. At a result,it was found that the gripper cannot maintain appropriate cardiomyocyte grasping because of creep phenomena. Therefore in this research,the gripper which is made in nylon material and have fluid chambers of the bellows structure is developed. As an experimental result,in comparison with the previous gripper,the quantity of creep is restrained from 107μm to 34μm. Namely the device can realize accurate positioning as the gripper for cadiomyocyte. Actually,the gripper grasps a small piece of the rubber which is a glass beads.

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We propose and develop a multi-DOF MEMS-based ER microgripper system using an alternating-pressure source,which is high power density and space-saving for in-pipe working micromachines,medical microrobots,and so on. Proposed system utilizes an ERF flow induced by synchronizing ER microvalves and the pressure source. The ER microvalve controls the electro-rheological fluid (ERF) flow through its apparent viscosity change due to the applied electric field. Each ER microfinger has only one pipe for supply and return with small diameter by transmitting pressure with low viscosity water. An ER microfinger having l mm long PDMS finger part with high-aspect ratio is fabricated by newly developed MEMS process,then the ER microgripper is experimentally characterized.

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We propose a constant-temperature operation mode of a phase-controlled traveling-wave type ultrasonic motor, which is different from the conventional frequency-controlled one. In contrast to the conventional one, where the decrease in the rotational speed with increasing the temperature of the motor is compensated by changing the resonance frequency,undesirable effects due to variation of the temperature can be reduced by use of the proposed mode of operation.

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There has been increased interest in use of pneumatic actuators in many fields, such as medical care and welfare. In particular,proposed pneumatic soft actuator with soft material has many advantages such as low mass,flexibility,safety and user-friendliness. We therefore focus on the pneumatic actuators as a drive source of a rehabilitation device. The purpose of this work is to develop a rehabilitation system to prevent contracture of the finger joints using the pneumatic soft actuators. We prototyped the system and measured the flexure angle and the extension angle in the rehabilitation test. As a result, we confirmed the problem of rehabilitation system with unlimited to the joint range of motion.

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In our previous study, it was revealed that tightening characteristics of aluminum alloy bolts obviously differ from normal steel bolts. In case using the steel bolt, it is well known that their torque coefficients depend on the tightening speed. An influence of tightening speed on the torque coefficients of aluminum alloy bolt has been investigated in this study. The results showed that the torque coefficients and their scatter bands decreased with an increase in the tightening speed if MoS2 grease and machine oil was used for lubricant of tightening. However if a special lubricant for bolt tightening was used, the torque coefficients did not depend on the tightening speed.

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Tensile strength of bolt or screw is usually obtained directly through the tensile test specified in ISO 898-1. For bolt or screw with shorter length. however, tensile test is not feasible. In such a case, torsional test specified in ISO 898-7 is applied, in which the breaking torque calculated from the tensile strength and the strength ratio assuming lhat the threaded portion is circular shaft with root diameter d_3 is evaluated. In this study, torsional rupture test on M8 bolts and 3-D FE analysis were conducted to find out the influence of the thread lead on the breaking torque. Discussion includes the equivalent diameter which used in the calculation for the polar modulus of section. It was clarified that the thread lead had a significant effect on the bn・aking torque, and it was advised that the equivalent diameter should be evaluated taking into account this effect.

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It is known by past researches on the loosening of a screw that rotation of loosen will arise if the radius direction vibration is given to a bolt head or the bearing surface of a nut. 0n the other hand, it is known that it is effective in ultrasonic vibration reducing apparent friction, and the method of performing screw tightening with little variation is also studied, it is performed by tightening with the ultrasonic vibration. In use of ultrasonic vibration, a stronger effect can be acquired by using resonance. In this research, the bolt head or the nut was fastened with axial ultrasonic vibration by vibration resonance of Cross-shape Oscillator, and it is investigated about the effect.

