This paper presents one million degrees Of freedom (DOFs) structural vibration analysis on a parallel computer. Lanczos method was adopted to the solution of the eigenvalue problem. The triangular decomposition of the matrices was executed in parallel applying the parallel decomposition algorithm. In order to save the huge memory size required in the analysis. the memory saving method was applied. One million DOFs problem was solved in 74 hours using 32 processors. The convergence of the eigenvalues and eigenvectors was confirmed.

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This paper studies chaotic behaviors of nonlinear vibration system with stochastic excitation. Previous studies dealing with mechanical chaotic vibrations have mainly focused on their deterministic properties even if the corresponding vibration system contains stochastic properties which are sometimes unavoidable in practical mechanical vibration systems. From this point, this paper mainly focuses on a random vibration arising in a stochastic nonlinear vibration system, which the authors call SCB (Stochastic Chaotic Vibration). The SCB has a negative largest Liapunov exponent while it behaves in a similar way to determinstic chaos, exhibiting expanding and folding process of chaos. This result is in good agreement with that of a practical chaotic behavior occurring in our experimental apparatus and implies that the practical chaotic behavior may not have a positive largest Liapunov exponent even though it behaves in a chaotic way. This kind of chaotic properties of the SCB and the experimental chaos can be characterized by a probability density function of local expansion rates.

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Solid horns are used to magnify the displacement amplitude for power ultrasonics. They have half a wavelength and are connected vertically with the transducer. Therefore the ultrasonic vibration system usually becomes too long and heavy to handle. Thus a new type of solid horn with a metallic diaphragm has been developed by the authors. The horn transduces the little longitudinal vibration to the extremely large flexural one. Therefore it is possible to shorten and to make lighter the ultrasonic vibration system by replacing connected horns to a simple new horn. It is thought that the horn is suitable as a high power ultrasound source, further the high efficiency of the sound radiation is obtained by the larger area and in-phase vibration of sound radiation face. Thus the authors have attempted to expand the diameter of the diaphragm by keeping in-phase vibration. In this paper, the free vibration of the solid horn with a diaphragm and the one with double concentric diaphragms are analyzed using FEM and theory. The analytical results on the natural frequency and the vibration mode are confirmed experimentally.

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A new type of solid horn with metallic diaphragms has been developed by the authors. The horn transduces the little longitudinal vibration to the extremely large flexural one. Therefore it is possible to shorten and to make lighter the ultrasonic vibration system by replacing connected horns to a simple new horn. It is thought that the horn is suitable as a high power ultrasound source, further the high efficiency of the sound radiation is obtained by the larger area and in-plase vibration of sound radiation face. Thus the authors have investigated a free vibration of a solid horn with double concentric diaphragms which has large displacement amplitude, large diameter and in-phase vibration. In this paper, the directivity of the solid horn with double concentric diaphragms are verifyed theoretically and experimentally, and compared to other ultrasonic sound sources. Furthemore, the stresses applied on the diaphragm analyzed using FEM to design the dimensions and to avoid stress concentration on diaphragm.

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Seismic proving test of a process computer system was carried out to investigate its dynamic characteristics and functional capability. In this test, two seismic waves were selected as design earthquakes for the process computer system. The process computer system, including magnetic disc drive, CRT displays and a printer, was shown to be able to maintain its function against earthquake acceleration of up to double the design earthquake acceleration. The magnetic disc drive was found to be the equipment having the least seismic margin. It was also confirmed that the functionalcapability of a magnetic disc drive under earthquake acceleration can be evaluated by using the offtrack response.

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In order to maintain the functional capability of a process computer system used in nuclear power plant, it is necessary to keep both structural integrity and information processing function during design earthquake.Based on failure mode analysis of the process computer system against the earthquake, a method of evaluating functional capability of process computer system is proposed. In this method, the acceleration responses of computer equipment are calculated by FEM and compared with the allowable accelerations obtained by the seismic proving test. The proposed method is examined its usefulness in evaluating the functional capability of an actual process computer system in a nuclear power plant and its validity is verified.

