First, I introduced various kinds of plastics, showed relationships between the relative prices of the principal ones and their heat resistant temperatures, and described various characteristics of plastics, taking the examples of polyamide (nylon) and polyacetal, which are commonly used plastic gear materials. Subsequently, I studied the dynamic behavior of plastic teeth, which is not observed in metal teeth and is related to the viscoelastic properties of plastics, and described various phenomena such as the temperature distribution on the tooth profile, the change in the tooth profile, the recess (groove) occurring near the pitch point, and breakage of the tooth, which are problems of plastic gears.

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This paper presents an integral equation formulation for design sensitivity coefficients of frequency responses in acoustic problems. The implicit differentiation approach is applied in the derivation of the sensitivity formula. The integral equation relating the pressure at an internal point to the boundary pressures and velocities is regularized and differentiated directly with respect to a design variable such as shape design parameter, frequency, mass density and impedance. The resulting integral equation for the design sensitivity coefficients has no Cauchy principal value integrals and can be applied continuously across the boundary of the acoustic field. The effectiveness of the present formulation is illustrated through some numerical examples for three-dimensional problems.

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A method to estimate the stochastic response of hysteretic structures under combined random loads regarded as Gaussian white noise is investigated. The response statistical moments of structures, with hysteretic characteristics approximated by Wen's mathematical model, are obtained by using the Fokker-Planck equation method with a cumulant truncation technique. This paper deals with the formulation for the multi-degree-of-freedom system, and demonstrates that resulting variances of the response for a three-degree-of-freedom structure, as a numerical example, agree well with a Monte Carlo simulation.

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This paper presents a structural optimization approach to reduce vibration, which is a key issue in the structural design of components for head positioners. This method can be used in the concept design stage of head arms for hard disk drives. Head arm vibration modes that affect the accuracy of head positioning are discussed to obtain the feasible design domain of eigenvalues. An optimization algorithm based on a projection method is formulated to obtain the shape with the maximal eigenvalue under a constant weight. The formulation is applied to a primitive head arm model, simultaneously considering the bending mode and the lateral bending mode. The conditions for maximization of the eigenvalues are not the same for both modes. This paper treats the vibration problems of head arms and shows that a feasible domain of natural frequencies can be found for any given weight.

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A method for designing an engine mounting system using hydraulic insulators has been developed with the aim of controlling low-frequency engine vibrations in the roll and bounce modes. This method includes a design optimization theory for each hydraulic insulator and a procedure for determining the equivalent mass for various modes at the mount locations, and is applicable to integrated system optimization. Computer simulation results show that resonance peaks can be effectively reduced with a hydraulic engine mount system designed on the basis of this method.

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This paper describes the principle of an active lead screw mechanism (ALSM)and the basic characteristics of its experimental mechanism. The ALSM comprises a lead screw, two nuts, piezoelectric actuators (PEAs) and a movable table. The table is connected to the nuts through the PEAs so that the PEAs can control not only the backlash between the screw and nuts but also the position of the table. The ALSM has the following capabilities : (1) when the table is to be driven at a high speed and positioned coarsely by a motor, sufficient backlash can be created between the screw and nuts, (2) after the table is positioned coarsely, the backlash can be eliminated by the PEAs so as to give the ALSM a sufficient stiffness, and (3) while keeping the backlash at zero, the table can be positioned precisely by the PEAs. The experimental mechanism achieved the following : (1) the maximum table speed of 130mm/s, (2)the positioning accuracy of better than 10nm, and (3) the positioning time for a 10mm step input of 369ms.

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This paper deals with a newly developed underwater displacement sensor utilizing the acoustic resonant frequency of water in a submerged pipe. Both ends of the pipe are closed. A speaker to generate sound is fixed on the end of the pipe with the reflector at the other end. A piezoelectric ceramic is used as a speaker. Sweeping signal is radiated from the speaker to the water column in the pipe. The sound pressure takes the largest value at the resonant frequency. The displacement of the reflector which is inserted from the other end of the pipe by the plunger, corresponds to the length of the water column. The displacement of the reflector has good correspondence to the resonant frequency of the water column. It is found from the experiment that it is possible to measure accurately underwater displacement using this sensor.

