For a single-degree-of-freedom system having a spring function (in addition to a linear term) with a cubic term (Duffing oscillator) or a quadratic term (Helmholtz oscillator), the exact solutions of the free vibration are expressed in terms of Jacobian elliptic functions. However, for a system having a spring function with all terms from a constant (0th order) up to a cubic (3rd order), the most generalized 3rd-order polynomial including an asymmetrical spring, the situation has not always been clear since Duffing's early days. A certain transform was proposed to convert the relevant system into a standard (symmetrical) Duffing system previously, but the algorithms were poor and some difficulties were found in the computation In this paper, revised algorithms are discussed to realize accurate numeration. It also becomes possible to obtain the solution for a given natural frequency as well as for a given initial rest amplitude. As an example the result for an asymmetrical soft spring system is demonstrated.

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Three dimensional analytical results for the levitation force of a vibrating high-Tc superconducting levitation system were presented. When the levitated superconductor vibrates, the levitation force shows nonlinear relationships with the air gap, amplitude and vibration frequency, so that the convensional models which do not consider dynamic effects cannot be applied. In the model proposed by(Uesaka et al.), dynamic effects are considered, but the critical current is constant. We propose an improved Kim-model which is applicable to vibration problems of conductors. Numerical results for the levitation force were obtained and compared with previously published experimental data. A modeling method for the superconducting levitation system was presented, and the nonlinear spring constants obtained in an analysis which included the effects of air gap, amplitude and frequencies were given. Numerical calculations were carried out for nonlinear vibrations of the system based on the modeling results.

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Magnetically levitated (MAGLEV) vehicle systems have been studied for use in future high speed transportation. It is especially important to investigate dynamic characteristics for running stability, safety and ride quality at high speed. This paper concerns dynamic characteristics of repulsive-type MAGLEV systems using electrodynamic suspension (EDS). Since the electrodynamic suspension is inherently stable but of low damping character, mechanical resonance is liable to occur in levitated body motion. Moreover, since the system uses conductive eddy current in coils or sheets on a guideway, the repulsive force is influenced by magnetic fields generated by adjacent magnets located in the longitudinal direction. In this study we investigate magnetically couped vibration between two independent levitated bodies running above an aluminum plate.

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Although the amplitude of tympanic membrane vibrations is only a few manometers when we speak in a low voice, we can understand clearly what is being said. This is speculated to be due to cochlear amplification. However, the mechanism of amplification in the cochlea is obscure. Therefore, in this study, cochlear basilar membrane vibrations in live, dead and hypoxic guinea pigs are measured directly using a laser Doppler vibrometer coupled to a compound microscope, and an attempt is made to clarify the mechanism of cochlear amplification. Results indicate that a cochlear amplifier exists in live guinea pigs and is influenced by a moderate level of hypoxia.

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This paper deals with the analysis of vibration mode of a drum-type rear brake and a countermeasure to squeal noise generation. Attention was paid to backing plate vibration since the vibration node of backing plate was usually difficult to recognize distinctly when squeal noise occurred in a bench test. In contrast' in a car noise test, the vibration node usually appeared distinctly. For determining a squeal noise characteristic, we carried out FEM vibration analysis and experimental modal analysis of the backing plate and obtained the characteristic frequency and vibration mode, and then identified the bending mode of 6 nodes located at the same position as that in the car noise test. A countermeasure to reduce the vibration was taken by stiffening the circumferential edge of a backing plate. Decrease in accelerance was identified by FEM frequency response analysis and impact testing. The effect of the countermeasure was confirmed in the car noise test.

