The Enriched Free Mesh Method (EFMM) is a Mixed Method using the Hellinger-Reissner principle. A highly accurate stiffness matrix is computed for each local cluster. As a result, the EFMM can compute the high performance structural problem of low-order mode without an increase in the number of DOF. In this research, a large eigen-frequency analysis of discrete model of the EFMM is performed using the Lanczos method. The EFMM has more nonzero elements in stiffness matrix than the FEM. Therefore, we convert the stiffness matrix of the EFMM into tridiagonal one for the memory saving. It is noted that the Lanczos method can obtain small number of eigen-frequency in high accuracy with less computation time.

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Gear rattle of multi-step helical gear system is treated. Mesh stiffness variations and higher harmonics of driving torque are considered in the system. The effects of higher harmonics of driving torque are studied by numerical analysis. As a result, the followings were made clear. (1) In the resonance region of lower mode, when the frequency of driving torque is nearly equal to the one which is the natural frequency of higher mode divided by some integer, the response contains the higher mode and its amplitude of acceleration becomes large. However this phenomenon is not so affected by the higher harmonics of driving torque. (2) First harmonic of driving torque generates higher harmonic resonance and higher harmonic of driving torque generates the main resonance, hence the interaction of these two resonances makes the amplitude of the resonance large. (3) Because of interaction of higher harmonics of driving torque and mesh stiffness variation, resonances like gear noise occur with many side-bands in low frequency region, and the region of the rattles becomes wide. (4) Gear rattles in the case of small constant torque are almost chaos, and chaos by intermittency is recognized.

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Impact vibration of two beams was treated as an example of the impact vibration of continuous systems that are expressed by vibration modes and following points were researched by numerical calculation and experiment. (a) The number of modes needed to express the impact vibration phenomena sufficiently. (b) Whether there is the grazing bifurcation or not. (c) The energy level of each mode that excited by the impacts. The followings were made clear. (1) By adopting six natural modes, the theoretical result and the experimental ones about bifurcation diagram agree well each other qualitatively, and the characteristic of the diagram is a little different from that of the beam impacted to the wall. (2) The transition from periodic vibration to chaos is interpreted as the grazing bifurcation and its bifurcation becomes a little different one depending on the phase relation of the beams. (3) The tendency of the energy levels of the modes excited by the impacts is similar to that of the beam impacted to the wall, but the levels are little lower.

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This paper deals with a design problem of an aaptive compensation input for a class of uncertain linear systems. The proposed robust control system with the adaptive compensation input achieves not only robust stability but also performance robustness, and the performance robustness means that comparing the transient behavior of the uncertain system with a desired one generated by the nominal system, the deterioration of control performance (i.e. the error between the real response and the deisred one) is suppressed. In this paper, we show a design method of the adaptive compensation input. Finally, illustrative examples are included.

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This paper deals with computer-based simulation techniques on automobile engine vibrations. In the previous study, we developed an in-house software package called EVAS (Engine Vibration Analysis System) for predicting engine vibrations under running condition. EVAS is a flexible multibody dynamics solver that can comprehensively analyze the coupled phenomena by using its predefined body elements and several types of force elements which express mechanical joints such as journal bearings. In this paper, in order to calculate crankshaft torsional vibrations more accurately and efficiently, we propose a new force element of piston-connecting-rod sub-system considering the dynamic effects induced by the elastic deformation of the crankshaft. The new force element is applied to an in-line 4-cylinder engine model and its effectiveness is discussed compared with the experimental results. Then, using the element, we also investigate the vibration transmitting mechanism from the torsional and bending vibrations of the crankshaft to the elastic vibrations of cylinder-block through the bearing dynamics forces.

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This paper presents a computational method of random vibration of the turbine blades using the multi-degree of freedom spectrum analysis. This computational method is applied to the cyclic symmetry method to the spectral analysis and enabled a large-scale calculation of the steam turbine blades. In this computational method, it especially focused on the turbine blade with one-ringed blade and grouped blade structures. We call this structure a compound periodic structure. The compound periodic structure has the feature from which the response of two or more modes is calculated with one harmonic number. Therefore, the mode characteristic is important to superpose the random vibration response. Also, the random vibration examination by a simple blade model was done. The calculation results were corresponding to the measurements well, and the validity of the computational method was confirmed.

