This paper presents the experimental results on chaotic vibrations of a cantilevered beam deformed by a stretched cable. The beam is deformed to a postbuckled configuration by a cable that is extended from the top to bottom of the beam. We call the deformed beam a 'tendon beam'. As a lateral load is applied to the beam statically, the beam changes to another equilibrium position accompanied with a snap through deformation. When the beam is subjected to periodic excitation, a large-ampltiude response is generated by resonance. Chaotic motion appears near the fundamental resonance region as well as the region in the higher mode of vibration. Both chaotic motions are confirmed as the chaos due to maximum Lyapunov exponent with a positive number. By recording the Poincare section of the chaos behavior, fractal attractors are clearly focused in the fundamental resonance region. The more complicated attractor is obtained in the resonance region of the second mode of vibration. The correlation dimension of the chaos in the second mode is higher than that of the fundamental mode. It is generated by the two-to-thirtees internal resonance between the fundamental mode and second mode.

View full abstract

A component mode synthesis method capable of estimating vibration responses efficiently in a high-frequency range is presented. In order to analyze the response in a high-frequency range, a high and low order truncatable mode superposition method is incorporated in the reduction process included in both the formulation of component mode synthesis and solving the superimposed global equation of motion. By truncating lower modes, it becomes possible to analyze a system with fewer degrees of freedom than the existing modal reduction methods. Frequency response analyses of several test problems of damped structures are performed and compared with the multipurpose versatile code, MSC/NASTRAN, to demonstrate the efficiency and versatility of the proposed method.

View full abstract

This paper presents an analysis of the dynamic interaction between a vehicle-passenger and a large-sized vehicle on a highway bridge. Dynamic deflection of highway bridge induced by a large-sized moving vehicle is a factor exerting serious influence upon vibration of a vehicle-passenger stopped on the bridge. The mathematical model has twelve DOF (degrees-of-freedom) ; the vehicle model with three masses has four DOF, the occupant model with four masses and hinged-beam model, six DOF, and the large-sized vehicle with spring mass has two DOF. The modal analysis technique has been adopted in equations of motion for highway bridge. The random roughness of the actual highway surface has been taken into account in the simulation system. During application of this system, the effects of specifications of highway bridge and parameters of large-sized vehicle on vehicle and human dynamic behavior were investigated. It was found that these factors exert serious influence upon vehicle and human vibration. Some results are presented in the form of parametric plots.

View full abstract

This paper presents the mode synthesis method for structures with nonlinear connective parts. The mode synthesis method is applied to large structures in order to decrease the computational loads of the dynamic analysis. The structures are divided into substructures in the mode synthesis method. The connective parts between substructures have been treated as linear spring models with viscous damping. However, the nonlinearity cannot be neglected in many cases. The connective parts between substructures are modelled by nonlinear systems considering the friction and the gap. The mode synthesis method is applied to a truck crane model with nonlinearity. The dynamic responses are numerically evaluated using the Newmark-β method. A crane boom model with a wire rope is treated as a model example. The dynamic responses of the crane boom operated in swing motion are calculated.

View full abstract

A steady-state periodic solution is essential in the study of the vibration theory. A new computer-aided scheme to determine the periodic solution and its stability is discussed, which is a remarkably precise, speedy and powerful method pursuing some classical schemes with the same aim, e.g., the famous harmonic balance method. Since the algorithm consists of a purely numerical procedure, the scheme is very effective for cases in which it is difficult to find steady solutions when employing conventional analytical methods. The scheme is based on a particular conception to determine the specific initial conditions which generate only steady-state solutions without transients. The specific initial conditions are computed by iteration applying a certain improving strategy using the Newton-Raphson method and numerical integration, e. g., the RKG scheme for the relevant differential equations. Illustrated examples are provided, which demonstrate the convergence of successive trajectories in a phase plane. A full listing of the program is accompanied by its instruction manual.

