A new design method is proposed for vibration of functional fibrous composite plates, which imitate micro structures of natural materials such as bones and shells. The material has local anisotropy induced by optimally distributed short fibers which are defined in each element of the finite element method. To design such locally anisotropic plates, the present optimum design method combines a genetic algorithm method (GA) with a layerwise optimization (LO) concept. The LO concept reduces a multi-layer optimization into iterations of a single-layer optimization, and the GA is used for the single-layer optimization to determine fiber orientation angles in each element. The fundamental frequency of the plates is chosen as the objective function to be maximized. It was revealed that the present plates give higher fundamental frequencies than conventional plates reinforced by parallel straight fibers. Further optimally distributed short fibers indicated specific orientations even though no constraint was imposed on those directions.

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This paper deals with response analysis of nonlinear vibration in continuous system excited by periodic displacement with arbitrary functions. A system of steady state forced vibration in a simply-supported-beam connected with a nonlinear spring at midpoint of span is considered. The restoring force is assumed to be a piecewise-linear system. For such a system, the beam undergoes a nonlinear vibration when the amplitude is large. In order to analyze the main resonance for the system, the Fourier series method is applied to obtain an exact solution for response vibration. The numerical calculation is performed to obtain the resonance curves. The numerical results show effects of the stiffness of attached spring and the amplitude of excitation on the resonance curves. The experiments are also carried out to verify the numerical results.

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This paper deals with nonlinear liquid surface and interfacial wave motions in a tank containing two incompressible irrotational fluids of different densities. In order to investigate time history responses and nonlinear characteristics, we apply canonical equations (Hamiltonian equations) to this problem. The time histories and the transitions of surface and interfacial wave motions are given by solving the canonical equations of this system. This study is intended to clarify the nonlinear coupling characteristics for this system. We have focused on the N-Wave Resonant Interaction (NWRI) and investigated occurrence conditions of the NWRI. In particular, the time history responses on the resonant state caused by the Three-Wave Resonant Interaction (3WRI) are discussed for the rectangular and the circular cylindrical tanks. On the other hand, the validly of the theoretical analysis is verified through the experiments. These results are in good agreement with each other.

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Currently, some kinds of helicopters use pendulum absorbers in order to reduce vibrations. Present pendulum absorbers are designed based on the antiresonance concept used in the linear theory. However, since the vibration amplitudes of the pendulum are not small, it is considered that the nonlinearity has influence on the vibration characteristics. Therefore, the best suppression cannot be attained by using the linear theory. In a helicopter, periodic forces act on the blades due to the influences of the air thrust. These periodic forces act on the blades with the frequency which is the integer multiple of the rotational speed of the rotor. Our previous study proposed a 2-degree-of-freedom (2DOF) model composed of a rotor blade and a pendulum absorber. The blade was considered as a rigid body and it was excited by giving a sinusoidal deflection at its end. The present paper proposes a 3DOF model that is more similar to the real helicopter, since the freedom of the fuselage is added and the periodic forces are applied to the blade by aerodynamic force. The vibration is analyzed considering the nonlinear characteristics. The resonance curves of rotor blades with pendulum absorbers are obtained analytically and experimentally. It is clarified that the most efficient condition is obtained when the natural frequency of the pendulum is a little bit different from the frequency of the external force. Various unique nonlinear characteristics, such as bifurcations, are also shown.

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In the flux-path control magnetic suspension system, the force acting on a floator is controlled by moving a control plate made of ferromagnetic material, which is located between the permanent magnet and the floator. In this paper, the three-dimensional attractive forces acting on the floator were measured with a manufactured force sensor. The force actuating in the vertical direction is measured with the load cell built in the sensor. The force actuating in the horizontal direction is measured with the plate springs with strain gauges. These measurements clarify the relations between the positions of the control plates and the three-dimensional attractive forces. In addition, stable suspension and three-dimensional positioning were achieved by applying PD control. Several dynamic characteristics were measured in both the vertical and horizontal directions.

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The authors are developing a vibration evaluation system, which consists of field-portable exciters (actuators) and data processing software, to estimate vertical vibration and ride quality of railway vehicles. One of the main characteristics of the system is that the acceleration power spectral density (PSD) at arbitrary point on the carbody in running condition is synthesized numerically from measured data obtained when each axle box or each wheelset is excited individually using limited number of actuators. This paper focuses upon the data processing method for the vibration evaluation system. A series of excitation tests for a commuter vehicle is carried out to confirm the basic concept to estimate the PSD by using the rolling stock testing plant at Railway Technical Research Institute. Some excitation methodologies and data processing formulae are compared among each other. It is clearly shown that the estimated PSDs well agree with actual PSD. It is found out that the estimation gives high accurate results when only excited axle box acceleration are used in estimation analysis.