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For satisfactory prediction and reduction of the vibrations in centrifugal fans, it is necessary to consider the forced vibration with not only unbalance due to rotary machinery but also V-belt excitation. The object of this paper is to show the mechanism of the vibration caused by the V-belt and present an analysis method that is applicable to predict this vibration. The fluctuation of the belt tension takes place when the belt seams pass through the pulleys during operation. While operating, it is considered that the excitation force due to the fluctuation of the belt tension should be a periodic pulse. Hence, the amplitudes of the higher harmonics are predicted by Fourier series and the amplitudes of the frequency response are calculated by using the modal analysis result. As a result, it was concluded that the analyzed data were consistent with the measured data. In addition, it was shown that there is a higher harmonic resonance between the fourth order component of the belt rotation and the natural frequency of the tested fan.

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Modal differential substructure method, which can quickly predict effects of structural modifications, has been proposed by the author. This method is a kind of modal synthesis and utilizes dynamic current characteristics of modified structure. The method is convenient because it does not require the user to determine the structure modification beforehand and the user can choose the segmentation after checking dynamic characteristics of current structure. This paper elucidates the difference of formulation between the proposed method and conventional methods. As with other building block approaches, however, the predictions of effects of structural modifications with this method involve errors. In this paper, a technique to reduce those errors is proposed and the method is compared with conventional methods in terms of error reduction effect and computational efficiency.

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The identification of external force acting on a machine or a structure is important for the diagnosis. One of the force identification methods is based on the frequency response function. The method is very useful although it requires the information of location of force acting. In this study, an identification method is proposed for the case of unknown excitation points. In the method, the distributed force is approximately expressed by using some unknown variables, thus this method can be applied for the case of widely distributed force and concentrated force. And the final identification result is determined through the check of the objective function for various singular values. The validity of the method was shown by the numerical example and its feasibility was also shown by an experimental result.

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There are several formulations for beam elements in the multibody dynamics. Recently, the absolute nodal coordinate formulation (ANCF) is studied for such problems. In this formulation, the mass matrix and the stiffness matrix are described as simple equations, even in the case of the large deformation and displacement problem. However, degree of freedom of the beam element of ANCF increases from conventional finite element method, since the beam element is formulated by 8 absolute nodal coordinates. In order to reduce the degree of freedom of this beam element, authors have tried a new formulation by using 6 absolute nodal coordinates. The shape function of the beam element has been expressed in terms of the quadratic function, and the equation of motion has been described simply. But, this formulation had to use differential-algebraic equations for the assembling method. In this paper, the authors propose an assembling method of beam elements formulated by using 6 absolute nodal coordinates. In this method, beam elements can be assembled by superposition of the matrix like the conventional Finite element method. The usefulness of the proposed method is verified by the numerical simulations.

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In the field of ultra accurate positioning system, such as semiconductor lithograph machine, an active isolation system is generally used. Especially, it is an indispensable unit in the system which is required a highly accurate isolation performance from outside in the semi-conductor exposure machine. In a present lithograph manufacturing machine, the scanning type is a main current, furthermore the main structure supported projection lens is separated from stage which can be freely moved in the stage stroke, and the stage is supported by independent isolation system on the base. At this time, the controller cannot achieve enough performance which is required of the system, because mechanical resonance limit control bandwidth. In this paper, the control band-width can be given by making compensates using many actuators mounted under approximate layout for mechanical resonance of structure. Therefore it is able to get high control bandwidth, and achieve enough performance and robustness for disturbance is improved.

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A control method to always excite a multi-degree-of-freedom system efficiently at a resonance frequency was developed. When an excitation point corresponds to a vibration detection point in the multi-degree-of-freedom system, a phase lag at a resonance frequency and a phase lead at an anti-resonance frequency alternately appear in the vibration characteristics, and the phase lag becomes 90° at all resonance frequencies. Therefore, if a controller that has a phase lag of 90° and a constant gain in a wide frequency range is used, self-excited vibration is generated at all the resonance frequencies. The self-excited vibration controller can be expressed as the sum of the positive velocity feedback control with a high gain in a high frequency domain and the integral control of the displacement with a high gain in a low frequency domain. A local feedback controller for each actuator consists of a self-excited vibration controller, a saturation element that limits excitation force, and a negative velocity feedback controller that provides active damping. A driving at a resonance point system using many actuators with local feedback control, that is, decentralized control, is excellent in its adaptability to the environment, in its extendibility, and in its fault tolerance. In addition, the self-excited vibration mode can be freely switched on by changing the frequency of the sine wave that causes the self-excited vibration.

