To clarify rolling contact fatigue strength in terms of fracture mechanics, various flaking modes in practical rolling bearings, the relationship between rolling contact fatigue life and fracture toughness in Mode I, and recent studies on crack initiation and propagation through fracture mechanics are reviewed. Surface-origin-type flaking is becoming more important than the traditional subsurface-origin type as nonmetallic inclusion in steels is reduced. A new flaking mechanism wherein tensile residual stress in the radial direction in the subsurface initiates cracking has emerged and was verified by an experiment. Another new type of flaking, referred to as brittle flaking, was reported ; here cracks are remarkably numerous, large and deep, accompanied by a new type of microstructural change. The cause of the brittle flaking was assumed to be tribological reaction on the raceway which decomposes the lubricant to cause hydrogen embrittlement. To establish a new bearing life calculation equation, it is necessary to create proper models for the various failure modes and to measure fracture toughness in Mode II.

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A new technique in time domain for the identification of nonlinear multi-degree-of-freedom vibratory systems has been proposed. The main procedure of the technique is to divide the regions of displacements and/or velocities into small subdomains, express the nonlinear terms of the system by interpolating over these subdomains and determine system parameters as well as nonlinear terms based on the equations of motion. The technique is shown to be valid by numerical simulation. Comparison is then made between the proposed technique and other related main techniques, i.e., the technique using power series expansions, and the technique using Chebyshev orthogonal polynomials.

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The occurrence of combination tones in a nonlinear beam subjected to an excitation having two harmonic components with frequencies Ω₁ and Ω₂ is investigated. For theoretical analysis, the perturbation method of multiple scales is used. It is found theoretically that combination tones with frequencies (±2Ω₁+ Ω₂), (2Ω₁- Ω₂) and (±Ω₁+2Ω₂), and subcombination tones with frequency (±Ω₁+Ω₂)/2 can occur in a single mode. It is also found that in addition to these, a new type of combination tone can occur in multiple modes. The occurrence of all of these combination tones is confirmed experimentally.

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Exact solutions of the free vibration in a single-degree-of-freedom system having a nonlinear spring composed of cubic and constant terms are established. With the use of a certain bilinear transformation, the equation of motion is successfully converted into a regular Duffing equation whose exact solution already exists. The transformation and the reduced Duffing's nonlinear spring are identified by solving simultaneous nonlinear algebraic equations along with the given initial displacement. The waveform of the solution resembles a suspension bridge. The so-called skeleton curve is also asymmetric, and the maximum and minimum amplitudes must be distinguished. The response reveals combined soft and hard spring characteristics and possesses a two-branched property within a certain frequency range. The exact solution is successfully applied to verify the accuracy of an analytical approximate solution obtained by the perturbation method, as well as of the numerical integration by the Runge-Kutta-Gill scheme.

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This report deals with a fundamental study of inelastic seismic design methodology of tall structures with attention to anchor bolt yielding during earthquakes. To investigate the dynamic behavior of these structures, first, shaking table excitation tests were conducted for a tall slender model structure. Next, to interpret the experimental results, a simple mechanical model was proposed and the numerical response analyses were carried out. The following conclusions were obtained from these experiments and analyses. ( 1 ) When the response of the model structure dominantly increases under the resonant condition causing plastic deformation of anchor bolts, a greater amount of reduction of seismic design load for tall structures was observed in comparison with an elastic design. ( 2 ) As for the structural response time histories, satisfactory agreement between the experimental results and the numerical simulation results was obtained.

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Suppression phenomena of resonant oscillations in a strongly nonlinear system with a geometrical clearance between a support and a beam by the use of additional asynchronous excitations are studied. By adding another excitation to the system together with the main excitation, new non-linear phenomena in which the primary resonance curves become unstable in certain intervals and system behaviors shift to nonresonant solutions with smaller amplitudes are found. The relationship between the additional excitation coefficient and the frequency region for effective suppression is investigated for three types of single-degree-of-freedom systems subjected to complex excitations such as parametric excitation and forcing excitation. The similarity of those suppression phenomena in the system is recognized. Then it is shown that the location and the width of the frequency interval of suppression can be easily controlled by changing the parameters of additional excitations. The physical explanation of such suppression phenomena is also revealed in the phase plane analysis.