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The bolted joint has the optimum tightening force to show its sufficient function. Even if the target value of tightening force is obtained, it is a problem to control it in the practical field. Control of tightening force is very difficult though tightening is important in a small screw. Therefore, it is necessary to improve the accuracy of the tightening force in a small screw. The device that simply measured coefficient of friction was produced. Coefficient of friction of a small claimed were requested by the simplified assay. And, the torque factor were able to be led easily. Coefficient of friction of thread surface and bearing surface show the decrease tendency to an increase in the load.

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This paper describes the characteristics of the ball screw taking account of its inner state, especially the ball and the re-circulator called as deflector, by using an actual model. The experimental setup that can detect the dynamics of both the ball and the deflector has been built. Several sub-miniature displacement sensors were installed in the experimental setup. In comparison with experimental results and theory, it was clarified that the ball moved with a sliding on the thread groove. Then, we have recognized that three-dimensional dynamics of the deflector were good correspondence with the fluctuation of the torque of the ball screw.

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In order to clarify the effect of surface profile on friction characteristics of viscoelastic material such as oil seal, sliding test was conducted under oil lubrication with the NBR (Nitrile Butadiene Rubber) in combination with steel. The sliding surface profiles with different feature in the steel specimens were introduced by polish process and blast process. The NBR specimens with different surface feature were also employed. Under a rather low load condition, steel specimens with plateau surface showed the lower friction coefficient. Similar effect was provided by the NBR specimens with rough profile and dimples. The reduction of contact area and pocket effect could lead to the lower friction coefficient. On the other hand under a rather high load condition, where the deformation of NBR specimen was rather large, the effect of surface profile on friction coefficient was little.

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In this study, case-hardened steel rollers with an effective case-hardened depth of 2 mm were fatigue-tested using a roller testing machine in order to elucidate their rolling contact fatigue life. They were made of three kinds of steels. These experimental results were compared with the results of the case-hardened steel roller with an effective case-hardened depth of 0.7 mm. The surface properties of all the test rollers were almost the same. The failure mode of all the test rollers was pitting due to surface cracking. The fatigue life and the surface durability of the rollers with an effective case-hardened depth of 2 mm were improved by the toughness effect due to nickel and the reduction of sulfur content in this experimental range. On the other hand, those with an effective case-hardened depth of 2 mm were far superior to those with an effective case-hardened depth of 0.7 mm. It was confirmed that the surface durability of the case-hardened steel rollers increased as their effective case-hardened depth increased under the same surface hardness.

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This paper described a study on the bending fatigue strength of thin-rimmed helical gears with web arrangements. Root stresses from the beginning of engagement to the end of engagement of the thin-rimmed helical gears with web arrangements were measured by means of the strain gage method, and the changes of the root stresses in the meshing process, the maximum root stress O_cmax, and the worst meshing position (the meshing position where the maximum root stress occurs) were determined. Bending fatigue tests were carried out for the thin-rimmed helical gear pairs of different rim and web thicknesses and helix angles meshed at the worst meshing position and S-N curves were obtained. Effects of rim and web thickness and helix angle on the bending fatigue strength of the thin-rimmed helical gears with web arrangement were determined.

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This paper provides an intelligent diagnosis method for gear damage based on techniques of empirical mode decomposition (EMD) and support vector machines (SVMs). By the data processing of EMD, the original signal is decomposed into a finite set of intrinsic mode functions (IMFs). The characteristic energy ratios of IMFs are acquired as representative parameters of the signal. Furthermore, statistical parameters such as standard deviation, root mean square value, maximum value, mean value, crest factor and shape factor are extracted from the original signal in time-domain. The characteristic energy ratios and statistical parameters are combined as failure feature vectors to be input to the multiple classifiers developed from SVMs for gear damage diagnosis. The validity of the presented method is confirmed by the application of monitoring the gear conditions during the pitting experiments, and the diagnostic accuracy is 72.7%.

