Dynamic behavior of smooth hysteretic systems subjected to harmonic excitation is analyzed. Wen's differential equation model for hysteresis, which can be applied to a large class of hysteretic systems, is used. A piecewise power series expression is derived from Wen's model assuming primary resonance and weak hysteresis. First and second order averaging methods are applied to the equation of motion with piecewise power series terms. Resonance curves obtained from the first and second order averaged equations are compared with the results of numerical simulations in order to examine the validity of the present analysis. It is also shown that chaotic behavior occurs in the hardening hysteretic system even when the excitation amplitude is not so large.

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Self-excited vibration of a spring clutch used in an electrophotography fuser was investigated. From the results of theoretical and experimental investigations, the following points were deduced : (1) The vibration is basically induced by an asymmetric friction force due to asymmetric contact at a slipping surface. (2 ) Lissajous figures of the vibration were circular and the vibration was forward-whirling. (3 ) Calculated results based on the present model qualitatively agreed with experimental observations, and several methods of suppressing vibration were proposed. The spring clutch should be designed such that it has the following characteristics : (a ) sufficient damping, (b ) low friction coefficient, (c ) sufficient gap during slipping period and perfect fastening during transfer-ring torque, and (d) small initial spring static displacement. These measures have been used to overcome the abnormal vibration problem.

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The purpose of this paper is to study the transient response of a string which is influenced by a lumped mass attached to its lower end. We especially focus on phenomena around a resonance point. Lateral oscillation of the string is excited by horizontal displacement at its upper end and the frequency of the excitation is time dependent. It is expected that out- of-plane oscillations of the string will occur due to nonlinear terms related to the inertia force of the lumped mass. The oscillations of the string are investigated theoretically and experimentally. First, the resonance curve character is clarified. The resonance curve of the out-of-plane oscillations is different from that of the in-plane ones. Also, we observe an irregularly precessing oscillation at a certain frequency of excitation. Next, we discuss the influence of variable frequency. We conclude that out -of-plane oscillations may occur easily when the frequency of the excitation decreases. The maximum amplitude of those oscillations becomes close to that of the resonance curve of the out-of -plane oscillations, when the frequency of the excitation increases.

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The problem of the forced harmonic vibration of a visco-elastic beam with a rectangular cross -section having a single edge crack in an arbitrary position is investigated by means of the Boundary Integral Equation Method (BIEM). In the analysis, the crack is simulated by an equivalent rotational spring, connecting the two segments of the beam. The BIEM formula is applied to each segment of the beam. Some simple problems of beams subjected to harmonic exitation are considered and the computed results are compared with the exact solutions. In order to demonstrate the efficiency of the proposed method, the more complicated cracked beams are analyzed, and the response curves of the system and the effects of the crack location and the depth are investigated.

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In a rotating shaft driven by a universal joint (Hooke's joint), the secondary moment induces lateral vibrations while changing the joint angle. A torsional vibration then differs from that in the case of a shaft that has no deflection. Furthermore, the change of the joint angle influences the secondary moment. Therefore, we analyze equations of motion in terms of the second power of the deflection, the angle of deflection and the angle of torsion. Asymptotic analysis for the equations of motion exhibits that the universal joint must couple the lateral vibration with the torsional vibration. These vibrations become unstable and grow when the driving shaft rotates with the angular velocity nearly equal to half as large as the sum of the natural frequency of the whirling and that of the torsion. The experimental results support and confirm the analytical results.

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The forced response of continuous systems with nonlinear boundary conditions which are motion limiting-constraints or clearances is of great importance for several engineering applications. In analysis of such systems, an analytical model with restoring force characteristics in which stiffness increases after collision is generally used. On the other hand, there occurs energy absorption which is represented by the coefficient of restitution. However, few studies on vibration analysis of a system with collision considering energy absorption have been carried out. Modelling of energy absorption can be carried out by assuming hysteresis loop characteristics in the relation between force of restitution and penetration. One of the authors proposed an analytical method for steady-state response by expanding the force of restitution into a Fourier series. Using this method, steady-state response of a continuous system was shown for the case of symmetrical collision in which the beam end collides with stop once in half period of its vibration. In this paper, an analytical method of approximate solution for the continuous system with asymmetrical collision characteristics in which the beam end collides with stop once in one period of its vibration is presented. Some numerical results for steady-state response are shown.