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The concepts and the damping characteristics of an active damper using electrorheological (ER) fluids containing numerous dielectric particles have been proposed, and applications to vibration isolation control have been investigated numerically, based on the analytical model of the ER damper involving the approximate function of pressure drops across an ER valve obtained experimentally. The ER damper was found to be analogous to the hybrid damper having a viscous damper with constant damping and an electrically variable friction damper. Therefore, the ER damper under constant input voltage behaves like a coulomb friction damper, and the active damper can be constructed, by electrically varying the friction like forces proportional to the piston speed, to be a linear viscous damper with electrically variable damping coefficient. Three methodologies of vibration isolation control using the ER active damper were applied to a single-degree-of-freedom excited vibration system consisting of a mass, a spring, and the ER damper. Among these control methodologies, the nonlinear feedback control of the square root of the absolute velocity of the mass was found to be most effective to reduce the vibration transmissibility of the system, and to enable control of transmissibility approaching that which can be achieved with a full active vibration isolation system using an actuator.

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This paper presents active vibration control of a 2-bed pendulum using H_∞ andμ controllers. This paper is a first step to the study of the active control of a suspension bridge tower under construction. Since the suspension bridge tower is flexible, the undesirable wind-indused vibration arises. Thus it is necessary to reduce the vibration to an allowable level. The 2-bed pendulum, which has almost same natural frequency and damping as those of the suspension bridge tower, is adopted as a simple example of this problem. The mathematical model of the 2-bed pendulum is obtained by mechanical laws, and a nominal model is obtained by the reduction of this model. For the designing of a controller, we use both the H_∞ theorem based on the "normalized coprime factorization" and μ synthesis. From the experimental results obtained for two types of 2-bed pendulums, the H_∞ and μ controllers are proved to be effective for reducing vibration.

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This paper describes a new energy-saving high-speed control valve using a multilayer piezoelectric actuator and a spool valve. This valve controls the flow rate by controlling the amplitude of the spool vibration at 2kHz. Because piezo displacement is too small to drive the spool, this valve has springs and a spool as a mass. 2 kHz is the resonance frequency of this spring-mass system. Leaf springs and a linear ball bearing are used to reduce friction and prevent loose support. Experimental results show that a resonance frequency of 2kHz can be achieved by this structure and the flow rate can be controlled by the amplitude of the spool vibration. However, the flow-control characteristic is strongly influenced by unsteady flow forces.

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Active microvibration control systems are becoming necessary in high-technology fields such as semiconductor manufacturing. In this study, an active 6 DOF microvibration control system using a giant magnetostrictive actuator was developed. The actuator consisted of a giant magnetostrictive rod of a 50mm length and a 6 mm diameter surrounded by a driving coil. A control law was adopted to provide almost the same performance as that of sky-hook systems by using only absolute acceleration, instead of achieving feedback of absolute displacement and velocity. Through vibration control experiments, it was shown that performance of the system was sufficient for implementation, including isolation performance against micro floor motion, damping performance against direct disturbance, and control system robustness.

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A method for modifying the analytical model of a large structure is proposed. We assume an initial, undamped, finite-element model to be characterized by its mass and stiffness matrices. These are corrected by minimizing the Euclidean norm subject to constraints specified from physical points of view. These constraints include mode orthogonality, symmetry of mass and stiffness matrices and structural mass properties. The connectivity of finite elements is also considered in this method. Therefore, corrected mass and stiffness matrices are sparse, as are analytical ones. This method is programmed using DMAP (Direct Matrix Abstraction Program) on NASTRAN (NASA STRuctural ANalysis program) for application to large structures. An example is given to show the effectiveness of this method.

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In this paper we propose an optimal design methodology for the mechanism, guidance and control law of dynamic systems. Optimization under operating conditions is necessary for design of dynamic systems. This design means to optimize not only mechanical parameters of the system, but also guidance inputs and control law of the controller. From another point of view, the designed system and controller are required to be robust for uncertainties of operating conditions. The guidance and control systems must satisfy the requirements under different operating conditions. The design methodology, proposed in this paper, uses multiple design points for robustness of the controller. The mechanical parameters of the system, feedforward input variables and feedback gains of the controller are designed simultaneously to minimize the same criterion. This design methodology is applied to a manipulator system which carries objects whose mass is not accurately known. The results show that the proposed design methodology produces a guidance controller which is robust for uncertainties of operating conditions.