View full abstract

This paper is intended as an investigation of frequency response function (FRF) estimates for structural dynamics modeling. First, a new method for reducing errors caused by window effects concerning FRF estimates is proposed. The main feature of the method is that both the input force sample function and the output response one, which are obtained as finite-length time functions, are converted to periodic sequence functions before discrete Fourier transform of those functions is performed. Secondly, advantages of the method are demonstrated through the use of simulated FRF estimates. In conclusion, (1) no window effects appeared with the use of the proposed method; (2) the method can be applied to various types of excitation, e.g., random or impact.

View full abstract

This paper describes the experimental study on suppression of torsional vibrations of a rotor by attaching a hollow cylinder partially filled with liquid. The hollow cylinder is divided into identical sectors by radial walls. In addition to measuring torsional vibration, surface waves were photographed to observe the motion of the contained liquid. The number of divisions of tested hollow cylinders is 2 or 4. Experimental results show that the surface waves move backward, that is, travel in the direction opposite the rotation.

View full abstract

This paper deals with the problem of quenching self-excited vibrations by an impact damper composed of a ball and impact walls. The Runge-Kutta-Gill method with variable time division is applied to the numerical analysis of the self-excited system of Rayleigh's type. The solutions obtained from this method are divided into two main categories, that is, periodic solutions and chaos. Furthermore, two types of chaos are determined, namely, chaos after period doubling bifurcation and intermittency. An optimum approach for quenching of the self-excited vibration was discussed. As a result, it was clarified that for the optimum design of the impact damper there existed a certain relation between coefficient of restitution and clearance. An experiment was performed in order to quench vortex induced vibration by the impact damper. The experimental results agreed well qualitatively with those from the numerical computational analysis.

View full abstract

This paper describes active control of vibration, which is generated in a vibration isolation system in an automatic guided vehicle, using controlled electromagnets. To suppress the vibration due to resonance, an active vibration isolator is added to the passive vibration isolation system. The experimental apparatus consists of two rigid plates, eight rubber springs and four sets of active vibration isolators. One set of active vibration isolators has an electromagnet, a power amplifier, a controller, a displacement sensor and an acceleration pickup. An absolute velocity feedback damps the vibration isolation system and realizes a skyhook damper. Vibration tests show that the use of controlled electromagnets increases the structural damping of the vibration isolation system and reduces the vibration amplitude in the system.

View full abstract

This paper proposes a method of active vibration control for flexible structures using a wave-absorbing control. The method is based on the active restraint of the formation of the standing waves which are formed in the process of continuous vibrations. The Euler-Bernoulli beam is dealt with as the control object. Considering the general solution of the wave equation, we obtain an active control law which eliminates the reflection waves at the boundary. The effectiveness of the restraint of the resonance is shown in frequency domains. We then apply the method to the impulse responses which have wide frequency domains. Consequently, we show that the vibration of the beam is effectively controlled in the short time before the standing waves are formed.

View full abstract

The authors have proposed a basic theory for precisely estimating the frequency response of sound power radiating from plates due to their flexural vibration. In this theory, the equivalent viscous damping ratios of all the natural modes of flexural vibration are required to calculate total loss factor, radiation loss factor and driving point mobility, which are the three most important parameters for the estimation. At present the equivalent damping ratios are only determined using the experimental modal analysis of plates. However, if the damping ratios can be estimated by means of a theoretical method, the radiated sound power may be completely estimated by calculation. As the basis for that, the internal damping of metal is assumed to be viscous damping and is incorporated into the equation of flexural vibration of plates ; then, the relationship between the internal damping and the natural frequency of flexural vibration is derived using Mindlin's thick plate theory.

View full abstract

The equations for estimating modal total loss factor were determined for S45C steel, SUS 304 stainless steel, spheroidal graphite cast iron, brass and A2017B alminum, based on their experimental modal total loss factors which were measured using experimental modal analysis of a circular plate with a center hole and a circular plate with a solid shaft. The frequency responses of total loss factors of the five materials were then calculated by estimating the modal total loss factors based on the equations. The radiated sound powers of circular plates were estimated using the frequency responses obtained. Consequently, the radiated sound power estimated using the estimated modal total loss factors compared well with the radiated sound power estimated using the experimental modal total loss factor. The equation for estimating total loss factor, which was derived in a previous paper, is hence effective for estimating radiated sound power.

