Reinforcement learning has recently been receiving increased attention as a method for robot learning with little or no a priori knowledge and higher capability of reactive and adaptive behaviors. This paper presents a framework of the reinforcement learning, and several issues in applying the method to real robot tasks. Then, examples of real robot applications, especially vision-based reinforcement learning methods are intorduced to show how they cope with these issues.

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In this paper, we propose a method for detecting both robots and obstacles using a local infrared communication system. If every robot in the environment has its own ID number and transmits it, then a robot can detect another robot by receiving the ID number. The robot can also detect an obstacle by receiving its own ID number which is reflected from the obstacle. We also propose a method for detecting interference in transmission when several robots transmit to one robot. Finally, we describe the development of a sensor system named LOCISS (locally communicable infrared sensory system) and fundamental experiments carried out to evaluate its performance.

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This paper first discusses cooperation between the human operator and the decentralized autonomous robotic system. To realize cooperation, the operator must know condition of the mutli robot system. Therefore, monitoring methods which let the operator know system's condition are needed. Then strategies of communication between the human interface and agents are discussed. We propose explicit and implicit communication strategies to monitor the system, and several monitoring methods to implement them: time-based and event-based monitoring for the explicit monitoring and eavesdropping messages for the implicit monitoring. We compare the monitoring methods in order to ascertain how much information the human operator can gather in each method using simulation. Finally, the characteristics of each monitoring methods are analyzed.

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We describe the method in which a visually guided swing motion for a 16DOF two-armed bipedal robot is acquired by applying GA (genetic algorithms) to a NN (neural network) controller. The evolutionary approach to the acquisition of various motions for robots has been successfully used by many researchers, but most studies have been carried out only through computer simulations. In this research, we adopt a real robot with a complicated body used in a noisy environment. The evolutionary processes are examined in a virtual world constructed on a CRS-CS6400 parallel computer which simulates such factors as swing dynamics, visual processes, noise reduction processes, and timelags in a control system. It took about 2 hours for an artificial evolution to create a successful individual after 50 alternations of generations from an initial population of 200 unsuccessful genes. Using the NN decoded from the most successful individual of the last generation, a real two-armed bipedal robot that could swing successfully was obtained.

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In this paper, we propose a new kind of manipulation, the releasing manipulation. Releasing manipulation gives an object a certain initial velocity, allowing it to slide on a plane. The object stops at a certain position under the influence of friction. There are two problems which must be overcome to achieve this manipulation. (1) How much velocity is required to slide the object to a target position and orientation. (2) How to give the object initial velocity. We will show physical models describing the motion of the object to solve these problems. This manipulation makes use of environmental constraint such as friction between the object and the plane. Therefore it is strongly affected by uncertainty in the environment. As a result, the motion of the object should differ from that of models. In order to overcome this problem, we use robot learning, and ensure the efficiency of learning experimentally.

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In this paper we describe the research for automatically creating Lisp programming to represent the path of robot movement. The path is that of a robot moving in a FA factory. In order to create the program, a genetic algorithm using the scrap and build fitness method (SBM) is used. SBM divides one robot path cycle into several parts and conducts a simulation of each cycle under restricted times. After simulations for the FA system which has four machine tools and a robot, the usefulness of SBM is ascertained.

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In this paper, a local torque optimization strategy for a redundant manipulator based on observer is proposed. The calculation of the torque-optimizing controller becomes more complicated as the number of degrees-of-freedom increases because a pseudo inverse Jacobian matrix is generally used and the controller needs to calculate dynamical torque. To resolve this problem, the disturbance observer is applied to the redundant manipulator to simplify the controller calculation. Then, the torque-optimizing controller is realized without much effort required for calculating the null space term and dynamical effects. Furthermore, we find that the good performance of the workspace position response is obtained in the proposed controller. The validity of the proposed method is confirmed by the numerical and experimental results in the 3-link planar redundant manipulator.

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This paper describes new mechanisms, principle, control methods, computer simulation and experimental results of the second version of an all-direction steering-type mobile robot which has a spherical monowheel. Basic simulation results of straight running and rotation coincide with experimental results of the robot, and these results clarified, firstly, relationships between center of gravity and running ability of the robot, and secondly, the relationships between the robot's rotational angle and friction torque of the spherical wheel with the ground. Furthermore, it was confirmed experimentally that the new robot has high maneuverability, such as omnidirectional travel with zero-turning-radius rotation on any kind of surface. Therefore, it is expected that the spherical-wheeled robot developed here can be applicable as a safe personal service robot that can work with human beings in a limited space.

