Many studies were carried out on flow characteristics along a rotating hard disk, but few studies have been carried out to clarify the disk's unstable vibration at a highspeed rotation. This paper deals with experimental investigation of vibration characteristics of double flexible disks rotating in a confined fluid. Experiments showed the following results: (1) The disks underwent an unstable vibration for a particular range of rotational speed, and a buckling mode deformation was observed at further high rotational speed. (2) The unstable vibration magnitude exhibited a hysteresis character for the normal boss supporting the double disks to the shaft, but the hysteresis disappeared for the case when the fluid was connected through the holes made in the boss. (3) The dominant frequency of the unstable vibration was found to be the triple harmonics of the rotational speed.

抄録全体を表示

This paper deals with the characteristics of unstable self-excited vibrations of a rectangular, flexible weir installed between two tanks, over which the water in the upper tank discharges into the lower one. Experiments were done for measuring vibrational strains of the weir, oscillation of the overflow water thickness, and the oscillations of the water surface in the upper and lower tanks with changing inlet velocity of water into the upper tank and water discharge height. Four unstable vibration modes were found in our experiments. The 1st unstable vibration mode was sloshing-dominated weir vibration and its vibration frequency was almost equal to the sloshing one for the lower tank. The 2nd one was a high frequency vibration of the weir unrelated to the sloshing oscillation and the 3rd one was a torsional one of the weir with a high frequency different from the 2nd one. The 4th mode was peculiar to the experimental system due mostly to the coupling between the inlet water jet and the weir The phase relations between the weir vibration and overflow water thickness were experimentally investigated.

抄録全体を表示

This paper reports on the unstable vibrations of an asymmetrical shaft rotating with a fluctuating angular velocity. For lateral vibrations of this rotor-shaft system, the equations of motion are derived and solved by using an approximation which was previously proposed by the authors for analyses of unstable vibrations of an asymmetrical shaft supported by asymmetrically flexible bearing pedestals. The second-order approximation is carried out, and a solution of free vibrations and a frequency equation are obtained. When a rotating speed of an asymmetrical shaft fluctuates periodically with N times in a revolution, the results of the analyses show that unstable vibrations occur at the angular velocity not only near the major critical speed but also near 2/|(2±N)| times the major critical one.

抄録全体を表示

This paper describes an analytical approach of the coupled vibrations between railway vehicle wheels and a rail in the horizontal direction using an approximate model. The model is an analytical one with an infinite number of vehicles in which these vehicles are arranges with a certain periodicity on the top of an infinitely long and straight rail installed on two distributed springs. It is effective for the analysis of the actual system of railway vehicle wheels and rail. The authors treated the wheel as a rotating Mindlin circular plate and the rail as a Timoshenko beam of coupled bending and twisting, and analysed the coupled vibrations taking the creep forces acting on the points of contact between rotating wheels and rail into account. The numerical computational results of Shinkansen vehicles demonstrated the validity of the present model, and were compared under the various conditions.

抄録全体を表示

This paper presents an analysis of the free vibration of a toroidal shell with an interior partition consisting of a concentric circular cylindrical shell. For this purpose, the governing equation for vibration of a toroidal shell including a circular cylindrical shell is written as a coupled set of first-order differential equations by use of the transfer matrix of the shell. Once the transfer matrix has been determined by quadrature of the equations, the entire structure matrix is obtained by the product of the transfer matrices and the point matrix at the joint of the shell system, and the frequency equation is derived in terms of the elements of the structure matrix. The method is applied to toroidal shells with interior partitions, and the natural frequencies and the mode shapes of vibration are calculated numerically.

抄録全体を表示

A mathematical description of free lateral vibrations of a pipe string, which is designed for mining manganese nodules in the deep ocean, leads to an eigenvalue problem containing a small parameter multiplying the highest derivative of its differential operator. This problem is analyzed by an asymptotic theory, de Groen's method, and natural frequencies and modes are evaluated. furthermore, The effects of internal fluid on the motion of the pipe string are investigated. It is shown that the algorithm developed is an effective one, providing highly accurate solutions even if only the zero approximation is used.