View full abstract

This paper considers an acoustic power minimization problem from the viewpoint of active noise and vibration control. It is the purpose of this paper to elucidate a common link between : actively attenuating noise in a variety of acoustic environments, using vibration or acoustic control sources. It is shown that if acoustic reciprocity holds between each point on the primary source and each point on the control source, then the acoustic power output of the control source under optimal conditions will always be zero, with the converse also being true. This concept is demonstrated for systems operating in free space, using both acoustic and vibration control sources. The physical meaning of this concept for the employment of vibration control sources, applied directly to a vibrating structure in an effort to attenuate the radiated sound field, is shown.

View full abstract

This paper is concerned with the computer-based sliding-mode control of a flexible rotor-magnetic bearing system (FR-MBS). The plant dynamics, consisting of actuator dynamics and flexible rotor dynamics, are described. The reduced-order model for controller design is given by eliminating higher-order modes beyond the first flexible mode. A discrete time sliding-mode controller for the reduced-order model is proposed, and its robustness is evaluated with several simulations based on the mathematical model. This controller is implemented as an alternative to a conventional linear analog compensator. Several experiments on the proposed digital controller are carried out and compared with those on an analog compensator. The unstable modes can be easily controlled with good stability, and spillover phenomena due to ignored higher order modes do not appear. It is shows that the discrete time sliding-mode controller is robust enough for model parameter variations and external disturbances.

View full abstract

A neural network can be applied for identification and optimal control of nonlinear systems. However, much information is necessary for identification because of lack of the learning ability of the neural network with the sigmoid function as the output function of the neuron. In this paper, the neural network with the sinusoidal function as the output function of the neuron is proposed. This neural network approximates the nonlinear function well. Using this neural network, good results of identification of 1-degree-of-freedom Duffing-type system are obtained with less information. and optimal control of this system by means of dynamic vibration absorber is shown to be possible through computer simulation.

View full abstract

For practical reasons, past studies on vibration control of a cantilever beam with a piezoelectric actuator have been devoted to reducing the free vibration in which the first mode is dominant. In the case of forced vibration, higher modes must be actively damped. This paper describes a control method for improving modal damping ratios of a cantilever beam up to the third mode using a piezoelectric actuator. First, an inverse system is designed to provide estimators of the entire state. Next, the control law, which is based on the feedback of linear combination of modal velocity, is discussed. Finally, an experiment on free and forced vibration is carried out. From calculated and experimental results, we find that modal damping ratios of a cantilever beam are improved by use of the above control method.

View full abstract

This paper describes a method of robust vibration control of a cantilever elastic beam in a uniform smooth wind stream. As the actuator, a pair of piezoelectric columns is fixed under base aluminium plates at which the cantilever beam is clamped. Its natural frequencies are calculated by the transform matrix method, and then the mode coordinate is introduced to establish state equations of this control system. A robust controller is designed to suppress galloping of the cantilever beam by applying H_∞ control theory. Simulation and experiment were carried out, and the results were compared with those of LQR control. It was found that robust stability and nominal performance were achieved, and an excellent control effect was obtained by H_∞ control. The usefulness of the proposed control technique is verified by simulation and experiment.

View full abstract

In a beam subjcted to electromagnetic force, that is, the three-current carrying-beam system, the catastrophe of the lateral deflection due to the increase of such force is theoretically investigated by taking account of the nonlinearity of the electromagnetic and elastic forces with respect to the lateral deflection of the beam. Not neglecting the imperfection of the bifurcation, the reduction of the equation with respect to the lateral deflection, to a low-dimensional bifurcation system, is achieved by means of the Liapunov-Schmidt reduction and the center manifold theory. Through the above nonlinear analysis, the bifurcation equation is derived, and the correction of the mode in the higher-order analysis is discussed. Furthermore, by analyzing the bifurcation equation, the bifurcation diagram, equilibrium space and bifurcation set are theoretically obtained, and the characteristics of the catastrophe are qualitatively clarified.

View full abstract

In this paper we discuss the pivot operation of moving an object using a multifingered robot hand. The pivot operation has the merit that its fingertip forces are smaller than those in pick-and-place operation, because an object is supported by fingers and the floor. We propose a method that calculates the optimal fingertip forces by linear programming, as well as a method for task planning.