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The robot investigated in this study is involved in the construction of conduits of telecommunication cables. A conventional method using electromagnetic waves for measuring the horizontal position of this robot has been used 6 stroke-by-stroke (one conduit-by-conduit) by operators on public roads; however, it is very inefficient and dangerous. Moreover, operators can't know the horizontal position stroke-by-stroke while this robot is moving. In this paper, we show a method to provide the horizontal positioning information of the movement section not measured by the conventional method and to provide operators with horizontal positioning information while the robot is moving. First, we propose a horizontal position model based on the geometrical relationship between the past locus of this robot and the present locus in the underground. The proposed model can approximately calculate the horizontal position stroke-by-stroke without using the conventional method. Next, we propose a method for predicting the horizontal position based on the Kalman filter using both the conventional method and the proposed model. The proposed method can calculate and predict the horizontal position stroke-by-stroke. Finally, we show results of computer simulation using data measured in the actual construction of a tunnel. We compare the results with those of the conventional method to verify the applicability and usefulness of this method.

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Time delay usually makes a master-slave system unstable, even if the system is stable in the absence of time delay. In this paper, we propose a control scheme for a master-slave system with time delay which maintains stability as defined by scattering theory. We define 4 types of realization of the ideal response and describe control schemes which realize the ideal response. Based on these schemes, we propose a practical control scheme and its stability is proven. We also discuss the stability of conventional schemes, and show that they cannot maintain stability. Finally, some experimental results are presented.

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The age of space development is approaching, and development of space robots is becoming increasingly important. We have developed a small mobile robot on an H-type space truss structure to perform maintenance tasks on the space structure. This robot has two hands which can hold the truss, and moves on the truss by the inch worm mechanism. The remarkable feature of this robot is the compact extension mechanism. It is connected with pantographs in series. This mechanism enables the realization of a high rate of expansion with light weight. In this paper, we present the mechanism and control method of this robot and results of mobility experiments obtained under the gravity compensation system.

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Manipulator motion on a spacecraft becomes disturbance for the Spacecraft attitude stabilization. The conventional satellite attitude control system based on the feedback control does not have enough capability against the manipulator's reaction. This paper shows how to realize spacecraft attitude control system for the robot satellite using state-of-the-art reaction wheels and gas jet thrusters.

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Manipulator motion on a satellite disturbes the stability of the satellite attitude. Since the reaction of a robot arm is too large to be compensated by the satellite attitude control system, it is necessary to control the satellite-mounted manipulator so that it does not to generate excess reaction torque against the satellite. In this paper, a simple and effective manipulator motion management algorithm is proposed. The manipulator motion is determined by considering the satellite attitude, attitude rate and the angular momentum which the manipulator will produce.

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In this paper, we propose a control algorithm of multiple manipulators handling a flexible sheet metal, and to discuss how to deform a sheet metal and manipulate. First we derive the relation between static deformation of the sheet metal and bending and twisting moments exerted on the flexible sheet metal based on a finite-element model. We then design a control algorithm by which the deformation of the sheet metal is controlled using the internal force applied to it. Experimental results obtained from two industrial robots illustrate the validity of the proposed control system.

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This paper proposes a new design method for a sliding mode control system using μ synthesis theory. This concept is based on a frequency-shaped approach. A general hyperplane consists of a reference model without dynamics. Therefore, a conventional sliding mode control system often becomes unstable due to spillover phenomena of high frequency caused by high-speed switching. The proposed design method suppresses such spillover phenomena because of frequency shaping. Also, it has good robustness on the hyperplane to realize a minimum value of H_∞ norm and the structured singular value from some noise to state variables. We have just applied this new method to the flexible structure of a test rig with four stories such as a high-rise building. We have obtained good performance from simulations and experiments.

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Generally, for the position control of industrial robots, a semi-closed-loop control which only utilizes information of the motor angle is adopted, since it contributes to the stability of the control system and does not require a high-resolution encoder. In this method, however, precise positioning cannot be attained because of uncertainty and flexibility of the driving system. Since the cost of a high-resolution encoder is generally no longer prohibitive, direct measurement of joint angle is now possible. In order to realize high performance, precision, speed, and robust stability, we propose a control method which utilizes information of both motor and joint angles. The controller is derived from a hierarchical design method which is based on the H_∞ control theory and proposed in this paper. Moreover, we introduce a 2 DOF control in order to improve tracking performance of the joint angle. Experimental results show that the proposed controller is useful for achieving the desired performance.

