There are many structural vibration problems which include fluid motion; one example is that of an oil-filled power transformer tank. In fluid vibration analysis, the wave equation is commonly solved using the velocity potentials or pressures as unknown variables in FEM, FDM and BEM. On the other hand, for structural vibration analysis, displacements are generally used as unknown variables. However, it is difficult to solve problems involving vibrations of fluid and structure simultaneously by taking into account fluid-structure interactions, except by using added masses instead of fluid, or Herrmann's special variational principle. These approaches include special and complex techniques which are unfamiliar to most engineers. In this paper, a new vibration calculation method which can treat fluid and structure simultaneously is proposed; it uses an FEM displacement method which is familiar to most engineers. When the displacement method is applied to two-or three-dimensional fluid vibrations, spurious vibration modes caused by excessive degrees of freedom are observed. These modes are not only bothersome, but also hinder analysis accuracy. In a previous paper, a rejection technique, in which natural frequencies of spurious modes are made to be 0 Hz, was developed. But, matrix size is unchanged, because spurious modes are still contained in the matrix. As a result, a large memory and long calculation time are needed to solve the matrix. In this paper, an extraction method is developed for them and the matrix size is reduced. Then, the new calculation method is applied to solve coupled vibrations of fluid and structure. The method is judged to be applicable to actual vibration analysis.

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When an acoustic field in an enclosed space is controlled using the structural vibration control by the piezoelectric actuator, electric system, structural system and acoustic system are influenced each other. Thus this system must be considered as electric-structural-acoustic coupled system. In this paper, the analysis in the required frequency band of electric-structural acoustic coupled system has been carried out. In this analysis, the structural vibration is approximated by the superposition of the electric-structural coupled vibration modes which are included in the required frequency band, and the truncated frequency band are compensated by the residual terms. This truncation method is the application of the authers' previous method. As a numerical example, a flexible rectangular prism model is taken up and the vibration of structure, the voltage of piezoelectric actuator and the sound pressure in the model are calculated using the proposed method. It is shown that the analysis of coupled system has reached the accurate results comparing with the one of nucoupled system, the calculated results using the proposed method agree with the exact ones which are obtained by using the full frequency band, and calculation time is saved.

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This paper investigates the pressure response of fluid in small-bore piping under seismic conditions. We conducted experiments to determine the influence of flexible piping on the pressure response. Our test models consisted of a single pipe and a tank, both containing fluid (water). One model had a pipe that was entirely rigid, while the other model had a pipe with one flexible section. The natural frequency of the partially flexible pipe, when empty, was close to that of the fluid contained in the entirely rigid pipe. The pressure was raised using either a shaking table or a pulsation generator, and either artificial earthquakes or sinusoidal waves as input. The results showed that in some cases the pressure responses of the flexible-piping model were larger than those of the all-rigid piping model. Numerical analysis using the finite element method agreed well with the experimental results.

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To investigate the influence of crankshaft torsional and bending dampers on the crankshaft vibrations, we first designed three kinds of dampers, each for the reduction of the crankshaft vibration, in the torsional, axial, and radial directions. Next, we developed two kinds of dampers for the simultaneous reduction in the torsional and axial modes, and in the torsional and radial direction modes. We mesured the three dimensional vibrations for the crankshaft, under engine operating conditions with a four-cylinder in-line diesel engine. The effectiveness of the axial dampers and the bending dampers (i.e. radial dampers) was investigated carefully. The coupling behavior of the torsional, axial, and bending vibrations was also investigated for the dampers and the crankshaft. In the series of experiments, we found that, in some cases, only by attaching one simple torsional damper, significant reduction of the axial and bending vibrations could be obtained together with the reduction of torsional vibrations.

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It is known that self-excited vibration in cylindrical grinding occurs if the work speed is high. In this paper, the effect of the work speed on the occurrence of self-excited vibration is investigated analytically and numerically. In analytical study, Nyquist's stability criterion is used. The results are as follows: If the work speed is low, self-excited vibration does not occur. On the other hand, if the work speed is high, self-excited vibration always occurs. It is also shown numerically that the phase of the work displacement is delayed in phase by ;π/2 to that of previous grinding. The theoretical result about the critical speed of the work is in good agreement with the experimental one.

