A rotating disp is utilized in many industrial flelds, such as a magnetic memory disk and a rotational mixer, and higher rotational speed is needed to achieve high performance. However it is well known that a flexible disk rotating in a confined fluid undergoes unstable vibration when the rotational speed exceeds a critical one, and that the unstable vibration occurs due to the interaction between the flexible rotating disk and the swirling fluid flow around it. Up to now, I have studied experimentally the characteristics of unstable vibrations induced in a single flexible disk rotating in a confined fluid, and found that the unstable vibration exhibits different mode shapes depending on the rotational speed, and visualized the unstable vibration mode shapes. This paper deals with detailed experimental investigation of the influence of the gap width between the rotating flexible disk and the side-shroud wall on the unstable vibration characteristics of a flexible disk rotating in a confined fluid. It was found that the gap width is an important parameter for the unstable vibration characteristics.

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A middle-load thermal power turbine generator frequently exceeds its critical speed, and it must be balanced at the critical speed carefully. Also, it is desirable to thermally balance the generator rotor to reduce the shaft vibration stroke caused by a load change at rated speed. In particular, when the generator capacity exceeds 500MVA, the generator rotor shifts from the secondary mode to the tertiary mode, and the in-phase unbalanced sensitivity increases due to the thermal bending of the shaft and other causes. As a result, thermal balancing is required in addition to conventional mechanical balance. This paper deals with 3 items. The first is the three-dimensional rotor vibration analysis method considered as asymmetry bearing supporting condition and thermal and magnetic unbalanced force. The second is to clarify bearing support condition using the actual rotor vibration response. The last is to explain an agreement between theory and experiment for rotor vibration phenomenon due to an artificial field coil layer short.

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The derivation of fundamental equations for the free vibration of curved and twisted cylindrical panels is presented in this paper. First, the strain-displacement relationships based on assumptions of the three-dimensional finite displacement theory are derived. Then, the principle of virtual work for the free vibrations of curved and twisted cylindrical panels is formulated in order to analyze the vibration behavriors.

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We propose a method which facilitates the calculation of natural frequencies of bending vibration of a straight rod subjected to axial compression and supported at an intermediate point and the estimation of the axial force. This method is an extension of Rayleigh's method. First, the effect of the position of the support on the mode shapes is studied using the results of a rigorous analysis. Deflections of the rod assumed in the calculation of this method are modified principal-mode shapes of the bending vibration of the rod free from axial compression and intermediate support. Comparison between calculation results and experimental ones shows that this method yields a good approximation for 1st and 2nd natural frequencies irrespective of the position of the support and for up to the 3rd natural frequency if the position of the support is limited to the central part of the rod, which covers about three-fifths of the total length.

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An exact solution procedure is presented for solving free vibrations of a rotating thin laminated composite circular cylindrical shell. Based on the classical lamination theory, equations of motion and boundary conditions are obtained from the stationary conditions of the Lagrangian. The equations of motion are solved exactly using a power series expansion for symmetrically laminated cross-ply shells. Frequencies and mode shapes of the shells with both ends clamped and both ends freely supported are presented showing their variations with rotating angular velocity, number of laminae and other parameters.

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The finite-element method (FEM) and modal analysis have been used for vibration prediction in relatively low frequency domains, and statistical energy analysis (SEA) has been conducted in order to evaluate the vibration in extremely high-frequency domains. However, modeling and vibration analysis by FEM and modal analysis become more difficult as the frequency becomes higher, and some approximations and hypotheses that have not yet been proven to be accurate are used in SEA. Therefore in hign-frequency domains that exist between the two frequency domains in which FEM and SEA can be appropriately applied, no effective vibration analysis method has been proposed. In this paper, a vibration analysis method based on modal analysis and the statistical method which enables analysis of the high frequency vibration is presented. Example results are shown for a single-plate structure and an L-shaped structure, and a comparison is made between the results from the asymptotic modal analysis and from the experiment.