抄録全体を表示

This study presents a feedforward control design method of an active dynamic vibration absorber for multi-degree-of-freedom systems. The feedforward control, obtained by assuming that the shaping filter possesses the same natural frequency as primary structure in the frequency range of input disturbance. Furthermore, to improve reliability, a digital control system consisting of a reduced order feedback control and the feedforward control, using kalman filter, is synthesized. By carrying out numerical calculations and experiments, it is demonstrated that active DVA, which is optimized by the present design method, is useful for not only stationary random inputs but also nonstationary random inputs.

抄録全体を表示

The dot-matrix impact printer is widely used because of its simplicity and reliability. The biggest problems with it are the vibration and noise excited by the impact force. This paper introduces an improvement technique for reducing noise and vibration using a sandwiched plate on the impact surface. An optimum design condition is proposed to yield the highest damping of the impact surface. The proposed technique is applied to a cash register printer to confirm its efficacy.

抄録全体を表示

Two variable velocity feedback control methods were proposed in the first report. One is the design in a actual domain and the other is the design in a modal domain. These two methods not only realize an optimal pole assignment for the controlled modes, but also have no effect on the uncontrolled modes. The latter method has a wide range of applications and a general character. We have applied these methods to a flexible rotor system. The test rotor is supported by linear actuators through bearing housings which we call active control bearings. There are three critical speeds, up to 3000 rpm. The variable velocity feedback control system design is based on an experimental modal analysis instead of a mathematical model. We have completely controlled three modes by means of a digital controller. The unbalance responses with variable velocity feedback are similar to the unbalance responses with an ideal model control.

抄録全体を表示

Control systems whose controls can only take given discrete-level values are called quantized control systems. Optimization of such systems has conventionally been performed by mathematical programming methods, including dynamic programming or integer programming. In this paper, the author formulates a quantized discrete linear optimal control problem with terminal conditions using Halkin's formulation and derives the quantized discrete maximum principle for discrete-level valued solutions, which is a Pontryagin-type control condition. An algorithm based on this maximum principle is presented, along with a numerical example.

抄録全体を表示

Experimental modal analysis has been widely used to identify the modal parameters of structures. Mainly, it is based on analyzing the individual test signal either in the frequency domain or in the time domain. The main defect is the inaccuracy of the spatial mode shape caused by analyzing the individual measured signal. This paper introduces a new method of identifying the modal parameters from its decaying response. First, the multivariable discrete model is identified from the measured signal. Then the identified characteristic matrix is analyzed by an eigenvalue routine to get the vibrating poles and its associated modes. The proposed technique is applied to a plate structure and its accuracy is tested.

抄録全体を表示

Using a model of a DC-motor-driven vehicle running along a horizontal, straight rail, we experimentally investigated the characteristics of a fuzzy control for driving the model to a given destination. Fuzzy control rules were constructed in a microcomputer using fuzzy information about the location and the velocity of the model and then applied to be the DC motor to drive the model. Experiments on the fuzzy control characteristics were done with respect to the magnitudes of sampling time and control gain as well as the fuzziness parameters of the model's location and velocity. We found unstable oscillations in the motion of the model around the destination position depending on particular ranges of those parameters. Linearized stability analysis of the control system showed a rather good agreement for the experimental unstable oscillations.

抄録全体を表示

The measurement system described in a previous report was applied to examine the sideslip characteristics of block tires for uneven grounds, driven on concrete roads. Two dimensional polynominal equations were proposed to make approximate expression of the relationships of the slippage and sideslip angle to the driving force, side force and axial torque. The characteristic equations were used for numerical confirmation of the local and wide range stabilities of the measurement system. The approach was, also, found to be effective in analyzing the sideslip behavior of a vehicle. The measurement system proposed in the present study has the following features. (1) Measuremests on real roads are possible without a large equipment. (2) The system operates on simple principles and requires no special component force meters. (3) Measuring four wheels simultaneously, the average characteristics can be obtained.