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Planetary gear set is widely used in hybrid vehicle as a power distribution system or in electric vehicle as a high reduction system, but its noise and vibration problem has emerged. There are many reports dealing with two-axes driving or displacement of planet gear under its condition, but we can see few reports dealing with about three-axes driving. In the present report, three-axis driving is tested with three-axes torque measuring and dynamic characteristic is investigated focusing on planet gear. As a result, it's confirmed that transition forces around planet gear are balanced and torque is also balanced around instantaneous rotation center. Meshing frequency in this condition are harmonics of two meshing frequencies, which are meshing frequency of ring gear and meshing frequency of planet gear. Input power of ring gear is distributed to carrier and sun gear through planet mode, star mode and solar mode.

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In the present paper, strength of DLC film was evaluated by gear operating test rig using DLC deposited POM gear pair. DLC films are easily detached or broken by high contact pressure. So that these are not applied to gear tooth flanks or raceway of bearings. If DLC films can be applied to gear tooth flank and they work for a long time, applicable field of them become widespread. Ni plating, Cr/C gradient interlayer and DLC film deposited POM gears were prepared for operating tests with changing plating time (for changing thickness of Ni plating) and substrate bias voltage (for changing hardness of DLC film). Results of operating tests using DLC deposited POM gear pairs indicated usefulness for evaluation method of DLC film strength. From operating tests results, it was clear that large thickness of plating made DLC film strength higher. And much DLC film deposited -100V substrate bias voltage, which had high hardness, remained on tooth flank after gear operating test.

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Low carbon steel is one of the materials widely used in engineering fields. It has been known that decrease in carbon content leads to a high welding workability. However, it makes the hardness low. One of the effective methods to keep high welding workability and hardness is minor and trace element doping to the steel. The doping of the minor and trace element improves hardness of steel due to refinement crystal grain size. This method is used in various fields because a part of the minor and trace elements is effective for cost reduction and reinforcing steels. In order to apply such a modified weld steel to slide elements, we investigated the tribological characteristics.

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In this study, simultaneous and direct observation of visible and infrared images of frictional surface was conducted to understand the scuffing phenomenon. A contact area was produced between a rotating sapphire disc and a stationary steel ball. Visible and near infrared images, load, and friction were synchronously recorded during tests. After the tests, hardness of scuffed steel balls was measured. It was found that temperature was significantly increased at macro plastic flow areas, which were observed to move at a veiy short time in visible images.

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In this paper, the relation between the friction coefficient and the specific ware ratio of stainless steel, ceramics, polymer and diamond like carbon (DLC) coated steel slid with stainless steel under line contact condition was described. The sliding tests were carried out using block on ring type friction and ware testing machine. The results of the relation between friction coefficient and specific ware ratio show the typical region of each material. The DLC coating shows the lowest friction and lowest ware. The polymer materials also show low friction and medium ware especially in ultra high molecular weight polyethylene and polyetheretherketone composite material. According to the ceramics materials, the silicon carbide (SiC) shows the high friction and ware different from the case of SiC-SiC contact.

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Oil film journal bearings are used widely in many rotational machines such as engines, turbines, compressors. The oil film in journal bearings had been investigated experimentally and theoretically by many researchers. In this study, we focus on the behavior of the oil film. By using the semiconductor laser unit mounting multi laser elements proposed in this study and high-speed camera, experimental visualization of the oil films are conducted under starved lubrication and flood lubrication conditions. Moreover the video data are analyzed by PIV (particle image velocimetry) and the characteristics of oil flow especially around cavitations in flooded and starved lubrications are compared.

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Amorphous Carbon Nitride (CNx) coating is promising for high hardness, low friction property and affordability. Though it is reported that transformed layer is important to show 10w friction, it is unclear that transformed layer makes an effect on low friction. To clarify the effect, we proposed the way to measure thickness, sp^2/sp^3 ratio and density of dangling bonds of transformed layer in-situ by using reflectance spectrometer while sliding.