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This paper deals with a recognition method of plant devices and equipment using the visual method for the plant maintenance robot. For this purpose, the fiber grating (FG) method described in this study employed to identify and recognize three-dimensional (3D) plant objects, such as pipelines and flanges, which generally have curved surfaces. The FG itself is made of optical fibers through which the laser beams make discrete dot patterns without any mechanical scanning structures, unlike other scanning methods. Thus the proposed method has the following advantages : ( 1 ) it is possible to obtain 3D image information by means of a single camera ; ( 2 ) the processing time is generally shorter than that of other methods. Although the proposed method does not give a fine analysis method of image data like a common scene analysis, it is suitable to obtain rough information on the working environment of robots. This paper introduces a rule-based expert system capable of recognizing plant equipment from processed image data. The rules are made based on typical data of each device, irrespective of their size. Some experimental results are shown to verify the proposed method.

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In the preceding papers, the authors proposed a new method of differential PWM for a hydraulic actuator operated by two 3-way solenoid valves. An arbitrary pulse width of the pressure difference across both sides of the actuator piston was realized by adjusting the switching time of each valve. The actuator operated by differential PWM shows good linearity as a control element, achieving accurate positioning. This study, as an application, deals with a hydraulic servo system composed of a 4-way spool valve and a load cylinder, where the spool valve is driven directly by the differential PWM actuator. The servo system is designed based on the optimal regulator method of the state variable model. The system performance is investigated through simulations and experiments. Consequently, it is shown that the actuator, operated by differential PWM, plays the role of a linear control element, and that the servo system is well designed by the optimal regulator.

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One of the most significant vibration sources of higher-frequency noises in refrigerant compressors used for air conditioners or refrigerators is the reed valve which controls the refrigerant gas flow from the discharge port. In order to examine the higher-frequency vibrations of the reed valve exposed to compressed gas flow, we conducted a vibration test for a simple axisymmetrical model consisting of a valve, valve plate, cylinder and piston. First, compressed air entered the flow chamber through a capillary tube at the piston center, and the valve was excited to induce a forced vibration over as wide a frequency range as possible. Then, the fluid pressure in the flow chamber was measured for different cylinder volumes to determine the amplitude and the phase lag relative to the valve vibration, thus making it possible to obtain a dynamic stability criterion for self-excited vibration of the reed valve. Secondly, a free vibration test was performed on the reed valve to verify that the reed valve actually experiences self-excited vibration when the dynamic stability criterion obtained from the forced vibration test is not satisfied. In addition, the vibration frequency and self-excitation level of the reed valve were examined.

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This paper deals with a new concept of an optical servosystem and presents an experimental analysis on photostrictive ceramics for use as an optical actuator in the optical servosystem. The optical servosystem proposed here is characterized by introduction of an optical actuator into the system. PLZT ceramics is used as an optical actuator which is directly driven by light irradiation. The photostrictive effect in the PLZT ceramics produced from the superposition of the photovoltaic effect and the piezoelectric effect is experimentally evaluated from the viewpoint of its applicability to an optical actuator. The experimental results show that the PLZT ceramics generates a mechanical strain as large as conventional PZT ceramics but at a very slow dynamic response of about 40 seconds. The slow dynamic response is attributed to the time lag in the photovoltaic effect.

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A new accurate measurement of variation in cavity volume in the container has been investigated. It is difficult to obtain a stable measurement with an air jet due to variable factors such as the compressed air pressure and pipe dimensions. This paper deals with a new resonance method using the radiated sound from a speaker. The sound frequency obtained by the experiment is compared with the calculation result of the frequency found by the theoretical analysis in which the cavity system is composed of two acoustic pipes. This method of measuring the volume is applicable measurement of not only liquids but also solids, animals, etc.

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A precision steel ball is attached to the end-face of the spindle and an electronic capacitance-type transducer mounted on the tool slides of a three-dimensional sliding stage. Relative displacement in the axial direction between the ball and the transducer is detected during spindle rotation. The measurement principle of the central position is based on the fact that the undulation component synchronized with the rotational speed of the spindle in the displacement signal reaches a minimum value at the central position of rotation. The results of preliminary experiments are summarized as follows. ( 1 ) The new method allows detection of the central position with a resolution of 0.5μm. ( 2 ) In the case of the spindle with hydrodynamic bearings, the rotational speed of the spindle and the resonance vibration of the headstock affect the central position of the spindle rotation.

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In this paper, we present the feedback control of a one-link flexible arm having reduction gear friction. Tip position control was very difficult when large friction was treated as an equivalent viscous friction. Experiments showed that tip position feedback control was possible using the dither signal. We investigated the influence of the dither amplitude on linearizing the nonlinear friction and the response of feedback control. The acceleration signal from the accelerometer at the arm tip, like the signal from the strain gauge at the arm root, could use feedback control for the fundamental vibration mode.