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In the present study, a twelve-D.O.F. mathematical model of a motorcycle-driver system, including tire modeling and the hand force of the driver, has been developed and the equations of motion are solved for the high-speed stability of the wobble mode. The effects of the main factors governing the high-speed stability have been clarified, especially for the handle force of the driver and frame stiffness. The calculated results are compared with the experimental ones, and a satisfactory concordance between them is obtained.

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Recently, the image processing system has been used in autonomous vehicles for environment recognition. The system recognizes environmental complexities, for example, detecting lanes and obstacles on a road. However it is almost impossible to do real time analysis for recognition of both own vehicle behavior and other vehicle behavior with image processing because of the large amount of information. Thus, this study proposes the image processing method for a vehicle behavior recognition using image flow with a slow shutter speed video camera. As a basic study, experiments on forward velocity, lateral velocity and yawing velocity were performed respectively for one degree of freedom motion, while steady state turning was performed as three degrees of freedom motion, The analytical values from the image processing method agreed well with the experimental values of direct measurement.

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A system for recognizing the road environment to determine the danger mode has been developed in order to avoid accidents when driving a car. Binary images of lane markings and obstacles were produced from road images taken with a CCD camera. Various patterns of road information extracted from the binary images were classified into 35 road forms in order to determine three danger modes using neural networks. Neural networks allowed determination of the danger modes from the road forms, distances of an obstacle from the car and the traveling states of the car without using the model-matching method which is most widely used for recognizing the road environment.

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Most of the sound generated by vibrating structures is structure-borne sound. The purpose of this study is to investigate the generating mechanism of the structure-borne sound using vibrational energy and sound energy. The analytical model is a rectangular plate which is one of the basic elements of structures. The plate is excited sinusoidally at one point on the plate and proportional damping is taken into consideration. The dynamic response of the plate is calculated using the finite element method to obtain vibrational energy and sound energy. This paper describes the relationship between sound energy generated by a vibrating plate and vibrational energy flow patterns at different excitation points. As a result, sound radiation efficiency varies under the condition that generates the vortex flow patterns of the vibrational energy, while it is constant under other conditions. Sound energy under the influence of the vibrational energy flow can be estimated from sound radiation efficiency and two kinds of energy ratios. The influence of the vibrational energy flow patterns on sound field can be expressed by the phase distribution of complex displacement on the vibrating plate.

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In the previous report, the authors proposed a method for arranging noise sources and an error microphone for active acoustic power control systems. The theoretical estimations and experimental results of the acoustic power reduction were also presented. Two assumptions were made in the estimations; one was that the error signal becomes zero and the other was that the sources are small encagh to be regarded as point sources. In actual cases, however, it often occurs that those assumptions are not sufficiently satisfied. The assumptions are examined in this paper, and more precise estimations are presented. In addition, the experimental results obtained using the duct opening are discussed and compared with the theoretical estimations.

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We studied acoustical properties of a single dust expansion in an infinite circular duct. As is generally known, in the case of long duct expansion, its properties depend on interference of sound waves propagating in the axial direction, but in the case of sufficiently short duct expansion, it behaves as a resonator muffler. In this study, we considered duct expansions with short axial length in between the above two cases, and indicated the change of properties of such duct expansion according to its length by experiment and numerical calculation. The incident waves were the plane wave and the (1, 1) mode wave. The calculated results were in good agreement with the measured results. Hence the applicability of the calculation method in this study was confirmed. Form the results of this study it is shown that such duct expansion behaves as a sound attenuator which is effective in a wide frequency range.

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Active noise control (ANC) which is very effective for reduction of low-frequency noise has received much attention. However, the performance of the ANC system is generally not of a sufficiently high level for practical applications. In order to improve the performance, we propose a new feedforward ANC system which uses the fast Kalman filter algorithm. First, computer simulations are carried out to compare the conventional ANC systems which use the LMS and the LIM algorithm with the proposed ANC system. Based on the comparisons, the proposed ANC system is superior to the conventional ANC systems. Finally, experiments are carried out in an anechoic room to verify the superiority in practical use.