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Using the theory of degrees of freedom, we have developed a constant velocity joint mechanism which has triple spherical linkages and applied it to the wrist joint of manipulators. The wrist joint mechanism features are as follows: revolute type lower pairs only; singularity-freemotion; pitch and yaw angles greater than 180 degrees; 360-degrees continuous roll motion; internal cable routing passage; high precision; high rigidity; remote driveability; back driveability. In this paper, the process of the mechanism development is described, the performance of the mechanism is discussed, and the practical design conditions are explained. Trial wrist models have been designed and built, and one was mounted on an industrial robot.

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In a previous paper, a high-stiffness torque control system for geared DC motors was proposed. Here we describe methods to identify the parameters needed to achieve that control system. Furthermore, our enhanced scheme provides a method for selecting the stiffness of the torque-sensing element to achieve an accurate torque control system. The basic idea is to use an acceleration controller based on a disturbance observer instead of a position controller as proposed in the past. The advantage is that the effects of time delays due to the system dynamics and the effects of Coulomb friction are eliminated by the observer. We present experimental results of implementing this controller.

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A high-resolution, high-speed microforce sensing method using a simple displacement sensor with coupled-cavity-laser is presented. A resolution of 0.5mN is achieved for frequencies up to 3kHz using a leaf spring with a stiffness coefficient of 500mN/μm. This method has been applied to detecting micro-frictional forces for micromechanical systems. The microscopic static- and kinetic-frictional forces have been measured and estimated under various magnitudes of load, neglecting the force of inertia.

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Prior to investigating the resonant response characteristics of a finite group of blades, such as resonant stress increasing and decreasing effects, fundamental characteristics of the natural vibration in question must be elucidated. By means of the method described in Chapter 6 of the 3rd report, "coupled natural Vibration of axial deflection and torsion" is solved for the "shroud/blade thickness ratio" which is purposely changed from zero to infinity. The results are analyzed and itemized in comparison with tangential flexural vibration. Thus, the fundamental characteristics of natural vibration of such a coupled vibration are clearly shown.

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Based on the fundamental characteristics of coupled natural vibration of axial deflection and torsion, which were presented for a finite group of blades in the 4th Report, its resonant response characteristics are thoroughly investigated. The numerous phenomena related to resonant stress increasing and decreasing effects are put in order for the coupled vibration, and the plural factors controlling such effects in this case are deduced. In the case of uncoupled tangential flexural vibration, a single factor controlled such effects.

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A numerical method for analyzing free vibrations of composite laminated twisted cantilever thin plates is presented. The proposed method is based on the Rayleigh-Ritz procedure using algebraic polynomials as assumed displacement functions. The frequency parameters obtained are compared with previous theoretical results. Free vibrations of three-layer laminated (θ/-θ/θ) and four-layer laminated (θ/-θ/θ/-θ) plates are studied and the effect of fiber orientation and twist angle on the vibration characteristics of the plates is investigated.

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The analysis of composite rectangular sandwich plates composed of an orthotropic core and composite laminated faces is presented for bending and free vibration. A method of solution based upon the Ritz method is used. A displacement field which includes transverse shear deformation of the face layer is applied to the honeycomb sandwich plate. The effect of transverse shear deformation on the center deflection and natural frequencies is studied, and the applicability of the displacement field is discussed. Also, the effects of fiber angle on the face layer, core thickness and transverse shear modulus of the core on natural frequencies of the honeycomb sandwich plate are discussed.

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We theoretically and experimentally investigated the unbalance response characteristics of a miniaturized laser scanner rotor supported by self-acting grooved-journal air bearings. In the analysis the elastic deformations of the fixed center shaft and its fitted point are taken into account. The validity of the analysis was confirmed by experiments in terms of the amplitude and phase of unbalance vibration. The lowest natural frequency decreases from more than 100000rpm to 60000rpm when considering the elastic deflections of the center shaft are considered. Then, we numerically analyzed the frequency response characteristics of a laser scanner rotor caused by external excitation of transverse and angular vibrations. The excited vibration characteristics are analyzed for the two cases where the fixed center shaft is assumed to be rigid and its elastic deformations are taken into account. Furthermore, we evaluated the maximum allowable vibration where the worst vibration amplitude is half of the bearing clearance. As a result, it was found that although the rotor-bearing system has a sufficient resistance to transverse excitation up to 4G, the resistance to angular excitation is as weak as 0.5 revolution/s in a low frequency-region of less than 200Hz.