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This paper deals with a bending and torsional vibration control method for flexible structures arranged in parallel, and a method for making a multi degree-of-freedom model by using uncontrollability and unobservability. According to these methods, it is easy to make reduced-order-models of flexible structures, and a pair of flexible structure are controlled actively by controlling each other by means of actuators placed between them. Therefore it is able to obtain enough control force under the low frequency, and control vibration of the super tall building by the strong wind. In this paper, two real structures are reduced to 4DOF models respectively including bending and torsional modes for controlling the bending and torsional vibration. These models are evaluated by means of comparing the simulated frequency response with the measured one using real structures. The effectiveness of these methods is demonstrated by the vibration control using LQ and semioptimal control theory theoretically and experimentally.

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Rubber belt systems have recently been applied to many kinds of industrial machinery, for example, fan belt of automobile, driving system of automated teller machine and so on. However, vibration of belt systems have been an unacceptable problem accompanied by the increase of the operational speed. In this paper, an axially moving belt is investigated experimentally with respect to vibration characteristics and vibration control using parametric excitation. As the result, the vibration source is estimated as the eccentricity of pulleys. The parametric excitation control has significant effects to damp the vibration. This paper reports the possibility of vibration control about axially moving belt systems by producing torque fluctuation.

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In the 1st report, we experimentally indicated the possibility of vibration control in terms of axially moving belt systems by producing torque fluctuation that causes parametric excitation. In order to clear generalities concerning vibration occurrence and vibration control of the belt system, the corresponding theoretical analysis is required. In this paper, we suggest forced vibration generated the pulley unbalance and vibration control owing to parametric excitation induced by the fluctuation of the belt speed. The belt system is analyzed by quasi-modal model transformed by inner system mode and deflection mode. As the result, quasi-modal model was applicable for forced vibration acting on a nodal point. The obtained results with respect to the forced vibration and the vibration control agree well with experimental data.

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This paper deals with a robust vibration control problem of a flexible structure with parameter variations. We use the six-storied structure as controlled object, with a pair of hybrid mass dampers. We use a descriptor form to describe parameter perturbations independently and apply μ-synthesis to design of the feedback controller. We show the performance of the μ-synthesis controller with descriptor form compared with that of the conventional μ-synthsis. This research work has proved that μ-synthesis with descriptor form is superior to the conventional μ-synthesis for active vibration control with mass dampers.

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The purpose of this paper is to propose a novel active control strategy to reduce noise and vibration. Much work has been done on the active control of noise and vibration. However, one of the limitations of the technique is that controllers tend to be application-specific. Careful identification of the system to be controlled and reference signals are essential and that often proves difficult to arrange. Hence a versatile control strategy, which is non-application-specific, has been sought in this research. The power absorbed by an active vibration controller was taken as a cost function to be maximised. Theoretical investigations into simple string models have been conducted with this idea, suggesting that power absorption maximisation within the time taken for a wave emitted by the controller to come back to the control point, i.e. within a sing around time, is promising. A maximum power absorber based on this strategy was developed for experimental purposes, and applied to string and plate models for its validation study. These experiments confirmed that the absorber attenuates vibration effectively, supporting the good prospect of this control strategy.

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Aseismatic effects of perlite, which is used as thermal insulator in a cold box of an air separation plant, are investigated. A hysteresis loop and packing density dependence of the perlite are observed in a cyclic compressive loading test using vertical piston/cylinder apparatus. The increase in the perlite stiffness with loading cycles is also observed in a test using horizontal piston/cylinder apparatus. These phenomena are mainly explained from the fact that the perlite drops into the clearance between the piston and the compressed perlite during unloading. These deformation characteristics of perlite are modeled by a piecewise linear spring. Aseismatic effects of perlite to the air separation plant are estimated by implementing the piecewise linear spring model into a commercial finite element code.

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This paper presents a vibration isolation mechanism without resonance. The mechanism is consisting of a linear sliders, ball screw, servo-motor and a table in which there is no spring element, so the table behaves like a rigid body. In the mechanism, the servo-motor rotates the ball screw with the same displacement as the base displacement in the opposite direction. Hence the disturbance is canceled. A well known relative displacement feedback control method was first discussed, and it was shown that the method was insufficient for isolating vibrations, then a method of disturbance cancellation was presented. To validate the present mechanism and the control method, experimental tests were carried out for a model of the mechanism.