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Solid horns for "power ultrasonics" usually magnify the vibration amplitude by a decrease in sectional area along their axis. However these horns are usually too heavy to handle easily and their fatigue strength is reduced by the stress concentration induced by their profile. Thus we have attempted to develop a new type of horn based on a different magnification principle by connecting simple round bars of different specific acoustic impedances. Vibration of the round bar horn is analyzed using the longitudinal wave theory and FEM to achieve a practical design. We have fabricated the new type of horns and performed experiments to confirm their magnification capabilities. Analytical and experimental results show that the simple round bar horn is satisfactory for practical use.

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In order to realize ductile regime cutting of brittle materials, it is important to determine the initial contact between a tool and a workpiece with high accuracy. Thus the detection of initial contact in diamond turning of Al and Si was examined using an AE transducer. The sensitivity and the response speed of an AE signal were evaluated in comparison with those of an electric contact signal. Treatments to improve the conductivity of a diamond needle as a tool and a Si wafer as a workpiece were made in order to determine an electric signal representing the initial contact between a tool and a workpiece. The resistance of 65Ωwas obtained by spattering of a diamond needle using Ar ions. The resistance of a Si substrate was reduced to 300Ω by doping P ions into it. As a result, the detection of initial contact during cutting of a Si substrate was accomplished on the 1O nm level. Moreover, the sensitivity of detection using an AE transducer was found to depend on the impact energy ; thus, the sensitivity was improved with the cutting speed.

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Much research has been made no natural networks (NNs) for pattern recognition with promising results. We have proposed a structure reduction method of the NNs, where we adopt slab values. Here, the slab values are the sum of input pixels generated as characteristics of the inputs by masks. The mask covers some parts of the input. The slab values enable us to distinguish the difference between input patterns. Initially, we use random numbers to determine the masks. However, mask optimization has not been elaborated, sufficiently. In this paper, we adopt a genetic algorithm (GA) which is a search procedure based on the mechanism of natural genetics to determine the masks. Adopting the GA to mask determination, we show that useful masks are automatically determined using US dollar bills in the simulation.

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Traction drive has many advantages over a gear mechanism. For example, its backlash is negligible and instantaneous variation of reduction ratio is very small at any rotary angle. These advantages are attractive for high-precision servomechanisms that rotate at constant speed, such as NC gear processing machines. However, there has been little research reported on this subject so far. Thus, we developed a constant-velocity servomechanism that uses traction drive as its reduction mechanism, and carried out experiments to confirm its performance. Moreover, we propose torque compensation using slip-speed feedback to compensate the effect of torque disturbance and confirmed its usefulness by experiments. In this paper, the dynamics of the traction drive applied to constant velocity servomechanisms is introduced, and the method of disturbance compensation using slip-speed feedback is discussed. Then, details of the traction drive, control system and detecting systems are described, and the experimental results are presented.

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In this paper, a controller design by H_∞ control theory for active suspension of maglev vehicles by the use of superconducting magnets (SCM) is considered. The following two items are focused on for designing the controller. In maglev vehicles SCMs are very heavy. SCMs are intended to be suspended from trucks. The fundamental vibration model is composed of three masses and it is different from conventional suspensions of rail vehicles. Maglev vehicles are planned to be articulated vehicles. Enormous number of degrees of freedom exists for a model of a train. In this paper, it is shown by simulation that the H_∞ controller functions successaully when applied to a three-mass system, i.e., good ride quality is obtained without a peak actuator output in the respective frequency domain, and in articulated vehicles, the H_∞ controller can maintain a good of control when superpositioned for each direction of car-body vibration.

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This paper describes the switching characteristics of torque transmission and their improvement by modifying a rotating disk and case in a magnetic fluid coupling, as was discussed in our previous report. Whenever a magnetic field is applied to a fluid coupling, the magnetic fluid shifts to the outer area of the rotating disk, and a torque is transmitted via the viscous friction of the magnetic fluid between the disk and the case. In order to enhance rapid and smooth movement of the magnetic fluid, slits were cut in the rotating disk. A channel for magnetic fluid was cut at the bottom of a case to cancel the output torque under a non-magnetic field. As a result of these modifications, a large torque difference was obtained whether a magnetic held is applied or not. The response of the output torque was also improved whether the input signal is turned on or off.