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In this paper, two types of an earthquake isolation system based on the theory of the pendulum for wooden houses are investigated. One is a system consisting of linear bearing having a certain curvature to give the superstructure a proper natural frequency and the other is a friction pendulum bearing which has already been reported by one of the authors. The purpose of these systems is both prevention of overturning furniture and destroying house in itself. Both systems are based on the theory of the pendulum, and one of the most desirable isolation systems for light-weight structure, because a fundamental natural frequency of these systems is easily obtained by choosing a suitable curvature of the systems. In this study, response analyses are carried out to investigate the motion of a wooden house with these earthquake isolation systems against the severe earthquakes.

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In this paper, a trillnear-type elastoplastic damper using two kinds of V-shaped plates is proposed in order to obtain a hysteresis damper which gives damping even for a small displacement and has a fale-safe mechanism. The trial damper was made, and the resisting force characteristics and fatigue strength of the damper were measured. The seismic responses of an L-shaped pipe supported by the damper were discussed analytically and experimentally. These results are compared with the results obtained for bilinear-type elastoplastic dampers.

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In a Fourdrinier paper machine, the fiber and water mixture flows to a wire-screen belt. As the wire-screen belt travels horizontally, water is drained through the screen, leaving the fibers on top. In some operating conditions large vertical vibrations of the wire-screen belt occur. The mechanism of this phenomenon is investigated experimentally. Analytical study is also done, which shows qualitative agreement with the experiment results. Consequently, the screen vibration is self-excited vibration due to the pressure variation of the water on the wire screen belt.

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Dynamic model of viscoelastic material may be described by fractional differential Voigt model. Free vibration and forced vibration of a single-DOP (single degree of freedom) system with viscoelastic material have been described by the equations of motion with fractional differential term. This paper deals with bibration reduction of a single-DOF mechanical system with viscoelastic DA (dynamic absorber). Property of stationary vibration response of a 2-DOF viscous camping system has been fully known, yet a 2-DOF viscoelastic damping system is still unknown. Here, the responses of the 2-DOF system with the viscoelastic DA are analyzed and compared with those with the viscous DA.

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Many classes of nonlinear systems can be represented by Volterra kernels. One of the authors has proposed a method for obtaining the Volterra kernels by use of M-sequences and cross-correlation function. In this paper, the authors propose a new method for identification of nonlinear mechanical systems by use of Volterra kernels. The nonlinear mechanical systems are approximated to a combination of a linear system and its square and cubic portion. Then, the parameters, which represent the relative maginitude of the square and cubic part, are calculated by use of the crosscorrelation function. In order to show that nonlinear mechanical systems can be identified by the parameters, computer simulations are carried out. The nonlinear mechanical system simulated consists of a DC servo motor and 1-link arm. From the results of simulations, it is shown that the nonlinear mechanical system can be identified by the proposed method.

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It has been explained that the position of the shoe center of a ski has a very important effect on skiing, especially on the ski turn. Although the position of the shoe center is impossible to change by using most of the binding available on the market, it is possible to adjust its position by using special bindings. However, we can not find any reports or instructions that explain how to determine the best position of the shoe center. The authors have already developed a numerical approach for estimating the ski turn caused by a skier's edging action. Since the dynamic bending deformation and movement of the ski can be analyzed by the approach, we can estimate the effects of the position of the shoe center on the ski turn by using the approach. In the present study, the ski turn of various skis with a different position of the shoe center are estimated numerically, and the effects of the position of the shoe center on the locus of the ski turn and the relative direction of the ski to the tangent of the locus of the ski turn are discussed.

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This paper deals with aerodynamic sounds generated by the curved columns in a uniform air flow experimentally. The curved column is formed in V-shape by bending a straight column to an angle of 2θ. The angle θ means the angle between the direction of air flow and a one-sided straight part of V-shaped column. The bend part has a radius of curvature of R. In the experiment, the effects of θ's and R's on the aerodynamic sound have been examined in detail. The results of the frequency analyses of aerodynamic sounds show that when θ≤90°, eminent aeolian tones are generated by the curved columns and moreover, that the peak frequencies of aeolian tones are affected by the values of R and θ. However, when θ > 90°aeolian tones are not generated but whistling noises generated in a broad frequency range.