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Magnetically levitated (MAGLEV) vehicle systems have been researched for future high-speed transportation. It is especially important to investigate their dynamic characteristics from the viewpoint of running stability, safety and ride quality at high speed. This paper deals with repulsive-type MAGLEV systems using electrodynamic suspension (EDS). Although the EDS is inherently stable, the damping force is not large enough to suppress the vibration excited by guideway irregularities and other disturbances. Therefore, this paper investigates theoretically and experimentally the damping force control of EDS systems with a hybrid magnet configuration of a permanent magnet and an additional electromagnet of which the current is compensated by a feedback control loop. The dynamical characteristics are analyzed by an experimental setup in which a one-degree-of-freedom mass is suspended above an aluminum rotating plate. According to the experiment, the damping coefficient is significantly increased by the additional control circuit.

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This paper presents a study on the flutter suppression of a vertically cantilevered pipe conveying fluid. The response of the cantilevered pipe is controlled by the torques produced by two pairs of tendons attached to the pipe and two servomotors. The equation of motion is solved by means of the Galerkin method. To reduce the system order, a suboptimal control law is used. The good agreement between the numerical and experimental results shows that this method is effective for the flutter suppression of the vertically cantilevered pipe conveying fluid.

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Parameters of the secondary unit system, similar to other electrohydraulic servo systems, change with the operating condition and time. It is certain that the system performance will be affected. The application of the robust optimal controller in the speed control of a secondary unit system is examined in this paper. This controller consists of an optimal part and an auxiliary part. The optimal part is utilized for specifying the dynamic characteristic of the whole closed-loop system, which is designed based upon the ARMA (autoregressive moving-average) model. The auxiliary part is developed for rectifying the uncertainties which a simple ARMA model is unable to handle. The robust optimal controller is demonstrated from the results of a series of simulations and experiments to be superior to the suboptimal PI controller under the situation of a change in working pressure and load inertia. The proposed control scheme is also indicated by these results to be robust to the external torque disturbance.

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In this paper, a model reference adaptive control (MRAC) with integral compensation for motor drives was proposed. The system's robustness and transient behavior were greatly improved by incorporating a switching controller together with an integral compensation to attenuate the influence due to external disturbance. Modifications were also proposed to alleviate the chattering due to the high-frequency switching activity in control efforts. Furthermore, integrator windup due to integral action under actuator saturation was also considered. Experiments were performed on a single-chip microcomputer to control a DC brushless servo drive with adjustable shaft inertia to demonstrate the effectiveness and applicability of the proposed controller.

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A fuzzy controller is employed to control an electrohydraulic four-bar above-knee prosthesis for the swing phase in level walking. A two-dimensional (sagittal plane)mechanical model of the above-knee amputee is developed and the amputee prosthesis system is simulated for the swing phase. The man-machine system has two fuzzy controllers : a knee fuzzy controller which adjusts the knee damping moment so the prosthetic knee angle trajectory will track that of the patient's sound knee in the previous swing and a hip fuzzy controller utilized to model the way that an amputee will manipulate the prosthesis. From an optimal design procedure, a set of fuzzy controllers is found and an optimal relationship between variations of initial stump velocity and initial artificial shank velocity for the amputee is found. The results showed that the amputee swing gait can be controlled to a near normal one and walking with varied speed is possible.

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We propose an instantaneous inverse kinematic solution for redundant manipulators based on virtual arms. The virtual arm has the same kinematic structure as the manipulator except that its end point is located on the joint or link of the manipulator. Providing that the appropriate number of virtual arms is used, the configuration of the manipulator can be represented by a set of end points of the virtual arms. First of all, we formalize the kinematics of virtual arms and derive instantaneous inverse kinematics. Then, the method is applied to winding control for hyperredundant manipulators. The proposed winding control algorithm is divided into two steps : 1) planning desired positions for virtual end points, and 2) integrating them into joint trajectory of the manipulator. The desired positions of each virtual arm can be planned in a parallel and distributed manner, and there is no necessity for considering joint space of the manipulator. Finally, computer simulations show that the winding control for a hyperredundant manipulator can be performed in 3 D-space.