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In this paper, we present a hierarchical intelligent control system. We propose this system for generalization of the neural network-based controller using the higher-level control based on AI technology to acquire knowledge heuristically. Therefore, this system comprises two levels : a "learning" level and an "adaptation" level. The neural networks are employed for both the long-term learning of the control process and the short-term adaptation of the dynamic process. The learning level has a hierarchical structure for recognition and is used for the strategic planning of robotic manipulation in conjunction with the knowledge base in order to expand the adaptable range to the environment. New information from the adaptation level updates the learning level through the long-term learning process. On the other hand, the adaptation is used for the adjustment of the control law to the current status of the dynamic process. The motion controller at the adaptation level is particularly useful in non-linear dynamical systems having uncertainty in the environment.

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This paper presents a convenient analysis method for plane cams. This method is based on the principle of the offset curve of a plane curve and has the features of conceptual clarity and simplicity of computation. Almost the same methods can be used for the calculation of both the cam profile and the tool coordinates in manufacturing and for the influence analysis of the errors which occur in the manufacturing and assembling of cams, because the cam contour, the pitch curve and the path of the tool center are the offset curves each other. The validity of the method is confirmed with some examples. This method can be effectively applied for CAD/CAM of plane cam mechanisms.

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The sealing characteristics between a turned surface of soft material such as copper and a smooth seal surface of a rigid steel ball in static contact were investigated. This seal surface received not only a normal force but also a tangential force. The following results were obtained from calculations using a model that considered surface roughness on a turned seal surface as a wedge-shaped asperity, and gas leakage tests. ( 1 ) The linear sealing load P_c/l decreased with a decrease in the conical half-angle θ of the conical inside-seal surface. In the case of a surface roughness of 8 μm, the value of P_c/l at θ=15° was about 0.4 times that at θ=60°. ( 2 )The recommended values of θ were in the range of 5° to 35°, and the P_c/l values corresponding to this range were predicted.

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Modified tooth profiles and their deflections cause a gear pair to contact away from the theoretical line of action and result in transmitting inconstant rotational motion. Those actual points of contact and their tooth actions can be described using tangential-polar coordinates by giving the measured single flank error and the tooth-spring constant. From this point of view, the rotational motion is analyzed to obtain the dynamic increment of tooth load in this series of papers. In this first paper, the engagement between modified tooth surfaces of a helical gear pair is replaced with that between eqivalent tooth profiles of a spur pair with the same single flank error. The equivalent profile is expressed algebraically as an involute curve with an instantaneous base circle whose radius varies, the tooth actions of which are analyzed geometrically. By giving the tooth-pair spring constant, the equivalent profile under load, its instantaneous base circle and the equivalent tooth-pair spring constant in the region of both single- and multiple-tooth-pair mesh are also analyzed.

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A continuously variable power transmission, CVT, has potential for the improvement of fuel economy and cruising comfort as an automotive propulsion system. A traction drive CVT changes its speed ratio by the control of side slip force on the Hertzian contact. This mechanism has the features of equal torque transmission of every rolling element and low wasted power for the speed ratio change, but sometimes falls into self-excited vibration at higher rotating speed. This paper describes the principle of the speed ratio changing mechanism of a half-toroidal traction drive CVT and offers a compensatory measure for stabilizing the electrohydraulically operated speed ratio control servomechanism.

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In this study, the optimum shape of the magnetic pole on an electromagnetic damper is determined by means of an optimization technique with an eye to compact design. The Lagrange multiplier method was used as the optimization technique. Firstly, damping coefficients were evaluated from the distribution of eddy currents occurring in the conducting slab. The distribution of eddy currents was calculated by the boundary element method combined with the finite-element method. Secondly, the optimum shape of the magnetic pole was obtained by the optimization technique under several conditions. Thirdly, each optimum pole shape was verified experimentally through comparison between the experimental value of the damping coefficient and the objective value.

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An index of motion-transmission characteristics τ of the planar six-link mechanism with a prismatic pair is presented through investigations of the sensitivities of the angular and linear displacements of the links to the deviations of the kinematic constants and the forces acting on the pairs due to the external forces on the links. Generally speaking, the average of the sensitivities S and the average of the forces acting on the pairs F decrease rapidly in the interval [0, 0.3] and slowly in the [0.3, 1]as τ increases. The τ-S and τ-F relations are approximated to the regions bounded by two rectangular hyperbolas. Consequently, it is possible to estimate the values of S and F for any mechanism at the given crank angle by means of τ.

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