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Bending vibration characteristics of railway vehicles have been investigated in general under excitation tests, in which a carbody was directly excited by a shaker. It is however very difficult with their results to evaluate the ride quality of passengers under conditions that the vehicle runs on a certain track. The authors are therefore developing an evaluation system for vertical vibration of railway vehicles. This system consists of an excitation system equipped with linear actuators, the elastic supporting device installed between wheels and rails, and analytical techniques to estimate the power spectral density (PSD) and the ride quality level (L_T) which feature the ride quality. In this paper, we describe the excitation tests performed using an actual commuter car and the estimated PSD and L_T are compared with what substantially measured under the running conditions.

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For a functional driver assistance system to work property and provide cooperation between the driver and the vehicle, it must be configured to fit the preference of the driver. A brain—computer interface (BCI) provides communication between the driver and vehicle by translating human intentions, as reflected by brain signals represented in an electroencephalogram (EEG). This paper presents an algorithm for classifying a driver's steering intentions, based on a BCI that uses data from an EEG. Experiments were conducted with five able-bodied subjects, with varying driving experience, using a driving simulator. The off-line classification results show that the driver's steering intentions can be classified with an accuracy for about 65% for all subjects.

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Biomass resources are drawing more and more attention as alternative fuel for combating the energy crisis and for atmospheric environment protection. The small gas engine in a distributed power generation system is an efficient system to use, because the biomass resource is stored in large area and its energy density is low. The heat quantity of gas fuel converted from biomass is low, and the gas composition is affected by the source type, the gasification method, and the gasifying condition. Therefore, the gas engine must be modified and operated stably with high thermal efficiency in view of these fuel fluctuations. In this study, we aim to develop a small gas engine system for biomass gas by modifying the control system of a conventional spark ignition engine. The engine control system for the biomass gas that was developed analyzed the fuel type in real time by measuring the in-cylinder gas pressure. With this control system, stable automatic engine operation was successfully achieved under different fuel composition percentages of methane and the mock biomass gas.

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Active noise control (ANC) in a three-dimensional sound field (e.g., in an office) is investigated in this paper. Since the size of the controlled area generally depends on the wavelength of the target noise, it is difficult to control the noise in a whole room using ANC. Instead, noise control in the vicinity of a subject's head (referred to as around-head control) is investigated in this paper. To realize around-head control, an evaluation point that mimics head movement is required. However, movement of the evaluation point during controlling has not been considered in conventional ANC. A new algorithm is proposed in this paper to address this issue. The algorithm calculates filters as a function of position by using a time-delay filter and a distance-attenuation coefficient, which are calculated from the position of the evaluation point. Computer simulations of acoustic characteristics in an anechoic chamber and an ordinary office are conducted. The results of these simulations demonstrate the effectiveness of the proposed algorithm.

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Recently, research and development has focused on robots that work in place of people. It is necessary for robots to perform the same flexible motions as people. Additionally, such robots need to incorporate high-level safety features in order not to injure people. For creation of such robots, we need to develop a robot hand that functions like a human hand. At the same time, this type of robot hand can be used as an artificial hand. Here, we present artificial muscle-type pneumatic actuators as the driving source of a robot hand that is both safe and flexible. Some development of robot hands using pneumatic actuators has already taken place. But, until now, when a pneumatic actuator is used, a big compressor is needed. So, the driving system also needs to be big; enlargement of the driving system is a major problem. Consequently, in this research, we develop a low-pressure, low-volume pneumatic actuator for driving a robot hand that works flexibly and safely on the assumption that it will be in contact with people. We develop a five-fingered robot hand with pneumatic actuators. And, we construct a master-slave system to enable the robot hand to perform the same operations as a human hand. We make a 1-link arm that has one degree of freedom using a pneumatic actuator, and construct a control system for the 1-link arm and verify its control performance.

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Quadruped animals switch gait patterns with speed for energy-effective movement. This is similar to the phenomenon that excited natural vibration modes switch with vibration frequency in a multi-degree-of-freedom system. Therefore, in this paper, it is assumed that quadruped animals move by using the natural vibration of their own musculoskeletal systems. In the simplest rigid-body-link model consisting of one body and four legs, there are natural vibration modes similar to the gait patterns (trot, pace, and gallop) of quadruped animals. However, all the natural frequencies in the model exist near the natural frequency of the free leg and are accordingly different from the walking frequencies of actual quadruped animals. When a scapula and a pelvis are added to the rigid-body-link model on the basis of observations of quadruped motion, the natural frequency of the gallop mode used at high speed increases greatly and approaches the walking frequency. If the body characteristics of a horse are applied to the rigid-body-link model with leg joints, the natural vibration modes of the model are close to the gait patterns of the horse.