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Three-dimensional nonlinear liquid motion in a rigid rectangular tank partially filled with liquid, in response to pitching excitation, is investigated. In the case that symmetric modes are dominant, the nonlinear ordinary differential equations governing the liquid surface oscillation are derived by applying Galerkin's method to the basic equations. It is confirmed that vertical excitation causes parametric excitation. In addition, it is noted that pitching excitation also causes parametric excitation when the pitching axis does not intersect the vertical line passing the center of the tank bottom. An experiment was conducted using a model tank. Good agreement was found between the theoretical and experimental results.

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The pressure fluctuation caused by the ring vortex shedding from a perforated plate with some holes installed in a pipe was investigated experimentally. Measurements were made using pressure transducers at Reynolds numbers from 6.74 x 103 to 4.02 x 104 based on the velocity through the hole. A lock-in phenomenon is affected significantly by the flexural rigidity of the perforated plate. When this phenomenon occurs, the amplitude of the pressure fluctuation increases markedly. While the velocity range generating the lock-in phenomenon shifts to a higher velocity as the plate thickness increases, the frequency of the pressure pulsation is independent of it. It was also found that the pipe length both upstream and downstream of the plate exerts a great influence.

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Many analytical results have already been reported on the imbalanced exciting moment of V-type multi-cylinder engine. These analytical methods generally follow the steps in which the cylinder arrangement and the bank angle of the engine are determined initially and then the exciting moments are analyzed. In contrast, in our analytical method, effective cylinder arrangements are selected initially using the reduction condition of exciting moment, and then the most suitable bank angle is determined. We have already determined new bank angles of V-type 6-cylinder and 8-cylinder engines using the method mentioned above. In this paper, we study the exciting moment of a V-type 10-cylinder engine that was developed by an American automobile company. We have not deter-mined a way to completely suppress the imbalanced moment of the engine, but we found new bank angles of the practical engine. In this report, we show the method for calculating the effective cylinder arrangements and the bank angle of a V-10 engine.

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The demand for high quality and high performance of an automobile internal combustion engine is increasing steadily. Thus the shift toward producing multi-cylinder engine and V-type engine has also intensified. In the first report, we have clarified a general analytical method that reduces the exciting moment and determines the suitable bank angle of V-type engine. We have also clarified that the effective cylinder arrangements of a V-type 10-cylinder engine are divided into 24 groups. In this report we calculated numerically the 1st-order exciting moment and obtained the suitable bank angle for each group. We obtained practical bank angles of V-type 10-cylinder engine with small pitching and yawing moment using a balance weight. We also describe in details concrete examples and the evaluation of a V-type 10-cylinder engine.

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When calculating the resonant response of bladed turbine disks, it has proved useful to assume that all blades on a given disk are identical. This leads to the prediction that all blades experience the same amplitude of displacement and stress when excited by forces harmonically related to the rotor speed. However, it has been shown experimentally that significant variations in these ampli-tudes occur for different blades on the same disk. These variations arise due to the effects of mistuning, which refers to small differences in the blade characteristics. In this paper, vibrational characteristics of a bladed disk of mistuned grouped blades is studied using the substructure synthesis method and modal analysis. It is found that a bladed disk system of grouped blades is very sensitive to mistuning, and the fundamental vibrational characteristics of grouped blades with mistuning is shown.

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This paper presents a robust control method for a microvibration control system with elastic vibration of a table. In order to avoid the spillover phenomena, reduced-order mathematical models, which include higher modes, are used in this design technique. The feedback controller is derived by using the generalized model-matching method described in this paper. The system uses a 453-kg, 2.0 x 1.4-meter aluminum table as the vibration isolation object, being supported in 10 places (six vertical and four horizontal) by piezoelectric actuators. Rubber supports are installed between the table and the actuators. In the design technique, the overall system is divided into modal systems with the control system for each being independently designed. Experimental results are also presented.

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We propose a vibration control method for flexible structures using a multi-degree-of-freedom system. We previously proposed the active vibration control of two structures arranged in parallel using two actuators placed between them. In general, a reduced-order model is necessary to design a controller using 3-3 degree-of-freedom parallel structures. Using a root locus plot, we clarify the relationship between weighting parameters and control effect in LQ control theory. To control parallel structures using the 3-3 degree-of-freedom model, 6 sensors are needed in general. We proposed a vibration control method that uses only 4 sensors using suboptimal control theory. By means of simulation and experiment, it is demonstrated that this control method can be used to control vibrations of parallel structures without spillover instability.