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A hybrid experimental method, in which an actuator excited vibration experiment and a response analysis performed by a computer are on-line combined and simultaneously conducted, is being developed as a new seismic experimental method for structural systems. It is necessary to conduct a hybrid experiment in real time so that the dynamic characteristics of the structure under experiment can be considered in the response calculation. We developed a real-time hybrid experimental system with compensation of actuator response delay, which is equivalent to negative damping in the system. In this report, the developed system was used in experiments on a multiple-degree-of-freedom (MDOF) structural system. First, the stability region of the conmpensation for MDOF systems was evaluated. This was verified by the results of actual hybrid experiments using the developed system. Then, the accuracy of the developed system was investigated by comparing the experimental results with those obtained without response delay. Since the results were similar, it was shown that the developed system with conmpensation can be used for seismic experiments on MDOF structural systems.

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In this paper, a two-dimensional isolation table using circular arc beams and a magnetic damper is proposed, which has a simple construction, large loading capacity and the capability of vibration isolation in the horizontal direction. The isolation table is composed of a table board, four spring units using circular arc beams, four struts having a free ball on the top, a copper disk, rare-earth magnets and a baseboard. It has approximately the same stiffness and damping coefficient in every direction in the horizontal plane. A trial isolation table was made and its frequency responses were measured using an electrohydraulic -type shaking table. The experimental results were compared with the calculated results.

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A smart structure was tested for active vibration control of frame structures, in which bending moment of the columns was controlled by stack-type piezoelectric actuators integrated into the columns. Excitation tests were carried out for a model of a four-story building 3.7 m in height and 2000 kg in total weight in which 32 piezoelectric actuators 25 mm×25 mm×36 mm^H were used for the bending moment control. The actuators were installed in two ways: in one case eight actuators were attached to each column of the first story, and in the other case four actuators were attached to each column of the first and second stories. Two control strategies, a model-matching method and the H^∞ control theory were examined for the smart structure. The tests showed that the smart structure could effectively reduce the responses of the building model, and all combinations of actuator installation method and the control strategy had almost the same performance.

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We propose a vibration control method for the main tower of a large scale bridge and a method for constructing a reduced-order model using uncontrollability and unobservability. During the construction of the main tower, it is known that vibration modes including not only bending modes but also torsional ones are excited by strong winds, which may endanger construction workers and destroy main tower. Therefore it is necessary to control vibration of the main tower during construction. In this paper, a reduced-order model expressed by a 5DOF system to control the bending and torsional modes is proposed for preventing spillover instability using uncontrollability and unobservability. The LQ control and semioptimum control theories are applied for designing the control system. The control effects of the two systems are compared experimentally.

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We propose a vibration control method for triple flexible structures. In recent years, tall buildings have been equipped with active dynamic absorbers in order to maintain living comfort because the absorbers reduce the vibration of the higher floors due to strong winds. However, these absorbers are not suitable for vibration control of ultratall buildings because it is difficult to obtain sufficient control force under the low frequency. We propose a new control method to overcome this problem. In which a group of two or three ultratall buildings are controlled actively by means of actuators placed between them. Thus, it is possible to obtain sufficient control force at low frequency. In this paper, a modeling procedure is proposed using uncontrollability and unobservability and a digital filtering technique to prevent spillover instability. The model is a reduced-order model for control objects, each expressed by a 2DOF system to control each of the first and second bending modes. LQ control theory is applied to the design of the control system including the filter. The effectiveness of the proposed method is demomstrated theoretically and experimentally.

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In a previous paper, the first two authors proposed an experimental identification technique for boundary conditions of a beam. In that paper, however, the boundary conditions were assumed to be linear. In this paper the technique is generalized so that it can be used when the boundary conditions are nonlinear. The proposed technique is based on the principle of harmonic balance, and enables one to determine the boundary conditions in terms of spring and damping properties and equivalent masses and moments of inertia. Numerical simulation is conducted, and the applicability of the proposed technique is confirmed.

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We propose a high-capacity hydraulic shock absorber using electrorheological (ER) fluid having apparent viscosity that can be modified by an electric field. In this report, we determine area of an orifice of the ER shock absorber during impact of a light body (1 250 kg), and characteristics of resisting force of the absorber due to the ER effect during impact of a heavy body (2 250 kg) by extending a method proposed in a previous paper using a constant resisting force of the absorber. Furthermore, we show by simulation that the maximum accelaration of the light body nearly equals that (about 1g) of the heavy body during impact for a two-mass system containing the ER shock absorber, while the maximum acceleration of the former is about 2 times that (about 1g) of the latter during impact for a two-mass system containing an existing shock absorber with a metering pin.