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This paper deals with modal control of one-dimensional planar structures using both distributed-parameter film sensors and actuators with a view to extracting as well as suppressing the designated structural vibration mode. First the fundamental properties of a modal control system based upon distributed-parameter sensors and actuators are discussed. It is shown that the utilization of distributed-parameter sensors and actuators leads to the elimination of spillover destabilization. A photo-resist technique on electrode patterning of a PVDF film and a laminating technique are then introduced, hence termed a multi-layer PVDF film. The use of the multi-layer PVDF film per se is found to possess the potential of modal control. Furthermore, a multi-layer PVDF film-based one-dimensional planar structure is developed, which has the attribute of modal control. The experiment is finally conducted, demonstrating the capability of modal control for suppressing the structural mode of interest without causing any spillover effect on the other structural modes.

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A boiler and a heat exchanger are widely used in various plants such as power plants and chemical plants. However unexpected high level sounds are generated when these plants are operated and it becomes a serious problem. This kind of problem is called the acoustic resonance and it has been considered that the resonance generates when the frequency of the vortex shedding behind the tube bank coincides with the natural frequency of the duct system. However, it has also been thought of self-sustained tone. In general, the self excited phenomenon arises when the exciting energy becomes greater than the dissipating energy. Then in this paper, in order to clarify the mechanism of self sustained tone experimentally, the instability region is tried to be obtained by changing the number of tube row and acoustic damping. As a result, it was clarified that the self-sustained tone generates when the number of tube rows becomes large and the acoustic damping becomes small.

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In order to establish quantitatively a design method for the McKibben type rubber artificial muscle with the optimal characteristics, analysis of force is performed by means of the three-dimensional finite element method. First, the three-dimensional finite element method model which does not take into consideration friction between plastics fiber codes is proposed as a simple model for acquiring the design manual of the McKibben type rubber artificial muscle. Moreover various parameter study of the McKibben type rubber artificial muscle is carried out, and the characteristics of the McKibben type rubber artificial muscle can be predicted. The proposed analysis can be applied to the useful design method.

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Sub-pixel digital image correlation (Sub-DIC) method is effective for health monitoring of structures, because the Sub-DIC method can measure full-field deformation and strain distribution. However, the effect of analysis parameters of Sub-DIC method on measurement accuracy is not clarified. In this paper, we discussed the relation between the analysis parameters and the measurement accuracy of the Sub-DIC method. We demonstrated the analysis parameters such as a sub-set size, scan-step interval, and averaged point size on the standard deviation of measured deform and strain error distributions. Moreover, we found measurement accuracy is correlation related to the half width of spatial FFT spectrum of measured object and strain distribution. Finally, it is basically confirmed the measurement accuracy of Sub-DIC method depends on the central limit theorem.

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In this paper, a haptic sensor system for evaluation of human hair under dry and wet conditions is developed. The polyvinylidene fluoride (PVDF) film, which is a kind of piezoelectric material, is used as the sensory receptor. The sensor consists of an acrylic base, a silicone rubber, a PVDF film. A surface projection is put on the PVDF film as the contacting part. The sensor output is obtained by contacting and scanning objects. Evaluation for human hairs has problems due to randomicity and difficulty of putting them uniformly without overlapping. Therefore, panels imitating the physical and chemical properties of human hair surface are fabricated and used as measuring objects for stable measurement. First, these panels with dry and wet conditions are measured by two sensors with different contacting parts. The measurement results are compared with human sensory evaluation, and the suitable sensor is investigated. Next, panels cleaned down with several kinds of treatment are measured by the sensor. By comparison between the sensor output and human sensory evaluation, it is confirmed that the sensor system can discriminate the treatment effects in dry conditions. Finally, the surface projection on the PVDF film and the sensor structure are improved in order to measure under wet conditions as well as under dry conditions. The sensor outputs have a good correlation with human sensory evaluation. It is found that the improved sensor system is available for monitoring hair conditions in both dry and wet conditions.

