In the seismic design of nuclear power plant, it is recently considered to use probability method in addition to certainty method. The former method is called Seismic Probability Safety Assessment (Seismic PSA). In case of seismic PSA for some components of a nuclear power plant using a shaking table, it is necessary for some limited conditions with high level of accelerations such as actual conditions. However, it might be difficult to achieve the test conditions that a current shaking table based on hydraulic power system is intended for the test facility. Therefore, we have been planning out a test method in which both a current and another shaking table called a booster device are applied. This paper describes the verification test of a synchronized control between a current shaking table and a booster device.

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When a thin walled cylindrical liquid storage tank is exposed to a very large seismic base excitation, buckling phenomena such as elephant foot bulge at the bottom portion and nonlinear ovaling vibration at the upper portion may be caused. In the 1st report, elephant foot bulge phenomena and the liquid pressure effect were investigated. In this report, nonlinear ovaling vibration phenomena were investigated based on the dynamic buckling tests and the external pressure buckling analysis by FEM, using scale models of thin cylindrical liquid storage tanks for the nuclear power plants. The mechanism and the effects of vertical excitation and liquid sloshing were studied and discussed. As a result, it was found that the negative pressure will dominate the occurrence of the nonlinear ovaling vibration and the effects of sloshing and vertical excitation are relatively small. Moreover it was thought that the nonlinear ovaling vibration observed here is buckling phenomeon due to the external liquid pressure.

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The tandem cold mill chatter in sheet rolling has not always same phenomena even if under constant operating condition. For example, rolling speed and diverse frequency are not constant when chatter begins to occur. The reason why conditions of chatter are changeable is that the tension between mill-stands and the friction coefficient at the roll-bites are easy to be changed. In order to study the influence of tension and friction on rolling speed, two stands tandem systems based on two degrees of freedom vibration model are investigated. The following findings were obtained : (1) As the rolling speed increases, rolling mill vibrations become less stable. (2) The allowable range of the friction coefficient and tension condition to ensure the stability becomes narrow under high-speed rolling. (3) The fluctuation of tension and friction coefficient have a lot of influence on the natural frequency of chatter under high-speed rolling.

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In this paper, we propose the exact derivation method of all periodic solutions for forced impact oscillator systems, and clarified its mathematical structure. The key idea is to determine initial condition for periodic solution that enable the solution arising any current time to the future or past make periodic. By means of substitute derived initial condition to initial condition of general solution and evaluate it, periodic solution can be globaly represented by superposition of periodic stationary solution of linear system and finite number of periodic functions which is induced from evaluate of infinite summation of periodic pseudo feedback responses in terms of impact nonlinearity. According to comparing this result and our former result that was induced by feedback superposition method, new insigth about mathmatical structure of periodic solutions is derived.

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This paper presents a design procedure of H_∞ controller for bending-torsional coupled vibration of fiexible robot arm. In the case that the robot arm does not hold the inertial center of the payload, it processes uncertain bending-torsional coupled vibrations which affect in the accuracy and the stability of the controller. In this research, H>_∞ robust control design scheme taking account of parameter variations as structured uncertainties and model error of uncontrolled modes as unstructured uncertainties is utilized to describe the uncertainty in coupled vibration to guarantee robustness against such uncertainty. An experimental robot arm system is built and its parameters are identified by using Seto's method. A controller is obtained by applying the present design method. Control experiments are performed and the robustness of the synthesized controller to the parameter variations and model error are confirmed. The robustness of the obtained controller against uncertainty in coupled vibration is compared with ordinary H_∞ controller. The superiority of the presented controller design method is certificated.

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This paper proposes a design method of multi-degree-of-freedom dynamic absorbers which can suppress multiple vibration modes passively. Design parameters of the dynamic absorber are determined by utilizing the theory of the H_∞ static output feedback control theories and by solving Bilinear-Matrix-Inequality (BMI) problem. Finally, numerical simulations for the two-DOF dynamic absorber show the advantages of the proposed design compared with the conventional SDOF dynamic absorbers.

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New strategy for 10 MWh class energy storage flywheel system supported by superconducting magnetic bearing is reported in this paper. From the results of vibration analysis, we had confirmed that there are two rigid modes and a flexible mode in the range of control. This paper reported the adaptive vibration control for passing over the flexible critical speed in the range of control. In order to improve the performance of 10 MWh class energy storage flywheel system while the system passing over it's critical speed, H_∞ and a unbalance vibration control algorithm is used to control the system in this paper. From simulations, we can see the system can pass over it's critical speed with very small amplitude by H_∞ and the unbalance vibration control algorithm. Lastly, the stability of system with and without gyroscopic effect is reported in this paper.

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For the high accuracy attitude control of spacecraft, reaction wheels (RW), which are used as actuator, can be a major disturbance source. Therefore, it is important to comprehend the disturbance characteristics of RW. In this paper, the result of the following experiments and analysis are presented. Firstly we have developed the distrubance measuring system, which enables us to detect low-frequency disturbance in extremely low level of force. Next we have measured the disturbance with RW rotating at constant as well as time-varying velocity. Finally we have modeled the dynamic model of RW. Additionally we compare the simulation results with the experimental results, and it turns out that the simulation model has a high fidelity.