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The oil hydraulic servo control system has a long history of application to various machines. However, a cleaner hydraulic fluid is necessary as we are faced with problems of fire or contamination due to oil leakage. We succeeded in improving the performance of a water hydraulic servo control syrstem over that of the oil hydraulic servo control system. Our water hydraulic servo control system is based on the analysis of the advantages of the physical properties of water for servo control. Furthermore, we can fabricate a simple water servo control system consisting of least components which can cover a wide dynamic performance range and can guarantee the same applications fields as the oil hydraulic servo control systems. Important components are the wide-dynamic-range water hydraulic pump system and the high-response, wide-dynamic-range water servo valve. The performance and durability of the system and components were tested and verified. As a result, the water hydraulic servo control systems are found to be the same as or superior to the oil hydraulic servo control system. Applying the advantages of the properties of water to a design, we can achieve better performance and lower cost with the water hydraulic servo control system than the conventional oil hydraulic servro control systems.

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In photoelastic tomography two-beam methods for reconstructing the secondary principal-stress differences and directions are theoretically investigated utilizing polarized light scattered from the intersection of two beams propagating through a model. The data are collected in the direction normal to the crossed beams by shifting the two beams stepwise from the surface of the model to its interior. A ligth path in the model is regarded as a series of linear retarders, and two methods for calculating the retardation and orientation of each retarder are used. One is the retarder approximation and the other is the finite difference method. Algorithms for reconstruction based on these methods are given. The algorithms are numerically examined by using a known stress distribution of a cylindrical bar exhibiting the rotation effect. They are found to be effective.

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A measurement system for refractive index distribution using optical computed-tomography has been developed. A shearing interferometer with a double-frequency diffractive grating was used to obtain the optical path differential. The double-frequency grating generates fine parallel fringes which are modulated by the optical path differential. The interference fringes were analyzed by the Fourier transform method. For the calculation of the index distribution, we applied an algorithm for beam deflection tomography to our system. This reconstruction algorithm is a modified filtered back-projection method, which determines the index distribution directly from the optical path differential with no integral operation.

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Two methods for superconducting magnetic levitation are investigated to enhance levitation characteristics such as levitation force and horizontal stability. In one of the investigated methods, not only a repulsive force between a permanent magnet and a superconductor but also the force between two permanent magnets is utilized to achieve strong levitation force and horizontal stability. In an other method, a high Tc superconductor was preliminarily magnetized by a permanent magnet via a field-cooling process. Levitation forces and horizontal stability in the proposed system were numerically evaluated using a computer program based on the critical state model.

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A numerical optimal trajectory planning method is extended to determine the optimal motion trajectory of a giant swing which is an example of the nonholonomic constraint system. The human body is modeled as a 2-DOF serial link system. In order to obtain an optimal motion trajectory which approximately satisfies the hand constraint, the penalty method is used, and the trajectory is approximated by the 5th-order Hermite polynomial functions. The features of six types of local optimal trajectory obtained from a 2-DOF basic model are discussed. It is found that each trajectory changes in form according to the motion period and that the global optimal trajectory is also changed with change of the motion period. Optimal trajectories for improved models including the friction torque at the first joint and the angle region restriction at the second joint are also obtained. The validity of the analysis is proven by comparing the analytical and experimental results for a 2-DOF direct-drive robotic arm.

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The reduction of traffic accidents has become an increasingly important issue during recent years with the advance of the automobile society. Thorough investigation of the behavior of drivers, especially in the case of suddenly encountering an obstacle during driving has been regarded as a key in coping with this issue. Assuming an obstacle avoidance, taking full consideration of the nonlinearity of tires, we study the behavior of the driver under the critical condition by way of genetic algorithm (GA). Computer simulations are carried out, which indicate that the GA is a very successful means of determining the driver's behavior under the defined emergent situation. With its powerful ability to search for optimal solutions to certain problems, GA is expected to be a very useful method in studying human factors to gain knowledge for the development of future intelligent traffic system.