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Active magnetic bearing (AMB) equipped rotating machinery requires control for low unbalance vibration at low driving power. In order to estimate both the unbalance resonance vibration and the bearing reaction force, an unbalance response analysis program considering the bearing reaction force is developed. Using this program, the optimum control technique is evaluated for flexible rotors supported by AMBs, regarding the following four means: PID, Ncross, Ncut+Ncross and Feed Forward (FF) Excitation. FF Excitation is recommended with respect to low resonance amplitude and low control current in order to pass the first bending critical speed.

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This paper describes a novel vibration-mode filtering method for one-dimensional structures such as a cantilevered beam using a two-mode optical fiber as a distributed-effect sensor. One of the most important problems regarding the optical measurement is how to alter the sensor sensitivity spatially along the longitudinal direction of the beam when the sensor is mounted on the beam surface. In this study spatial variation of the sensor orientation with respect to the longitudinal direction is included in the sensor model. The sensor sensitivity can be experimentally measured and used for design, incorporating the orthogonality of the mode shapes of the structure. Moreover, in the light of practical considerations, a design procedure of optimal fiber placement utilizing bipolar weighting functions is presented. Finally, theoretical predictions are confirmed by experimental results and efficient vibration-mode filtering is demonstrated.

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In our previous paper, we have reported an ultrasonic motor using a plate vibrator with displacement amplification mechanism. But the maximum linear speed and the efficiency of the ultrasonic motor are only 0.075m/s and 1.58% respectively. And any optimum design of plate vibrator has not been shown yet. In this paper, by means of the finite element method, the vibration characteristics of a plate piezoelectric vibrator with projections for displacement amplification are analyzed. Some basic relations between structural dimensions and vibration state are given to obtain an optimum structure, and a new plate piezoelectric vibrator and ultrasonic motor are designed and manufactured. Through experiment, it is verified that the optimum design is appropriate and the resonance of the projection itself increases the displacement amplification effect. Measured maximum revolution, linear speed and efficiency are 900rpm, 0.65m/s and 8%, respectively.

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Recently, the application of active suspension has been studied for improving the ride quality of railway vehicles. In active vibration control of railway vehicles, it is important that the control system be robust against parameter variations. In one such study, it was indicated that a LQG controller had low stability of the robustness to mass variation of the car body due to the varying number of passengers. In this paper, the H_∞ controllaw is adopted for a 3 d. o. f. half-vehicle model, and the improvement of control performance is investigated experimentally. As a result, it is shown that the addition of a bogie-related state variable to body-related ones provides better control performance. The control performance is improved further by shortening the sampling period. Moreover, it is also shown that the H_∞ controller is more robust against mass variation of the car body.

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Experimental study of rail corrugation developed on tight curve has been carried out using a corrugation simulator, which can apply longitudinal and lateral creepage on rolling contact surfaces. Vibrations, dynamic creepage and surface deformations were simultaneously measured throughout the corrugation development. The relation between vertical vibration and oscillation of creepage vibration has been clarified from the experimental results. In addition, the wear rate determined by these vibrations agreed well with the deformation rate of the surface. The mechanism of the initiation and development of rail corrugation has been clarified from these results.

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This paper deals with the pre- and postimpact motion of vehicles. We have already proposed an analytical method for motion analysis of four-wheel vehicles, solving the wheel loads as unknown values. However, it was not considered in the previous paper that the wheels may be lifted from the ground due to such effects as impact force, sudden braking or handling. We take floating of the wheels into consideration in this work. We determined the state of contact between the road and the wheels by checking the displacements of the springs of suspensions at each time step of calculation. Finally, we show several numerical results and discuss them.