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When a magnetic bearing-rotor system is excited by ground motion, the rotor may come into contact with the stator because of its low stiffness and the system may suffer heavy damage. Although magnetic bearings are equipped with touchdown bearings for the emergencies such as earthquakes, it is better to design a controller which can restrain the foundation-excited response of a rotor within the designed gap. In PID control, gains have to be adjusted for many purposes and trade-offs in control performance will occur. Therefore, an acceleration feedforward control method is presented in this paper to reduce the response of the rotor system excited by ground motion without sacrificing other control performances. Applying this acceleration feedforward control to an experi-mental apparatus, the response of a rotor to ground motion is reduced to about half of the response with ordinary PID control. Furthermore, this suppression of the response is carried out with less control current.

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We developed a torque-fluctuation reducer, which can almost completely cancel a screw compressor's torque-fluctuation and reduce its vibration and noise. The device consists of inner and outer rings. Each ring has eight pairs of permanent-magnets arranged in a circle-one S-and-N pole pair for each of the male rotor's lobes. The inner ring is fixed to the male rotor shaft, and the outer ring is fixed to the casing. Turning of the inner ring, produces magnetic forces, which in turn cause sinusoidal torque fluctuations. We tuned the reducer for a 7.5 kW oil-injected air screw compressor. With the best match, the male rotor's rotational vibration decreases to less than 10% of its original. The level of noise due to meshing frequency decreases to 5 dB (A) at 1 m from the front of the compressor package.

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Using an air spring and a subtank, the mechanism of variable spring rate can be realized only by operating an on-off valve located between them. When the valve is opened, static spring rate is determined by the volume of the air spring and the subtank. However, in the dynamic case it is expected that spring rate is harder than static spring because of the conduit influence which ratard the pressure transmission. Hence, it is necessary to clarify the efiect of the conduit on the dynamic spring rate. In this paper, frequency response tests, which indicate dynamic spring rates for cyclic displacement, have been conducted for various arrangements of the conduit. Results in high fre-quency show that the spring rate shifts to value calculated from only air spring volume though in low frequency range static spring rate is obtained. As result, it is found that the air mass in conduit causes this phenomenon and decides the shift frequency. These results can be simulated numerically and can be explained by the proposed model in which the conduit is treated with a lumped model.

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An identification scheme to adaptively identify the time-varying amplitude of principal modal components from the time domain operating deflection shapes (ODS) is studied. The ODS depend on their excitation sources and have fixed quantitative values. Since the mode shapes cannot be used to synthesize the ODS, the actual forcing vector applied to the system usually cannot be identified. Therefore, measurement of the time domain ODS requires a set of vibration responses obtained from a multichannel data acquisition system under actual operating conditions. However, the responses are highly affected by noise. First, we present an identification scheme of the time-varying amplitude of principal modal components based on both principal component analysis and the total least squares method. Then we adapt the scheme for application to time-varying systems, making use of URV decomposition. The resulting scheme can adaptively decompose the deformation of a structure into the underlying superposition of several modes. We demonstrate its performance on artificially generated response data. The results show that this scheme can be used to accurately provide estimate the time-varying amplitude.

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The proposed control method is based on Hirschorn's Algorithm extended with Silverman's structure algorithm, and facilitates easy determination of the control law using the relationship, between the output and the input, which is obtained by differentiating the output. This method is the extension of the linear model matching control system for which the control law was proposed by Wolovich. The proposed control system is applied to a flight control system (for example, pitch angle, vertical velocity and C* control system) and numerical simulations are shown to investigate the feasibility of the proposed approach.

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This paper presents an application of a new concept gain-scheduled H_∞ control which was recently proposed for linear parameter varying(LPV)plants. These plants are a certain class of linear time-varying plants whose state-space matrices are a flixed function of time-varying physical parameters. Rotor-bearing systems with considerable gyroscopic and imbalance effects can be considered LPV plants due to the affine dependence of their state-space plant matrices to rotational speed as a varying parameter. Using a LPV plant model with the linear matrix inequality(LMI)-based approach, the designed H_∞ controller exhibits a continuous gain scheduling with respect to rotational speed measurements and maintains stability and good performance against the parameter uncertainty. In this study, a commercially available and vertically designed active magnetic bearing(AMB)system, which is called a turbomolecular pump, is modeled and controlled using LMI-based gain-scheduled H_∞ control and compared with an actual PID control. The results obtained here are reasonable and encouraging for future studies of gyroscopic AMB systems.