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This paper considers modal filtering of the vibration of a rectangular plate with an equally segmented piezoelectric film sensor. The simply supported and clamped boundary conditions are mainly concerned. Estimated modal coordinates are calculated from the sum of the weighted voltages of the segmented piezoelectric film. The weights determination is based on least-square method, and the effects of the spatial aliasing are also considered. Experimental results demonstrate the efficiency of this method.

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In this paper, an identification of a crack in a plate using characteristics of vibration is investigated. It is known that natural frequencies vary with growth of crack in the various structures. Then relationship between change of natural frequencies and change of stiffness of structures is clarified. We propose an estimation method by using natural frequencies, which are related to stiffness of structure. We apply the proposed estimation method to a rectangular plate with numerical analysis. The numerical analysis is performed with some mode of vibration. As a result, the proposed method can identify a location and length of a crack in a plate.

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This paper presents a new development in the experimental method for identifying the set of spatial matrices. That is, to realize the identification on the spatial matrices in sparse matrix form in accordance with consideration of structural connections between measurement points. In the previous method that the authors proposed, spatial matrices are usually identified in full matrix form due to the difficulty of realizing sparse matrix. In this paper, the difficulty is broken through using the simplex method of nonlinear optimization. A simple beam structure is identified in sparse matrix form by the newly developed method and in full matrix form by the previous one. Some static and dynamic prediction analyses are then carried out to compare both methods. That is, to verify the validity and the usefulness of the spatial matrices identified by both methods. The results show some advantages of the new method.

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In this paper, we propose a real-time image recognition method for downward stairways. Our proposed system uses a part of images is various situations. This system judges from existence of stair slope with databases made beforehand to predict danger. In Addition, it observes the distance to downward stairways. If this distance becomes smaller than a threshold value, the system starts to measure an inclination angle between a floor and downward stairways with two CCD cameras by stereovision. It uses a Hough transform in order to extract lines from edges of stair steps, too. One of characteristics of this paper is a limitation of polar coordinate area to search maximum values. In result, processing time becomes about 200 msec and maximum recognition time is about 50 msec. We consider that these scores are effective to control an electric wheelchair because in the processing time the distance it moves is small enough for a human.

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This paper deals with model following adaptive control of linear time-invariant systems with two sampling rates : a slower one for the output and a faster one for the input. It is known that intersample ripples often arise in the outputs of the closed-loop multirate sampling systems although multirate control has interesting advantages. In this paper, a ripple-suppressed multirate model following control scheme is presented. A state observer is designed at the output sampling instants and a filter is constructed at the input sampling instants in order to estimate the output at the intersample instants of the outputs. Next, an adaptive version of the algorithm for systems with unknown parameters is shown. Experimental results applied to a position servo system with a supersonic sensor are given to indicate the effectiveness.

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In this paper, additive effects of a control method derived by combining the internal model control and LQ control are proposed. Robust stability for parameter perturbation is also discussed from LQ control point of view. Then the proposed method is applied to tracking control for a two-finger robot hand. Effectiveness of the proposed method is confirmed by comparative experiments. The results show that the proposed method is effective on tracking control and improving the disturbance estimation property.

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In this paper, a new approach to robust finite RHC (receding horizon control) of constrained systems with structured uncertainties and bounded disturbances is proposed. The control problem is formulated as a minimax optimization problem of quadratic cost function with bounded constraints conditions. The proposed approach using the S-procedure can solve this problem efficiently. Numerical examples are given to show the advantage of this approach, the reduction of conservativeness, with respect to other preexisting methods.

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Impedance control is one of the most effective control methods for interaction between a manipulator and task environments. The force resulted by the interaction, however, does not occur until the end-effector of the manipulator touches its environment. A non-contact impedance control method has been proposed in order to achieve the impedance control before the contact. The method can regulate not only the end-point impedance but also the virtual impedance such that the end-effector is surrounded by a virtual object which can touch the environment before a real contact. This paper proposes a learning method using neural networks to regulate the virtual impedance parameters for given tasks. The validity of the method is verified through computer simulations and experiments with a conventional robot manipulator.

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In this paper, we propose the controller based on feedback-error-learning and physical properties of mechanical system. We applied the controller to flexible robot arm with two-mass structure. In the control system, at first, the desired trajectory of the tip point of the arm is transform into the desired signal of the driving point of the arm by equation of motion. And then, the driving point is controlled, the trajectory at the tip of the arm is controlled with high precision. And, when the controller has modeling error, the controller learn it with neural networks. So, the controller can control the tip point of the arm without motion sensor. We simulated trajectory control of the tip point of the flexible robot arm. And, we experimented about it. As a result, we obtained the improvement of performance of the arm by the proposed controller.