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The wavelet transform is used to represent all possible types of transients in vibration signals generated by faults in a rotational machine. First, the selection of the wavelet parameters is discussed, and it is shown that the transform provides a highly sensitive tool for fault diagnosis when the most suitable parameter sets are selected. Second, a numerically generated fault signal is used to calculate the time-frequency distribution of the wavelets. Features contained in the time-frequency distribution are classified according to fault type. From this classification, by extracting the features of actual abnormal vibration signals, the cause of the fault can be deduced. The fault diagnosis method is implemented in a fault diagnosis system for pump vibration sounds. The results suggest the developed method provides a powerful tool for early detection of contact between the rotor and the stationary units.

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When an object in motion crashes against something, a shock is generated. An equipment to relieve this shock is a shock absorber. In this paper, a shock absorber is made on an experimental basis by using piezoelectric actuators and its damping characteristics can be controlled activity. Piezoelectric actuators have a fast response and a large generation force and these characteristics are suitable for the shock absorber. In this shock absorber, an displacement of piezoelectric actuators is enlarged by connecting in series and an area of orifice is controllable widely by improving the shape of its valve. Fuzzy control theory is applied to the shock absorber and a resisting force is controlled in order that nearly ideal shock absorbing characteristics are realized for various crashes compared.

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Uplifting of legs of container cranes is often observed in strong earthquakes, and assumed to be one of the main causes of their structural damage. However, strong nonlinearity of such behavior has prevented us from taking it into consideration in the design of container cranes. Therefore, in order to develop a method to simulate the behavior, we carried out finite element analyses and excitation tests on a 1/25 scale model of a container crane. Comparing those results, we proved that nonlinear finite element method with gap elements is an effective method to simulate the uplifting behavior. Furthermore, we carried out finite element analyses on an actual container crane. Those result showed that the deformation of legs due to uplifting is a cause of structural damage, as actually seen in the Hyogoken Nanbu Earthquake.

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The purpose of this paper is to present a method for establishing an autonomous mobile crane system which takes into account obstacle recognition and path planning by off-line, and suppression of sway for the transfer object. The system has three different parts: a visual system, a planning system and a control system. In the visual system, an environment map is generated by the Slid-Ray Projection method using a CCD image sensor and a laser-line marker. In the planning system, the obtained environment map is used to derive an optimal transfer path such as a minimum distance path or a minimum energy cost path from the start to the goal position. The path is generated through the use of a path auto generation algorithm using a Branch and Bound method. In the control system, an optimal regulator system is used to achieve position control and the suppression of sway for the transfer object. Finally, the validity of the proposed method is confirmed by simulations and experiments.

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In the present study, we described a method for improving the influence of flux creep on the levitation property in HTSC magnetic bearing. The scenario of this method is to induce reverse flow shielding currents in two regions of the HTSC bulks through varying the distance between the permanent magnets and the HTSC bulks. The magnetic forces produced in both these regions also take opposite directions. In this case, the difference between the two forces will give the net magnetic force in the HTSC magnetic bearing. Obviously, the actual force decay observed in the HTSC magnetic bearing is determined by the difference between the force decay in these two regions, therefore being resultantly reduced. This phenomenon can be called as 'Hysteresis Hardening Effect'. For the evaluation of the mentioned approach, numerical simulations were carried out with the configuration of a practical radial-type HTSC magnetic bearing. The numerical results show the validity of the present method. Also some discussions were added with concerning of its practical application.

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The single-phase natural circulation in a single loop system had been studied by many researchers. In a multiple loop system, the characteristics of natural circulation was more complicated because of the interaction between the loops. In this study, the effects of the multiple loop on the natural circulation instability were investigated experimentally. As the simple multiple loop system, the troidal loop with insulated connecting tube between both sides (θ-loop) was evaluated. The variation of flow regime in θ-loop was almost the same with that in single loop. However the chaotic condition in inclined θ-loop was narrower than that of inclined single loop. The flow and the pressure transfer in the connecting tube played an important role in the chaotic condition in θ-loop.

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A static analysis of deformable object grasping based on bounded force closure is presented. First, we introduce a new concept of bounded force closure, which is an extension of force closure condition. Secondly, we investigate the necessary conditions for the bounded force closure in order to derive the properties of bounded force closure grasping. Thirdly, the deformation of rod-like objects is formulated. Then, we propose a procedure to evaluate the stability of deformable object grasping. Finally, some numerical examples are shown in order to demonstrate the effectiveness of our proposed method.