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For positioning control of flexible structures, robustness at the terminal point of positioning is important. In this study we discuss a practical method for positioning control of flexible structures using the nonstationary robust regulator (NRR). In this method, in order to adapt the positioning control to arbitrary distances, the closest trajectory input among the inputs obtained a priori for certain objective distances is used as a feedforward control and the positioning error at the terminal point is compensated by the robust feedback control to which it is smoothly switched. This method is applied to the positioning control of a flexible structure. The usefulness of the method is verified theoretically and experimentally. From a comparison between this method and a two-degree-of-freedom stationary robust servo control method for positioning control of a two-mass-spring system, the advantage of the NRR is verified.

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An optimum design problem of structures, considering control performances, is presented. In this paper, we assume that a structure is subjected to initial loads and timevarying disturbances, and is controlled by an H_∞ controller to suppress the effect of disturbances. The purpose of the design is minimization of an objective function which represents the effect of the initial loads, under a constraint imposed on the weight of the structure. We have already reported a solution to this problem using a state feedback H_∞ controller. However, the state is not always measurable in real structures. For this reason, we adopt an output feedback H_∞ controller in this work. Deterministic initial loads and statistically known initial loads are considered and the objective function for the control system is proposed in the case that the initial loads are known statistically. A numerical example of a 3-D truss structure is presented.

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In this paper we propose a quantitative evaluation method for preliminary layout of electronic systems. Preliminary layout is conventionally determined by a trial and error method based on a rough sketch by a skilled engineer. This study is based on the assumption that the skilled engineer adopts a distance concept between design cases. First, a representational method for evaluation of design cases is demonstrated using similarity on the basis of a pattern attribute vector. The mahalanobis distance between design cases is formulated using this similarity, and a statistical calculation method for the evaluated function, which consists of the mahalanobis distance, is shown. A prototype of a layout design support system was constructed to demonstrate the advantages of this evaluation method. This method is useful because of its short calculation time and the generality of its methodology.

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In order to maintain the safety of steel tubes which have been used externally as structural members in buildings and large scale structures for a long period, the inner walls of the tubes are often investigated by inspectors using industrial endoscopes. In the present study, to reduce the necessity of visual inspection, we have focused on the color of the rust which appears in the corroded wall, and have tried to detect corroded regions using color image processing. Namely, the input RGB color images are transformed to color sensitive space L*a*b*, and three parameters, lightness, chroma, and hue angle are calculated and investigated around the corroded region. Moreover, we have developed this method to facilitate inspection of the video tape of the corroded regions in real time using a commercial high speed image processing board.

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Humans can master the skill of micro manipulation which differs from the simple task of positioning through experience and years of training. Since the human ability is not quantifiable, it is impossible to substitute completely human ability for a robot. However, it is necessary to develop effective and suitable methods that lead to easy execution of micro manipulation in order to reduce exhaustion. Telerobotics and master-slave technology are useful methods for solving this problem. In this study, a new system that combines the master and the slave structurally is proposed. This combined master-slave system is designed as a compact tool which can be manipulated easily by the fingertips. Maneuverability of the master tool is improved by suspending itself electromagnetically. An electromagnetic sucking force is also used as a driving force of the master. In this study, a stabilized control of the electromagnetic suspension system and a bilateral control of the master-slave system are accomplished simultaneously. Furthermore, the validity of the developed master-slave tool is confirmed by control experiments.

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A close-fitting acoustical enclosure effectively reduces machine noise especially at high fre-quencies. At low frequencies, however, the reduction performance is degraded because of acoustical resonances of the air space inside the enclosure and of mechanical connections between the machine and the enclosure plate. To solve this problem, a new concept of active control system is developed. Using a piezoceramic actuator, the control forces are inputted directly to the enclosure plate to minimize the vibration of the plate. The control action improves the insertion loss of the enclosure plate particularly at some low modal frequencies of enclosure plate. Using this new control scheme, the enclosure plate can reduce radiated noise by more than 10 dB at almost all frequencies.

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In this paper, we discuss the development of a new noncontact method for determining cylinder configurations using sound phase delay. In order to improve the accuracy of the measurements, the effect of the cavity in which the cylinder is placed has been studied. When the cylinder is placed near a side wall of the cavity, the phase delay angle increases, particularly for cylinders with odd periodic deflection. Thus, by varying the gap between the cylinder and the side wall, it is possible to determine the cylinder configuration even if the deflections are small. We propose a new method, in which the influence of noise is avoided by measuring the noise interference using a pair of microphones in the cavity.