View full abstract

This paper deals with two-dimensional motion of vehicles. Since the general four-wheel vehicle model is statically indeterminate, the motion of vehicles has been analyzed by replacing the vehicle with the equivalent two-wheel one proposed by Marquard. Because this approximation is based on the axisymmetry of vehicles, it causes significant errors in the general case. To improve the accuracy of the analysis of vehicle motion, a four-wheel model is suggested. In this model, it is assumed that the chassis remains in a flat plane during motion. By introducing this condition, the motion of the vehicle can be analyzed. Several results from the four-wheel model and the equivalent two-wheel model are shown for comparison, and the vehicle trajectories with time are discussed.

View full abstract

This paper deals with the impact phase of the vehicle-to-vehicle traffic accidents. Usually in this analysis, a two-dimensional rigid body collision theory is applied. Up to now, in collision theory, the vehicle was assumed to be a rectangular plate with sharp corners. In this assumption, however, singularity is included in the determination of the contact plane when the corner-to-corner collision occurs. In this paper, it is considered that the vehicle has round corners. Due to this consideration, the singularity is avoided, and the formulation of the vehicle corner-to-corner collisions becomes realistic and reasonable. Several results of corner-to-corner collisions are shown for comparison between the vehicles with round corners and right-angle ones. Then the vehicle velocities just after impact and vehicle trajectories are discussed.

View full abstract

A model experiment was conducted to study the moving characteristics of a shield tunneling machine with a multi circular face in soil. Linear equations derived in the previous study for a single circular face shield were extended to the multi circular face shield. Furthermore, methods of controlling the movement of the machine based on unbalanced forces on cutter disks were proposed.

View full abstract

This paper presents an electromagnetic actuator consisting of rectangular permanent magnetic chips and a cylindrical coil, which is applicable to bending moment control of plates. The analytical expression for obtaining the control force against the control current is obtained based on the electromagnetic theory. A control method is presented for producing the required deflection of the plate by means of the bending-type electromagnetic actuator. Numerical calculations are carried out for some typical problems which will be of practical importance. It is clarified that the actuator and the method of control presented are valid for controlling plate shapes.

View full abstract

Silicone gel is a very promising new material for reducing shock and vibration in mechanical systems. An insulator composed of a coil spring and silicone gel is used for reducing small-amplitude vibration of mechanical and electrical parts. In the design stage, before insulator production, the vibration characteristics of the insulator, i. e. natural frequency and damping ratio, must be known. To achieve this, the vibration experiment and the finite element (FE) analysis have been conducted. The results of FE analysis are compared with the experimental ones. The two sets of results are shown to be in good agreement. From this study, it has been found that the composite type insulator is very effective in reducing the vibration of mechanical systems.

View full abstract

The authors have studied a howling canceler system for active noise control in a duct. The effect of howling canceler employing an echo canceler or two kinds of 2-microphone systems (one is a 2-Microphone delay system and the other is a 2-Microphone transfer function ratio system) was confirmed from the viewpoint of eliminating the sound pressure signal from the secondary source. In this paper, the noise reduction effect of the adaptive control system utilizing this howling canceler, particularly utilizing the 2-Microphone transfer function ratio system, is examined. A filtered-X algorithm was used, because an acoustical transfer function from the secondary source to the evaluation microphone exists. A problem in applying the adaptive control system was identified : occurrence of an overflow phenomenon of the discrete system in the low frequency range because of the low efficiency of the speaker in this range. In this case, the high-pass filter effect of the 2-Microphone howling canceler system was useful for achieving stable control. This result is introduced theoretically and confirmed experimentally. The adaptive active noise control system with howling canceler was applied to axial fan noise. A good noise reduction effect was obtained.