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Crossed helical gears are engaged geometrically in a point contact between two tooth surfaces, but this contacting point changes to an elliptic contact due to elastic deformation of tooth surfaces under applied load. Therefore, the contacting area between two contacting tooth surfaces is quite small, so that the Hertzian pressure on the tooth surface is comparatively high. Since the sliding speed is also very high, the limiting load for scoring is low and the wear is comparatively high. Although crossed helical gears can transmit only light loads, they have many advantageous features ; e.g., the crossed helical gears are easy to produce and mounting error has no effect on engagement. Therefore, in practice, one of the major problems is to find a way to increase the load-carrying capacity of crossed helical gears. In this study we examined limiting load for scoring, specific wear and friction loss of crossed helical gears with various kinds of surface treatments. We found that the influences of surface treatment and lubricating oil on limiting load for scoring are very strong, which is useful in practical applications, particularly from the viewpoint of power transmission.

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A theoretical analysis of the number of teeth in contact of a gear-type shaft coupling which has random pitch errors and their load capacity is made based on the statistical theory, and the results are compared with those of a numerical simulation. The results of the theoretical analysis agree well with those of the numerical simulation. The probability distribution of the pitch errors and the allowable stress of material of the gear-type shaft coupling are presumed to be Gaussian. The numerical simulation is carried out using Gaussian random numbers which correspond to the pitch errors or the allowable stress. The design formulae for calculating the number of teeth in contact and the load capacity are also presented.

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The dynamic increment of tooth load derived from the new theory is verified by experiment, which is expressed as a function of two variables, velocity and operating load, with the parameter of tooth surface modification, when the dimensions and the tooth-pair spring constant of the gear pair are given. This dynamic incremental load can be used as an index of the dynamic performance of a gear pair, such as noise, vibration and dynamic load. A gear design method to minimize the index is discussed theoretically, which clarifies that there are combinations of tooth surface modification, tooth-pair spring constant and static load which minimize the index and that, in the gear pair which realizes no dynamic incremental load (the index=0) under any load, the tooth surface is not modified and the equivalent tooth-pair spring constant does not vary. In other words, designing a gear pair to show good dynamic performance under any load means realizing an equivalent tooth-pair spring constant with variation as small as possible by choosing the optimal dimensions and realizing tooth suface modification as small as possible by choosing proper manufacturing processes.

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A Brillouin scattering optical system using a Fabry-Perot interferometer and a diamond-anvil cell was designed and set up for the evaluation of the mechanical properties of lubricants under high pressure in elastohydrodynamic lubrication of ball bearings, gears and traction drives. Brillouin scattering spectra for alcohols, hydrocarbons, and synthetic lubricants were measured, and sound velocity and density under high pressure were obtained. The density was compared with Dowson and Higginson's density-pressure equation of lubricants, and density-pressure characteristics of paraffinic oils and naphthenic oils were described considering the molecular structure of solidified lubricants.

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Measurements of the static forces were performed for various types of superconducting magnetic bearings at liquid nitrogen temperature. It was found that the stiffness of the superconducting bearing was rather small ; however, both the electromagnetic forces and the stiffness could be increased by using a combination of a thrust and radial bearing. It was also found that the stiffness could be increased by using the attractive force due to flux pinning. Based on these measurements, a practical superconducting magnetic bearing was designed and constructed, where a 2.4 kg rotor could rotate at 33000 rpm.

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To elucidate the effect of hardened depth on the fatigue strength of carbonitrided gears, gears with three kinds of hardened depths were fatigue-tested using a power circulating gear testing machine. In the case of gears with the shallowest and intermediate hardened depths, the failure mode was spalling. In the case of the gear with the greatest hardened depth, the failure modes were spalling and tooth breakage due to bending at the tooth fillet. The surface durability was higher with greater hardened depth. The bending strength of the gear with the greatest hardened depth was lower than that of the gear with intermediate hardened depth under the same loading condition. Therefore, when carbonitrided gears are designed, it is important to determine the optimum hardened depth of those gears. The change in dynamic performance of every gear was slight during the fatigue processes, since the change of tooth profile of every gear was slight.

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A new concept of "friction-assisted extrusion" to produce a thin metal strip was proposed. In this process, a rectangular prismatic workpiece inserted into the container is compressed by a punch against an anvil, and the anvil is forced to move horizontally. A thin strip can be extruded through the gap by exerting a high friction force over the anvil surface. Very thin strips of aliminum up to about 15μm in thickness could be formed up to the extrusion ratio R-667 with a considerably low punch pressure ratio p/2k=1∼2 (P : punch pressure, k : yield shear stress), which agreed with the theoretical value estimated by the upper bound approach analysis. The friction-assisted extrusion process was applied to a forming of thin strips from aluminum powder. The thin strips formed from the aluminum powder have superior mechanical properties to those formed from bulk aluminum materials.