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A radio frequency tag device is comprised of an inductor, a resistor and a capacitor. These devices are widely used as a resonant markers for detecting shoplifting and in other applications. They are small and light and so may be applicable for use in position sensing, vehicle navigation, or product verification. When the excitation frequency of an electromagnetic wave radiating from an antenna traverses resonances, an electrical ring-down may be generated in the detected circuit, so an RF tag device can be easily detected and its resonant frequency can be easily determined. In this paper I have examined the performance of a detection system consisting of RF tag devices and an antenna. In particular, I have measured and calculated resonant frequencies in the cases of two tag devices located with slight horizontal or vertical displacement with respect to each other. Experi-mental and theoretical examinations reveal that changes of the resonant frequency can be described in terms of mutual inductance between the two tag devices and that the surveillance range depends on the mutual inductance between an RF tag device and an antenna. These results prove that an electric system composed of RF tag devices and a detection antenna can be useful for positioning in the fields of flexible manufacturing systems.

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Much researches on the aspect graph has been done since 1979 when Koenderink and van Doom first described it in their paper. The main problems of image recognition using the aspect graph are the representation method of aspect and the matching elements between the aspect graph and the image. In this paper, we propose a new solid model, named the Modified coded boundary representa-tion (MCBR) method and the image matching method for model-based recognition using the MCBR method. MCBR method is similar to B-reps, which is well known as a solid model used in the many 3-D CAD systems. However, B-reps has absolute coordinates, the MCBR method does not have it, but has relative coordinates. Because of this feature, it is easy to extract the relationships between the object elements, for examples faces, edges and vertexes. This proposed method is used as a 2-D model to represent the aspect graphs which made from the 3-D models and the objects extracted from the images. And the system uses the relationships between the positions of faces as a matching index. This present method is useful without change of the relationships between faces of the object by changing the gazing line of camera.

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Two-beam interferometers and differential interferometers are used for optical computed tomo-graphy (CT) to reconstruct refractive-index distributions. In this paper, the two types of interfer-ometers have been compared with respect to the effects of random noise in the projection data and the spatial resolutions of the reconstructed index distributions. The reconstructions are assumed to be performed using the filtered back projection method. The noise effects were evaluated using the random variable theory and numerical simulations. The result shows that when the amount of shear for the transmitted light in the differential interferometer is larger than the sampling distance of the projected light distribution, the noise level in the index distribution is smaller than that of the two-beam type. However, the large amount of shear restricts the spatial resolution of the distribution.

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A newly developed linear electrostatic microactuator is described. It produces vibration and is fabricated by a bulk silicon micromachining process. The moving part (slider) is sandwiched between two glass plates whose surfaces have many electrodes (fixed electrodes) . The slider is attached to these fixed electrodes by turns and actuates linearly on a macroscopic level. This mechanism is advantageous with regard to frictional influence and can achieve a large stroke. However, several difficulties have been identified regarding an attachment/detachment mechanism. The accumulation of charge caused by contact between the stators and slider is one of the most difficult problems. Our actuator incorporates micro pyramid stoppers, which prevent the accumula-tion of charge, on both surfaces of the moving part. The prototype has a casing size of 8 x 8 x 1.2 mm and achieves a 2 mm range of movement. The minimum driving voltage is 80 V and the maximum velocity is 2.0 mm/s. The behavior of the slider is not simple and further analysis is essential in order to improve positional accuracy, increase output force, and decrease driving voltage.

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A damping design is developed to achieve heavy damping of an objective-lens actuator with dual-parallel link suspensions for CD and CD-ROM drives. The actuator is supported by four suspensions of straight bars for reducing directionally-coupled vibration. An objective value analysis is conducted to determine the desirable damping ratio at the lowest mode as well as at higher modes for high-speed access and stability of the servo system. To construct an actuator of the damping terget, we developed a damping box with gel. This system ensures heavy damping at the lowest mode ζ0 of 0.13 and at the pitching mode ζpit, of O.1. To make the damping coefficient of pitching mode, upper suspensions have slightly elastic bending. The heavy damping of the pitching mode in the frequency band of around 1 kHz can allow the assembly error of normalized center of gravity by 10%. We also developed a heavy-damping actuator with a good frequency response and with no phase disturbance.

