The cause of an instability phenomenon in the positioning control of a mechanical system with some vibration freedom is that the phases of vibration modes are opposite to those of rigid body modes between a sensor point and a control input point. In this paper, the stabilizing design method of a swinging arm actuator, which is commonly used in magnetic disk storage, is discussed based on the modal analysis. The two lowest vibration modes due to the isotropic bearing stiffness at the pivot are considered in addition to the rigid body mode. As a result, it is found that the two vibration modes can be in-phase with the rigid body mode, if a control input point to a pivot line is tilted with respect to a sensor point to a pivot line at a small-angle, and the center of gravity is settled within the vertically opposite angle and a specific region between a sensor point and a pivot.

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This paper presents a time domain method to identify the mass, stiffness and damping parameters of a mechanical structure. First, the characteristic matrix of the structure system is obtained from the modal parameters of the structure. Secondly, the mass parameters are determined from the autocorrelation function of the measured responses and the ones calculated from modal parameters. Consequently, the stiffness and damping parameters are obtained from the characteristic matrix and mass parameters. Finally, two simulation examples, of which one is a five degree-of-freedom model including a rotation mode, are demonstrated in detail with figures and tables. The results are in good agreement with the analytical ones.

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An automatic liquid balancer is proposed, which consists of a cylindrical vessel fitted with a pipe and a reservoir containing liquid to compensate for rotor unbalance. Under the centrifugal field the liquid moves through the pipe from the side of the unbalance mass to the reservoir located on the symmetrically opposite side. From the experimental study, the device proposed is confirmed to be useful for the balancing of the rotor under the critical speed, and can operate repeatedly for changes of unbalance. Furthermore, it is clarified analytically that the device can work well for the unknown condition of unbalance.

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This paper presents an analytical method for determining the free vibration and the steady-state response of a laminated FRP (fiber reinforced plastic) rectangular plate resting on some elastic point supports. The bending rigidities are assumed to be complex quantities (taking into consideration material damping), and are obtained using the classical lamination theory. The Ritz approach is used to yield a governing equation of motion for the plate, and the natural frequencies, mode shapes and the steady-state response solution to a sinusoidally varying point force are derived. The method is applied to a laminated square plate elastically supported at four points symmetrically located at the corners or on the diagonal. The mechanical impedance of the plate is calculated for three types of FRP materials, and the effects of the point supports and the lamination properties upon the vibration characteristics are studied.

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The sound pressure level of the sound generated from a guide-tube-type ball screw is influenced mainly by the pulse sound, which is one of the components of the sound. In the present paper, the pulse sound was investigated in order to obtain basic information for the sound reduction of the ball screw. The test ball screws were operated by the ball screw sound testing machine installed in a soundproof room. The sound generated from the ball screw and the vibrations at its return tube were picked up by a condenser microphone and two piezoelectric accelerometers, respectivery. Using the signals thus obtained, sound and vibration waveform observation, sound pressure level measurement and real-time frequency analysis of the sound etc. period were carried out. From the experimental results and considerations, the fundamental characteristics of the pulse sound and its generating mechanism were clarified, and some basic information on the sound reduction of the ball screw was obtained.

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Crawler-type vehicles have a higher mobility on the soft ground than wheel-type vehicles because of a low-ground pressure and a high-driving force. Therefore, it is important to understand the dynamic interaction between the soil and the track shoes during propelling on the soft ground, but there are few studies on such phenomena. Also the dynamic driving force, the dynamic ground pressure distribution and the dynamic behavior of the vehicles have not been developed theoretically at all. In this paper, a suitable simulation model, which considers the dynamic effect of the soil, has been proposed, and the equations of motion have been developed by Lagrange's equation.

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This paper presents a theoretical analysis of the dynamic instability and postflutter vibrations of a pipe string designed for mining manganese nodules in the deep ocean, which conveys fluid from its free lower end to the simply supported upper end. First, for the simulation of a more general and practical case, the equation of motion of the pipe string is formulated by considering the effect of the constant relative velocity between the sea current and the towing motion of the pipe string during mining operations. Second, by using Galerkin's method, the equation of motion is discretized into a set of coupled nonlinear differential equations, which are then solved by means of the Krylov-Bogoliubov-Mitrorpolsky method. Finally, the critical internal flow velocity and the limit cycle amplitude with its frequency are evaluated, and then the results are compared against those obtained by the method of direct numerical integration in order to check their validity and accuracy.