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The reduction of traffic accidents has become an increasingly important issue during recent years as the advance of the automobile society, and thorough investigation of the behavior of drivers, especially in emergent situations, such as in the case of suddenly encountering an obstacle during driving has been regarded key in coping with this issue. Assuming an emergent situation of obstacle avoidance, taking full consideration of the nonlinearity of tires, we study the behavior of the drive under the critical conditio nusing genetic algorithms (GAs). Computer simulations are carried out, which indicate that 1) the genetic algorithm is a very successful means of determining the driver's behavior under the defined emergent situation; 2) the initial distance at which the driver starts the avoiding operation greatly influences the driver's performance; 3) the changing patterns of the steering gain G_h and preview time T_p obtained by GAs agree very well with the general empirical knowledge on driver behavior under emergent situations.

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We present an application of two degree of freedom control combined with H-infinity control to an electronic speed controller for a gasoline engine. The electronic speed controller is used for speed control of the gasoline engine of a forklift truck. This system needs a function of engine speed follow-up to the reference speed set with open rate of the accelerator pedal. It also needs a function of constant engine speed against torque disturbance, that is the load of a hydraulic pump during loading operation. The results of both simulations and experiments show that two degree of freedom control combined with H-infinity control enables excellent in the capabilities of follow up control, torque disturbance control and robust stability.

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We propose a swing-up and stabilization control scheme for an inverted pendulum system. Using the Lie theoretic technique, the inverted pendulum system is roughly linearized by partial nonlinear compensation. Then, the state-space equation of a roughly linearized system is described as a combination of an approximate linearization model and a nonlinear modeling error. A stabilizing controller is designed based on nonlinear H_∞ control theory for the state-space equation so as to guarantee robust stability and robust performance of the closed loop system in the presence of uncertain nonlinear perturbations. A swing-up controller is designed based on the Lyapunov stability theory. The effectiveness and robustness of the proposed control scheme are demonstrated via experiments.

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NKK has developed a new combustion controller that reduces both NO_x and CO concentrations in the exhaust gas discharged from municipal refuse incineration furnaces. We have found that the manipulation of the cooling air flow rate is important because it affects the furnace temperature and O₂, NO_x and CO concentrations in exhaust gas. This controller manipulates the flow rate of the cooling air. It monitors the furnace temperature and O₂, NO_x and CO concentrations as process variables, and outputs the cooling air flow rate control signal as a manipulated variable. This multi-input/single-output controller was designed using by a fuzzy control algorithm and tested on site at a municipal refuse furnace. The result of the on-site test was quite successful.

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Form optimization problems of truss structure are analyzed by means of the genetic algorithms (GA). Agenetic algorithm incorporating the idea of variable mutation ratio in mutation operation is developed. This idea corresponds to treatment in the simulated annealing method in statistical mechanics. This GA is applied to dynamic form optimization of truss structure on the eigen-frequency. Moreover, not only form optimization problelm on the constraint on eigen-frequency but also the problem on three kinds of constraints on eigen-frequency, homologous displacement and minimum weight are discussed through comparison of numerical results. The effect of monoploid model and diploid model in GA on numerical computation is also examined.

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Methods and results are presented for applying neural networks to the prediction of positioning error due mainly to thermal effects. Experiments on a machining center show that the positioning error is affected by the running conditions, such as the temperature variation of the nut of the ballscrew and the feedrate. In this study, we have tried to identify the relationships between the thermal-induced positioning error and running conditions. Both recurrent and feedforward neural networks have been used in the identification and their learning effectiveness has been compared. The results have shown that the recurrent network performs better than the feedforward network in this case. To further improve the error prediction accuracy of the network, a training technique that uses additional input has been proposed and its effectiveness has also been proved.

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In this paper we report a design method for controlling a travelling crane mounted on a flexible structure. In order to control the position of the crane cart, the sway of the crane rope and the vibration of the flexible structure, a robust servosystem is designed using the normalized coprime factor H^∞ robust stabilization approach. We consider varying the lenght of the crane rope in positioning control and schedule the H^∞ compensator in accordance with varying the natural frequency of the crane rope. By numerical calculation the settling performance of the gain-scheduled H^∞ compensator is compared with that of a switching H^∞ compensator. We verify the efficiency of the gain-scheduled H^∞ compensator.