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Conventional methods for predicting the reflection and transmission coefficients for non-uniform ducts yield high dimensionality of the resulting numerical problem due to segmentation of the duct into a number of subsections, or require iterative calculations, so that the numerical computation is time-consuming and expensive for obtaining a satisfactorily accurate result. This paper presents a more effcient analytical method, which requires neither segmentation nor iterative calculation by virtue of the use of spherical coordinates. Numerical calculations are carried out for the planar and non-planar waves. It is confirmed that the numerical results are in good agreement with conventional theoretical predictions which have been experimentally validated.

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This paper describes an analysis of contact wire vibrations under pantograph passages observed by video images through an anamorphic optical lens. After processing the images obtained at Shinkansen line sides, the wire displacements of greater than 1mm over several ten meters are accurately measured. This method provides a means to get not only vibration at some discrete points but also its distribution along the wire, wihch can afford us various vibrational quantities to determine the wave propagation. In particular, the wave intensity that would closely influence the contact force is estimated from the gradient and the velocity of the contact wire. It is confirmed that the stronger waves of contact wire are generated by a pantograph in the latter half of span, wihch propagate to a pantograph that follows and coincide with it in the former half of span. The force in hanger and contact force are also estimated from the images.

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There are many studies on vibration control for building using an active dynamic absorber. When applying active vibration control, it is most important problem to achieve higher performance within a certain constraint on actuator. However, it is difficult to solve this problem by using a stationary controller because seismic wave has nonstationary characteristics. This study presents a controller design method based on the nonstationary optimal control. In this technique, the characteristics of nonstationary intensity such as a seismic wave is considered by using the time-varying criterion function. Time-varying weight corresponds to the envelop function which gives noncriterion function. Time-varying weight corresponds to the envelop function which gives non stationary intensity of a seismic wave. And this controller is designed by solving the time-varying Riccati equations. By considering uncertain characteristics of seismic wave, a modification method is presented, in which the time varying feedback gain is varied continuously depending on the mean square value of seismic wave. To compare the performance with a stationary control, numerical calculations and simulations were carried out. As a result, the effectiveness of nonstationary optimal control was shown.

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This paper proposes a method of structure/controller design via robust pole assignment for active vibration suppression of flexible structures. The proposed method assigns the closed-loop poles at the target location and quasi-minimizes the condition number of the closed-loop modal matrix by designing structure and controller parameters. Closed-loop target pole locations can also be redesigned as the design parameters. Reducing the condition number improves stability robustness and control performance of the designed closed-loop system. This paper introduces a new index of condition number as the cost function. Use of this index in place of actual condition number reduces computational effort significantly. Feasibility of the proposed method is illustrated by numerical examples.

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Electrotheological (ER) fluid has notable characteristics of viscosity. Viscosity of ER fluid can be varied over a wide range in about several milliseconds according to the applied electric field. In this paper, an active small rotary damper using ER fluid is made on an experimental basis and its applications to velocity control and impedance control are examined. The characteristics of the rotary damper are small, simple structure and fixed electrode type. Then, it is suitable for control experiments because it can be incorporated into mechanical system safety and easily. As ER fluid is fairly nonlinear and the control of the ER damper is complicated, fuzzy set theory is applied. Responses of the angular velocity and impedance characteristics of the ER damper are desirable in experimental studies.

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This paper describes simultaneous control of attitude and swing of a pendulum having a rotational free body which is a simple lifting load model using two inertia rotors. Rotor torques controlling the free body's rotational attitude and the pendulum's swing are obtained by the computed torque method which is based from linear feedback accelerations of sliding mode control and the coupling characteristics of system's dynamics. Simultaneous control of attitude and swing is clarified to be possible from the experiments of position and sin trajectory following attitude controls under swing disturbance. But, from the experiments, simultaneous control cannot be performed in the case of large swing disturbance due to the motor's angular velocity saturation of the attitude inertia rotor. To avoid the velocity saturation, increasing moment of inertia or using high rotational motor are considered and these are related with estimating value of swing disturbance.