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Transient vibrations in a clamped isotropic rectangular plate caused by the impact of a steel ball are investigated numerically and experimentally. In the numerical approach, the contact law between the plate and the steel ball is approximated by the Hertzian contact theory which was proposed for a static contact problem. The in-plane forces due to the deflection of the plate are not taken into consideration. Since the effect of the in-plane forces is negligible in the case of a very small plate deflection, the numerical approach is justified by comparing the numerical results with the experimental results. The effect of the in-plane forces on the collision between the plate and the steel ball is evaluated by comparing the numerical results with experimental results for various impact velocities and plate thicknesses. Although the contact force cannot be measured experimentally, the effect of the plate thickness and the plate shape on the contact force is evaluated numerically.

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An approach is presented for the identification of modal parameters in the frequency domain in an experimental modal analysis with multiple frequency response functions. In the case of many modes, with automatic optimum partition of the frequency domain, computation time for calculation becomes shorter and required memory size becomes smaller. Accuracy of the results is improved using inertia restraint, residual compliance and 2 pseudo-mode. The validity of this method is verified by comparing the results with those of other methods.

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The purpose of this study is to clarify the mechanisms of the kip motion, or the upstart, which is a technique in horizontal bar exercise. Motion of a player is experimentally analyzed using a movie camera. Under the assumption that the player who performs the kip may be modelled as a triple pendulum, the equations of the kip motion are derived and computer simulation is performed using various parameters. Furthermore, the kip motion of the triple pendulum with two active joints is executed and measured. It is concluded that the kicking moment must do the proper work which increases the kinetic energy of body translation. For this purpose, the angle between two vectors (the force acting on the hip joint and the velocity of the joint) should be acute.

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A technique based on the reciprocity principle has been developed for measuring mechanical-acoustic transfer functions for vehicle road noise induced by forced displacement inputs from the suspension. With this technique, acoustic excitation is applied to the car body and the resulting constraint force of the tires are measured by means of tri-axial load cells with a loudspeaker installed at the driver's ear position. This paper will first explain the mechanical-acoustic reciprocity principle corresponding to forced displacement excitation. Empirical examples will then be given of applications of this technique to the reduction of low-frequency road noise of a passenger car. The results indicated that the reciprocity technique is applicable to a fully trimmed vehicle that includes an engine and suspension and is often cheaper and more convenient than the equivalent shaker-based excitation method for measuring mechanical-acoustic transfer functions.

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We report the dynamic characteristics of the reaction force from the floor, its application point, and the velocity and the displacement of the center of gravity of human body in stair walking when transferring from or to level walking. The reaction force and its application point are obtained using two large force plates, on one of which a stair model with five stairs is fixed, and the velocity and the displacement of the C. G. of the body are calculated by integrating the force once or twice. Discussions of these dynamic characteristics and their transient properties are given. One of the remarkable transient characteristics in stair walking is observed in the sagittal components of three physical quantities: reaction force, the velocity of the C. G. of the body and its displacement.

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In order to clarify the grasping mechanism of tools and machine handles, sensory tests to evaluate the optimum grasping diameter have been performed on forty-three people from age seven to fifty-three. It was confirmed that the sensory evaluation of the optimum grasping diameter was difficult for children under age ten due to insufficient growth of skeletal structure. The optimum grasping diameter was evaluated for persons above age ten. The optimum grasping diameter depended on the hand size, and the dependency was marked for children under eleven. In the case of adults, the optimum grasping diameter depended on the dimensions concerned with the length of the hand but only depended slightly on the hand breadth or fist. The optimum grasping diameters evaluated for males were 30∼40mm, which were about 10% larger than those evaluated for females. As a result of investigating above data, it was found that the tube could be grasped well by a human hand if all fingertips and the entire palm area contact it.

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In this paper, we discuss the modeling of flexible manipulators, for which there are two approaches: one based on distributed-parameter modeling and the other on lumped-parameter modeling. The former has been applied to control and analysis of simple manipulators requiring precision, while the latter has been applied to multilink spatial manipulators, because of the model's simplicity. We have already proposed a lumped-parameter modeling method for multilink spatial flexible manipulators. In this paper, we apply our lumped-parameter modeling method to a simple manipulator, and investigate what degree of precision we can obtain using the model. Experiments and simulations are performed and, based on comparison of the results, the approximation performance of our modeling method is discussed.