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We propose a method of minimum-energy collision-free trajectory planning for a redundant manipulator utilizing the B-spline function and a mathematical programming method. We use the B-spline function for determining the approximate trajectory of a joint angle of each manipulator and the expressions of the outlines of obstacles. We maximize a performance index in order to choose the most dexterous posture of the manipulators. The approximate trajectory is then improved by minimizing another performance index expressing driving energy in consideration of the dynamics of redundant manipulator. According to the simultaneous consideration of driving energy, collision-free and dexterity, it is shown that the proposed method is efficient and practical for the trajectory planning.

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In this paper a bilateral master-slave method is proposed which enables a slave manipulator to contact maintain with a rigid environment stably. In the conventional force -reflecting position control method, control loops on the master and slave sides are connected in series, which causes unstable motion when the slave manipulator comes into contact with rigid objects. The new method is much more stable, since the phase lag of the control loop is smaller due to the symmetric structure of the system. Our system consists of two parallel manipulators. Advantages of the parallel manipulator such as simple inverse kinematics, a light movable body, and stiffness, also improve the system stability. The stability of the proposed method is evaluated by the Hurwitz method and compared with that of a conventional controller. Metal-to-metal contact and peg-in-hole experi-ments demonstrate the practical and wide applicability of the method.

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In this paper, we propose a new learning method for obtaining a behavior controller which consists of several sub-controllers to indicate the desired trajectories for actuators. This algorithm selects a sub-controller which will be tuned in the next trial, by evaluating each sub-controller using multiple regression analysis based on previously obtained evaluation values. This can reduce the learning times by avoiding the necessity of trying to tune good controllers. The proposed method is applied to the problem of selecting and tuning sub-controllers at a middle layer in a behavior-based control system in order to compensate imperfect initial controllers. The behavior-based control system is applied to the problem of controlling a seven-link brachiation robot, which moves dynami-cally from branch to branch like a gibbon swinging its body in a pendulum fashion.

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Hybrid position/force control is one of the most effective methods to control the position and force of robot manipulators accurately. In most research into the hybrid position/force control it is assumed that the property and shape of the environment is previously known. In this paper, we propose a fuzzy environment evaluator and the concept of a fuzzy vector which can be used to make the fuzzy-neuro position/force controller intelligent. The intelligent hybrid position/force controller can be applied in an environment whose property and shape are unknown. At first, the intelligent controller searches the force control direction using a fuzzy vector as it applies force to the environ-ment. The controller is able to deal with noisy signal from the force sensor more efficiently using the fuzzy vector. Then the intelligent controller applies the force effectively to the environment whose properties are unknown using the fuzzy environment estimator. The effectiveness of the proposed control method is evaluated by computer simulations.

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When a grasped object is in contact with the external environment, it is necessary to perform assembly tasks to identify contact conditions. In this paper a new algorithm for identifying unknown parameters using the data collected by a 6-axis force sensor is proposed. It explicitly expresses the contact conditions. We subdivide the constraint conditions and reduce the number of unknown parameters. The problems of identifying the contact conditions are nonlinear, but they can be transformed to linear problems. The necessary number of active sensing motions is clarified for identification of the unknown parameters. We establish an efficient algorithm for identification of the contact conditions.

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In this paper, a new mechanical model for studying the shock-absorption mechanism of lower limbs is proposed. In this model the mass of the human leg is taken into consideration and the plantar elasticity is regarded as a nonlinear spring. Force and acceleration when a human jumps down from a height are measured using a force plate and an accelerometer. Through comparison of the theoretical and experimental results, this new mechanical model is confirmed to be appropriate for numerical simulation of the force on the toe and the acceleration on the waist during vertical jumping down. Furthermore, the effect of the legs' inertia upon the force on the toe and the acceleration on the waist is investigated for the cases of consideration of and neglecting the inertia of the legs. It is found that in the case of consideration of the mass of the legs, the model is suitable for quantitative estimation of the force on the toe and acceleration on the waist ; whereas in the csse of neglecting the mass of the legs, the model is suitable for qualitative study of the shock absorbing mechanism.

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It has been generally accepted that biomechanical analysis is an important factor in the preven-tion of sports injuries and improvement of sports skill. In all sports in which the players use rackets, the first problem all prospective players must address is the manner in which the racket is held. Tennis players continually seek added power, control and a reduction in the unpleasant vibrations produced by offcenter impacts. It is belicved that a grip-firmness on the racket at impact is one of the most important factors in determining the effectiveness of the return and that ball control of skilled players is significantly dependent on the level of grip pressure. In this study, a contact pressure measurement system using electric conductive rubber sensors was developed to study the manner of how a player can get to the ball as quickly as possible while maintaining an optimal level of grip pressure to give control and power for the stroke. The direct linear transformation technique was also applied to the motion analysis of the upper extremity during the forehand stroke. It was found that skilled players hold the racket with three fingers and clasp it gently in the palm of their hand during strokes.