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Free vibration and buckling of axisymmetric shells, with thickness which are changed locally, are analyzed. the displacement functions of these shlls are expanded using the free vibration modes of the axisymmetric shells with constant thickness around the circumference. These basis vectors for expansion are calculated using a conical shell finite-element. The expanded functions are used to express the strain energy and kinetic energy. the eigenvalue equations are derived by substituting the strain energy and kinetic energy into Lagrange's equations. Analytical results using the present method show good agreement with analytical results obtained by other methods or experimental results.

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The fluid forces acting on a long seal due to rotor conical rotations are experimentally studied. a test apparatus is constructed in order to measure the dynamic fluid restoring moment and lateral forces under the basic parameters of rotational speed and axial flow velocity across the long seal. It is found that for submerged motors, there is an instable region caused by the fluid moments. These fluid forces are interpreted as the force and moment rotordynamic coefficients. As a result, the authors conclude that conical rotation influences the force coefficients, and that axial flow in the seal influences moment and force coefficients.

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This report deals with a base isolation system for the protection of precision machinery systems from seismic excitation. This base isolation system is called the Ball Bearing Isolator (BB Isolator), and consists of a bowl-shaped base and ball bearings. When an earthquake occurs, the isolator can reduce acceleration by the movement of the ball bearing rolling on the base. In order to examine the dynamic properties and isolation effects of the isolator, shaking tests and theoretical analysis were conducted. From the experimental results, it was confirmed that the response acceleration of the isolator would almost always be less than about 40 Gal even if it was subjected to big earthquakes such as E1 Centro and Taft. From the analytical investigations, it was shown that the proposed equation is effective for estimating the dynamic response of the isolator.

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This paper describes the stiffness and energy loss of the contact surface. We measured the stiffness, energy loss, electrical resistance and Coulomb coefficient of friction on the contact surface in the following two cases. In one case, the specimen is covered with surface filems. In the other case, the specimen is not covered with surface filems. The oscillating tangenntial force-displacement is illustrated by hysteresis loop. The histeresis loop can be analyzed in this experiment by using Mindlin's theory. As the number of cycles increases, surfce films are destroyed and the Coulomb coefficient of friction increases, so the stiffness increases and energy loss decreases.

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In view of the troublesome nature of impact sound, a series of studies have been undertaken in order to find out a way to reduce this effect. Studies have been performed on the generation of impact sound due to the collision between a ball and a square steel plate. This fifth report shows the effects of the boundary conditions of the plate on impact sound. For the boundary conditions of a plate, free edge, four point support edge, and clamp edge were selected. When the ball collided with the plate, the pulsatile contact force and impact sound were simultaneously measured. The signals thus obtained were stored in a wave memory instrument and reproduced on a oscilloscope. Furthermore, the signal of impact sound was analyzed by an FFT analyzer. From the results of the analyses and considerations, the effects of the boundary conditions of the plate on impact sound have been clarified.

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For the analysis of nonstationary signals and time-varying signals such as impact sound, the use of a discrete pseudo-Wigner distribution (WD) is particularly suitable. Review of its mathematical properties indicates that its expression is suitable to represent the signal simultaneously in the time and frequency domains. In order to compute the WD, digital signal processing is necessary. WD for digital processing can be carried out simply by adapting the fast Fourier transform algorithm. Analyzing several types of time-varying transient acoustic signals by means of the WD, we can illustrate their dynamic features jointly in time and frequency representation. Especially for the sandwich steel sheet, the damping characteristic of the signal can be clearly represented in the time-frequency domain.

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Simplified, low cost and precise sensors are required in industrial factories. This paper deals with the development of a simple, low cost and precise sensor used to detect the displacement and position of a physical solid. Sound generated when compressed air is blown onto the open-ended face of the pipe. The sound frequency varies with the displacement of a substance which is placed close to another open-ended face of pipe. This principle is adopted in this sensor. In order to improve the features of this sensor small, pipes with sharp drop and taper differences in the inner diameter are used in the experiment. Also, the sounding mechanism of the pipe used as a sensor is analyzed.