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In this paper we propose an approach of unsteady flow rate measurement by using a drag-plate-type drag force flowmeter (DPFM). This type flowmeter has not been used as an unsteady flow rate sensor because the dynamic characteristics of this type flowmeter are not well known. In this study, we aim to realize an unsteady flow rate measurement with fast response and without expense. In this paper, we propose a simplified mathematical modelling of the DPFM, and real time unsteady flow rate measurement method using the dynamic modelling. As a calibration method, we employ cylindrical-choke-type instantaneous flowmeter (CCFM) and remote instantaneous flow rate measurement (RIFM). It is shown experimentally that the proposed unsteady flow rate measurement method is valid. Obtained results are as follows. As comparing the flow rate of the DPFM with that of the RIFM, first, the gain and phase characteristics of the DPFM show a good agreement within 1 dB and 10° with the RIFM over frequency range of 100 Hz, secondly, the DPFM demonstrates sufficient accuracy up to frequency of 400 Hz that is a resonant frequency of the beam system.

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In order to know the motion of an automobile, it is extremely significant to measure the lateral force that acts on road surface when the automobile runs. Therefore, we considered many approaches to measure the lateral force in a short section of a road over wide speed range from extremely low to very high. And we contrived a new structure of a measuring apparatus that used strain gauges. Finally, we successfully made the apparatus that possessed good response characteristics in wide range from D.C. to extremely high frequency, enough sensitivity and very low cross-axis sensitivity. In this paper, we describe the structure and characteristics of the apparatus and example of measurement by it.

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Impedance control is one of the most effective control methods for a robot manipulator in contact with an object. It should be noted, however, that a practical study on such a method has not been successfully applied to an industrial robot with 6 degree-of-freedom. Recently, a hybrid compliance/force control (HCC) in this field was suggested to deal with the practical problem, in which a desired damping coefficient is determined by repeating many simulations, or by trial and error. In this paper, we first propose a fuzzy environment model that can estimate the stiffness of environments and give a generation technique of fuzzy rules learned with genetic algorithms. To determine suitable compliance without trial and error, we next introduce a method that produces the desired timevarying compliance, giving the critical damping in contact with an object by using the information on the inertia matrix. Simulation results show that the proposed method is very effective for deciding the desired compliance without any complicated tuning and is very robust to the change of environment.

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As an application of virtual reality to welfare work, an obstacle experience system was proposed in which a healthy person can experience the situation with a wheelchair. It is considered that such wheelchair experience system is necessary in dealing with the wheelchair's problems such as the development of new wheelchair and other welfare implements, and the design of cities and various facilities. In this research, a wheelchair experience system, which is capable of moving in a virtual environment with vision information and force feedback, was constructed. This paper describes mainly the development of force feedback system and a fundamental experiment about the movement characteristics with spatial recognition. Experiments of distance assessing by movement are done in the real and virtual environment with the attention to concept of sensory integration and active to evaluate the necessary of force feedback. The results of the experiment are discussed and the effectiveness of present system are inspected.

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Cooperative transportation of an object by two or more mobile robots requires each robot to exert an appropriate force to support and move the object, to move along the object, and to maintain the robot's attitude stably. Studies of cooperative transportation by multiple robots so far have scarcely considered the stability of the robot's attitude influenced by the force from the object. To take part in cooperative transportation, a mechanically unstable robot, such as a wheeled inverted pendulum, needs to control the force and follow the object as standing stably against the force in an integrated manner. We call this a cooperative behavior. To realize this behavior of a wheeled inverted pendulum, we built a control system to estimate the external force and maintain standing and to exert a specified force. Experiments were conducted of cooperative transportation between a human and the robot.

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We have developing an intelligent mobile robot for service use which can be utilized as a "secretary or helper robot" in day time and "security guard or maintenance including floor-cleaning robot" in night in office buildings. Since the service robot works or moves autonomously living together with human being in office environments, it must be able to recognize its absolute position and environment. In this paper, we proposed two types of self positioning method based on a visual sensor. One is the global self positioning (GSP) which is realized by recognition of a room number plate. The another is Iocal self positioning (LSP) in which the position is calculated by the relation between the robot and three lighting landmarks, such as two exit lamps and a fire hydrant lamp in corridors. Experimental results show that proposed methods are very effective in self positioning for the autonomous mobile robot.