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In this paper, we developed a real-time and high-speed glossy surface scanner, which estimates surface reflectance properties for conveying objects in one direction. Using the glossy surface scanner, a single image was condensed with reflected rays of light in different angles by using a cylindrical lens, and it was processed for surface reflectance properties estimation on a high-speed vision platform. Surface reflectance properties were estimated at 1000fps for 1024×1024 pixel images. Experimental results for several glossy-surfaced objects were verified for evaluating its performance.

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We describe a new robotic assist device: a passive assist arm (PAS-Arm). PAS-Arms are intended for direct physical interaction with a human operator. PAS-Arms are physically passive. The force to manipulate the arm end must be provided by the operator. Their purpose is not to enhance human strength, but to provide virtual guiding surfaces, which constrain and guide the motion of the operator. PAS-Arms have three joints and a three dimensional workspace, but possesses only a two degrees of freedom, due to the reduction of degrees of freedom created by a combination of continuously variable transmissions (CVTs) and differential gears. In this paper, we firstly discuss manipulability ellipsoid for the PAS-Arm. The major axis of the ellipsoid is the direction that the arm end may be easy to manipulate, and vice versa. We have developed an experimental system of the PAS-Arm. The CVTs of the experimental system may not adjust the transmission ratio to zero. We secondly describe an algorithm that handles the problem. Finally, we present initial experiments that verify the PAS-Arm mechanism. The experimental results were successful in producing the virtual guiding surfaces.

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Autonomous control of an articulated steering type vehicle such as a wheel loader, which is usually used at surface mining fields to load mineral resources and rocks, is highly expected for operation cost reduction. A wheel loader is one of heavy machines which is also used for snow removing and/or loading operation at construction fields because of its high mobility. Its steering system is articulated steering and the rear wheels follow tracks where the front wheels have traveled. We have introduced a new virtual velocity constraint of the vehicle and formulated nonlinear state equations using two velocity constraints. A nonlinear state-feedback controller is designed using exact linearization. Simulation and experimental results show that an articulated steering type vehicle can follow a straight line with the proposed feedback control method.

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We propose a car transportation system termed as iCART (intelligent Cooperative Autonomous Robot Transporters). In this system, two robots approach the car autonomously, and lift up it for supporting its weight from right/left side respectively. Then, two robots transport the car in coordination. Collision-free trajectories for approaching and transporting the car are generated based on the potential field in the configuration space. In this paper, we describe details of the way to construct a configuration space, to apply a potential to the configuration space, and to generate a trajectory. Additionally, for generating the collision-free trajectory on the environment where two robots exist, repulsive potentials are applied to each robot. Described methods are integrated to iCART and experimental results illustrate the validity of the proposed method.

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This paper considers the problem of controlling both the planar position and the orientation of underactuated balloon robots with a reduced number of actuators by sampled-data control. The robots are nonholonomic systems described by a set of nonlinear differential equations. The systems are discretized by a zero order hold and a sampler, and a new discrete-time observer-based output feed-back controller without measurement of velocities is obtained for global exponential stabilization of both the position and the orientation. A time-varying coordinate transformation is utilized to reduce the stabilization problem to a standard pole placement problem of a linear time-invariant discrete-time system. The proposed design method is simple and straightforward. A numerical simulation shows the effectiveness of the proposed systems.

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This paper considers the problem of controlling both the planar position and the orientation of an underactuated airship with a reduced number of actuators. The airship is a nonholonomic system described by a set of nonlinear equations and the dynamics are subject to bounded uncertainties. A smooth and time-varying coordinate transformation is utilized to reduce the robust stabilization problem of the airship to that of a linear time-invariant system. A new robust feedback controller is obtained for global stabilization of both the position and the orientation of the underactuated airship with parameter uncertainties. The proposed design method is simple and straightforward. Experiments are performed to validate the effectiveness of the proposed controller.

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Our previous studies proposed an admittance and an impedance control method of a finger-arm robot with a 3DOF finger and 6DOF arm robot to guarantee the finger manipulability under arm compensatory movement, whose results show that satiny movement of the finger-arm robot was realized in constrained space. Although these results were applied for one finger system, it is necessary to extend these methods for a multi-finger system. This paper shows an admittance control method and its results of multi-finger-arm robot to guarantee its finger's manipulability. Both averaging method and mini-max method are examined to evaluate its manipulability of multi-finger. Both results are discussed in the viewpoint of both stiffness and viscosity and finger's manipulability.