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We have proposed a new optimum trajectory planning method for a system with nonholonomic constraints due to passive joints based on a function approximation method. The trajectory is approximated by a linear combination of Hermite functions and Fourier series. The combination variables are solved by a nonlinear programming method that considers the constraints in the same function space as that of the trajectory. We have examined the validity and features of this method by applying it to the optimum trajectory planning of a steady giant swing motion. It is found that this method has efficient convergence characteristics in regards to iteration calculation and can provide accurate solutions depending on the order number of the approximating functions. Optimum giant swings with no input torque can be obtained for various motion periods.

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A low-cost digital control system is developed for self-sensing magnetic suspension using hysteresis amplifiers. A single-quadrant hysteresis amplifier is designed and manufactured for experimental study. Since the switching rate of the hysteresis amplifier is sensitive to the load impedance, the gap between the electromagnet and the suspended object is estimated from the switching signal. In the developed system, the frequency of the switching signal of the amplifier is converted to a digital form by counting by a counter circuit. The converted signal is inputted to a computer calculating control input for stabilization. The developed digitally controlled magnetic suspension system succeeds in actual self sensing operation.

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A simple and practical method to control the right and left distribution control of braking forces and the four-wheel-steering cooperatively is proposed to improve the steering response and stability of automobiles. Our theory of four-wheel-steering is composed of the feedforward control function on steering angle and the feedback control function through the difference of actual and target yaw rates. Also, direct yaw moment which uses yaw rate feedback control is configured to augment control of four-wheel-steering. According to our analysis and computer simulation, it can be confirmed that when the vehicle applied this control system an improvement of the maneuverability and stability on cornering behaviours with braking was realized. In addition, we investigate that this system makes it possible to achieve good control effects on low frictional roads.

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An experimental approach is presented for getting of accurate frequency response function. Automatic impact hammer which is fixed in position greatly decreases the noise which is added in input force. Incidental errors are decreased. And, examples of systematic error which can not be removed by statistical method are mentioned here and improved.

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In the stereo vision, to estimate a distance more precisely, a wide disparity range and a high resolution are required. They increases the number of the false correspondence and makes the correspondence difficult. That is, trade-off problem occurs between the disparity range and the resolution. Motion stereo vision was proposed as one way which deals with the trade-off problem. In the motion stereovision, precise disparity can be get by controll of coarse-to-fine from short base line to long base line. However, in the motion stereo vision, when there are mistakes in an any matching result on short base line, false matching occurred because mistakes. To solve the problem, in this paper, it is examining about stereo matching with used motion trinocular stereo vision.

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This paper presents a new method for evaluation of microbial flocs coagulation based on the fractal dimension and image processing. Microorganisms are used widely in sewage disposal plants and wastewater treatment facilities. Plant operators evaluate the state of coagulation from their experience on the basis of complicated shapes observed in the coagulation process. However, it is difficult to recognize and evaluate the shapes of the coagulation quantitatively. In order to evaluate the shapes, we employ a technique based on the fractal dimension which has been applied in the analysis of irregular and complex shapes. We captured the image of coagulation with a CCD camera and measured the fractal dimension of the shapes in the image. The standard deviation of the fractal dimention was then analyzed. The result shows that the fractal dimension can quantitatively express the state of the coagulation and that the coagulation process can be evaluated by the standard deviation.

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A novel ultrasonic inspection method is described. The propagation characteristic of an ultrasonic echo changes when the echo passes along the flaw surface. This behavior is investigated by using ultrasonic longitudinal wave and applying the time-frequency analysis to bottom echo of a slit specimen. From the experimental results, it is found that both arrival time and phase of the echo vary with its frequency. This method is applied to estimate the slit depths of 2∼10 mm, by using an immerison technique with focusing probe. The results demonstrate good linear relations between slit depth and both phase and arrival time difference. Hence the methodology gives the new way of inspection. Unlike the conventional pulse echo method, this method utilizes the bottom echo with high intensity instead of the flaw echo. Therefore, this method can be effective as an ultrasonic testing for high attenuation materials and near surface flaws.