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This paper deals with handling of a floating object by several space robots. Operational ability of a space robot depends on its scale, and the scale of a space robot is restricted by the capacity of a rocket, which is used to launch the space robot into space. For this reason, a cooperation of several smaller scale space robots is useful and necessary in space development. In this paper, system which consists of two space robots and a floating object is considered, and two partition methods of its kinematic relation equation is proposed. Moreover, Resolved Motion Rate Control schemes for the system are designed based on the partitioned kinematic relation equations, and computer simulations are carried out to verify the control law.

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A magnetic bearing system using forces of repulsion between permanent magnets is developed. In the developed system, the radial motions of the rotor are passively supported by repulsive force. The suspension system of such configuration is inherently unstable in the axial direction so that it is stabilized by using motion control of the permanent magnets for passive radial suspension; these magnets are driven by voice coil motors according the motion of the rotor in the axial direction. The characteristics of the system are studied both theoretically and experimentally. The experimental results demonstrated that the developed magnetic bearing can suspend a rotating mass without any mechanical contact, and realize positioning control of the rotor in the axial direction.

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This paper considers the optimization of systems having uncertain parameters by using minimax strategy. An optimization problem is converted to a minimax problem to treat system design variables as a minimizer which improves a performance index and uncertainties as a maximizer which worsens the same index. The solution of the minimax problem improves the worst case performance most, so the systems designed by the above formulation has robustness to uncertainties. We propose the method which uses the historical information of the optimization process to solve the minimax problems which don't have a saddle point. As a numerical example, we investigate a control system design for a tracking problem of a rigid robot manipulator. In this system, parameters of a first-order lag element between a controller and a actuator have uncertainty, and we design feedback gains of a PD controller. The robustness of the control system design by a proposed method against the uncertainty is demonstrated.

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This paper describes the characteristics of the magnetic systems of active magnetic radial bearings that are combined with permanent magnets to provide bias force and electromagnets to supply control force. The permanent magnets are placed between two ring-shaped stators, and share their pole-legs with those of the electromagnets. The stator and rotor cores are made of silicon steel strips. Incremental magnetic fluxes with fixed working airgap are detected with search coils near the pole leg faces. Their frequency characteristics are obtained to sinusoidal input to the power amplifier of electromagnet. The experimental results are compared with the numerical result based on a model using identified parameters.

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A high-speed visual sensing system for robotic seam tracking in automobile body sealing has been developed. Based on technology that has sub-mm sensing accuracy for high-speed seam-tracking of a complicated seam with position tolerance, an advanced sealing robotic system minimizing the necessary sealant has been achieved. The featured technologies are as follows: (1) a compact and high-speed laser range finder mounted on a robotic manipulator of high-speed spatial motion, (2) an adaptive seam-recognition algorithm which accurately determines the seam feature point by detecting the noticeable gap in non-uniform range profiIe data, (3) a high-speed trajectory planner supplying stable and well-timed servo references for a sealing-gun actuator by suppressing the sensor data noise, (4) a sensor-enhanced teaching advisor utilizing a graphical user interface. Results obtained in field testing with almost 10 000 bodies on an automobile sealing line show significant sealant cost reduction and reliable system performance.

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This paper proposes a driver model for merging, based on the analysis of actual merging behaviors of human driver on an entrance of highway. The rule-based behaviors of drivers are modeled with fuzzy logic. The merging model consists of the models of on-ramp vehicles and on-lane vehicles. The control strategies of two models are designed independently, and merging is accomplished in cooperation with each other. The control strategy of on-ramp vehicles determines merging timing, and that of on-lane vehicles selects a suitable maneuver not to interfere the merging action of on ramp vehicles. The propriety of the proposed model is verified by a series of simulations.

