The dynamics of high speed rotating machinery, generally referred to as rotordynamics, has developed into an important area of specialization within the general area of dynamics.This development started with the construction of the first waterwheels and windmills several thousand years ago and progressed rapidly during the past two hundred years with the introduction gas turbines and other high speed rotating equipment.A review is presented of some of the modeling and analysis procedures that have been developed to provide a means for understanding and simulation of the characteristics of rotordynamic systems.

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The overall aim of this research is to establish an effective method for accurately estimating the airborne noise power radiating from the gear blank of aircraft gears.For this purpose, the estimation theory of sound power radiated from a circular plate with a solid shaft and a solid cylinder, which is a simple model of the gear blank of an aircraft gear, has been described.The forced vibration of the circular plate with a solid shaft and a solid cylinder was solved by assuming that the displacement of forced vibration is equal to the linear sum of the eigenfunctions of the displacements of the circular part and the cylinder part.Using the obtained result, the equations for calculating the frequency spectra of three important parameters-the radiation loss factor, driving point mobility, and total loss factor of the circular plate with a solid shaft and a solid cylinder, were derived.Calculating the frequency responses of the three parameters and measuring the spectrum of the excitation force, the sound power, when the circular plate was subjected to the axial and three-dimensionally excitations, were estimated, and compared with the measured frequency responses of sound radiation power obtained by means of the sound intensity method.The estimated freqyency spectra of sound radiation power coincided with the measured values.The derived estimation theory and the associated formulae are valid, consequently.

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The pressure fluctuation caused by the ring vortex shedding from a perforated plate with holes installed in a pipe was investigated experimentally.Measurements were made using pressure transducers at Reynolds numbers from 6.74×103 to 4.02×104 based on the velocity at the hole.A significant lock-in phenomenon is caused by the flexural rigidity of the perforated plate.When this phenomenon occurs, the amplitude of the pressure fluctuation increases markedly.While the velocity range generating the lock-in phenomenon shifts to a higher velocity as the plate thickness increases, the frequency of the pressure pulsation is independent of it.It was also found that the pipe length both upstream and downstream of the plate exerts a major influence.

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This paper proposes a design method for an active vibration isolation controller for a multi-degree-of-freedom structure with uncertain base dynamics.It is demonstrated that a controller with a desired performance can be designed even if we don't know precisely the base dynamics by using the criterion function for the purpose of suppression of the interaction between the controlled structure and its base.In order to minimize this interaction we select the acceleration of the lowest mass of the controlled structure and the relative displacement between the lowest mass and its upper mass as the controlled variables.By simulations and experiments it is verified that the designed controller improves both the control performances and the robust performance under existence of the base dynamics with uncertainties.

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A two-dimensional X-shaped microphone array system can measure horizontal and vertical distributions of exterior noise sources on moving vehicles such as highspeed trains and automobiles, which is essential for reducing noise levels.The system is positioned close to the vehicle track like the letter "X".Numerical simulations show that the spherical wave consideration and the time average of varying directivity are necessary for the system, and that an X-shaped configuration has better resolution of noise sources than a cross-shaped one.Results also show that a microphone interval larger than half-wavelength is allowed by arithmetic decibel averaging over the array directivity for different source positions.

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This paper describes the three-mode response of simply supported, rectangular laminated plates subjected to harmonic excitation.It is assumed that the linear natural frequencies, ω₁, ω₂ and ω₃ of the symmetric vibration modes have the relationship 2ω₂ ≈ ω₁+ω₃ and that internal resonance occurs.Galerkin's procedure is applied to the governing equation in consideration of the geometric nonlinearity, and the method of multiple scales is used to analyze the steady-state response.The effects of the lamination sequence, the amplitude of the excitation, and the relationship among the linear natural frequencies on the three-mode response are studied.In order to confirm the analytical results, the equation of motion is integrated numerically using the Runge-Kutta method.Numerical simulation shows that the three-mode response is not a periodic motion but a quasi-periodic motion.

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This paper is concerned with a stabilization method for nonlinear time-delay systems.Generally, hunting will often occur due to the time delay.Though the Smith method is known to be able to prevent it, there are many difficulties in its application.In this research, a new stabilization method is proposed, which can prevent hunting and reduce the steady-state error to zero by parameter adjustment.First, the stability analysis of nonlinear time-delay systems is clarified using the circle theorem.Second, in order to analyze the robustness of the new compensator, its robust stability condition is derived for such control systems with a time delay and a saturated-type nonlinearity, and the stability margins under the identified errors of time delay are evaluated.Third, the new compensator is directly represented by a form of z transform, and its stabilization and dynamical characteristics are analyzed using the root locus method.From these studies, it is verified that the new stabilization method is useful for general nonlinear time-delay control systems.