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Modal domain distributed fiber optic sensors by using a birefringent single mode fiber can be applied for measurement of mode coupling distribution along a fiber attached to a structure. Some fundamental experiments were conducted to understand relations between the mode coupling and the external force. The relations were derived theoretically by using a coupled mode equation. Experiments were conducted to measure the mode couplings of a coated or an uncoated fiber subjected to a transverse load at one point. Experimental results showed relation between a mode coupling and an external load was almost linear on a logarithmic graph. It was found that an uncoated fiber measured load more quantitatively than a coated fiber. A fiber optic load sensor module for a serial multiplexed sensor system was developed for future application of the present study. This technique can be combined with the p-OCDR (phase-modulating Optical Coherence Domain Refiectometry) technique developed by K. Hotate et al. to quantify the applied loads along a fiber on structures.

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This paper is concerned with the development of a palpation sensor for detecting the prostatic cancer and hypertrophy. The sensor is a layered medium with two polyvinylidene fluoride (PVDF) films embedded in the matrix rubber block. The temporal mean values, I₁ and I₂, of absolute voltage signals from the polymer films are calculated and their ratio I₁/I₂ is used as the sensor output. First, the fundamental characteristics of sensor are examined on a rectangular sensor with a plane surface. Then, the surface geometry of sensor is designed so that the sensor output clearly extracts the features on the stiffness of the materials. Finally, a compact cylindrical sensor which is inset in the doctor's forefinger is presented and its characteristics as a palpation sensor are studied experimentally. Some representative clinical data on the hardened and normal prostate glands are also presented.

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The working principle and characteristics of a new sound isolation panel, containing ventilation holes, was described in the first report. The panel provides a considerable sound isolation effect in the required frequency band by controlling the acoustic anti-resonance frequency of the sound field inside the panel. However, when the panel is used close to a sound source, a standing wave is generated between it and the sound source. As a result, the sound isolation effect changes due to the coupling of the sound fields inside and outside the panel. This paper describes a way to locate the panel taking this phenomenon into account.

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When the grasped object is in contact with external environment, it is necessary to perform the assembly tasks with identification of contact conditions. In the previous paper, we proposed an algorithm for the identification by using pure data. This paper treats the case when the data are contaminated with noise. We provide mutual relationships among criteria, and clarify properties of the criteria. We establish an algorithm for the identification.

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This paper presents a method for model based bilateral control of master-slave teleoperation with time delay between master and slave arms, where the system supports cooperative action between manual and automatic modes. In the proposed system, a real time simulator model of the slave arm and a graphic display, visualizing the real and simulated motions of the slave arm, are provided to assist the operator. Based on signals from the simulator model, human operators can manipulate the master arm to move the slave arm without confusion of time delay. As long as a priori information in the computer is accurate for recognizing the working environment, the computer operates master-slave arm by using a priori knowledge. When it is necessary for human operators to adjust the motion of the slave arm, human operators can intervene in the computer operation to reduce the speed of the slave arm and change the course of the motion by moving the master arm and grasping the grid of the master arm. In this method, the fuzzy rules are applied to determine the manipulated force given to the bilateral control system so that the skilled technique of a human operator can be incorporated into the computer operation. In accordance with this manipulated force, master and slave arms are controlled by sliding mode control method respectively. Through some actual trials in a one-degree of freedom arm, this proposed method is proven to be practical in the operation of a master-slave arm, even though there were time delay between master and slave arms and the working environment were changed.

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In this study, a robot using a parallel mechanism as parts of the body is proposed. The robot integrates locomotion and manipulation, and mainly consists of four 3 DOF parallel mechanism with linear actuators and two grippers attached to both sides of the body. "The robot has high redundancy with 14-DOF without grippers". The purpose of this study is to realize "Intelligent Motion" of the redundant parallel manipulator that performs basic motion of the proposed robot. The robot determines the motion with considering its redundancy and improves it by using actuator informations that are taken in through the motion. First, this paper treats the analysis of kinematics and statics about the parallel manipulator, and shows the method to optimize the solution of inverse kinematics that includes redundancy problem. Next, the intelligent motion task planning of the parallel manipulator using actuator informations is mentioned. Two methods are proposed based on optimization of inverse kinematics. One optimizes the motion by iterative exercise. The other optimizes the motion successively in continuous motion tasks. Finally, the effectiveness of the proposed methods were verified through the experiment.