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Adopting an electronically control throttle valve has many possibilities of improving the automobiles performance thanks to its freedom. One of them is an optionally tuning for the accelerator pedal sensitivity, It can be attained by using two feedback signals of the speed signal and torque signal of the wheel axle. In the control, torque signal is desirable to get without any hardware device because of cost saving. Therefore, the control used the software torque meter which newly developed, was attempted in this paper. The principle of the software torque meter depends upon Luders-Narenda type adaptive observer. Experimental results showed the expected supreme tuning ability. That means the objective of cost saving has been achieved. Moreover, it was found that the control adopting the software torque meter is better than the one adopting a hardware sensor in performance, because of the characteristic of low pass filter of the software torque meter.

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This paper describes an advanced vehicle control method using independent four wheel steering system for vehicle handling and stability. At accelerating and at braking on a vehicle cornering, each tire force coefficient of the vehicle is quite different because of load transfer and non-linear characteristics of tire forces. Therefore, 4WS system is not effective for the vehicle control and stability at high lateral acceleration condition. If the tire force coefficient are controlled, it is possible that the vehicle has been more stable at high lateral acceleration cornering evan at critical situation. For the control, there are two kinds of method to control the tire force coefficient, one is direct yaw moment control method with traction and braking force and the other is with independent four wheel steering system. This paper shows the effect of the independent 4WS to the vehicle behavior.

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This paper presents steering ability around curves of the proposed self steering truck with asymmetrical suspension and independently rotating wheels in the trailing axle for rail vehicles. Using a simple linear truck model theoretical analysis was made and introduced the condition for wheel conicity and primary stiffness to improve the steering performance comparing with conventional trucks with normal rigid wheelsets. The steering ability of the proposed truck is examined using test stand which can simulate curving condition and lateral force and truck behaviors are measured. These experimental results are agreed with theoretical prediction and numerical simulations. It was found from these experiments and theoretical calculations that the proposed steering truck has better curving performance especially in very tight curve with flange contact than conventional trucks.

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This paper treats the self-powered active vibration control system, which realizes active control without external energy. A typical active controller requires external energy which is not required by a passive or a semi-active controller. This is one of the drawbacks of the active control system. The proposed self-powered active control system uses the vibration energy supplied by the energy regenerative damper. This paper examines isolation performance of the self-powered active control by utilizing random input and proposes to apply this system to a cab suspension of a truck. In the self-powered active control system inflicted with random input, vibration energy regenerated from high frequency vibration can be used to control low frequency vibration. Through experiments, it is proved that the response to the random input is better than that to the sinusoidal input in low frequency range. Numerical simulations demonstrate better isolation performance of the self-powered active control in the cab suspension system.

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The first step in systematically establishing all automatic crane control system is to build a mathematical model. This paper presents the modeling of an overhead traveling crane in a three dimensional (3-D) complex transfer trajectory including hoisting motion and curve trajectory. The crane model for object positions in a 3-D transferring space is derived in terms of force's balance, in which the swirling motion can well be expressed. The validity of the proposed model is confirmed by simulations and experiments.

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An overhead traveling crane system has been largely used as one of the most vital transfer elements. This research presents the modeling and control of an overhead traveling crane in a three dimensional (3-D) complex transfer trajectory including hoisting motion and curve trajectory. In the present report, we describe a system design which can resolve the trade-off relationship between tracking the reference trajectory and suppressing the sway of the object, and can achieve an effective control system for the change in rope-length of the crane system during the hoist/lower motion. In this design, the 3-D tracking control systems for the object position of a crane system in terms of a variable gain controller with fixed pole are independently oriented in the X and Y directions. The usefulness of the present approach is demonstrated through control simulations and experiments.

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This paper describes the dynamic characteristics of a one-pad contact slider subjected to wavy excitation and collision to determine the optimum specifications for the head-disk interface used in contact magnetic recording. Wavy roughness, asperities, and the lubricant of the disk surface are respectively modeled in the form of a planar sine wave train, a linear spring, and a damper system. The suspension is also modeled as a linear spring and a damper system on a two-degrees of freedom. In this paper the contact force, the friction force, the equation of motion considering the pitch motion are formulated. Numerical results have been provided to obtain effects of a damping coefficient of the lubricant layer as welI as the suspension preload on spacing fluctuations and the optimum wavy roughess.

