This paper deals with the flexural wave control of a flexible beam with an infinite number of vibration modes. It is the purpose of this paper to present a new vibration control method, the active sink method, which makes it possible to suppress all vibration modes of the flexible beam. Unlike a conventional vibration control method which attempts to suppress several vibration modes already excited, the active sink method seeks to keep all the vibration modes inactive. First, this paper presents the principle of the active sink method and shows a means of realizing its system. Next, in order to describe the principle of the active sink method mathematically, transfer matrices of a beam using a progressive wave solution to the wave equation are obtained. Then, the optimal conditions for the active sink system are derived, and the fundamental characteristics of the system are discussed. Finally, from the vdewpoint of vibration intensity analysis, the validity of the active sink method is clarified.

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A digital optimal regulator technique is introduced to the problem of vibration control of a cantilever beam. A pair of piezoelectrit cells is adhered to the upper and lower surfaces of the beam and used as the actuator. Influences of the mass and the rigidity of the actuator are taken into account in the analysis, and the equations of motion for the beam-control system are derived by applying the trsnsfer matrix method. Simulated transient response of the beam is compared with the experimental result. It is found that the effect of vibration suppression is obtained by means of the present technique which compensates for the delay arising from the computation time.

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A modal analysis is presented for predicting the response of a frame structure controlled by a small number of sensors and actuators with high accuracy, with short computation time, and without causing any observation or control spillover. The time response is determined by solving integral equations with respect to only the member joint displacements. The integral equations can be solved by transforming them into ordinary differential equations and by introducing additional mass corresponding to the inertial force due to the rigid-body axial translation and rotation of memhers. Detailed explanation is given on the complete elimination of the spillover by the present analysis. Numerical examples deal with the control of the position, attitude and elastic deformation of a space structure and a manipulator arm, a vehicle frame supported by nonlinear springs and a frame with a dynamic absorber used for economizing the energy consumed for the active control.

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Unstable vibration of the head assembly in flexible disk drives (FDD) induces read and write errors, and it decreases the life expectancy of the magnetic memory. This study experimentally analyzes the unstable Vibration using an FDD unit modified to rotate at variable speeds. The unstable vibration of the disk is measured by a non-contact photosensor. The head vibrates in a pitching mode and the disk vibrates toward the head in a wave-train mode ; these modes are coupled. Instability occurs only within a certain speed range, and the frequency of unstable vibration increases as rotational speed increases.

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The bouncing and pitching oscillations of a levitated body, which is assumed to be moved in a vertical plane and suspended by the magnetic force of a guideway, are examined theoretically and experimentally. A pair of nonlinear differential equations with periodic variable coefticients and nonhomogeneous terms, which governs the oscillation of the levitated body due to the guideway roughness, is derived. Using the above equations, it is shown that the oscillation is parametrically excited by the nonlinear component of the magnetic force even if the levitated body is symmetrical about the horizontal axis passing through the center of gravity. Also, the steady-state response of the oscillation under the parametric excitation is studied in more detail. Furthermore, the experimental results are shown to be in good quantitative agreement with the theoretical ones.

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A control system to reduce vibation in rolling piston-type compressors in room air conditioners is proposed. To suppress compressor vibration due to torque excitation, a torque control system is applied. This method uses a microcomputer, which makes the motor output torque nearly equal to the load torque variation which is caused by gas compression at any angular position. Theoretical analysis and computer simulation show that the control system, in which the rotational variaion (fluctuation of angular speed or angular acceleration) is caused by the torque difference, is detected during one revolution and is reflected to the motor output torque at the next revolution, due to the cyclic characteristic of the load torque. This shows that "repetitive control", can be adopted. Thus, reduction of compressor vibration is possible.

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A beam partially covered with a constrained viscoelastic layer shows superior damping capacity to that of a fully covered beam, depending on the beam geometry and the properties of the viscoelastic layer. This damping effect, the so-called partial cover effect, however, had not been examined in detail until now. In this paper, the strain energy analjsis of the three types of partially covered five-layered beam is carried out in order to explain the damping mechanism. The results of analysis for the center-covered beam and the end-constrained beam indicate that the partial cover effect is caused by the shear strain energy dissipation at the outer edges of the viscoelastic layer, and also, such energy dissipation depends on the tensile stiffness of the constraining layer. The separately covered beam has a superior damping capacity to that of the center-covered beam with the same cover ratio, due to the energy dissipation of the inner edges of the viscoelastic layers. These damping characteristics of the three types of beam presented are confirmed by experimental results.