View full abstract

This paper is concerned with the design of a nonlinear tracking control system utilizing recent H^∞ control theory. We introduce a reference system according to an actual system and leading to a state tracking error system. Then we set the condition of equilibrium state for this system. As a result, we turn the nonlinear tracking control problem into a nonlinear regulation problem and develop a solution using H^∞ control. It is treated by replacing the Riccati equation in linear H^∞ control with the Hamilton-Jacobi equation ; finding the solution of the Riccati equation thus entails finding the so-called generating function which is the Hamilton Jacobi equation's solution. From the generating function we can calculate the H^∞ optimal feedback function of the nonlinear tracking control system under the condition of minimal norm of the transfer function from disturbance to output. Its effectiveness is proven by application to the longitudinal control of an electric vehicle. The results are shown by simulation as well as bench experiment.

View full abstract

This paper deals with a model following control using static output feedback with relay elements. The stability of the control system is guaranteed on the assumption such that the plant satisfies the so-called ASPR condition. Furthermore, model output following control is achieved by using additional on-off controllers of which gains are chosen so that they may cover the amplitude of the ideal model matching input introduced by Broussard and O'Brien(IEEE Trans. Autom. Control, 25-4(1980), 851.). An extension of the method to a sort of non-ASPR plant is also discussed. The effectiveness of the proposed method is examined through several numerical simulations.

View full abstract

Adaptive feedforward control, consisting of a precompensator for feedforward control and an adaptive mechanism for parameter estimation, is applied to an electrohydraulic servo system. Mathematically, a higher-order model is preferable for an electrohydraulic servo system. However, such high-order models in an adaptive control system require longer calculation time. A shorter period of sampling of system variables is another requirement of an adaptive control system. Therefore we must consider the trade-off between system simplification and sampling period. We discuss a first- and a second-order model for the servo system. For the first-order model, a simple inverse transfer function is used in the precompensator ; for the second-order model, a ZPETC is used in place of the inverse transfer function. Influence of sampling period and order of the model on tracking error is discussed based on results of simulation. Experimental results show that the two systems are stable and have sufficiently small tracking error for practical applications.

View full abstract

Although many researchers have investigated the antisway control of container cranes, a successful system has not yet been formulated. One obstacle is the development of an adequate sensor. Although potentiometers or acceleration sensors have been used for antisway control, these ones could not directly detect the position of the spreader of container cranes. We have succeeded the very precise antisway control of container cranes by developping the new sensor. This sensor consists of CCD camera, line marker on the spreader and image processing unit which can stably detect the target by the use of correlation method. In this paper, We report the results of fabrication of a new sensor for direct detection of the position of a moving object hanging from a crane.

View full abstract

This paper deals with a micro mobile robot in water utilizing a PZT [Pb(Zr, Ti)O₃] as an actuator. A robot driven by a PZT requires a magnification mechanism and the effects of the resonance condition to enlarge the displacement of the PZT to some extent. In this paper, we show a prototype micro mobile robot in water (double-fin-fish robot), which posesses a pair of fins and moves them symmetrically. Thereforl, the momentum of this robot is canceled and the tendency to move straight ahead is improved. The size of the robot is 50 mm in length. We propose a structure for the magnification mechanism, which is made by the wire cut method. The magnification ratio is 326 geometrically This robot has many possible applications, such as small pipeline inspections and use in bio medical fields.

View full abstract

This paper presents a new concept of the wall surface mobile robot which is designed with the aim of moving over complicated wall surfaces using a variable structural crawler. The variable structural crawler is made of rubber and can easily deform its configuration. The joint frame consists of pieces of blocks connected serially which support the variable structural crawler. The crawler belt has 25 suckers on its surface. A simply designed mechanical valve is set at each sucker which opens only when it touches the surface. The sucker whose valve is open clings to the surface, and this allows the robot to cling to the surface. There are three actuators in the body. One is used for rotation of the robot's head up and down. Another is used for rotation of the robot's head right and left. The last is used to move the robot forward. We named this robot "MARK II". MARK II runs over a curved surface, changes its direction, transfers from one wall to another wall, and passes over a small obstacle. We investigated the influence of surface roughness and curvature radius on the running capability, especially on a curved surface. We show the mechanism and the experimental results.