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In vehicle systems occupational drivers might expose themselves to vibration for a long time. This may cause illness of the spinal column such as low back pain. Therefore, it is necessary to evaluate the influence of vibration to the spinal column. Thus the modeling of seated human body is conducted in order to evaluate the effect of whole-body vibration to the spinal column. This model has the spinal column and the support structures such as the muscles of the back and the abdomen. The spinal column is made by the vertebrae and the intervertebral disks that are considered the rigid body and the rotational spring and damper respectively. The parameter of this model is decided by the literature and the body type of the subject with respect to the mass and the model structure. And stiffness and damping parameters are searched by fitting the model simulation results to the experimental measured data with respect to the vibration transmissibilities from the seat surface to the spinal column and the head and with respect to the driving-point apparent mass. In addition, the natural modes of the model compare with the result of experimental modal analysis. The influence of the abdomen and the muscles of the back are investigated by comparing three models with respect to above vibration characteristics. Three model are the proposed model, the model that has the spinal column and the model that has the muscles of the back in addition to the spinal column.

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Unstable vibration of multi-connected bodies supported by damper and spring systems moving in a narrow flow passage are reported. These vibration phenomena have been often observed in high-speed trains running through tunnels, cleaning robots going through pipings, medical machines in human blood vessels and core internals in nuclear reactor vessels. The equations of motion of multi-connected bodies are derived by Lagrangian method. The fluid forces acting on the multi-connected rigid bodies are obtained analytically on the basis of the Navier-Stokes equations applied to a narrow flow passage. The equations of coupled motion of the multi-connected bodies and fluid are derived. Using coupled equation, a stability analysis is performed. The critical velocities at the onset of the unstable behavior are estimated by plotting root locus. The flutter type instability and the divergence type instability are observed when the flow velocity increases. The variation of the coupled mode shape corresponding to the increment of the flow velocity is shown, and the relation between the coupled mode shape and unstable phenomena is discussed. Furthermore, the effect of the number of bodies and the pressure loss at the connecting points on the coupled mode and pressure distribution is investigated. The mechanism of occurrence of unstable phenomena is studied.

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The emergence of intelligence in an autonomous robot exists in the dexterity of humans or creatures as complex systems and research and development procedures along this approach seems necessary for realization of an intellectual robot. However, although strict judgment is required during stabilizing control of an unstable system, such as an inverted pendulum on a cart by human operators, it is assumed that human operators exhibit complex behavior intermittently. A previous paper investigated the skill of a human operator and investigated the formation of a complex system in the learning process of human operators with objects difficult to control. It also considered the mechanism of robustness of human operators against such a disturbance. The current paper shows that the neural network controller identified from time series data of each trial of several operators exhibits the human-generated decision-making characteristics with the chaos and a large amount of disorder. It also confirms that the estimated degrees of freedom of motion increases and the estimated amount of disorder decreases with an increase of proficiency. In addision, this paper shows that the agreement between the neural control simulation and the experimental results of neural control for the degrees of freedom of motion and the entropy ratio is particularly good when the simulated wave form and the measured wave form are similar in appearance.

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A differential pressure transmitter with an orifice is widely used as a major field flowmeter. A major drawback of this flowmeter at operation site is blockage of an impulse line, which connects a differential pressure transmitter with an orifice tap. By conducting experiments at a water line, we have developed a method to diagnose the blockage of the impulse line based on the evaluation of pressure fluctuations; this is installed on a multi-sensing differential pressure transmitter. This paper utilizes this method to diagnose the blockage at an oil line that carries a highly viscous fluid. In particular, we focus on the relation between the amplitude of the pressure fluctuations at the oil line and the kinetic viscosity (1.0 × 10^-5 to 3.0 × 10^-5 m²/s). Through experimental investigations, the following results are derived: (1) The highly viscous fluid in the impulse line does not attenuate the pressure fluctuations transmitting to the multi-sensing differential pressure transmitter. (2) Highly viscous flow in the main line has small pressure fluctuations; however, these fluctuations have the same characteristics of the impulse line blockage as those at a water line. Therefore, the proposed method can diagnose the impulse line blockage at an oil line as well as at a water line.

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