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This paper presents a new optical method for measuring the flying height of a slider on a n actual magnetic disk. The slider used in the measurements was of the taper-flat type and partly made of quartz glass. The surface of the glass was coated with a half-mirror membrane, by which the laser beam applied to this membrane was divided into two beams: one reflecting on the glass surface, and the other transmiting through the glass and reflecting on the magnetic disk surface. The intensities of these two beams and their interfered beams were measured independently, so that the change in reflectance of the disk surface could be taken into account in the measurement of the flying height.

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Dynamic walking is often required in a quadruped robot for the purpose of quick locomotion. It is generally known that the walking pattern of animals is changed to the trot or the pace in middle speed locomotion. Trot walking was recently studied by several groups because of its stability. In the trot, diagonal legs form pairs. While one pair of legs provides support, the other pair of legs swings forward in preparation for the next step. In the trot of the quadruped robot with point-support feet, a rotation around a diagonal line formed by the supporting leg can't be controlled directly by using torques at the articular joints. In this paper, the 3D behavior in trot walking is analyzed from the viewpoint of foot force, duty factor and the roll angle of the body. The effects of the stance and the center of gravity of the body are also examined experimentally using our quadruped robot 'COLT-2.'

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In order to apply pneumatic cylinders to actuators of machines and equipments for flexible automation such as the robots, accurate velocity control together with precise position control is indispensable. The electric servomotors utilized in advanced robots are controlled by computers following excellent software curves through which smooth starts and stops as well as high-speed driving and accurate positioning of the robot manupurators, are achieved. Software servocontrol of a pneumatic cylinder was investigated in this study. As a reference curve for velocity and position, the modified trapezoidal curve was chosen and stored in the computer's memory cells in a digital system. In addition to PD and PID feedback control of the position and velocity deviation, the feedforward control method for velocity and acceleration of the cylinder was examined. It is confirmed experimentally that the software servocontrol applied in this study is applicable for the advanced control of the pneumatic actuators.

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To clarify the scoring resistance of the gears with the sulphurizing process, which is an anodic sulphurization performed in a molten bath with a temperature of about 463 K, scoring tests were run. From the test results obtained by a power-circulating gear machine, it was found that the sulphurizing process has a significant effect on decreasing gear noise, and the scoring resistance of the gears is increased significantly due to the sulphurated layer formed on the meshing faces of the gears and to the tooth profile modification with the sulphurizing process.

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The main purpose of this paper is to clarify the effect of residual stress on thee bending strength of carburized gear steel whichc has an intergranular oxidation layer in the top surface and also to study the effect of residual stress by shot peening on the bending strength. The residual stresses were measured by an X-ray diffraction method. Bending fatigue tests of gear model specimens were carried out under the condition of constant stress range. Correlation samong relation stress, hardness, and the bending strength were found that there were good correlations between residual stresses near the surface layer and the bending strength, and the latter was related to the hardness of the surface and the core in both cases of carburized and shot-peened gear steels. It was also found that it was important to remove the rough surface of the intergranular oxidation layer of carburized material and harden the surface layer by means of shot peening from the point of view of the fatigue strength.

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The decrease of frictional loss of gears is today one of the most important problems from the viewpoint of economizing energy and improving the load carrying characeristics of gears. so experiments in order to clarify the tendency of the frictional loss of spur gears were carried out. We carried out the experiments to clarify the influences of tooth form, sliding velocity, load, surface roughness of tooth, viscosity of lubricating oils, and the kind of oils upon the frictional loss of spur gears. The rate of frictional loss of the spur gears decreases with increasing sliding velocity, increases with increasing surface roughness and decreases with the increasing viscosity of lubricating oils. The rate of frictional loss is kept very low by using a synthetic oil of the SHF type. The friction reducing agent (FM) is also quite effective for reducing the frictional loss. Finally thee relationship between temperature rise of teeth and frictional loss was expressed with an empirical formula.