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In order to evaluate the wear properties of CVD TiN coatings, its wear process was observed in -situ during sliding against a diamond pin in a SEM VTR Tribosystem. Wear depth and a cross-sectional area of the wear grooves were also measured using this system after in-situ observation, and specific wear amount was calculated. When coating delamination occurs, specific wear amount increases with the number of friction cycles. On the other hand, without coating delamination, specific wear amount decreases with increasing number of friction cycles. The relationship between micro-scopic wear properties and wear modes was investigated. The order of the specific wear amount for each wear mode was obtained as follows : specific wear amount μ's≤ 1 × 10^-5 mm³/Nm for ploughing, 1 × 10^-5 mm³/Nm≤ μ's ≤ 1 × 10^-3 mm³/Nm for powder formation, 1 × 10^-4 mm³/Nm≤ μ's ≤ 1 × 10^-3 mm³/Nm for flake formation and 1 × 10^-3 mm³/Nm≤ μ's for coating delamination. From these relationships, it was concluded that the observation of wear modes with a SEM VTR Trybosystem can be used to evaluate wear properties.

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To solve the tribological problems of existing knee prostheses, the application of new materials and geometric designs for improvement of lubricating film formation are necessary. For this purpose, the applications of artificial articular cartilage and duo-radius knee prostheses are proposed. The tribological behavior of knee prostheses with a silicone rubber layer was examined for different viscosity and motion conditions. Duo-radius femoral components were tested for three tibial components with silicone rubber. The tribological severity was evaluated in terms of frictional torque and degree of separation using the electric resistance method in a knee joint simulator. As a result, the importance of swing phase of walking pattern was shown and duo-radius knee prosth-eses showed better frictional behavior than cylindrical one for low-viscosity lubricant.

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The formulation of a general numerical method for fluid film lubrication of irregular bearing shapes in the high bearing number region is presented. We expand the formulation of the divergence formulation method to the triangular element used in the finite element method. Here, the pressure function is not an element-interpolation function but a node-interpolation function. The mass flux is evaluated along the sides of the triangular elements, so that several calculation schemes, which are commonly used in the divergence formulation method on structured grid systems, can be introduced for unstructured grid systems easily. The formulation is suitable not only for acute-angled triangu-lar elements but also for obtuse-angled triangular elements. Numerical examples demonstrate the applicability and accuracy of the method.

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In this paper we describe the static characteristics of an actively controlled hydrostatic thrust bearing using a floating disk with a voice coil motor (VCM) . This new type of restrictor can control the mass flow rate of operating fluid using both the balance of the fluid forces exerted on the disk and the electromagnetic force of VCM. The static characteristics of a hydrostatic thrust bearing with the proposed restrictor are investigated theoretically and experimentally. It is shown that the proposed bearing can control bearing clearance with nanometer order accuracy by controlling an input current of VCM and have an infinite static bearing stiffiness over a very wide range of imposed load.

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One of the design method for closing the end of a pressure cylinder is to screw down a screw plug on the threaded end of the cylinder. In the design of a pressure cylinder, it is very important to investigate stress and strain distribution in the threaded end of the cylinder which is subjected to internal pressure in the vessel. In this study, in order to clarify the behaviour of the threaded end of a pressure cylinder, the authors present a simple strength analysis method using the finite element method and the results calculated using it. The method proposed here makes it possible to analyze easily the stress and strain distributions in the threaded end of the pressure cylinder and to investi-gate speedily the effect of specifications such as cylinder thickness, plug length, screw thread size and initial clamping force.

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This paper presents a study on the root stresses of thin-rimmed spur internal gears with asymmetric web arrangements for planetary gear units of the caterpillar drive of construction machinery and automatic transmissions of automobiles. Tooth deflections of thin-rimmed spur internal gears with asymmetric web arrangements due to a concentrated load in the normal direction of the tooth surface were calculated by the three-dimensional finite element method (3D-FEM). On the basis of the calculated results, an approximate equation for the influence function of tooth deflection was derived. The load sharing factor and the load distributions on contact lines were calculated using the approximate equation and Kubo and Umezawa's method. The root stresses of the thin-rimmed spur internal gear in mesh were calculated by 3D-FEM, and the maximum root stress and its position were examined. These results were also compared with those of the case of thick-rimmed or solid gears. Furthermore, a simplified calculation method of the load distribution on the contact line and the root stress of the thin-rimmed spur internal gear in mesh by 3D-FEM, considering the mating planet gear as a rigid body, was determined.