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From the head positioning control system design viewpoint, the development and the evaluation of the control technique to improve positioning precision are important problems and the positioning error analysis becomes a key guide for the control system design. In this paper, a control system that uses a feedforward compensation method based on the adaptive filter theory to suppress head positioning error repeatable-run-out components was designed. A time response characteristic of the control system was examined by the simulation. In the positioning error signal analysis, a spectrum was evaluated using Fourier transform and the maximum entropy methods. Positioning error signal characteristics are clarified by these spectrum analyses including investigation of the time evolution behavior of the spectrum.

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This paper describes a position and force hybrid control problem in a robot manipulator with artificial rubber muscle actuators. Three control laws, the PID control, the fuzzy control and the PID plus fuzzy control which have no information on a mathmatical model of the control object, are applied to this problem. Since it is not easy to optimally determine many PID servo gains, we introduce a new fuzzy control method in which train's and errors required to tune the fuzzy controller can be reduced, compared with the conventional method. In addition, this fuzzy controller can also be applied to compensate a PID servo controller without tuning feedback gains. The effectiveness of the three control laws is illustrated by conducting some experiments on a two-link manipulator.

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Multilayered piezoelectric elements are capable of very quick response and very small displacement of about a micron, though their size is small and the structure is simple. Hence this device appears promising for such applications as the actuator for a precision stage or a micromachine. In this paper, the equation of motion of multilayered piezoelectric elements taking material damping into consideration is proposed and solved by Duhamel's method. Then the value of the material damping coefficient is estimated experimentally. The calculated results are in good agreement with the experimental results.

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A solid-type piezoelectric actuator generates a large force, but the generated displacement is significantly small. In particular, the actuator has a large hysteresis between a control voltage and the control displacement. Hence the application of the actuator has been limited to some special areas. This paper presents a linear piezoelectric actuator without hysteresis. The actuator presented has linearization control circuits and a displacement enlargement mechanism made of elastic hinges, so that the generated displacement is in the range of displacements required for vibration control of machines. To control the actuator, a displacement sensor is used in general, but one of the ends of the sensor must be fixed to a wall. This implies that the application of the actuator is limited. Hence in this paper, an acceleration sensor is used instead of the displacement sensor. This enables us to use the actuator as a conventional linear actuator. Theoretical analysis was given, then experimental tests were carried out to validate the method and the analysis.

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We developed a lens actuator suitable for high-speed seek and thin-type CD-ROM drives. The actuator is supported by 4 suspensions which are put in order in a plane and radiated to outer fixed ends arroud the center pin. Each suspension has a flexible part that adjusts the lowest-main natural frequencies in the auto-focus and tracking direction. The main natural requencies are determined taking into consideration for controllability. Dynamics design of the actuator at the frequency around 1 kHz is important for keeping the servo system stable. We investigated the phase-delay phenomina at the frequency in our prototype actuator. The phenomina are modeled by a vibration system which consists of a contact stiffness between lens holder and center pin and the moment of inertia of the actuator. The normalized imbalance of the actuator is to be within 2% to achieve the stable condition in auto-focus servo system.

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Template matching is a popular method for visual recognition. However the method has two major problems: (1) Much time is required to detect the target object, and (2) Mistakes in recognition of the target object occur is some cases. In order to solve problem, (1) we apply a fuzzy neural network algorithm. However, problem (2) remains to be solved. In this paper, we propose a robust visual recognition algorithm for autonomous mobile robot navigation. The proposed algorithm employs Fuzzy Template Matching with a target object as well as similar objects in the environment. As a result, the robot verifies its tentative recognition by comparing the likelihood of plus elements (target objects) with that of minus elements (similar objects). The validity of the proposed navigation system is shown through some experimental results.