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In the control of a hydraulic excavator using hydraulic actuators, it is difficult to obtain desired trajectory or response due to its nonlinearity, for instance, variation of the moment of inertia, the unsymmetrical effect of single rod cylinders, interference between axes and unknown external forces caused by excavating resistance. In this study, to begin with, we construct a servo system as a first step for realizing autonomous control of hydraulic excavators. We propose applying a disturbance compensation robust control system using a disturbance observer for the system to which several disturbances including parameter change are added. Using this control method, we realize improvement of robustness of a system without increasing loop gain by compensating its nonlinearity. For experiments, a Hitachi Mini Excavator EX40 is reconstructed so that the boom and the arm are driven by servovalves. Circular trajectory of the end of the arm in addition to step response of the boom and the arm are experimentally obtained. Also, the results obtained using a disturbance observer are compared with those obtained using only position feedback. As a result, it is experimentally shown that this control method can improve positioning accuracy and trajectory tracking performance required in surface excavating operation.

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This paper deals with digital adaptive control for a space manipulator mounted on a free-flying robot (FFR), after capturing an unknown object. Most of the previous control methods are based on the supposition that all physical parameters of the FFR system are known. However, if the endeffector captures an unknown object, the physical parameters of the robot are changed, and the control performance worsens. In this paper, we propose digital adaptive control using a discretized kinematic equation and a simplified generalized jacobian matrix. Computer simulation shows that the control performance can be improved using the proposed method. Moreover, in order to verify the result of the simulation, the experiments are conducted using a simulator that simulates the microgravity environment. The experimental results confirm the validity of the proposed control method.

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In this paper we discuss the stability of the equilibrium grasp. We replace a grasp system with an elastic system, and we take into consideration the curvatures of fingers and objects. The potential energy function of this system is derived. The grasping stability is determined by the positive definiteness of the Hessian matrix of the potential function. Several numerical simulations show that the grasping stability depends greatly on the curvatures of both the grasped object and fingers.

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This paper deals with experimental examination of the feasibility of a neural network control scheme for reducing fluid drag force, which is developed to select the patterns of air-bubble injection from the surface of the 2 link-2 degree of freedom aqua-robot manipulator arm to result in reducing the fluid drag force acting on the manipulator arm. Two neural networks are implemented in the control system of the manipulator immersed in water ; one is for the inverse dynamics of the manipulator between the state variables and fluid drag force, and the other is for selection of an air-bubble injection pattern to minimize the fluid drag force in accordance with the manipulator motion. This neural network control scheme achieves a 30% reduction in fluid drag force for a high-speed motion during manipulator arm operation.

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This paper shows an application of a YT-mechanism to self-standing quadrupedal robot of which each leg is constructed with a main arm, a connecting arm and a foot, and is a one-degree-of-freedom system. In walking with a trot gait, quadrupedal robots lose their balance due to the movement of feet positions which support the center of gravity. In order to compensate this imbalance, the developed robot is equipped with a the movement mechanism of balancing mass, which is used as the power supply of the control system itself, and controls the synchronization of mass position with feet position. Experimental results demonstrate the effectiveness of the YT-mechanism and the balancing methods.

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In this paper, we propose a method for automatically generating task trajectories of a sealing robot using a three-dimensional vision sensor to teach a sealing task. In this method, the desired trajectory of a robot for a sealing task can be generated by detecting its position and orientation at a seam position through a vision sensor attached to a robot hand. A method for determining the control parameters of the teaching system is also presented by simplifying the block diagram. Since the accuracy of the trajectory generated for the sealing task by this method is not under the influence of the motion of the robot, the task trajectory can be obtained with high accuracy. The effectiveness of the present methods is demonstrated experimentally, and the robot has been shown to move smoothly by determining the control parameters from the simplified block diagram of the teaching system.