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We calculate the transient dynamic response of the human finger skin and strain energy distribution at the tactile receptors. Especially, we focus on the effect of epidermal ridges on the tactile sensation. First we make a FE (finite element) model using measured geometric and material properties of an actual index finger. Next we show a method of dynamic contact analysis using FEM (finite element method). Then we analyze the contact between the finger with/without the epidermal ridges and a plane plate moved in the tangential direction after indented in the normal direction. We found that Merkel's corpuscles are relatively sensitive for detecting the indentation of the plate. Next, we analyze the contact between the finger and the plane plate moved in the tangential direction at a constant velocity. We found that Meissner's corpuscles are sensitive to detect the vibration due to the stick/slip.

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In this paper, a new method was proposed to theoretically analyze the forces on the toe, ankle and knee joint using a musculoskeletal model of lower limb. It was shown that the maximum force on the knee joint when a human jump down vertically from a height of 0.3 meter could come up to 11.2 times of his weight without an active movement of shock absorbing. Moreover, the optimal movement of lower limb muscle during a vertical landing on a hard surface was proposed to be solved by converting the multi dimentional and monlinear optimal control problem to a parameter optimazation problem. Detail investigations were performed in three cases when minimize the forces on the toe, on the ankle and on the knee joint, respectively. By using this optimal movement, it is possible to reduce the forces on the toe and knee joint by half. It was made clear from the optimization result that it is more appropiate to use the forces on the toe as an object function. Furthermore, it was found that the force on the toe and the activation level of lower limb muscle predicted by parameter optimization agreed well with the experimental results.

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When a gear pair which has tooth surfaces (elastic) modified slightIy and convexly from involute holicoids for one member and the conjugate surfaces (rigid) of the involute hellcolds for the other is given, the path of contact and the inclination angles of the contact normals of the gear pair under load are obtaind as functions of angle of rotation. They are expressed through the deviation of the tangent plane at a point of contact under h)ad from that at the corresponding point of contact under no load. To calculate the deviation of tangent plane in the region of multiple tooth pair mesh, the equivalent tooth load is introduced, which transmits the same torque that the multiple tooth pairs carry at the same time. The diviation of tangent plane under load is a periodical function of angular pitch of the gear pair and is continuos but non-differentiable generally at the point where the number of tooth meshing at the same time changes. The starting and ending points of mesh of a tooth pair and the actual contact ratio which depend on load are also calculated.

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The contact stress of helical gears is calculated with 3-dimensional finite element method. The relation between the contact stress and the profile correction amount is investigated and the foliowings were obtained; (i) The tooth stiffness of helical gears is able to be estimated with that of virtual spur gears. (ii) The stress decrease at the tooth tip results in partial increase of the stress at the correction starting point. (iii) About 1.5 times the tooth deflection amount of the virtual spur gear is reasonable for the profile correction amount of helical gear.

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In a previous paper, we have developed a ultra precision method of joining an alumimum polygon mirror and a Sic self-acting air bearing using a shrink fitter. However, after the joining, the mirror surfaces need to be refinished by an ultra precision lathe to the fiattness of under 100nm, because the fiattness of the mirror surfaces will deteriorate beyond the allowable level. In this paper, we tryed to maintain the allowable fiattness of the mirror surfaces even after the joining by changing the shape of the polygon mirror. Optimum shapes were theoretically seeked by 2-dimensional FEM analysis through trial and error. After some 23 shapes were examind, we succeeded in finding the optimum shape that maintain the fiattness below 146 nm at a rotational speed of 30, 000 rpm. The optimum shape obtained by the 2D-FEM analysis was examind by the 3D FEM analysis.

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Stepped type gas film bearings have an advantage of simple structure, high load carrying capacity and stability, so the bearings are used for supporting very high speed, relatively small sized rotating machinery. This paper describes the experimental investigations into the combined effects of gas film inertia and compressibility on the static and dynamic characteristics of bearings. The minimum film thickness, friction torque, spring and damping coefficients of gas film were measured under the constant mass of stator and fixed step height for a wide range of rotational speed from 10, 000 rpm to 40, 000 rpm. There were good agreements between theoretical results and experimental ones and it was clarified the combined effects of gas film inertia and compressibility on the bearing characteristics.