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Limiting load for scuffing using spur gears, which were case-hardened and ground, was investigated. The load was stepped up according to the provided load stage in our experiments to the load stage of scuffing failure. Before and after the running of test gears, the wear of test gears was measured with a balance. At first the running time of test gears at each load stage varied very widely and we found that, the running time at each load stage has no influence on the limiting load for scuffing. For our experiments four kinds of base oil viscosity were used. As antiscuffing additives ZDTP and EP additives at various concentrations were used. Influences of lubricating oil viscosity and concentration of ZDTP and EP additive on limiting load for scuffing and specific wear were investigated and the results summarized. Furthermore the integral temperature of tooth surface according to the ISO proposal was illustrated and discussed.

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The thermohydrodynamic performance of a large tilting-pad journal bearing including the inlet pressure effect is investigated experimentally. The continuous film pressure, film thickness and shaft surface temperature, and bearing surface temperature are measured along with the shaft speed and the bearing load for various flow rates. Considerably large inlet pressure is observed at the entrance of each pad, especially the lower pads. The inlet pressure is increased by the increase of shaft speed as well as bearing load, but is almost independent of the flow rate. The upper pads always maintain a slight wedge film shape owing to the inlet pressure, and scraping is not observed in the upper pads. It is observed that the shaft surface temperature is constant in the circumferential direction and increases with the increase of shaft speed in both low and high shaft-speed regions ; however, there exists a transition region where the shaft surface temperature decreases with the increase of shaft speed.

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This paper deals with the behavior of a machining-assembly automatic transfer line system operating under a race-matching method to produce high-quality ball bearings. A race-matching method is a method in which an outer race and balls are selected according to the machining accuracy of an inner race. This method complicates part flow and causes stagnation. Analyzing the part flow, we investigate the effect of applying a race-matching method, and investigate the effects of machining accuracy and buffer capacity on the production rate and the consumption rate ratio of parts supplied from the outside.

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Acoustic emission (AE) was used for in-process detection of ceramic workpiece cracking and chipping during grinding of ceramics. For this purpose AE signals generated during creep feed grinding of alumina were detected using a piezoelectric sensor attached to the workpiece and analyzed by computer. The results prove the sensitivity of different AE parameters to grinding conditions and grinding mode. Particularly, AE parameters show a good correlation with the abrasive grain depth of cut.

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In this paper, a systematic synthesis of the optimum arrangements of links and pairs in spatial mechanisms with multiple moving closed circuits is studied with consideration of the degrees of freedom of the mechanisms. Namely, the conditions required to construct the mechanisms with multiple moving closed circuits are formulated. Moreover, mechanisms with multiple moving closed circuits are constructed with some basic links and open chains, obtaining the optimum arrangement of links and pairs. Based on the above analytical results, a synthesis system is proposed which determines the optimum arrangements of links and pairs. Finally, the types of spatial seven-link mechanisms which satisfy requirements of the above-mentioned basic links and open chains are synthesized to illustrate the method.

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An optimum design method is considered as a method whose results are the most reasonable from various standpoints in the prescribed mathematical formulation. However, its formulations present difficulties in choosing objective functions, setting allowances to constraints and so on, because they are greatly concerned with the results of optimization. In this study, we proposed concepts of qualitative sensitivities and qualitative optimality compared to quantitative concepts, as well as a general algorithm of the qualitative optimization method. We newly defined three kinds of fuzzy language, assigned fuzzy sets to each of them and assigned them to each candidate for discrete design variable. We proposed fuzzy reasoning rules by using these two kinds of fuzzy sets. We also extended the proposed algorithm to multiobjective optimization. Through the numerical example of a single-objective problem, we obtained almost the same solution as in quantitative methods, and efficiencies were confirmed for this case. Also through the example of a multiobjective problem, the new method was shown to have more flexibility in determining the preferred objective functions compared to the conventional method.

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The displacement equation of the Bennett 4R mechanism is directly derived and the output angular velocity and acceleration are analyzed. The coupler curve, its higher order curvature analysis, and coupler-link motion are also provided. In practical applications, this mechanism is used for dimensional synthesis, function, path and motion generation in the optimization technique. Moreover, some numerical examples are provided to illustrate the design algorithm.

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