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In our laboratory, we developed a dual-arm handling robot, called C-ARM (Cooperative-ARM), with the aim of practical application in shipbuilding work. The robot consists of two three-degrees-of-freedom planar arms with force/torque sensors at each joint. The manipulating forces and moments on the object are measured by the sensors. In this paper, we present results of an experiment on cooperative control using this dual-arm robot. The experiment consists of two parts :a fundamental experiment on hybrid position/force control using a symmetric scheme, and an experiment on load sharing. The load sharing is an application of the first experiment in which a quadratic programming algorithm for optimizing the internal forces and moments is used. Experimental results show that the hybrid position/force control scheme works well in cooperative control and that the load sharing optimizes the joint forces/torques of the robot.

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This paper describes a new self-position measurement system for autonomous mobile robots working at building sites. The robots must be able to position themselves precisely at desired locations for building operations. Although the method depends on the basic principle of triangulation, no preparations are required for establishing reference points. On the floor of a large building, pillars standing in known positions at intervals of about 10 meters can serve as reference objects. Experimental results obtained using the prototype system, which was composed of a laser range finder and an angle-measuring unit, proved that this system was able to determine its position with an error of±5 millimeters.

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This paper proposes a motion planning method for cutting a three dimensional workpiece by a redundant robot arm. The method applies a genetic algorithm to optimize rotational angles of the end-effector on a path which is a redundant parameter. For a fitness function, an evaluation function is defined based on references from skilled operators. The proposed method reduces the operator's efforts, so that he only has to determine a path without considering redundant parameters. Through simulations and experiments the effectiveness of the proposed method is demonstrated.

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The application of dynamics of organisms to the field of engineering is very instructive. To construct an artificial propulsion mechanism based on bending of waves, a simulation study of a propulsion mechanism modeled on the bending motion of organisms in liquid was carried out. As the bending wave motion, flagellar motion was employed. In the simulation, the bending wave of the organism was converted to a construction of a multilink mechanism. This simulation model was defined as a "multilink model". Both the thrust force and the swimming speed of the multilink model were calculated. The characteristics of the thrust force and the swimming speed with changes in the bending waveforms and the number of bending waves were discussed.

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In this paper, we elucidate the standard creep movement forms (S-shaped curve) of a snake, which is the typical locomotive movement shown by snakes. Serpentine curve in the constant steady state velocity and ex-serpentine curve in the constant steady state acceleration are derived for the uniform creep locomotion of the snake, through analyzing physiologically its muscle characteristics, Muscular force is also discussed for these two types uniform locomotive curves. The results proposed here are demonstrated by computer simulation to agree with previously reported experimental results (Y. Umetani and S. Hirose, Trans. of the Society of Instrument and Control Engineers, 10-5 1974, 513-518, in Japanese).

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The aim of this research is to establish a method for estimating the rotational transmission characteristic of Rzeppa constant-velocity universal joints used in automotive drive shafts. Such a characteristic is related to the vehicle vibration. Equations are derived kinematically by determining the position of contact between the ball and the arc-shaped groove of each shaft. The equations are solved under the condition of an equilibrium of force. Phase deviation is defined as the phase difference found at the point of contact between the ball and groove of the input and output shafts, respectively, using the phase of one ball in relation to the joint as a reference. The relationship between such phase deviation and the dimension errors and clearance of the ball in the groove is shown.

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This paper proposes a new structure of a gas flow control valve that uses a piezoelectric actuator. The proposed valve has a moving seat driven by a piezoelectric actuator, which moves very quickly on the order of milliseconds, and controls the gas flow precisely. The motion of the moving seat and the squeeze effect between two flat seats are investigated theoretically and experimentally. It was demonstrated that the proposed valve was very effective for precisely and quickly controlling the gas flow and the squeeze effect prevents surface damage of the valve seats. Furthermore, it was found that the calculation method presented here predicted well the motion of the moving seat and the gas flow rate.