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Swimming velocity and propulsive efficiency of fish robots are extremely low in comparison with actual living fish. Therefore, using the sea bream as a model, a flexible fish robot was developed to study its propulsion performance. The individual effects of the shape, thickness, flexibility and moving pattern of the tail fin on the propulsive force were investigated experimentally by using Particle image velocimetry (PIV) measurements and three-dimensional computational fluid dynamics (CFD). Consequently, it was confirmed that the propulsive performance of the fish robot can be improved when vortex rings are successively formed downstream of the tail fin to form a reverse Karman vortex street.

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The objective of this study was to clarify the mechanical body load during walking in water by simulation, considering the fluid force acting on the lower extremities. First, joint torque and force were analyzed by simulation model of walking in water, which was developed by modifying the swimming human simulation model SWUM, and whose input data were obtained in the previous experiment. Second, muscle force was analyzed by a two-dimensional musculoskeletal model for the lower extremities. The following findings were obtained from those analyses: The hip extensor muscles are employed more greatly during the stance phase of the walking in water, compared to the land walking. The joint force in compressing direction during the walking in water is significantly lower than that of the land walking. From these results, it can be concluded that the walking in water is suitable for rehabilitation. In addition, it was also found that the joint torque due to the fluid force component mainly acts in the swing phase. Therefore, the lower extremity muscles can be trained effectively by use of the fluid force in the swing phase.

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We propose an entirely new model of the electric wheelchair that consists of the castors and the main body. The equations of motion about the castors and the main body are derived by the physical law. In particular, the dynamics of the castor is considered in this study. In order to confirm the validity of the constructed electric wheelchair model, the comparison between the experimental result and the simulation result about the castor behavior is performed. Then, we examine the parameter of the electric wheelchair to suppress the disturbance (for example, the behavior of the castor and the road gradient) as an application of the proposed model.

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In 2000, a new standard (Japanese Industrial Standard, JIS S 0011) was enacted in Japan. The standard provided the perceptual sizes of tactile dots and bars for use in consumer products. However, the numerical values about these sizes were not determined based on data reliable enough. Therefore, objective and quantitative data for perceptual sizes of tactile dots and bars is required for revising this JIS and for devising other standards. In this study, we focused attention on cellular phones becoming common around the world and evaluated the influence of the height of tactile dots (0.0, 0.1, 0.3, 0.5 and 0.7[mm]) on the operational performance of cellular phone. In this experiment, each 20 sighted younger and older participants, whose hand was covered by a curtain, was asked to operate cellular phones with tactile dot on its key 5 and without tactile dot. Both groups performed better with a tactile dot than without it. However, with a dot height of 0.7mm, participants felt significant pain. We determined that there is an appropriate range of the height of tactile dot that improves the operational performance of cellular phones.

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In order to keep a highly safe and reliable system of car driving, it is important that the system would be considered as a man-machine system including not only the feature of vehicle movement but also human perception, cognition, and motion of a driver. In this paper, it is examined to clarify the relation between feature of eye movements and driving behavior in conventional and unconventional situation by the experiments using the driving simulator and the eye tracking system. The measurements of time histories of eye movements during the driving a road vehicle were performed in the situation of different traffic regulation by the simulator. The experimental system proposed in this paper is useful for analyzing human error induced from the different traffic regulation between Japan and USA scenarios. It is recognized in both turns that typical patterns of eye movements in horizontal axis appeared between start and end of the turns. It is also found that there were several times of a set of eye movements appeared in horizontal axis from the beginning to the end of turns. It is found from the time histories of eye movements by synchronizing vehicle data when the overshooting in the right turn and undershooting in the left turn that resulted in head-on crash, the time and number of eye fixation with overshooting or undershooting spent in cognition and motion stages in vehicle operation became larger than that without overshooting and undershooting.