抄録全体を表示

The study deals with the development of a highly accurate rotational positioning actuator, based on the idea of an"Inchworm translator"for precise linear positioning. The actuator is designed for rotational motion and combines piezoelectric actuators with a stroke magnification mechanism. Based on experimentation, it is confirmed that the actuator correctly functions with a rotational resolution of less than 6.25×10^-7 rad and a holding torque of more than 0.26 N·m. As a result, the actuator is shown to have the potential to become an accurate rotational positioning actuator.

抄録全体を表示

Flexibility in harmonic drives produces robot arm vibration. The prevention of such vibration becomes an important problem in robot arm control since vibration decreases the operation efficiency and quality. High gain feedback of distortion in drive systems improves the oscillatory behavior of the robot system. This paper presents some properties of the high gain feedback of distortion and proposes a state estimator which estimates the distortion by suing the information from an acceleration meter or strain gauges. The proposed state estimater withstand parameter variation. Experimental results show that the proposed vibration absorption control method is effective and robust.

抄録全体を表示

This report deals with a new measurement method of the force and the moment of a robot application. The one component of the force and the three components of the moment can be measured by using the characteristic such that the phototransmissivity of the photosemiconductor (CdInGa 4) changes according to the pressure applied to the semiconductor. When the light radiate from the transmitter reaches the quadrant photo diode through this semiconductor, the output of the receiver gives the magnitude of the force. To measure the moment applied to the sensor, the light rays from the luminous diode reach the quadrant photo diode rectangular window, and the torsional angle of the projection of the rectangular window on the quadrant photo diode is used. The experimental results show that this photo semiconductor can be used as a new type of sensor for the force measurement of a robot hand, and the force and the moment can be measured without interference from each other.

抄録全体を表示

When an industrial robot with a power transmission mechanism such as a harmonic drive gear is operated, vibrations resulting from the torque ripple of the power transmission mechanism are frequently generated. However, few studies on robot vibration characteristics owing to torque ripples have been reported. In this paper, the vibrations of a horizontal two-link robot are investigated with consideration given to the torque ripple and the nonlinearity of the power transmission mechanism. In the numerical analysis, the torque characteristics are assumed to be the product of the nonlinear function of the torsional angle of the gear teeth and the torque ripple represented by means of the the Fourier series of the rotating angle of the input axis. Numerical simulation is carried out, and the effects of the torque ripple and the nonlinearity on the vibration characteristics of the robot are demonstrated. The experiment also shows that the torque ripple can cause a good deal of vibration.

抄録全体を表示

In this paper, the inverse dynamics of the quadruped robot is described which is the base of the trajectory planning and the costrol of the dynamic walk. The distinctive character of the solution described here is the use of the redundancy of actuators obtained by eliminating the constraint forces from the dynamic equations. In concrete terms, two subjects are described. The first is the realization of the control which is expected not to break the constraints. The second is the rotation around the yaw-axis without using yaw-actuators at supporting legs. Furthermore the experiments utilizing Collie-2 are described.

抄録全体を表示

Currently, robot manipulators are controlled by decentralized or independent joint controllers. That is, each joint is locally controlled using only local information. We discuss the asymptotic behavior of the closed loop eigenvalues of such systems in a case where the dynamic compensators are used as feedback controllers. The high-gain feedback is an effective control method because of its robustness to parameter variations and disturbances. By using theory of multivariable root loci, we present four theories about the behavior of the closed-loop eigenvalues when the high-gain feedback is implemented. It is supposed that the obtained results could be useful in the control system design of manipulators.

抄録全体を表示

This paper discusses the problem of stable grasping by a multifingered robot hand with a redundant degree of freedom. Firstly, the condition for stable grasping using virtual stiffness parameters at each finger tip was formulated through mathematical analysis. Secondly, in order to achieve the above stable grasping condition, the joint stiffnesses for each finger were adjusted by two stiffness control algorithms : the Salisbury method and the direct compliance control method (DCC). When the Salisbury method was applied to fingers with a redundant degree of freedom, the finger posture was mathematically found to become unstable. On the other hand, DCC was confirmed to be an effective method for maintaining stable finger posture in the grasping operation even when the redundant finger structure was employed. The above-mentioned results were experimentally confirmed.