View full abstract

This paper proposes an algorithm, for calculating the inverse dynamics of link manipulators. First, we derive a method to calculate the inverse dynamics of a general type of parallel link mechanism using the method proposed by Luh and Zeng., which is developed for a simple closed link mechanism and yields the inverse dynamics of the simple closed link mechanism using the Newton-Euler method of serial link manipulators. We then derive a calculation algorithm for the inverse dynamics of a Stewart Platform. The algorithm is applied to a dynamic simulation of a Stewart Platform by a unit-vector method, and the simulation results demonstrate the validity of the method.

View full abstract

Robust implementation of impedance control against modeling errors and disturbances is proposed. Deviation between desired impedance and actual impedance when applying the conventional method based on the computed torque is modeled as controlled impedance error. By estimating the controlled impedance error using a disturbance observer and compensating for this error with the usual feedback control, the desired impedance is realized while modeling errors and disturbances still exist. The proposed controller can be implemented easily on an actual robot manipulator because less computational burden is needed compared to conventional robust impedance control methods. The proposed controller was realized on a three-degree-of-freedom planar direct-drive manipulator, and its performance in peg-in-hole motion and damped oscillation motion was confirmed.

View full abstract

In a previous paper, the authors proposed, on the basis of experiments and thermoelastic analyses, a mechanism of cracking characterized by deep through-cracks formed on the surface of an alumina ceramic ring of mechanical seals, and discussed preventive methods. That is, cracking is caused by thermally induced tensile circumferential stresses. Cracks originate at the edge of the seal face that is wet by the liquid being sealed, and propagate in the radial and axial directions through the alumina ceramic ring. However, bending strengths of alumina ceramics measured at room temperature were two to three times larger than the calculated values. In this study, the cause was investigated. As a result, it has been clarified that the strength of the alumina ceramic ring is decreased by boiling water and surface defects produced during the finishing process.

View full abstract

Oil film seals of large diameter sometimes show low-frequency whirling of the deformation mode of a floating seal ring whose rotation is constrained by a stopper pin. Cyclic change of deformation and oil film temperature may cause fatigue damage of the seal ring after long-term operation. We present a theory for the mechanisms of deformation and its whirling, the results of which agree well with those of measurements, and which provides a practical design criterion to prevent this phenomenon.

View full abstract

To obtain dynamic characteristics of compressible lubricating films incurring surface roughness effects under rarefaction conditions, a numerical calculation methodology applying the ADI scheme is derived for the solution to the averaged Reynolds equation involving flow factors resulting from Boltzmann molecular free flow. This methodology features the transformation of the dependent variable in the Reynolds equation from pressure to the product of averaged pressure by averaged spacing, and the determination of the flow factor using averaged spacing. Applying this method to a head slider in practical use, transient responses made when flying over a bump and incurring surface roughness effects are compared for three roughness pattern cases. It is found that longitudinal roughness effects in the transient response appear in terms of decrease both in the natural frequency and in the damping speed. On the contrary, moving transverse roughness affects the response inversely and stationary transverse roughness effects it only slightly.

View full abstract

This paper presents the results of an investigation on basic experiments of tribological characteristics of two ferromagnetic bodies, S15C and S45C carbon steel, in the magnetic field, following experiments performd on the dry sliding wear. In the magnetic flux parallel to the wear surface, the values of induced voltage generated on the wear surface by both the AC and DC voltage were small. The value of induced DC voltage showed a change of polarity. The wear ratio in magnetic field was low compared with that in no magnetic field. Moreover, the wear ratio decreased further using the induced-voltage control method.

View full abstract

Carbon-fiber-reinforced plastics (CFRP) has been widely used in industry because of its attractive mechanical characteristics. When used as a sliding part, CFRP has proven to be self-lubricating. Such CFRP parts are invariably subjected to abrasive wear due to small indentations and machine vibrations. In this study, the abrasive wear characteristics of CFRP were investigated using a vibrating environment and coated abrasive paper. The results are as folows. 1) A wear model in a vibrating environment was proposed and it was confirmed that the model was practically appropriate. 2) In a vibrating environment, the wear volume increases in proportion to the degree of amplitude. In the T-direction under Y-direction vibration, wear volume is not influenced by vibration.