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Analysis is present of EHL traction with low-viscosity lubricating oils, which is the case encountered at higher temperatures. Extension is made of the approximate formula already derived by the authors, where it is assumed that viscosity, instead of viscoelasticity, predominates when the limiting Newtonian viscosity in an EHL film falls below a critical value, 10⁵ Pas, and an Eyring viscous solution is employed. The rheological parameters representing the traction characteristics of an oil then become the effective viscosity-pressure coefficient and the representative stress, and they are expressed as functions of mean Hertzian pressure and bulk temperature. Calculated results are compared with experimental data obtained on a four-roller machine for two diesters showing close agreement.

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The rigidity and the strength of an adhesive lap joint, in which one end of a beam is bonded to a base by an interface parallel to the axis of the beam and a bending load is applied, have been examined theoretically and experimentally. the deformations of the adhesive joint and the stresses caused in the adhesive layer were analyzed using the finite element method. Then, the rigidity and the strength of the joint were calculated. They coincided well with the experimental results. Effects of the dimensions of the bonded part of the beam, the thickness and Young's modulus of the adhesive layer on the rigidity and the strength of the joint were clarified. It was observed that the value of the rigidity of the adhesive joint was independent of the loading directions and was almost constant, and that the rigidity of the adhesive joint was greater than that of the bolted joint.

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It has been shown experimentally in the previous paper that the fitting strength of the shrink fit between the ceramic shaft and the metal ring with the use of a shrink fitter does not decrease at elevated temperatures. In this paper, the distributions of the contact pressure of the shrink fit assembly were calculated in order to research the effects of the slit number of the shrink fitter and the coefficient of friction on the fitting strength. The shrink fit assembly has two contact interfaces which are between the shaft and the shrink fitter and between the shrink fitter and the outer ring. There are also two interferences at the inner contact interface and at the outer contact interface. The sum of two interferences has been kept constant in the paper. The mean contact pressure at the inner contact interface becomes greater at room temperature as the interference at the inner contact interface increases. This tendency becomes stronger with a larger coefficient of friction. The mean contact pressures at the inner contact interface are, however, equal to each other at elevated temperatures. Under a frictionless condition, the mean contact pressure is approximately equal to that from the simplified formula used in the previous work from room temperature to 100°C.

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The present paper refers to experimental studies on tribological characteristics of lubricated ceramics for cylinder liners and piston rings. The experiments have been carried out under the large sliding velocity condition close to that of practical engines with pin-on-disk-type reciprocative slide test equipment. The major results are: (i) For the materials, it is desirable that the ring surface get a moderate running-in under the more elastic contact condition, and that the liner and the ring be superior in thermal diffusibility and in heat resistance, respectively; (ii) The respective influences of roughness and velocity on the scuffing are so large that the roughness should be kept smaller at the faster slide; and (iii) The effects of additives in mineral oil on the lubricity and the scuffing resistance disappear, and used oil has worse influences on the two, so it is necessary to select the proper lubricants.

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The loads on tools for coiling close coils are analyzed in a two-finger coiling system. The experimental results are compared with the theoretical results. The main results are as follows: (1) The loads on working tools are inversely proportional to the spring indices of coils. (2) The mean diameters of coils are related to the load on the 2nd finger. The load is in proportion to the square of the wire diameter and to the yield stress of wires. (3) Within the range of this experimental condition, the dynamical friction coefficient seems to be a value between 0.3 and 0.6.

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This paper presents the results of an investigation into the effectiveness of a circular cutting tool with a slit tooth on aerodynamic noise reduction. The aerodynamic noise from a circular cutting tool is caused by the vortices generated behind a tooth. It is possible to reduce the aerodynamic noise by controlling the vortices. Using a columnar tooth model with a slit which is made longitudinally through the tooth, the vortices are controlled by self-jet from a slit. From the experimental results, the sound pressure level of the aerodynamic noise is reduced and the influence of the ratio (slit width/tooth diameter) on the aerodynamic noise is clarified.

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In the first report, a computer aided piping design system was developed using an object-oriented language, "Smalltalk-80". In this report, the system is improved to support the design of complex piping networks. The system includes the functions of modeling and simulation, making possible: 1) flexible model building and easy modification, 2) calculation for determining the flow rate and headloss of pipings, 3) simulation of the dynamic behavior of the fluid transfer process, and 4) graphic representation of the design model of pipings and tank levels. The effectiveness of the system is ascertained through the design of a piping system for a tanker. The system provides a means of flexible manipulation that will assist piping design.

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