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This paper presents equations and computational graphs that determine the optimally tuned and damped dynamic vibration absorber attached to a linear system subjected to stationary random excitation. The optimization criterion is to minimize a performance measure defined by the mean square acceleration response of the primary system to unit input acceleration (assumed to be ideal white noise). The optimum design conditions of dynamic absorber can be formulated if the primary system has no damping. If there is damping in the primary system, the optimum conditions are obtained from the numerical solution of simultaneous equations. The optimum conditions obtained here are different from the classical ones evaluated by the so-called Ormondroyd-Den Hartog theory. It is due to the difference in the performance measure in these theories. The optimum conditions are tested on a vibratory model. It can be shown that a properly designed dynamic absorber operates efficiently for reducing the vibration induced by random excitation.

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Modal analysis is widespread and many curve-fit techniques which estimate modal parameters such as natural frequencies, modal damping ratios and natural modes have been developed. A new method based on the maximum likelihood principle which utilizes the frequency response function (FRF) as input data has been proposed by one of the authors. According to that method, it is necessary to estimate not only FRF itself, but also the variance of the FRF by a vibration test. Following the previous report, this paper presents a method of estimating FRF's variance for the "H_v" estimator in the case of multipoint excitation. Furthermore, an approximate estimation method of the H_v's variance is presented aiming at the convenience of calculation. Errors of modal parameters estimated by the maximum likelihood method are also evaluated in the form of standard deviation.

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An analysis is presented for the free vibration of a spinning polar orthotropic shallow spherical shell. The governing equations and the boundary conditions of the shell are derived by applying Hamilton's principle to the strain and kinetic energies of the shell. The variables in the equations of motion can be expressed as a sum of the quasi-static components and of the dynamic components. The linear equations for the vibration about the deformed state are solved by using the transfer matrix method. Applying the method to a spinning clamped-free shallow spherical shell, the eigenvalues of vibration are calculated numerically, and the effects of the spinning velocity and the orthotropy of the shell on the free vibration are studied.

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Kinematic and static characteristics of pantograph mechanisms have been analyzed and represented in the form of charts which enable rational syntheses of the mechanisms as robot arms and legs with two degrees of freedom. Namely, the maximum joint forces and bending moments of links when the mechanisms take arbitrary positions and attitudes have been formuiated by introducing two factors. Characteristic charts of statics have been made by plotting lines of positions of the output point where both of the factors are respectively constant in dimensionless working spaces. Making use of the characteristic charts, shapes and dimensions of working spaces, load conditions, strokes and arrangement positions of actuators etc. can be directly considered in the determination of kinematic parameters of the robot mechanisms with the optimum joint forces and bending moments of links.

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In their previous study, the authors demonstrated that noise can be greatly reduced by using gears which are made of plastic material (called P-nylon) consisting of nylon filled with a plasticizer. In apparatus such as acoustic equipment, gears suffer only a slight torque and their teeth need not be high in strength. Currently, the development of gears with low noise is in demand in this field. In the present study, gears are produced using a polyamide elastomer which is softer than P-nylon and harder than rubber, and tests are carried out to determine their noise reduction effect, the wear of their teeth and their operation life. The practical performance of these gears is studied based on the test results

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The correlation between the transmission error of gears and some factors which are usually considered to express characteristics of a tooth contact pattern, such as areal percentage and total length of simultaneous contact lines, is examined, but very poor correlation is found. A new method of estimating the transmission error from a tooth contact pattern is introduced. This is a method of supposing a triangular shape for the composite error on the actual contact line, which results in the ridge figure of the composite error surface as a function of the tooth contact pattern. The transmission error is derived as a function of this ridge figure. The results estimated by this method showed fairly good correlation with the actual transmission error, especially for a low transmitting load. Based on this method, an index value to estimate the amplitude of transmission error of a gear pair by the observation of tooth contact pattern is also introduced.

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Worm gears, which undergo a great deal of sliding, produce a large amount of heat and suffer from a high degree of wear, being low in resistance to heat and wear. However, plastic worm gears are currently demanded for use in food processing machinery which should be free of oil that can get into products. In the hope of developing practical worm gears from composite plastic material filled with fiber and solid lubricants, worm gears made of such plastics are produced, and tests are carried out to determine the degree of wear, coefficient of friction, surface roughness and changes in temperature.