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In the optimal control problem, all results are based upon the assumption of centrality, that is, all the information available about the system and decision making based upon this information arises at a single input. The design leads to systems in which every sensor output affects every actuator input. In the modelling and design of multi player control problems, the objectives in the optimal choice may be met by formulating the control problem as a differential game. The purpose of this work is to determine the decentralized control strategies with output feedback form which guarantee certain values obtained from the performance indices. We determine the suboptimal control strategies such that obtained performance indices are bounded by certain values of suboptimality degree γ_i where the bounded values are defined as γ_iJ^^-_i^* for the linear closed-loop Nash game. Thus, the suboptimal control strategies are not equilibrium solutions. The control strategies with output feedback form require neither state estimation nor reconstruction. In this work, the control strategies guarantee the trace criteria associated with each player which are interpreted as expected values of standard quadratic criteria. Sufficient conditions for suboptimal control strategies with output feedback form are given for the infinite problem.

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The conventional AI (artificial intelligence) technology has been criticized for its many drawbacks, one of which is brittleness under hostile dynamically changing environments. To overcome this problem, other approaches, such as behavior-based AI, new AI, emergent computation and animat approach, have been proposed and their usefulness has been confirmed. Since computational ability of mobile robots is limited in general, it is required that robots arbitrate output behaviors appropriately using obtained sensory data. On the other hand, in living organisms, there are two systems for coping with a dynamically changing environment: 1) the immune system and 2) the emotion system. Based on this, we present a new method for behavior arbitration in autonomous mobile robots by paying close attention to the emotion system in living organisms. We confirm the feasibility of our proposed method by applying it to an obstacle avoidance problem of a mobile robot as a practical example.

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A new leg-wheel hybrid vehicle called "Roller-Walker" is proposed. The Roller-Walker is a vehicle with a special foot mechanism which changes between feet soles for the walking mode and passive wheels for the wheel. On rugged terrain, the vehicle walks in the leg mode, and on level or comparatively smooth terrain, the vehicle moves by wtheeled locomotion using the passive wheel in a manner resembling roller-skating. The characteristics of the Roller-Walker are that (1) it has a hybrid function but can have lightweight design and, (2) it will have the capability for high terrain adaptability in the wheeled mode if the method of controling the Roller-Walking is fully investigated in the future. We perform basic simulation experiments of the Roller-Walk and clarify its fundamental behavior and demonstrate basic relations in the terrain adaptive trajectory control method.

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In this paper, we propose a new approach to noncontact manipulation of DNA molecules by dielectrophoretic force using the idea of a Micro DNA Flow System. Such systems can be constructed by using microfabrication technology. First, we designed a simple microelectrode-flow system and carried out experiments. Experimental demonstration of DNA transportation using dielectrophoretic force and direct observation of the DNA molecule in a nonuniform electric field was carried out using fluorescence microscopy. Motion of the DNA molecule is modeled in terms of the electric field generated by the electrode design. We compared the motion of the DNA molecule which is theoretically predicted with the experimental results. We demonstrated a simple electrode design and the possibility of transportation of DNA molecules based on the Micro DNA Flow System.

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We discuss cylinder insertion into a hole of a flexible rubber plate. The deformation of the rubber plate is modeled by that of long beams that are aligned perpendicular to the hole. The insertion force is analyzed in the relation to the depth, offset and inclination of the cylinder. It is clarified that the insertion force forms a hyperbolic field on a three-dimensional space composed of the coordinates of position and posture parameters. The magnitude of the insertion force is also discussed based on an insertion trajectory in the hyperbolic field. The man doing in cylinder insertion such as incline it at the beginning of insertion and make it straight to the rubber surface at the last sequence. We point out that the man sequence corresponds to the trajectory where the insertion force remains small. We also show experimentally the existence of a hyperbolic field on the position and posture space.

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Recently, the robot assembly industry requires research that deals with flexible parts using human-like skills. We discuss cylinder insertion into a hole of a flexible rubber plate. We show that the magnitude of the insertion force expresses a parabolic field in the three-dimensional space that is composed of position and posture of the cylinder. The parabolic field has a tunneling path from which we can obtain the local minimum insertion force. The tunneling path seems to correspond to the position and posture of cylinder insertion by human skill. This paper proposes a new search method for the tunneling path. The method uses a simple regression model that fits the parbolic field to a narrow zone. The fitting zone shifts as the cylinder insertion advances. Experimental results show that the regression method is a possible search method for the tunneling path.