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Using helical teeth for synchronous belt drives is very effective in reducing noise. However, it is necessary to find out how durable such belts are. In this study, running fatigue tests on both helical and conventional synchronous belts, used generally in industry and in vehicle engines, were carried out under a constant transmission force. The helix angles of the helical belts were 5°and l0°. Other dimensions were the same as those of conventional belts. The life of the helical belts was compared with that of the conventional belts. It was found that the belt life was almost the same for each type and was longest for both when installation tension set up as the slack side tension for the transmission force was the lowest. The results proved that when noise is a crucial factor, helical belts should be used.

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Magnetic fluid splashing due to high-speed rotation of a seal ring was experimentally investigated in relation to gap length and magnetic field strength around the gap to be sealed. Meniscus shape deformation owing to fluid rotation was accurately observed by means of its silhouette shading laser light illuminated behind the meniscus. The deformation was found to occur in three stages. In the first stage, meniscus static width shrank, while meniscus rotating height remained nearly unchanged. In the second stage, these relations were reversed. Finally, abrupt total shrinkage occurred accompanied with splashing. Splashing initiation was found to strongly depend on the magnetic field gradient at the top of the rotating fluid. This provided a simple and useful parameter to determine the splashing initiation.

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The measurement made by the technique of optical interferometry shows that the increase of the slip ratio tends to reduce the EHL film thickness, and fluid properties of oils influence the rate of film thickness reduction. There is a possibility that this experimental result is due to the effect of rising oil temperature caused by shearing heat and the effect of the non-Newtonian response of oils. In this study, the relationship between oil film thickness reduction and oil temperature increase was investigated through theoretical calculation of the elastohydrodynamic lubrication which takes account of the effect of viscous heating and the effect of Eyring viscosity. The overall agreement between the calculation result and the experimental result was recognized.

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Analytical and experimental study of rotational accuracy of superconducting magnetic bearings depending on the arrangements of permanent magnets is presented in this paper. With the aim of improving the rotational accuracy, the axial bearing magnet ring was divided into two rings in the radial direction and the radial bearing magnet sleeve was divided into three stacked rings in the axial direction. As a result, the magnetic flux density could be increased at the superconductor ring position, the static stiffness and the load capacity were increased, and hysteresis became large. Concerning the dynamic characteristies, the rotational accuracy of the shaft was improved remarkably and the shaft weighing 2.4kg could rotate within 15μm peak to peak at 12000rpm.

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Recently brittle porous materials such as graphite and advanced ceramics have been used in the fabrication of aerostatic bearings because gas flow through these porous materials can be limited to a small amount. However, aerostatic bearings consisting of these porous materials are prone to cause pneumatic hammer instability. Therefore, it is considered that reducing the parmiability of porous material only near the bearing surface is a very effective means for avoiding pneumatic hammer instability. In this study, the static and dynamic characteristics of aerostatic circular thrust bearings with such a restrained layer near their surfaces are investigated, theoretically and experimentally. Furthermore, the effects of the restrained layer on the bearing characteristics are clarified.

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In this investigation, the author proposes a calculation method of the cutting-edge profile of a barrel worm-shaped tool conjugate to the tooth profile of an internal gear, without considering an equivalent pinion meshed with it. The theory of gearing proposed by Litvin et al. is also utilized for calculation of contact points between a gear and a tool. It is examined whether or not this barrel worm-shaped tool can exactly finish an internal gear with a number of teeth and helix angle different from those used for design of the tool. It is shown that the tool is in point contact with the internal gear generated by it, and the tooth profile of the internal gear is finished by regular points of the cutting-edge profile of the barrel worm-shaped tool. Furthermore, it is confirmed that the regular generating point between the internal gear and the barrel worm-shaped tool is identical with that between the internal gear and a cylindrical worm-shaped tool.