抄録全体を表示

This paper studies robust control of flexible structure systems such as LSS (Large space structures) theoretically and experimentally. In control of flexible structure systems, it is important to desigh the robust controller which realizes low sensitivity for parameter changes of the controlled object and robust stability in residual higher modes which cause spillover instatability. In this paper, the robust model matching (RMM) method is adopted to design the low sensitive controller, and low -pass filters are used to increase the robust stability in the high frequency range taking account of their dynamics. Then, the controller designed by the proposed method is applied to the flexible spacecraft model, and the effectiveness of the controller is demonstrated in both computer simulation and control experiments.

抄録全体を表示

Since equations of motion of a manipulator are highly nonlinear, it is rather difficult to analyze the manipulator motion or to design the control system based on the equations. In order to overcome this difficulty, linearization of the equations of mosion about the nominal operating point sometimes becomes important. This paper deals with the effective algorithm of this linearization, which is closely connected with the algorithm of the derivation of the equations f motion. Using this algorithm, only 2 or 3 times as many mathematical operations are required in the linearization as that of the derivation in the case of a manipulator with 6 degrees of freedom. An optimal trajectory of a simple 2-link manipulator is obtained as an application of the linearization.

抄録全体を表示

This study compares the calculated results for the dynamic behavior of a comparatively small cooling-capacity variable-speed scroll compressor with those of a variable-speed rolling-piston rotary compressor of the same cooling capacity. The superior dynamic behavior of the scroll compressor can thus be shown. In order to derive the characteristic of the rotating speed, the rotating-speed fluctuation ratio and the rotatory acceleration, first the equation of motion of the rotating crankshaft is solved numerically for different mean rotating speeds. Thus, the unbalanced forces of the inertia exciting the whole compressor are calculated, and the vibration characteristics of the compressor can be shown. In the numerical calculation, the driving torque, the gas-compression load, the frictional coefficients, the mass and the moment of the inertia of the compressors are kept constant, thus, the calculated results for the two different compressors can be compared

抄録全体を表示

Rippling failure is well known as one of the phenomena resulting from plastic flow of the surface layer caused by repeated sliding-rolling contact. We previously investigated rippling failure occurring on gears and rollers made of SCM 415 H material, and whose contacting surfaces were hardened by gas-carburizing, using the power-circulating-type gear testing machine and the Amsler type abrasion testing machine. If the test rollers are made not of SCM 415 H but of another material, it is not clear whether rippling failure occurs on rollers. There, in the present paper, carbon steel (S 45 C) is chosen as the material of test rollers, and the rippling failure for S 45 C rollers is investigated. The contact surface of S 45 C roller is hardened by induction hardening, but its Micro Vickers hardness is small compared with hardness of SCM 415 H rollers. The results of the rippling test for S 45 C rollers are compared with those for SCM 415 H rollers.

抄録全体を表示

The effect of shear rate on the inception of gaseous cavitation in a low Reynolds number flow is studied. An experiment is carried out using a two-cylinder apparatus and paraffinic base oil with air dissolved in it as a test fluid. With a low shear rate, the observed inception time is considerably later than the time obtained in a calculation considering only the floating bubbles in the fluid. This fact can be explained by taking into account the slower growth speed of small nucleus attached to the wall, which results from the resistance encountered when the air passes across the interface of the bubbles. It is supposed that when the shear rate of flow becomes high, this resistance suddenly decreases. By considering the behavior of absorbed substances at the interface, the author arrives at a nondimensional parameter determining the shear rate and the size of the bubbles when the sudden change in resistance occurs.

抄録全体を表示

In this third report, the effects of cavitation patterns on the static and dynamic characteristics of submerged turbulent journal bearings are investigated theoretically. Considering break-up and fill-back boundaries in the diverging film region, we obtain analytical expressions for dynamic film pressure and cavitation pattern, and calculate the load-carrying capacity and attitude angle for a wide range of eccentricity ratios. Then, assuming a small displacement of the journal center, we obtain dynamic characteristics such as linearized spring and damping coefficients, the whirl onset speed of rotor-bearing systems, and the transient motion of the journal center. Numerical results are indicated in graphic form for a wide range of Sommerfeld numbers, and the relation between the cavitation pattern and the stability of turbulent journal bearings is discussed.