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Failures of machines having rotating parts are mostly caused by damage to bearings and conventional diagnostic methods have found difficulties in performing the early detection of such damage, so that more advanced diagnosis is necessary. This study therefore applies an ultrasonic technique to bearing life tests. The experimental results of ultrasonic wave pulse (UWP) echoes have demonstrated that the time intervals between peaks of UWP echoes varied in accordance with the movement of rolling balls. The autocorrelation coefficient has further been used to analyze the UWP echoes. The values of the autocorrelation coefficient were in good connection with the time intervals between peaks of UWP echoes and were thought to provide the possibility of the early detection of abnormalities in ball bearings.

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Amorphous Carbon Nitride (CNx) coating is an attractive material that satisfies both relatively high hardness and ultra-low friction coefficient. We tried to obtain CNx by using plasma-enhanced chemical vapor deposition (PECVD), which is more suitable for 3-dimensional coating than typical physical vapor deposition methods. In this work, the friction characteristic under oil lubricated of the Si-CNxHy film deposited by PECVD was made clear from the relation between the Raman spectroscopic analysis which is an index of carbon structure, and friction coefficient.

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油圧機器におけるキャビテーション壊食量の予測手法の再提案を目指して,噴流衝突式キャビテーション試験機で壊食させた試験片を直接的に秤量して求めた質量減の実験結果と,3次元非接触計測器で壊食面を測定した形状データから算出した壊食量の換算値との比較,検討を行った.壊食実験の条件は, ISO VG32 石油系作動油,油温40℃,絞り上流圧力10MPa, キャビテーション数0.02,最長スタンドオフ距離 32.5 mmとした.角度や形状をパラメータとしたアルミニウム合金製の試験片を対象とした.限定的な条件ながら,秤量値と換算値との間にはある程度の一致が見られた.

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Graphene oxide (GO) has a graphite monolayer sheet structure with a thickness of below Inm and a size of over 10μm. Since GO has a 10t of oxygen functional groups, GO is easy to disperse in water. In this study, tribological properties of GO monolayer sheets as additives in water-based lubricants were investigated for tungsten carbide (WC) and SUJ2 balls with diameters of 2 mm, against SUS304 substrates, with a load of 11.IN. The density of the GO dispersion was 1 wt.%. During initial friction, a friction coefficient of the GO dispersion for the wc ball was over 0.1, and rapidly decreased to 0.05. And then the friction coefficient gradually increased and reached to above 0.11. A friction coefficient for the SUJ2 ball was relative stable with the value of 0.08-0.10. Since GO would insert between the sliding surface, GO would prevent the balls and substrates from contacting each other directly. This would suggest that GO sheets may behave as protective coatings.

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Safety is one of the most important issues in rehabilitation robot suits. We have developed a rehabilitation robot suit equipped with two mechanical safety devices. The robot suit assists a patient's knee joint. We call one safety device the "Velocity-based safety device" and the other the "torque-based safety device". The velocity-based safety device can switch off the motor of the robot suit if the device detects an unexpected joint angular velocity. Similarly, the torque-based safety device can switch off the motor if it detects an unexpected joint torque. The safety devices can work even if the computer breaks down because they consist of only passive mechanical components without actuators, controllers, or batteries. In this paper, we first review the characteristics of the safety devices and tbe rehabilitation robot suit equipped with the safety devices. We then present the experimental results of the simulated knee joint motion when the motor has turned off by the velocity based safety device. Finally, we discuss the effectiveness of the structure of the proposed robot suit based on the experimental results.