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Cycloid gear which was driven by three crankshafts and had three thin rims, was chosen as the subject of study. The bending stress of the rim and the tooth load of the cycloid gear were analyzed using the two-dimensional finite-element method when the gear had no machining and assembly errors and no backlash. Then the effect of the rim thickness on the bending stress and the tooth load were discussed, and the following conclusions were obtained. Both the bending stress of the rim and the tooth load are proportional to the applied torque. When the rim thickness decreases, the tooth loads decrease on the teeth located on the thin rim and increase on the teeth not on the thin rim. The ratio of the maximum tooth contact stress to the contact strength of the gear material is much larger than the ratio of the maximum bending stress amplitude on the rim to the bending strength of the gear material. Therefore, the tooth contact stress on teeth not located on the thin rim, not the bending stress, should be considered when designing cycloid gear with thin rims.

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To meet the demanded for increased load capability of plastic gears, practical application has been attempted using nylon MXD 6 filled with glass fibers which forms high-strength and high rigidity plastic for use as gear material. In order to evaluate this plastic gear, first the bending fatigue strength is investigated. Then, operating tests are carried out on the plastic gears, and several characteristics such as state of wear progress and changes in its tooth profile accompanied with wear are clarified. Some investigations are also carried out concerning problems generated in this plastic gears.

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An evaluation of the strength of carburized gears has been proposed on the basis of fracture mechanics. In the evaluation, the bending load capacity is obtained using the criterion a₀≤a_th. This criterion is applied to the evaluation of the effect of surface treatments such as shot peening and surface polisihing on the bending strength of carburized gears. The crack length a_th is calculated from the threshold stress intensity factor, and a₀ is evaluated from the fatigue test results. The residual stress induced by shot peening is effective in increasing the crack length a_th, and surface polishing reduces the length a₀. The change in the lengths explains well the strength enhancement due to surface treatments.

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This paper reports on line contact skew gears, one of which is a spur gear, where the angle of the gears' axis is free. First, the expression for the subpitch line of the skew gears is derived. Second, the expression for the contact condition of the skew gears on the subpitch line is derived. Characteristics of the expressions are similar to those for spur gears and it is possible to solve the expressions directly. Third expressions of the zone of contact and the opposite tooth surface are derived from the contact condition. Finally, worm gears, one of which is an involute spur gear, are investigated and several findings are obtained.

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A new method and device for measuring motion errors of NC machine tools are proposed. The device consists of a plane two-link mechanism and two rotary encoders to measure the rotation angles of links. The working sphere of the device is a circle with a radius of double link length, except a small neighbourhood around the change points of the link mechanism in the center and circumference of the circle. Because the measuring method has a high resolution for any measured point in the working sphere, it is possible to measure most types of motion errors of NC machine tools, in particular, the error of the circular motion. The device is compact and its installation is simple and quick. The measuring tests show that the trial equipment has good response to a small displacement of about 1μm and the measuring results have high accuracy and good reproducibility. The influence of measuring noise is hardly observed in measuring results.

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Rolling-guided table systems are widely used for machine tools because of their low frictional resistance. They have, however, some demerits such as low damping ability, which causes chatter vibrations in machining. An effective method to improve the dynamic performance of the rolling-guided table systems is to apply an additional damping force to the tables. In this study, a variable damper using an electrorheological fluid has been proposed and attached to a rolling-guided table system. The apparent viscosity of the electrorheological fluid can be adjusted depending on the applied electric field intensity. Therefore, the additional damping force generated by the developed damper can be easily controlled by an electric signal. The performance of the developed table system was evaluated by means of the impulse force response method and cutting tests, and the effect of the variable damper was investigated.

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In the first report, a new material called ceramics resin concrete was developed for precision machine tool structures. Next, in the second report, thermal and mechanical properties of the material were clarified in order to design a machine tool. Then in the third report, Young's modulus of the material was improved to be comparable to that of cast iron, by means of a new manufacturing method. In this report, continuation of tool life using the material has been examined. Then the causes of continuation were investigated by FEM analysis and experimental analysis of the selfexcited chatter model with a holder. It is concluded that tool life in a NC lathe with a tool post using the material is five times that of a conventional NC lathe. In addition, it is verified that the use of ceramics resin concrete is effective for preventing self-excited chatter.

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