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Recently, not only high strength, but also high rigidity have been demanded of plastic gears. At present, a high-rigidity, composite polyacetal gear filled with a talc has been developed. However, filling with inorganic talc results in increased rigidity and a decreased sliding potential compared to polyacetal. Therefore, the applicability of talc to gear materials has been questionable. This study was carried out to elucidate the above phenomenon by manufacturing two kinds of composite polyacetal gears changing the filling amount of talc and by comparing the characteristics of these gears during operation. Furthermore, these characteristics were compared with those of other polyacetal gears which are known to be suitable for many applications, and the potential for practical use of this composite polyacetal gear was investigated.

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Stretch draw forming is used to fabricate electro chromium coated steel (ECCS) sheet which is thermally laminated with clear biaxially oriented polyethylene terephthalate (PET) copolymer film on the inside and PET copolymer film containing TiO2 on the outside. The forming involves drawing and bending of the cup wall with a die radius under high backward tension which is caused by flange shrinkage, friction between material and blank holder, and bending force. Our purpose is to clarify the effects of surface conditions on various conditions for stretch draw forming. From the results, surface roughness effect on various forming conditions is found to be strong at all points of a redrawn cup wall, in comparison to conventional redraw forming, and degree of roughness is distinguished in the height direction. Moreover, surface roughness curved line in the circumferential direction showed roughness with 0.4-0.5 mm cycle. Surface roughness of PET laminated sheet is rougher than that of an unlaminated sheet. Surface roughness effect on forming conditions depends on the die radius(Rd),tool temperature(Tt)and thickness strain( εt).

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A steel sheet for stretch draw forming uses with an ultra thin gauge for high-strength, temper-grade DR9 which usually has larger planar anisotropy. It is the purpose of this paper to clarify the effects of the thickness accuracy of walls obtained by stretch draw forming on the anisotropy of mechanical properties of a steel sheet. This is achieved by the controlling the coiling temperature during the hot rolling process. Experimental results indicate that sufficiently good earing rate property of the steel is obtained by controlling the coiling temperature to be high. The wall thickness of a cup redrawn by the stretch draw method was uniform and thin at center portion. On the other hand, the amount of deviation of the circumferential thickness on redrawn cup wall is increased at the upper portion, and this amount of deviation is related to the anisotropy of steel sheet.

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Precise slot grinding experiments are conducted on Mn-Zn ferrite using three diamond wheels with # 1 000, # 2 000 and # 3 000 abrasive grain respectively. By releasing the grinding wheel quickly from the contact zone during the grinding operation, the changes of kerf width and edge-chipping size are measured. Initial chipping size decreases with decreasing size of abrasive grain used with the grinding wheel. The rate of decrease in chipping size after initial chipping by increasing kerf width is higher when a wheel with finer abrasive grains is used. The wheel with finer abrasive grains has the function to restrain the size of the edge-chipping.

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Conventional mold design generally depends on the experience of the designer, however design principles have not been substantiated technically. Therefore, in the mold-size determining stage which is the first step in the design, the mold-size tends to be increased with the intent of achieving sufficient structural stiffness. However, increasing in the mold-size unnecessarily brings about increasing in cost, and requires a larger injection machine. In order to solve these problems and to develop a new mold structure, structural analysis of mold using nonlinear FEM analysis has been carried out in this study. Several kinds of mold structures which consist of those designed by conventional method, newly designed in parting surface, and increased in size, have been analyzed and compared as regards deformation of the parting surface, because an excessive deformation in the molding process will cause a molding flash at the edge of parting surface. The following are the results of structural analysis. ( 1 ) An inclined parting surface is the most effective to reduce a deformation at the edge of parting surface. ( 2 ) Mold structure in which the moving mold half is thickened in the clamping direction is also effective, but the mold clamping stroke will be limited.

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When a closed loop mechanism with one degree of freedom is assembled from its component links, several composition loops exist such that the functional relationships between the input and output variables differ. The parts of the functional relationship divided by the limit positions of the driving link, which are called branches, correspond to the composition loops of the mechanism. We derive the conditional equation of the limit positions of the RSCR spatial four-link mechanism and establish an identification algorithm of the composition loops. We show that the functional relation-ship between the input and output angles is classified into more than sixteen kinds.

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