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Design of nonintersecting-nonparallel-axis conical involute gears is established. As a result, any conical involute gears which transmit rotational motion between two nonintersecting-nonparallel-axis shafts can be readily designed and made. This design is composed of two methods. One is a method to determine mounting dimensions when the basic dimensions of a pair of gears are given first. The other is a method to determine the basic dimensions of a pair of gears when the mounting dimensions are given first. The test gears are designed and made for trial; tooth bearing tests are performed, and it is proven that this design has the applicablity.

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The present paper refers to the 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 that : (i) for the materials, it is desirable that the sliding 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 the contaminated oil has worse influences on both, thus it is necessary to select the proper lubricants.

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A numerical analysis of the elastohydorodynamic lubrication under high speed and high load has been made for a line contact using a modified Houpert-Hamrock method in order to examine the characteristics of the lubrication region which is called "rigid-variable viscosity" in Hooke's chart. Further, the influence of inlet pressure on the lubrication characteristics has been investigated. The results show that the effect of elastic deformation on the film is significant, and thus the film thickness in the region is more insensitive to the load than the film thickness formulated by Hamrock and Jacobson from numerical solutions in the usual elastic-variable viscosity (E-V) region where it is insensitive to the load. It is also shown that the inlet pressure in the examined region exerts a marked influence on the lubrication characteristics in comparison to that in the typical E-V region, and that the pressure spike point moves to the inlet direction, unlike in the case of the typical E-V region, as the load increases. Therefore, the E-V region in Johnson's chart can be divided further into the two regions.

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Continued experimentation with photoelastic simulations confirmed that our proposed hollow flange design for hex nuts is as effective against loosening by vibration as against loosening due to uneven load distribution by virtue of distributing the load evenly on the symmetrical periphery of the flange through raising the fulcrum point on the threads away from the bearing surfaces of the nut and its seat.

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In the design procedure, designers always analyse and consider various requirements and also conduct necessary information processing so as to obtain the most suitable result. In order to rationally automatise such a design procedure, it is necessary to process the design and its related information effectively by a computer system, especially from the aspect of decision making while processing the information. Thus, in this paper, a decision-making methodology for the basic layout design of machine tools has been proposed to establish an intelligent CAD system. The proposed methodology is based on the priority rule of the input specification, and its validity has also been verified through some case studies on the selection of the suitable bearing type and arrangement of the main spindle in machine tools by the usage of a developed system for supporting decision making.

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The dynamically recontigurable robotic system (DRRS) is a new kind of robotic system which is able to reconfigure itself to optimal structure depending on the purpose and environment. To realize this concept, we have proposed CEBOT (cellular robotics). Communication is needed in the CEBOT system as follows. When cells are separated, the communication master cell needs to know the other cel1's function and positions and determine the target cell for docking. Mobile cells should be able to coordinate with other mobile cells. When cells are docked, forming cell structure/module, a master cell should control the bending joint cell and know of which cells the construction is composed. In this paper, we propose a communication protocol for both the cases with an optical sensor applicable to CEBOT. Some experimental results are shown by realizing the proposed communication method between cells.

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In this paper, a new concept of a "Neural Servo Controller" is presented to show the applicability of the neural network to position and force, control of robotic manipulators. The proposed Neural Servo Controller is based on the self-organization capability of the neural network, which here consisfs of two hidden layers, and input/output layers. The controller can adjust the neural network output to the robot in the forward manner to cooperate with the feedback loop, depending on different characteristics of handling objects. In particular, the neural network can recognize the force-control modes. The proposed method can adapt the network of stabbing control to one with applications of position and force control. Simulations and experiments are carried out in the case of one-dimensional robotic manipulators. The results show the applicability and the adaptability of the proposed Neural Servo Controller to position/force control of manipulators.

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Recently, plastic gears with high strength and heat resistance have become necessary as office equipment becomes compact in size and the operating conditions become more severe. Engineering plastics with base polymers fi1led with glass fiber or carbon have been developed and applied to the gears. The endurance limit or wear resistance of the gears made of these engineering plastics has scarcely been revealed. In this paper, after the features of the errors of these plastic gears were inspected, endurance tests were conducted in order to determine the wear characteristics. It was observed from the results that the glass fiber filled in the plastic gears brought about abrasive wear on mating gear teeth. It was concluded that improvement in the surface durability of a gear pair can be attained by selecting the appropriate number of mating gear teeth such as each aliquot number.

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