抄録全体を表示

A new method for the direct numerical calculation of the dynamic characteristics of a fluid film lubrication is presented. The present method is derived by applying the boundary fitted coordinates system to the divergence formulation method. A generalized algebraic equation for perturbed-node pressures, derived by the present method, can be widely used to represent the arbitrary film configuration, arbitrary bearing shape, and arbitrary vibration mode. As an example of a computer program using the present method, influences on stiffness and damping factors of a spherical spiral-grooved bearing with a radially eccentric ratio are shown.

抄録全体を表示

This paper give a description of an experimental study of ultrasonic welding of ceramics and aluminium or copper. The ultrasonic welding technique can be carried out in many different ways, such as in direct welding of ceramics and metals, the coating of metal on ceramics surface by vacuum deposition, and in application of inserting of activated metals. The ultrasonic welding has made possible to weld various ceramics, such as SiO₂, Al₂O₃, SrO, BaO, ZrO₂, Si₃N₄, SiC, to aluminium or copper under the room temperature quickly and easily compared to other welding methods. For example, the ultrasonic welding of Al₂O₃ and aluminium could be finished under the condition of amplitude 23μm of ultrasonic horn top, welding pressure 20 MPa, required duration 0.3 s. The clean with a forced ultrasonic vibration of contact surface needs no surface treatment. Moreover, the material can be processed easily, and it gives out little heat, and hardly get weakness.

抄録全体を表示

A prototype flexible bending machine was made on the basis of a new method, idea which proposes to penetrate the tube into the die. Since the area of bending is limited and the cross section of the tube is restrained by the die, flattening, buckling and wrinkling at the inner wall of the tube can be prevented. The tube can be bent to any radius by using ths system. The effects of penetrated load flattening factor, variation factor of thickness, and bending radius are examined under various bending conditions. The results are concluded as follows: (1) In the beginning of bending, the penetrated load reaches the, maximum, and thereafter, the load decreases and remains constant as the bending continues smoothly. As the bending radius decreases the load increases. (2) The flattening factor increases as the bending radius decreases. The flattening nearly be prevented by the choice of bending conditions. (3) The reduce thickness of the inner wall of the tube is nearly prevented.

抄録全体を表示

The object of this paper is to clarify the mechanism of mirror surface finishing by the ironing process. The mirror surface is needed for electrooptical parts such as optical drums, magnetic discs, etc., which are currently being finished by diamond turning lapping, etc. In the ironing process, the metal surface on the die-side becomes the rubbed surface (Ra≒0.05μm). In the case of applying high viscous oil it is rather inferior to a die surface (Ra≒0.006, 0.011μm) and when lower viscous oils are applied, galling often occurs. The metal surface on the punch-side nears a replica of the punch surface as the reduction increases under the dry conditions at the punch-metal interface. In this experiment, the metal surface was finished to Ra = 0.004μm under dry conditions on the punch-side. high viscous oil on the die-side and 50% in the reduction.

抄録全体を表示

In the present paper, equations of output errors in open- and closed-loop robot arms have been derived with consideration of errors of link parameters, radial and angular clearances of bearings and input errors. Applying the equations to a 5-link closed-loop robot arm, effects of each error factor upon the output displacement are discussed. Changing systematically a ratio of link length and the output point position if the robot arm, charts which show working spaces and output errors caused by bearing clearances and input errors are obtained. Moreover a synthesis procedure of the 5-link closed-loop robot arm has been proposed. Making use of the charts, the robot arm has been synthesized by the procedure, revealing that the output errors due to bearing clearances and input errors of the obtained robot arm are respectively about 25% and 60% of those output errors of the existing robot arm and that the arm has almost the same precision throughout its entire working space.

抄録全体を表示

How to determine the parameters of a circle arc, Which has a better accuracy of approximation to an involute tooth profile, is an interest theme up to the present, because the circle arc is simpler than the involute in manufacturing and measurement of inspection. But it is not considered that this problem has been completely solved and its application may be limited. In this paper, a convenient method to determine the optimum parameters of a circle arc is proposed and the effect of the errors of the parameters on the accuracy of approximation is clarified, too.

抄録全体を表示