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In this paper, the method of extracting true abnormal information from the statistics comparison of relation between discrete parameters using LVQ is examined. In general, since a fluctuation occurs in a sensor measuring quantity in the normal state by various factors, such as a noise and environment, an incorrect diagnostics arises in the abnormality diagnosis system which use threshold value. In a lot of cases, fault detection system will detect more than the actually caused abnormalities significantly. In this case, the judgement to all the abnormal information is required, the treatment to an individual phenomenon becomes shortly, and it causes hindrance of accurate judgment. Therefore, for quick action and the maintenance, reduction of the incorrect information is desired. Then, in this paper, the method of extracting true abnormal information from the statistics comparison of relation between discrete parameters using LVQ is examined. In general, by the abnormality diagnosis system, existence or not of an abnormality is shown by the binary parameters. When identifying a time-series relation of parameters, a method suitable for correlation identification of discrete quantity is needed. LVQ was applied as an autocorrelation identification method. The simulation based on data of actual working railway monitoring system was carried out and the occurrence of the fault was detected by detecting the change of identified LVQ from a statistical test.

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In this paper, a new riveting method considering design for disassembly is attempted. The method can join the sheets by the high-speed blanking without drilling of the sheets as well as disjoin easily the jointed sheets. The joining is carried out by the following procedures: (1) A pair of a rivet with a rivet head and a rivet holder which has been already drilled in the center as the other rivet head is set on condition that their center axes may agree and two pieces of sheets are interposed between them. (2) The rivet axis set on the upper sheet is struck into sheets by the collision of the weight with high speed and the rivet axis penetrates the sheets. (3) The rivet axis which penetrated the sheets is inserted into the hole of the rivet holder and then the tip of the rivet axis which projects from the hole collides with a die. Then the axis and the rivet holder are joined because the plastic deformation of the axis generated by the collision fills up the hole of the rivet holder and the sheets are fastened tightly by both the rivet with the rivet head and the rivet holder. The experimental results showed that the joint strength by impact riveting was higher than that of caulking, and the deformation of sheets was small. In addition, the joined sheets could be disjoined easily.

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A novel method for measurement of vertical and lateral forces with a high sensitivity and accurate gap control has been presented. It combines a double-ended tuning fork (DETF) resonator for the vertical force measurement with an optical fiber probe for the lateral force measurement. The theoretical and experimental investigations revealed that this method can provide simultaneous measurement for lateral and vertical forces of nanometer-gap lubrication with a precise gap of control within 1nm. In addition, the attained force sensitivity is of the order of 10nN. This method can be useful to clarify the nanolubrication or boundary lubrication phenomena, which has not been fully understood due to the difficulty of the measurement.

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We present a kinematic design of a translational parallel manipulator with fine adjustment capability of platform orientation. In order to clarify possible kinematic structures for it, structural synthesis of fully decoupled mechanism and partially decoupled mechanism both with six degrees of freedom (dof) was carried out. All possible kinematic structures were obtained. Of these, one partially decoupled mechanism was selected and a kinematic design of a prototype manipulator was done. Its characteristics in terms of workspace, singularity, orientation adjustment capability, and coupling characteristics between translational and rotational displacement were discussed with experimental results regarding fine adjustment capability of platform orientation.

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We have developed a micro three port electromagnetic valve for micro chemical process. This study aims at integrating the micro three-port valve into micro reactor or micro flow control systems. We have applied the developed valve to slug flow generation by pouring two liquids into the ports to promote efficient chemical reaction. The slug flow is a stripe flow formed by serial segments of two liquids which appear alternately along the flow line. It greatly increases the interface between two liquids, resulting in very efficient chemical reactions. In addition, each set of the segments works as a kind of micro reactor chamber, in which many advantages of micro chemical reaction such as very uniform reactions and reactions under special conditions appear. Slug flow has been applied to copper ion extraction process. The effectiveness of the slug flow is clearly found. The results show the potential of the prototype valve to be applied to actual chemical processes.