View full abstract

It is very important to know the load distribution on the line of contact and the tooth root stress of a bevel gear under tooth end bearing. These are difficult to calculate, however, because the meshing of a bevel gear is complicated. Before these calculation under tooth end bearing, the tooth deflection due to the concentrated load was calculated by means of the three-dimensional finite-element method. With some characteristics of deflections which were found from these calculation values, the approximate equations for the influence functions for deflection of bevel gear tooth were derived. Furthermore, the effects of the number of teeth and the gear ratio on the characteristics of deflections were clarified.

View full abstract

The state of grinding of gear tooth flanks with a gear-shaped tool is simulated by a model of contact between tooth flanks of skew gears considering elastic deformation of meshing teeth and material removal by grinding. Basic data of the grinding were obtained by the experiment of grinding case-hardened steel discs with several kinds of disc-shaped grinding stones. The simulation model for the grinding of constant feeding displacement and that for constant feeding torque are developed. The results of the simulation showed that the deviation of the shape of ground tooth flank from that of target form determined by a geometrical consideration becomes larger when the amount of removal by one pass of the grinding tool increases or the contact pressure between tooth flanks of work gear and grinding tool increases. The possibility of modifying the design for tooth flank of tool gear to obtain the desired tooth flank shape of work gear is shown.

View full abstract

By developing the simulation program for the state of grinding gear teeth with a gear-shaped tool, a method for analysis of the relative torsional vibration between grinding tool and gear workpiece is constructed. The vibrational acceleration and dynamic forces acting on tool flanks during the grinding process are analyzed and the influence of feeding speed and dimensions of tool gear are shown. The results of the simulation confirm the experiences of engineers with this method of gear grinding, that the wear of abrasive on grinding tool increases the vibration and accelerates the damage of the tool. A low feeding speed can decrease the vibration. The possibility of reducing the vibration by choosing a definite value of helix angle of grinding tool gear is shown.

View full abstract

An over-ball measurement of a straight involute pinion-type cutter is newly developed. This method makes it possible to control the finished size of the pinion-type cutter by measuring over-ball distance in grinding. In this method, the pinion-type cutter is regarded as a conical involute gear. First the over-ball distance is obtained analytically. Next it is verified by experiments. Experimental results agree well with analytical data. In addition, how to apply this measurement to control of the infeed distance in practical grinding is presented. The final infeed distance of the grinding wheel is determined when the difference between the analytical and experimental over-ball distances is obtained. As a result, it is proven that this over-ball measurement is of practical application.

View full abstract

In cutting CFRP (carbon-fiber-reinforced plastic), the major problem is severe tool wear and inferior surface quality. The purpose of this study is to clarify the tool wear mechanism of CFRP cutting. Relationships between the cutting conditions and the tool wear are investigated in the edge cutting test of a CFRP pipe manufactured by the FW (filament winding molding) method. Moreover, the tool wear characteristics were theoretically analyzed in order to explain the difference in those of in cutting CFRP and GFRP. The main results obtained are as follows. (1) In cutting CFRP and GFRP the tool wear characteristics are different under ordinary cutting conditions but the tool wear mechanism is basically the same. (2) In cutting CFRP at less than about 200m/min, the tool wear is hardly influenced by the cutting speed but is influenced by the fiber length of cut. (3) In cutting CFRP, the wear resistance of the tool materials is in the following order, cemented carbide K 10, M 10, P 20, black ceramic, white ceramic and cermet, that is to say, the cemented carbide K 10 has relatively high wear resistance.

View full abstract

In this paper we describes the machined surface of the solid wood using NC router and estimated the machined surface by the texture analysis. The machined surface of solid wood was examined with the surface tester. Then the result showed that the value of the surface roughness is affected by grain direction, cutting speed and depth of cut. And the angle of grain direction is obtained using the disital signal processing (2-dimensional FFT). The machined surface can be calculated by relationship between the grain direction and the surface roughness. By this method, the machined surface along the cutter path of NC router, is estimated In order to estimate the machined surface as regard any angle of grain direction, the route of tool was made rotated. According to select the most suitable angle of grain direction, the integration of the surface roughness on route is minimum and the smooth surface is obtained.