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Recently, high speed and high precision have become very important qualities in industrial robots. To achieve high precision, it is important to reduce the vibration of the arm tip. However, high speed increases vibration. When the elasticity of the reduction gear and other components can not be neglected, the natural frequency becomes small, and vibration problems appear. In this study, we consider a one-link robot which contains a motor, a reduction gear, and an arm as a semi-closed servo system and investigate the relation between mechanical parameters and gains of the controllers. The optimum gains are determined for the position pd-controller analytically and it is shown that the optimum dynamic property is obtained when the ratio of the inertial moments of the motor and the arm is 1:4. We propose methods for obtaining an inertial moment ratio of 1:4 and study the dynamic property in relation to the input and the disturbance.

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A method for estimation of the noise level of a C-frame turret punch press is proposed using the results of its scale model. Scale models are often used in the experimental analysis of noise since their structural design can be easily varied. However, the waveform of a punching force is more complex than that of an impulsive force from an impulse hammer, and the supporting exeiting conditions of the scale model are different from those of the actual machine. It is, therefore, difficult to directly apply the similarity law to the experimental results obtained using a scale model. In this study, various waveforms of punching force reported previously have been analyzed in the frequency domain and a method for simulation of the punching force using an impulse hammer has been investigated. The difference between the supporting and exciting conditions of the actual machine and those of its scale model has been analyzed by a finite element method. It is found that two kinds of impulse hammers are necessary for the simulation of the punching force, and that the volumetric acceleration of the scale model is necessary for the estimation of the sound pressure level of the actual machine.

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We applied a set of turrets, which are used for providing punches and dies, to a damper for a C-frame turret punch press to reduce the vibration and noise. The upper-and lower-turret dampers have same characteristics as an impact mass damper. The damping characteristics can be changed by adjusting the preload. Those can effectively reduce the noise and the vibration although the contact area between the damper and the frame is small. In a wide frequency range, the effect of the sound pressure level reduction is the same for either one turret or a set of trurrets. In the lower frequency range, however, the set of the turret dampers can reduce the sound pressure level more effectively than one turret damper. As a result, the amplitude of the first tuning vibration, which is a natural vibration mode of C-type structures, is reduced up to 1/9 of the original structure, and the reduction in the sound pressure level is over 6dB. Furthermore, the complex structure of the turret damper and the double wall eliminates the first tuning vibration, and is estimated to reduce the sound pressure level in the actual punching by about 11dB.

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For the assessment of machinery noise, this paper describes a method of estimating normal particle velocity distribution from a sound pressure distribution measured at a single aperture close to the sound source based upon near acoustic holography (NAH) which is realized by discrete Fourier transform. In NAH, the distance between the surface of sound source and measurement aperture is required to be of one-tenth of a wavelength. Actualy, the distance between the machinery and measurement aperture is not short adequately for NAH because of the 3-dimensional features of a machine, so this method is investigated under the condition that sound pressure is measured about one wavelength from the sound source. The size of the measurement aperture was practically determined to be of the order of 1×1m. Through investigation of the effect of various source locations by simulation, it has been shown that the effect of evanescent waves should be taken into consideration. Experimental verification shows that this method can be applied practically in echoic situations.

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A nondestructive evaluation (NDE) system using a highly sensitive magnetic sensor, the SQUID (superconducting quantum interference device) magnetometer is developed. The system is composed of a SQUID magnetometer, a gantry which supports the SQUID dewar, a nonmagnetic rodless cylinder used to drive a stage for scanning a specimen under the SQUID magnetometer and a magnetically shielded room. First, the supply pressure condition for driving the stage at a low, constant speed is determined. Secondly, stainless steel bolts considered to be non magnetic are measured using the system and it is confirmed that the bolts contain a very small amount of magnetic material. Thirdly, the change in the permeability of a permalloy plate due to torque stress is detected using the system. From these results, it is confirmed that the system has a high sensitivity and spatial resolution.

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In this paper, the effects of foil bending rigidity on the space height characteristics of externally pressurized foil bearings with a hollow porous shaft are analyzed by the finite width bearing theory. In the analysis, in order to save computation time and to improve the convergence of solutions, the two-dimensional modified Reynolds equation considering the added flow through the porous shaft is reduced to an ordinary differential equation using the weighted residual method. The reduced Reynolds equation and elastic equation for the foil are discretized by the finite difference method and solved numerically by the Newton-Raphson iterative technique. This numerical solutions for the pressure and film thickness distributions between foil and shaft are obtained for a wide range of bearing width-to-diameter ratio under varios combinations of foil bending rigidity and foil wrap angle, and the space height characteristics of the foil bearings are examined theoretically.