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A walking assistance apparatus which can promote gait training for motor palsy patients and outdoor walking for the elderly was developed. We proposed the control method according to the purpose of the user. For example, to promote gait training, this apparatus can select the impedance control method. User's legs are assisted along the trajectory with the ideal gait as well as walking. To promote outdoor walking for the elderly, this apparatus can select the torque control method. The apparatus calculates the necessary torques of each joint according to the posture and motion of the apparatus and user. In the case of the impedance control method, by adjusting the natural frequency of the ideal dynamic equation for the flat steps under the soles, the user felt it was easier to walk by frequency entrainment. On the other hand, to promote outdoor walking of the user, this apparatus has to be used not only on the flat ground but also on stairs or slopes with freedom behaviors, and it has to make the user feel comfortable. To address this problem, the torque control method proposed to use real-time acceleration data instead of using the template trajectory. By using this method, the subject could walk on the slope and stairs continuously. Finally, %MVC of the user's EMG while walking equipped with this apparatus was measured, and the influence of the difference using between the impedance and torque control method was confirmed by interviewing the subjects. From the result, the impedance control method assisted the motion of kicking the ground, and the torque control method assisted the motion of raising-up the leg. Therefore, the impedance control method is good for gait training, and the torque control method is good for walk promotion.

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Abstract: Animal therapy is recognized as effective against improving the mental illness. This research proposes 'a deformed and short-legged bipedal walking-type bear' through a series of relevant studies conducted by the collaborators, and proves its therapeutic effects by a questionnaire survey performed in relation to the robot's prototype. However, there has been a lot of feedback in terms of its uncomfortable feeling of touch and excessive weight. Therefore, the objective of the project is set to develop a new- generation robot that improves on all these suggested points. We take a look at the technical side of the material used for the robot's body. It was reviewed and changed to Japanese cypress, from the previous material of aluminum alloy. Japanese cypress is lightweight, with its specific gravity of 1/5, and the aroma components it emanates can be expected to provide such positive effects as relaxation, sterilization and mite control.

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In order to utilize the phenomenon of kinesthetic illusion as a human interface which can present kinesthetic sense, it is necessary to define a minimum specification of the vibrator required to elicit kinesthetic illusion. In this study, the sensitivity threshold of the illusion has been investigated using the staircase method, which is an adaptive psychometric method in psychophysics. The result of the experiment reveals that the kinesthetic illusion can be elicited with an acceleration of about 40 [m/s^2], with vibratory stimuli of 50 to 90 [Hz]. Furthermore, at the highest frequency of 120 [Hz]the illusion cannot be elicited unless the acceleration is increased to 60 [m/s^2].

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In order to enhance quality of virtual reality (VR), we attempt to utilize velvet-hand illusion (VHI), which generates virtual smooth and soft film between hands when an operator touches and rubes a mesh wire. If we can use VHI for tactile displays, there is a possibility to control material feeling in VR. In this study, we use a pin-matrix-typed tactile display instead of the mesh wire because the display can generate general patterns and control VHI feeling. In order to examine whether the pin-matrix-typed tactile display can be used as a VHI generator, we compare the strength of VIII feeling generated by the pin-matrix-typed tactile display with the VHI feeling generated by the mesh wire and real feeling of velvet cloth. A series of experiments is performed by procedure of a magnitude estimation test. The VHI feeling generated by the pin-matrix-typed tactile display is almost same as that generated by the mesh wire.

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In a general rehabilitation situation, a walking stick, parallel bars and a walker are used as walking training device. Users of these devices are supposed to keep their weight by the hands or legs, in some cases of rehabilitation cause pain to them. In recent years, because the aging society makes rapid progress, a labor shortage in a field of welfare becomes a serious problem. A walker which can motivate a patient to train without the help of care-worker is expected to be developed. In this research, we design and develop the walker with the assist equipment translating the suspected walking motion to the rotating wheel motion・ Using the walker, the patients are supported by the saddle, so their hands and legs are relieved from pain keeping their body balance. The assist equipment is designed by using of slider-crank mechanism, which transforms a oscillating motion to a rotating motion. The joint angular displacements are measured by with the device. From the measurement results, the general trajectory in walk can be obtained. This mechanism is designed to make its pedal follow a foot motion in a walking by comparing the coupler curve with a trajectory generated by an ankle joint in a walking motion. By method of measuring the pedal reaction force, the load of user is estimated. Comparing the reaction force acting on sole of the user's foot between the walking and the using the assist equipment, the manner to obtain the stable output torque of the mobile walking training machine is discussed.

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