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Not only handicapped people but also elderly people living in Hokkaido, the northernmost island in Japan, desire to participate in outdoor activities during a winter season that is characterized by heavy snow and low temperatures.Most of these people venture outdoors to go shopping or to hospitals, even under severe conditions.A wheelchair is generally used for outdoor transport.There are, however, many problems with using a wheelchair during the winter ; roads covered with snow and ice are very slippery, casters are easily buried in snow, and handrims are too cold to handle.Therefore, an appropriate wheelchair for outdoor use during the winter season is greatly desired.We are developing an electric wheelchair effective for outdoor use during the winter.In this work, three types of electric wheelchairs with front-wheel drive, rear-wheel drive and front free casters, and rear-wheel drive and mechanically controlled casters, were tested for drivability on icy roads, snow-covered roads, and indoor floors.In addition, computational methods were proposed to simulate the drivability of electric wheelchairs under snowy conditions.

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The morphological responses of cultured bovine aortic endothelial cells to fluid-imposed shear stress under sparse and colony conditions were studied.Applied shear stress was controlled to 2 Pa and the exposure time was set between 1 and 24 hours.Before and after flow exposure, the shape index and the angle of cell orientation to flow direction of each cell were measured.In the experiment under sparse condition, the shape index was 0.33±0.13(mean±SD)and cells almost randomly distributed under the no-flow condition.This randomness continued following application of Shear stress for 24 hours, and no morphological difference between cells under the no-flow condition and those after exposure to shear stress was observed.In the experiment under colony condition, cells in the center portion of the colony were round and randomly oriented under the no-flow condition.After exposure to shear stress for 24 hours, cells in the center portion were elongated and aligned with the flow direction, although cells in the periphery were randomly oriented.From these results, we concluded that the degree of cell-to-cell contact affects the morphological response of endothelial cells to fluid-imposed shear stress.

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In this paper a class of unidirectional perturbations is considered for a perturbed singular system which is nominally regular, impulse-free and stable.Based on linear fractional transformations, a systematic approach is used to derive a closed form for the maximal unidirectional perturbation bounds under which regularity, impulse immunity and stability are robustly preserved.The approach can be successfully applied to both continuous-time and discrete-time singular systems.Two illustrative examples are given to show the feasibility of the proposed technique.

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This paper is concerned with the stability analysis of interval matrices.Improved sufficient conditions for the stability of interval matrices are given.These conditions are based on a theorem that determines containment regions for the eigenvalues of a certain matrix which are smaller than the regions determined by the Gerschgorin Theorem and thus giving rise to larger margins of stability.We obtain sufficient conditions for the stability of a perturbed matrix using similarity transformations.Numerical examples are given to illustrate the results of the paper.

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There are several tactile receptors in the tissue of human fingers.In this study we calculate in detail the deformation of finger tissue when a finger comes into contact with a rigid plate using a FE(finite element)model to clarify the reason for the precise location of the receptors.The FE model is constructed using measured geometry and meterial properties.As a result, we found that the strain energy is concentrated at the tactile receptor locations.When a frictional force is applied, the stress / strain is concentrated near the edge of the contact area.By calculating the stress / strain distribution using models with / without epidermal ridges / papillae, we found that the shape of the epidermal ridges / papillae influences the stress / strain distribution near the tactile receptors.

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We develop a new method of minimum energy collision-free trajectory planning for a redundant manipulator using the B-spline function and a mathematical programming method.We use the B-spline function for determining the approximate trajectory of the joint angle of each link and the expressions of the outlines of obstacles.We maximize a performance index in order to choose the most dexterous posture of the manipulators.The approximate trajectory is then improved by minimizing another performance index expressing driving energy in consideration of the dynamics of redundant manipulator.According to the simultaneous consideration of driving energy, collision-free and dexterity, it is shown that the developed method is efficient and practical for trajectory planning.