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The purpose of this paper is to present a graphical method for evaluating task performance of a manipulator for a planar peg-in-hole assembly task. The manipulator has three revolute joints, including a compliant element, and performs the task in a plane. Further, an RCC (Remote Center Compliance) is mounted on the end-point of the manipulator. First, a force condition to avoid jamming on the chamfer is derived. A stiffness condition at the compliance center of the RCC is then obtained from the force condition. Under the stiffness condition, the manipulator can avoid the jamming on the chamfer. Second, a graphical method is proposed on the basis of the stiffness condition and a DMA (Dexterity Measure for Assembly) that was previously derived by the authors. Third, the method allows us to evaluate the task-performance of a manipulator (e.g. PUMA 560). Finally, the evaluation results show that the stiffness condition for avoidance of jamming on the chamfer is important in evaluating task-performance of a manipulator for a peg in-hole task.

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In this paper, first, the equations of motion of the horizontal three-link robot arm in contact with an elastic object are derived. Then, the deforming control system of the elastic object by the robot arm is proposed. The deforming control system consists of the feedback control of the joint angles, the feedforward control by the robot arm dynamics and the adaptive feedforward control for the compensation control of the unknown elastic object dynamics. The adaptive feedforward control law is constructed by use of the on line parameter identification algorithm based on the least squares method, the zero phase error tracking control theory and the Jacobian matrix of the robot arm. From the numerical simulation rerults and the experimental results, it is confirmed that the control error in the deforming control by use of the present adaptive feedforward control method becomes small rapidly with the passing of time.

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This paper describes group robots which adaptively forms a mechanical structure. The group robots consist of identical cellular robots. Each cellular robot has same mechanical structure and control functions. We examined the specs of the cellular robots to generate harmonized grouping behavior by themselves under the following condition. There is a cliff on the ground, where a substance is going to move forward. The mission of the group robots is to support the substance by forming a mechanical structure like a bridge according to the movement. This paper mainly discussed the mechanical specs of the cellular robot required for execution of the mission. We pointed out that three mechanical parameters on sensing stress of the cellular robot are essential for formation of the structure. The formation of the structure was examined by computer simulations discussing the effect of the mechanical parameters.

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This study deals with autonomous distributed robots adaptively forming a structure for a loading condition. The simulation model consists of identical components (cellular robots). Each cellular robot has some functions about sensing, communication and mobility. In this paper, we discuss the following subject. There is a gap on the ground. A moving load lies at one side, but can not reach the opposite side. Mission of the cellular robots is to help the moving load to pass over the gap forming a structure like a bridge by themselves. After finishing the mission, they must return to the original place. We examined the required information processing of the cellular robots for execution of the mission and proposed the algorithms based on local rules. Using the algorithms, we simulated group behavior of the cellular robots on a computer and showed the validity.

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This paper describes a new type of space robot system consisting of a spacecraft and a robot attached through a tether to it. The system poses a number of interesting motion control problems. We especially focus on the control of translational motion of the robot from the spacecraft to the destination point in zero gravity. The translation distance is assumed to be short enough to neglect influences of the gravity and centrifugal force. For the purpose of the translation, we propose a casting strategy employing a spacecraft mounted manipulator arm. The robot is tethered to the end-point of the manipulator which applies tether tension. For path adjustment of translation of the robot in the casting strategy, a relevant control for direction of extension and tension of the tether is proposed. We derive bounds on acceptable disturbances based on the path adjustment capability of the spacecraft mounted manipulator arm. The validity and effectiveness of the approach is confirmed by computer simulations.

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We propose the Planning of Landmark Sensing (PLAS) considering environmental conditions for autonomous mobile robots. When an autonomous mobile robot moves, the robot usually resets the accumulated errors by sensing the landmark. In the previous work, the errors of robots are estimated based on the robot model, and Kalman Filter is used to reset the accumulated error after the landmark sensing. Based on this method, only the relation of robot and landmark position is considered as observation noise. But in actual visual landmark sensing, environmental conditions, like position of lighting, brightness of room and so on, are likely to cause the misrecognition of landmark. Then we consider environmental conditions for the calculation of the observation noise of Kalman Filter. This helps our system to determine the possibility of the misrecognition in case of bad sensing environments. Further, we also calculate sensing reliability based on environmental conditions, and use this sensing reliability in the adaptation of wheel noise of the robot model. As a result of the consideration of environmental conditions, our navigation system can navigate robots precisely, even if the environments are not suitable for landmark sensing.