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A conventionally shrink-fitted assembly of an aluminum polygon mirror and a SiC self-acting air bearing becomes loosened at temperatures as low as 60°C because of the great difference in the thermal expansions of these two components, although it exhibits sufficient strength at room temperature. Temperature rise and centrifugal force in operation deform the mirror end surfaces by the order of hundreds of nano Meters or more. The distorted mirror end surfaces adversely affect the quality of devices such as photocopiers and laser printers. This problem has been solved by using a shrink fitter, which is a new machine element developed in previous work. The shrink fitter is ring-shaped and has several slits in the radial direction. Its material needs to have a higher coefficient of thermal expansion than aluminum. Thus, polyimide was used for the material of the shrink fitter. Dynamic properties, such as jitter and tracking accuracy, of the assembly fabricated using the shrink fitter were one-fifth to one-tenth of those of the conventional assembly. This new joining method eliminates the need for maintenance. The shrink fitter made it easier to attach the polygon mirror to the air bearing. The omission of final cutting of the polygon mirror after fabrication was discussed.

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The ball load and contact angle distribution in single-row radial ball bearings under the combination of an oblique raceway and axial load have the same pattern for any oblique direction of the raceway. Such patterns under radial load are analyzed theoretically. The patterns of ball load and contact angle distribution differ greatly depending on the oblique direction of the raceway around an axis of the loading force line. In estimations of fatigue life of bearings and failure of the retainer, this difference must be considered.

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Thrust bearing tests were carried out under water lubrication with hot-pressed Sialon, ZrO₂ and Al₂O₃ fine ceramics. The life of Sialon balls mating with Sialon races was the highest, and it was reduced when mating with ZrO₂ or Al₂O₃ races. The lives of ZrO₂ balls and Al₂O₃ balls mating with Sialon races were longer than those of their self-mated contact. Th friction coefficient of thrust bearings consisting of Sialon balls and/or races was comparatively small. The amount of wear of balls or races mating with Sialon was small, while that of Sialon mating with ZrO₂ or Al₂O₃ was large. The main failure modes of Sialon balls were flaking in the case mating with Sialon races, and wear in the cases mating with ZrO₂ and Al₂O₃ races. Those of ZrO₂ and Al₂O₃ balls were wear with micro flaking, and wear, respectively.

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Reciprocating compressors are widly used for refrigeration systems, and an understanding of piston-ring lubrication in the compressor is vital for designers in reducing the energy loss due to friction because a substantial portion of friction in the compressor is attributable to the piston-ring assembly. In this study, the modified Reynolds equation of Patir & Cheng is applied in order to consider the surface roughness effects, and Greenwood & Tripp's model is also applied in order to cosider the contact of piston-ring face with cylinder wall. In the anlalysis, two types of inlet boundary conditions, fully flooded condition and starvation condition, are applied at the leading edge and the Reynolds boundary condition is applied at the trailing edge, respectively. It is clarified from the numerical results that surface roughness and quantity of oil supply significantly affect the friction force of the piston-ring in refrigeration compressors.

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In internal combustion engines, one of the most important issues is to clarify the friction characteristics between the piston ring and the cylinder liner because of the demand for improved fuel economy through the reduction of friction loss. In the present study, the floating liner method is used to measure the piston assembly friction force in a diesel engine. The piston assembly friction demonstrates that fluid film lubrication is dominant at midstroke, but a friction peak due to boundary lubrication is observed at dead center. A decrease in either the number or the width of piston rings is effective in reducing total friction loss, but this increases the maximum friction peak at the beginning of the power stroke. However, the friction peak can be reduced by using a ceramic-coated piston ring. The influence of the compression ring tension on friction loss is dependent on the oil ring tension.

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Generally, a shot-peening process is utilized in order to improve the bending fatigue strength of a tooth root of a gear. In this investigation, surface durability of austempered ductile cast iron (ADI) rollers is examined using a two-rolling-contact fatigue testing machine, and it is elucidated whether or not the surface durability is improved when an ADI roller finished by a cylindrical grinding machine is subjected to an additional shot-peening process on its surface. The pitting strength of shot-peened ADI rollers is just slightly improved. Furthermore, it is shown that austempered ductile cast iron rollers are more easily worn in comparison with steel rollers which are case-carburized and hardened. In particular, shot-peened ADI rollers show large amount of wear compared with non-shot-peened ones.