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Adaptive feedforward control and self-organizing fuzzy control are comparatively implemented to a hydraulic-control fatigue testing machine.The experiments are tested at 0.1-10 Hz sinusoidal positions and with force commands.Since adaptive feedforward control requires on-line parameter identification which needs increased computer time, its testing frequency is limited.However, adaptive feedforward control has combined pole-zero and phase cancellations.The experimental results prove their excellent tracking performance.Self-organizing fuzzy control can reduce the computer load to enlarge the testing frequency range.In addition, it has a learning mechanism to adjust the fuzzy rule for various operating conditions.Although the control response of self-organizing fuzzy control cannot achieve perfect tracking, its peak-peak magnitude can always match the command magnitude very well.

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In this paper a real-time estimation method is presented for identifying the tireroad friction coefficient.Taking advantage of the Magic Formula Tire Model, the similarity technique and the specific model for the vehicle dynamics, a reduced order observer / filtered-regressor-based method is proposed.The proposed method is evaluated on simulations of a full-vehicle model with an eight state nonlinear vehicle / transmission simulation model and a nonlinear suspension model.It has been shown through simulations that it is possible to estimate the tire-road friction from measurements of engine rpm, transmission output speed and wheel speeds using the proposed identification method.It would be useful to incorporate the tire-road friction information into a vehicle collision warning algorithm.The proposed method can be used as a useful option as a part of vehicle collision warning / avoidance systems and will be useful in the implementation and adaptation of the warning algorithm since the tireroad friction can be estimated only using RPM sensors.

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The mechanism of hydrodynamic load capacity generation on a slideway is analyzed theoretically and experimentally.It is found that oil inlet pressure is an initial source for the development of this mechanism.At low Reynolds number, oil inlet pressure develops due to viscous drag of oil ahead of the oil inlet into narrow inlet passage, rather than to inertia force.The moment that develops as a product of oil inlet pressure generates a wedge geometry on bearing surfaces, whose surface separation is initially parallel in the stationary state.Initiated by oil inlet pressure, the wedge geometry is considered as the mechanism for generating hydrodynamic load capacity.Taking metallic contacts into consideration, the variation of frictional coefficient with sliding velocity can be estimated.Then, theoretical results are compared with experimental ones.

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This paper deals with a software system for the displacement analysis of arbitrary mechanisms, which has been discussed by many researchers.However, concerning the topological analysis of a mechanism and the automated generation of joint information, several problems remain unsolved.We propose more general methods than those previously reported in order to handle spatial constraints involving higher paris by using solid models and to analyze the structure of the mechanism by considering the directions of multiple closed loops.Furthermore, the technique of mathematical programming is applied to the displacement analysis.The practical applicability of the developed system with the methods described in this paper is demonstrated through sevelal example.

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Cutting fluids are essential in metal cutting to increase the tool life and reduce the finished surface roughness.Due to increasingly strict legislation aiming at controlling environmental pollution, however, the cost of using cutting fluids is rising.Therefore, it is necessary to reduce the amounts of the cutting fluid used.In this study, we propose a method in which cooling and lubrication can be achieved using extremely small amounts of cutting fluids.The effect of the proposed method is investigated through experiment.

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In this paper we propose a quantitative evaluation method for the preliminary layout of electronic systems.The preliminary layout is conventionally determined by trial and error based on rough sketches by a skilled engineer.This study is based on the assumption that the skilled engineer adopts distance as the main criterion for comparison berween design cases.First, a method of describing past design cases is demonstrated using similarity on the basis of a pattern attribute vector.The mahalanobis distance between design cases is formulated using this similarity, and a statistical calculation method for the evaluated function, which consists of the mahalanobis distance, is shown.A prototype of a layout design support tool was constructed to demonstrate the advantages of this evaluation method.This method is useful because of its short calculation time and the generality of its methodology.

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We have proposed a new type of hydraulic shock absorber using electrorheological(ER)fluid with apparent viscosity capable of being modified by an electric field.This ER shock absorber is so constructed that it can return to a conventional hydraulic shock absorber when the electric current to the ER shock absorber has been blocked, so that the shock absorber can fulfill the intended function.We compared the present ER shock absorber proposed in this paper with an ER shock absorber, which can not return to a conventional shock absorber under the above situation, proposed by us in the previous paper, during the impact of a body(2250kg)at 2.875m / s by simulation.The results of the simulation made it clear that the maximum acceleration of the body using the present ER shock absorber when blocked was about 1.1 times that of the previous one when not blocked, while the maximum acceleration of the body using the previous one when blocked was about 3.5 times that of the previous one when not blocked.

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