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In order to elucidate the possibility of the application of inverse hydrodynamic lubrication theory to flexible materials with micro-asperities, the behavior of oil films formed between band-shaped nitrile rubber specimens with ten types of transversely oriented multiple bumps and an oscillating glass plate is directly observed and the friction and sealing characteristics are compared. The effects of the stroke length on the friction force are also investigated. It is found that the inverse theory is applicable to explain the friction and sealing characteristics when the overall film thickness is very thin.

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The torque compensating cam (TCC) mechanism which minimizes the fluctuation of input shaft torque is an effective means for reducing vibration and recognized as a valid technique for achieving faster operating speeds. In industry, a spring-type TCC mechanism is advantageous and suitable for a wide range of appli-cations due to its compactness and cost-saving feature. The parameters for the design of the spring-type TCC include positioning time, output shaft rotating angle, inertia moment of rotary table, cam curve and (a) spring constant, (b) cam stroke, (c) initial compression force. We concern ourselves how to determine unknown factors (a) to (c). TCC will invariably be custom-made. The spring, however, is supplied from venders in reality. This introduces the chore of selecting a commercially available spring that satisfies the requirements of the TCC, or of identifying the optimum spring specifications. This paper identifies the requirements of a spring suitable for the TCC, and the procedures for selecting an optimum spring.

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In the previous paper, the authors investigated the effects of viscosity of the base oil of cutting oil for hobbing on the synergism of EP additive and rape-seed oil. It was revealed that a mixture of 1% chlorine in the form of chlorinated fatty acid ester and 30% rape-seed oil added to a machine oil 68 with high viscosity showed the best performance in terms of reducing hob wear and improving finished surface roughness. The effects of viscosity of the base oil on the synergism of several kinds of additives were investigated in this work. Experiments were carried out using a single fly tool. A mixture of 0.5% sulfur in the form of sulfurized fatty oil and 1% chlorine in the form of chlorinated fatty acid ester added to a machine oil 32 with medium viscosity is optimal for practical applications.

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When the effect of thrust force due to helix angle of helical gear is considered, the vibration behavior of a gear unit becomes complicated. Therefore, it is important to reveal the behavior of the gear vibration in all directions as well as the vibration of shafts. In this work, the vibration of helical gear units with various gear ratios under both increasing and reducing conditions has been investigated experimentally. The dynamic responses of transverse, rotational, tilting and axial vibrations of helical gears are measured by acceleration pick-ups mounted on the gear blank and modal behavior is interpreted based on a scheme involving modulation due to shaft rotation. The modes of shafts and gears are measured precisely using a laser Doppler velocimeter. The experiments were conducted by interchanging a driving gear-shaft-bearing assembly with a driven one to eliminate the effect of tooth form errors. First, the effect of helix direction and bearing fixing configuration was revealed for a gear pair with unity gear ratio. Secondly, it was demonstrated that there is little discrepancy between increasing and reducing operation except for those effect of installing configurations such as bearing fixing conditions.

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A new measuring method for circular movement of NC machine tools has been developed. The new apparatus consists of a plane four-link mechanism and a displacement measuring sensor for measuring distance change between the opposite sides of the link mechanism. Current techniques for measuring the circular movement are not flexible in terms of measuring radius and their measuring capability is limited only to circular movement. These drawbacks led us to develop a new type of measuring method. The newly developed method is flexible in terms of the measuring radius, and it also has a potential to measure positioning error of a machine table, for example. The measuring principle of the method and configuration of a trial apparatus are described in detail, after which the principle is demonstrated by the results of experimental evaluations.

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The purpose of this study is to clarify the performance of high-efficiency belt grinding with superabrasive belts. Constant-load belt grinding of hardened SUJ2 steel was performed using CBN, diamond and alumina belts. Tangential force was measured using a small feather-type dynamometer, and stock removal, as well as decrease of height, was measured by a micrometer. Surface roughness and residual stress were also studied. The belt speed was 15m/s, and the contact pressure was 0.12∼0.50MPa. The variation of grinding characteristics with grinding time was investigated. It is evident that a CBN belt is superior in removal rate to an alumina belt, while a diamond belt is unsuitable for belt grinding of hardened SUJ2 steel due to low removal rate.

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