View full abstract

The background of this study lies in the investigation of the formation mechnism of ductile mode (nanometer-size) chips of brittle materials such as fine ceramics, glass and silicon. As the first step to achieving this purpose, this paper intends to observe the micro-deformation behavior of these materials in sub-μm depth indentation tests using a diamond indenter. As a result, some characteristics were experimentally observed on indentation curves plotted continuously against loading/unloading cycle, as well as various effects dominating them, such as creep, resporation, crack and residual stress. Moreover, from the characteristic curves obtained in the sub-μm indentation tests, possibility of evaluating the mechanical properties (including yield effect) of brittle materials under the sub-μm interference using an indenter was confirmed.

View full abstract

The blade behavior in the outer-blade slicing has been analyzed by computer simulation to clarify the machining mechanism. The main results obtained are as follows. (1) The blade deflection comes from a small lateral grinding force on the blade outer edge, and it is enlarged by the lateral grinding force on the blade side face. (2) The lateral grinding force on the blade side face takes the maximum value when the contact arc length between blade and workpiece tends to decrease in the machining process. (3) In the case that the blade was deflected in the machining process, the cutoff surface form obtained on the deflection side of the blade becomes concave and a large kerfloss occurs on this side. By contrast, the cutoff surface on the opposite side has a uniformly flat surface. (4) The values of lateral grinding force, blade deflection, waviness of cutoff surface and kerfloss increase with the asymmetric shape factor of blade, the speed ratio, the average tip angle of the grains on the blade side face and the inverse of blade thickness.

View full abstract

In an effort to develop a new acoustic lens for the scanning acoustic microscope (SAM), the spherical accuracy of a lens with 200μm in radius for a high frequency range was studied. A Fizeau-type laser interferometer was employed to measure the profile of etched cavities. Spherical accuracy was evaluated by counting interference fringe patterns appearing as a result of optical path differences between the reference and sample surfaces. Focusing area of the acoustic lens was estimated by means of geometrical optics based on measured and assumed accuracy. The spherical accuracy required to ensure good focusing of the acoustic wave to a spot size on the order of one wave length was calculated using the result of interference fringes. Sufficient spherical accuracy for a silicon acoustic lens at 400MHz was calculated to be -0.13times of one wave length.

View full abstract

The spindle head unit of most precision machine tools is temperature-controlled by forced circulation of liquid lubricant or coolant in order to reduce its thermal deformation. However, an over cooled or thermally unstable coolant may cause an unacceptable temperature distribution in the head unit. Thus it was proposed to incorporate two concentric cooling jackets into the unit. The inner jacket is for heat exchange with the undercooled oil, and oil at a constant temperature is circulated through the outer one so that the temperature distribution of the head unit may become uniformly moderate. Next, the feed-forward temperature control system was developed to control the oil temperature prior to heat generation at the spindle bearings. With a spindle head model and such an oil-temperature control device, it was demonstrated both from the experiment and the numerical simulation that the dual cooling jacket stucture is practically effective in decreasing the thermal displacement of the machine tool spindle as well as the machine tool itself in accordance with the related feed-forward temperature control system.

View full abstract

In the 1st report, a new material called ceramics resin concrete was developed for precision machine tool structures. Then in the 2nd report, thermal and mechanical characteristics of the material were proven in order to design a machine tool. Young's modulus and compressive strength are inferior to those of steel or cast iron, which are conventional materials for machine tool structures. Therefore, in this study, improvement of Young's modulus and compressive strength has been attempted. It is concluded that Young's modulus of the material was improved to be the same as that of cast iron, while compressive strength and fracture toughness were confirmed to show slight improvement.

View full abstract

The first report of this study established the basic theory and theory for application of torque compensation on the input shaft by means of combination of torque compensation cam (TCC) and spring. The aim of this study is to prove the validity of the theories through experiments. The use of TCC yields three main advantages, namely : to drastically decrease the peak required torque for input shaft, to decrease the fluctuation of input shaft speed and to bring the real angular acceleration of the rotary table closer to theoretical acceleration. For better motion of rotary table, or to minimize the peak required torque for input shaft, the fine tuning of initial compression of spring at a certain input shaft speed is essential. As the result of the experiment, the relationship of the initial compression of spring vs the selected speed is also proven to be correct.

View full abstract