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The application of hydrodynamic fluid lubrication theory is attempted to the thrust bearings with wave shaped axial end surfaces. The optimization of the wave height (especially three dimensional wave height) and of the surface porosity are experimentally determined concerning lubrication characteristics of the friction coefficient. The measurements of lubrication characteristics such as, a friction coefficient, the temperature rise, floating height and oil consumption rate for estimation of life expectancy etc. are evaluated. In this research, the results of this application on thrust bearings clearly showed considerable improvement over the conventional thrust bearings. Furthermore, this experimental research is clarified the lubrication conditions of respective thrust loaded axial end surfaces.

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A mathematical model of the piston in the cylinder on axial piston pump and motor has been indicated considering asperity contacts of surface roughness. The load carrying capacities by fluid film and asperity contacts acting on the piston have been calculated on the basis of Average-Flow-Model proposed by Patir-Cheng and the contact theory derived by Greenwood-Tripp, respectively. The calculations of the equations of motion have been performed by using Newton-Raphson method. It is clarified that whirling of the piston occurs for the narrow clearance between the piston and the cylinder and a long sealing part, similar to the oil whirl phenomena in journal bearing. The stability criterion of the motion has been examined according to Routh Hurwitz conditions.

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In order to predict the failure of rubbing surfaces through monitoring of wear particles in lubricating oil, an on-line particle image processing and analyzing system was developed using an optical microscope, a CCD camera, a stroboscope and image processing equipment. This technique has been used in the sliding wear tests of lead bronze bearing metal against a carbon steel counter face. The shape characteristics of wear particles, which closely correlate with wear modes, are distinguished by the relationship between the aspect ratio and newly defined roundness parameter. The wear particles with large aspect ratio and low roundness is related to promoting local seizure. It is found that the on-line image analysis of wear particles of greater than 40 μm helps in predicting severe failure of rubbing surfaces.

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Alcohol is considered one of the effective alternative fuels, with the intention of reducing air pollution and ensuring a stable energy supply. It is known that valve surfaces in fuel injectors are worn for methanol fueled engines. It is important to make the wear mechanism clear in methanol for the practical use of methanol fuel vehicles. In this study, to simulate the wear phenomena on injector valves, a steel bearing ball was collided repeatedly with a flat hard plate in some liquid fuels. Electric resistance between the ball and the plate, which is corresponded to metallic contact rate, and collision load were measured. Undergoing the impact, squeeze film was formed, and whose characteristic was investgated by examining the relation between the collision load and the metallic contact rate. It revealed that the viscocity of methanol is so low under the high pressure that the squeeze film breakes down easily and the wear of materials are remarkable in methanol.

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In internal combustion engines, one of the most important issues is to clarify the complicated friction characteristics of piston and piston rings because of the demand for improved fuel economy through the reduction in friction loss. In the present study, the floating liner method, in which the cylinder liner was supported by means of hydrostatic bearings, was developed to measure the friction force of piston and piston rings in an operating diesel engine. The decreases in either the number or the width of piston rings, the piston skirt area, and the lubricating oil viscosity were effective in reducing total friction loss, but these increased the boundary friction at the beginning of the power stroke. The boundary friction could be reduced by either a surface treatment on the piston and the piston ring or a friction modifier in the lubricating oil. The reduction in total friction loss was more significant when decreasing the total piston ring tension rather than changing the piston specification.

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The damping capacity of driving mechanism is one of the important factor for the dynamic characteristics of position control system. Generally it is relatively low to realize the high gain position control system or to suppress the external vibration disturbances. But, there is no enough study on designing means to generate the suitable damping capacity intentionally. This study deals with the development and application of electrically viscous controllable dampers with Ferro Magnetic Fluid and Electro Rheological Fluid (ER fluid) to generate suitable damping capacity to feed driving mechanism. This report describes on the study of auxiliary mass viscous damper with FM fluid which only to fit driving ball screw end. After theoretical simulation with mathematical model and actual experiments, it can be verified that the damper is very effective to give suitable damping capacity intentionally to driving mechanism. Moreover, it also can be found design parameter tuning procedure which performs most effectively.