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The roiling contact fatigue life tests of 50 Ball Ways (Type H 25 TA) under the test conditions of normal load F=5.9 kN, 9.8 kN and 14 kN and the linear stroke 1s=200 mm are carried out to investigate the fatigue life distribution of Ball Way. The results of Weibull analisys of life value are that the life of Ball Way fits well to the 2-parameter Weibull distribution and the average value of shape parameters is 4.4. The influence exponent of the normal load to the life, which is obtained from the life data, is p=3. From SEM analisys of the raceway surface, it is evident that the characteristic of rolling contact fatigue failure is pittings' initiation from the surface. And, the relation between linear stroke and basic dynamic load rating is described, which is obtained according to the life theory considered with the characteristic of fatigue failure and the life test results.

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This paper describes the application of the LM measurement method for measuring two types of motion accuracy, trajectory accuracy of the circular motion with a small radius and the linear motion containing a square corner, on a machining center. The measured results for both the motion paths have high precision and good repeatability and confirm the validity of the LM method for the measuring purpose. It is verified for the tested machining center that the radius decrease of an actual path with respect to its specified radius R is in proportion to the value of F² /R in the circular motions, and the error around the square corner is proportional to the feed rate F in the linear motion paths. Two potential profile errors in contour machining with a high feed rate are demonstrated by the actual examples, i.e. the error caused by different radius decrease relative to neighboring interpolation circular arcs in tool path and the error caused by the combined influence of the feed rate change near the connection point of two motion blocks and the radius decrease of circular path.

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Recently, vibration of some machine tools have become a serious problem because of improving surface roughness and machining accuracy of a work piece and reducing noise in a machine shop. Therefore, in this paper, at first, we have developed a powder composite damper in order to improve the structural properties of machine tools. The damper consist of coarse powder at 60% in volume, intermediate powder at 24% in volume, fine powder at 10% in volume and an air at 6% in volume respectively. The dampers were composed in the space of the machine tool structure. Then, the powder composite damper was evaluated in the experiment using some steel boxes and C frame type of punch press. It is concluded from the results that; (1) the powder composite damper has high damping vibration and high static stiffness at the same time. (2) sintered alumina was effective as a material of the damper (3) the C-frame type of punch press with the powder composite could reduce noise and vibration.

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The effect of cold 90° V bent-working on the reversed plane-bending fatigue strength of cold toiled carbon steel sheets was investigated with a fatigue machine developed previously using a ftuidic-device. The results obtained can be summarized as follows. (1)The fatigue strength of 90° V bent sheets was always higher than that of the fiat ones. Moreover, the fatigue strength of bent sheets increased with decreasing bending radius. (2) The fatigue cracks in the bent sheets always initiated at the inside of bent location. (3) The fatigue machine can be used to evaluate the reversed plane bending fatigue strength of bent sheets.

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The initiation of fracture induced in a compact by the difference between the elastic recoveries of tools during the unloading process of multi-level powder compaction is predicted from calculated results by finite element simulation. The loading and unloading processes in the compaction are simulated by the rigid-plastic and elastic finite element methods, respectively. In these simulations, elastic tools are modeled as springs connected with the nodal points on the interfaces between the compact and tools. This modeling leads to simple treatment of coupling of the tools and compact. The initiation of fracture is evaluated from the maximum principal stress, and the critical stress is measured by means of bending and shearing tests. Two-level compaction operations are simulated by the finite element method to predict the initiation of fracture. The predicted critical values of relative density for the occurrence of fracture are in good agreement with the experimental ones for iron powder compacts.

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In order to clear the behavior of material deformation and fracture during machining the hard and brittle materials such as a glass, the indentation tests have been carried out in various environment. The results of the experiments showed that the crack length and velocity of crack propagation, depends on a percent relation humidity in the environment, and on the stress of the surface of glass, and increases with increasing the percent relation humidity in the environment. The experimental data also showed that the dependence of crack length and velocity of crack propagation on humidity will be stronger with increases applied load. Experimental results are discussed in this paper.

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