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The wet blast technique has high potential for precision surface processing wherever tiny particles can be used. In this study, solid particle size effects on the wet blast processing mechanism of monocrystalline silicon wafers were investigated. Pure water, containing angular alumina particles of sizes ranging from 1.2μm (WA #8000) to 18.3μm (WA #800) at the concentration of 0.01mass% were impacted by using a micro slurry-jet erosion (MSE) apparatus. The impact scars due to single particle impingements were observed by SEM and AFM, while surfaces processed with a large number of particles were observed by a Laser Scanning Microscope (LSM). When the particle size was smaller than about 3μm, the impact scars were due to plastic deformation of the material, or to ductile fracture caused by micro cutting during single particle impingement. On the other hand, brittle fracture caused by lateral cracks was dominant for the particle size larger than about 3μm. The surfaces processed with a large number of particles showed the effects of repeated single impact scars. Therefore, the removal rate and the roughness were less in the processing by tiny particles because of the domination of plastic deformation or ductile fracture.

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A fluid-driven spindle with hydrostatic bearings was designed and tested. Several flow channels are designed in its rotor so that the driving torque can be generated by supplying pressurized flow into the channels. The rotational speed of the spindle can be controlled by the flow rate. In addition, the rotational direction of the spindle can be controlled by switching supply ports. The angular position control is thus achieved by designing appropriate feedback controller. A mathematical model of the spindle was derived and spindle characteristics calculated by the model were compared with experimental results. Furthermore, the angular position control system that has a disturbance observer in its feedback loop was designed based on the mathematical model. The step response of the designed angular position control system was experimentally tested. The designed controller minimizes the steady state error of the control system. Consequently, the steady state error was comparable with the resolution of the rotary encoder, 0.018 degrees. In particular, the experimental results indicated that the disturbance observer was effective to reduce the influence of various load torque on the angular position of the spindle.

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The objective of this investigation is to clarify a new and high efficient mirror machining process with using ultrasonic and low frequent vibrations, that has been named "superposition superfinishing (SSF process)". In the first report, it was confirmed that a stock removal rate of superposition vibration cutting as cutting process on this SSF process can be higher than that of low frequent superfinishing, and that a high efficient mirror machining can be practically achieved. In the second report, by analysis and consideration on superposition cutting track, it was found that cutting length of this superposition vibration cutting strongly influence on a stock removal amount. In this report, as one reason of obtaining a high stock removal rate, we have adopt equivalent grade characteristics of ultrasonically vibrated abrasive stone. It has be shown that the grade of abrasive stone decreases according as amplitude incleases. On the result of some experiments, it is found that this phenomenon can be controlled by an amplitude value of ultrasonic vibration, and that a rate of abrasive stone ware per one meter of superposition superfinishing is lower than that of low frequent superfinishing in the case of large maximum cross angle.

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A tool manufacturing technique for fabricating a microball endmill with a sharp cutting edge without chipping was developed using nano-polycrystalline diamond (NPD), which is harder than single crystal diamond (SCD), as the tool material. The NPD with a size of 2×3×0.6mm and diamond grain size of several tens of nanometers was roughly formed into a one-flute microball endmill with a radius of 45μm by milling and trimming using a pulsed fiber laser. In addition, wet and dry grinding using a polycrystalline diamond (PCD) disk as a truer were additionally conducted to sharpen the cutting edge without chipping and to adjust the tool radius at 50μm and a clearance angle of 5 degrees. The chipping resistance of the microball endmill was tested by applying the tool to the interrupted cutting of the cemented carbide with a hardness of 13.5GPa Hv. It was verified through the cutting test that the NPD had the potential to fabricate a surface roughness of 20nm Rz without any chipping when the radial depth of cut and the feed rate were set at 0.5μm and 0.5μm/rev, respectively.

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A diamond stone is worn away faster than a cBN stone when superfinishing a steel workpiece, because of the carbon diffusion into iron. However, if such a wear mechanism can hardly work, it is expected that the wear of a diamond stone decreases. This paper describes two methods to suppress the carbon diffusion; that is, nitriding process of steels and addition of reactive BaSO_4 abrasive to a diamond stone. When nitriding is applied to a steel, the face-centered cubic γ' nitride, Fe_4N, is formed at the steel surface. It acts as a barrier to deter the diffusion of carbon into iron. On the other hand, BaSO_4 abrasive added to a diamond stone forms an oxide layer of Fe_3O_4 on the steel surface during superfinishing process. The formation of Fe_3O_4 accelerates the deoxidization by diamond. Then, the diamond stone wears not by carbon diffusion but deoxidization of Fe_3O_4. Superfinishing experiments have showed that both these methods improve the wear resistance of diamond stone.

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