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The durability (pitting limit) of through-hardened steel rollers (about 500 HB) whose surfaces have R_max ranging from 0.2 to 6μm is examined using a rolling contact fatigue testing machine. Then, the torque of a driving shaft and duration of full EHL conditions between two rollers are measured during running. The greater the surface roughness is, the larger the traction coefficient, and the smaller the surface durability. When a pair of tapered rollers is used, a spin motion is induced. However a surfacc durability is not markably decrcased. If a pit might occur on a pair of rollers, it has occurred on the contact surface with minus sliding ratio of a following roller. The effective traction coefficient between rollers with a spin motion is calculated from those obtained in the absence of the spin motion.

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Two different methods have been proposed for determining the reference surface (datum surface) to define the form accuracy of tooth flanks of hypoid gears or spiral bevel gears. Based on these two methods, a computer program was developed to generate the tooth flank coordinates of these gears, and simulation programs have been developed to calculate the contact pattern on tooth flanks and the transmission error of the gear set. The calculated results of the contact pattern and the transmission error were compared with experimental results. Good agreement shows that both of these simulation methods are applicable to practical usage in gear engineering. Considering their practical use in industry, each has merits and demerits. The characteristics and scope of these two simulation methods are discussed.

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Contact pattern and transmission error were compared for two different methods of simulating tooth generation and power transmission characteristics of hypoid gears. One method incorporates pinion and gear tooth flanks that are generated individually as a function of the parameters of the tooth cutting machine, and the other method uses the same gear tooth flank, but a different pinion tooth flank. The reference pinion tooth flank is a virtual one generated mathematically by a computer and it is conjugate to the gear tooth flank. The latter method uses the composite error surface of mating tooth flanks in the analysis. The calculated results were also compared with measured results obtained for four hypoid gear with four different kinds of tooth contact patterns. These investigations show the validity of the latter method for simulating the performance of hypoid gears. With this method, a gear engineer can apply knowledge of cylindrical involute gears to hypoid or bevel gears in predicting their performance.

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This paper deals with an evaluation of the fatigue strength of sintered steel based on linear fracture mechanics. The fatigue crack growth is measured with bend test specimens of Fe-Cu-Cr sintered steel of various densities. From this result, the fatigue strengths of the specimens with initial length of crack a at the life N are calculated, and they are shown as N-S-A curves. A model, which has an initial crack at the surface but is homogeneous and has no internal flaws, is introduced to analyze the fatigue lives of sintered steel. The initial length of the crack basically depends on the flaw size of sintered steel, and it can be used as an index to evaluate the effect of flaws on the fatigue strength. The initial lengths of cracks are estimated from the N-S-A curves and the fatigue test results. The lengths are 165 to 251 μm for the bend test specimen of 6.6 to 7.0 g/cm³ density.

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This study concerns the cutting process of unidirectional SiC whisker-reinforced plastic composite. The effects of the grain size of the polycrystalline diamond tool and the SiC whisker orientation on tool wear were investigated. The tool with fine grains exhibited higher wear rates. The greatest tool wear occurred with the composite having longitudinal alignment of whiskers. The cutting processes of various orientations of whiskers were observed by SEM at low speed. Moreover, models were proposed for cutting the SiC whisker-plastic composite and for the wear of sintered diamond tools.

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This paper deals with an innovative injection molding process whose concept has been developed from the heat transfer point of view. The process enables improvement of the optical quality and promotes the molten flow of injection-molded polymer products by applying infrared radiation on the moving polymer melt being injected into the mold cavity. The effects of CO₂ laser heating on the skin layer of the molded polymer were observed using a mold with transparent windows. The residual birefringence frozen in the irradiated specimen was measured, and the surface transcription of the irradiated polymer strip was investigated. The results showed that the birefringence in the skin layer of the injection-molded polymer strip was reduced, and the surface transcription of the molded polymer strip was improved by CO₂ laser heating. Another advantage is that the processing time is only slightly increased by applying this method.

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