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This paper first proposes a magnetic lead screw which is comprised of a conventional steel lead screw and a magnetic nut. The nut is made from a helically-magnetized cylindrical permanent magnet and an external steel cover. A driving force from the screw to the nut is transmitted through the magnetic coupling without mechanical contact. So the magnetic lead screw can be used in vacuum, does not make noise and vibration, and is free from lubrication problem. However, the axial stiffness and maximum carrying load of the magnetic lead screws are smaller than those of ordinary lead screws. Experimental magnetic lead screws are made and it is proved that experimental results of the carrying load and stiffness in the axial direction agree well with simulated ones using the FEM models. It is also clarified that the thread depth and fiat width of lead screw affect the carrying load of the mechanism.

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In this paper, an induction-hardened sintered powder metal spur gear was compared with an induction-hardened steel spur gear in terms of dynamic performance using a power circulating gear testing machine. Tooth root strain, vibration acceleration of gear box and sound pressure near gear box were measured at rotational speeds of 1 600 rpm to 10 000 rpm. The tooth root strain was analyzed at time-frequency domain by wavelet transform. The dynamic performance of the sintered powder metal gear was superior to that of the steel gear. The vibration acceleration and the sound pressure of the sintered powder metal gear were lower than those of the steel gear. According to the result of the time-frequency analysis of the tooth root strain by wavelet transform, it was clear that the damping characteristic of the sintered powder metal gear was superior to that of the steel gear.

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Feature elimination method for computer-aided forging process planning is reported in this paper. The authors think that forming is the procedure adding features to a raw material and process planning is the procedure eliminating features from a product. This procedure is done only in planner, s mind. The authors attempt to implement this feature eliminating procedure for forging sequence design on computers. Eliminating order is determined by using characteristic vector of 'pair matrix.' Elements of 'pair matrix', called 'pair elements', are calculated from the possibility that one of features is formed earlier than the another. Each possibility is compiled from a forge expert's 'know-how' by comparing each two kinds of feature. Possibility is computed by fuzzy inference if it cannot be determined from only kind of a pair of features, but also dimensions. We call this case 'dimension problem'. The authors apply the above methodology on manufacturing sequence design of axis-symmetric forging products, and investigate data of pair matrix and reasoning rule for dimension problem by interview with forge experts.

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The purpose of this research is to increase the feasibility of a new lubricant test which is available for the plastic deformation processing of thick sheet. The feasibility of the new test has been already confirmed through a series of experimental procedures in which the friction coefficient could be evaluated from the dome height. In this research, an influence of the punch profile on the neutral point of the compressed material was evaluated by means of the "slab method". At first, the validity of the adoption of slab method was confirmed with the comparison between the result of FEM and the slab method. As a result the variation rate of the neutral point in relation to the friction coefficient in slab method was the same of the result in FEM. Next, the neutral point in the case of a convex profile punch was evaluated with slab method. As a result, the convex profile punch had an excellent performance since the variation rate of the neutral point in relation to the friction coefficient was more remarkable than that of the straight profile punch.

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In order to predict the performance of the diamond saw blades during grinding, an analytical method with applying the theory of Marcov process was suggested in previous paper. This theory, which basically have the probability components consisting of initial shape distribution, fracture, transition, dislodgement and appearance, enable us to predict variation of edge shape distribution on wheel surface with grinding time. However, these probabilities had to be obtained directly from the experiment. Therefore, this method inevitably follows new experiment and measurement whenever experimental conditions change. It remains a question how to decide the probabilities efficiently for more practical method. In this study, estimation of these probabilities is attempted by the neural network. As a result, it is found that reasonable values of the probabilities can be obtained from input data of grinding condition given. Hence, applying the neural network can develop the theory proposed for more practical method.

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The primary flow in a chip may sometimes bend backward in the center of thickness a little toward rake face. This phenomenon occurs always when gaseous oxygen is blown against the cutting edge from the beginning of cutting carbon steel with the speed range in which built-up edge occurs. For this reason, it is that a wedge-type built up edge with a sharp nose edge formed by the effect of oxide film occurs, the chip cut by the sharp built-up edge with a large rake angle impinges violently against the rake face of the tool and it is sheared again. The mechanism of the back-bending of primary flow can be explained by considering shear planes having the angle of φ₂, φ₂₁ and φ₂₂ in addition to the ordinary shear angle φ₁.

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