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We simulated skew phenomena of a flat belt running between cylindrical rollers with out-of-plane angular misalignment by means of the FEM software MARC. We investigated the effects of roller misalignment angle, belt initial tension, coefficient of friction, and an added tension roller on the belt skew. The results indicate that the skew transient state disappears very quickly and the skew rate is proportional to the roller misalignment angle and is about 60% in magnitude comparing with the inplane misalignment case. The tension roller greatly reduces the belt skew due to the out-of-plane misalignment, when it is placed in a suitable position with a certain in-plane angular misalignment. Both skew generating mechanism and skew reducing mechanism are also discussed.

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A printer may generate striped patterns in the printing images. This is known as jitter, and the jitter is one of most important themes for high quality printing. In a serial printer, jitter is mainly caused by velocity fluctuation of the print-head carriage system. The purpose of this paper is to find out a method for estimating the jitter. An image scanner is used to digitize the print image and a density fluctuation ratio is introduced to valuate the jitter level. It is found that the jitter level depends not only on the carriage's velocity fluctuation but also on the density of printing image, and it can be estimated by using density velocity curve. The printing experiments in the study have been carried out by way of dye-sublimation transfer, which is usually used for high quality photo printing.

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Slope finishing is one of the most difficult tasks for a hydraulic excavator. Using the system which we have developed, even unskilled operators can do slope finishing by only one lever operation. For this system, we have developed various control algorithms such as non-linear compensation, feedback plus feedfoward control, gain scheduling and learning control. Coping with the non-liner characteristics and large mass of a hydraulic shovel, these control algorithms bring high control accuracy and high stability. This system was experimentally shown to be useful and has been put to practical use.

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In this paper, a Neural Network position control system with both dither and PWM circuits is newly proposed for overcoming the inherent dead zone of a hydraulic motor. To decide the optimum frequency and amplitude of the dither, in the view of the steady characteristics, a design criterion was established by simulation results. The analytical solution using describing function and experimental works confirmed that these values are quite reasonable. Tracking characteristics were experimentally evaluated by providing sinusoidal waves with low frequency and small amplitude as the reference input. As a result, it is clear that the Neural Network control systems using PWM signals together with dither signals, and using only PWM signals considering an adjustable gain, have excellent performance compared to other systems. In addition, the two control systems attained accurate positioning when extremely small step responses are given. However it should be noted that introduction of the adjustable gain have not an effect on steady characteristics.

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This paper presents the curving performance of rail vehicles with air suspensions. Air suspensions sometimes cause reduction of wheel load at transition curve at low speed, so it is very important to evaluate the performance on transition curve. The air suspensions have non-linear characteristics, consequently the performance might be influenced by the initial condition, the entrance transition curve condition and so on. In this study, the effects of track and running condition on curving performance at the transition curve section were examined by computer simulations and experiments using the full scaled one-car-modeled test bench. It was found that the performance was influenced by the air flow through the levering valve into or out the air suspensions and the experimental results agrees with computer simulations. So it is effective to consider the characteristics of air suspension system to improve safety of running.

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The purpose of this study is to demonstrate how the friction control between wheel and rail can solve wheel/rail contact problems, such as wheel slip, rail corrugation, squeak noises, wheel/rail wear and so on. This paper presents the results of the fundamental tests which were carried out to clarify the physical performances of friction modifier, and general outline of “On Board Friction Control System” developed by authors. The performance of the proposed system is proved in experiments on the service line, showing the decrease of harmful wheel/rail forces, reduction of squeak noise, and prevention of rail vibration in lateral direction.

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In recent years, concern has been raised about automatic parking for a vehicle and several controllers have been reported. However, the control techniques are not yet matured for practical use. This paper proposes a real time optimization controller for automatic parking to aim at the practical use. First, the usefulness of the real time optimization algorithm is clarified. Second, simulation results show that the algorithm can produce a parking trajectory with switching operation, which is needed for a driver to park his/her vehicle in a narrow space. Third, output feedback controller for a vehicle is proposed. In this controller, the absolute coordinates of a vehicle are estimated by real time optimal state estimation algorithm; hence expensive devices such as a GPS or fixed camera system are not required to measure the coordinates. Last, simulation results demonstrats that the calculation time is short enough to realize the real time control.

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In some cases of developing a new product, response surface of an objective function is not always single peaked function, and it is often multi-peaked function. In that case, designers would like to have not only global optimum solution but also as many local optimum solutions as possible, so that he or she can select one out of them considering the other conditions that are not taken into account priori to optimization. Although this information is quite useful, it is not that easy to obtain with single trial of optimization. In this study, we will propose a screening of fitness function in genetic algorithms, and give rough search for local optima. Once after they are obtained we will carry out local search to obtain multiple quasi-optimum solutions. In this paper, we demonstrate the effectiveness of the proposed method through a simple benchmark test problem.

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A tip position of a wire-driven mechanism is controlled by an electric motor, so the three problems : slack in the wire, friction between the wire and coil sheaths protecting it, and change in the form of the tube must be solved. A model of the wire-driven mechanism was devised, and a method for controlling the wire-driven mechanism was then developed. First, a model base on a nonlinear dynamic equation including friction and wire slack was mode, then a reference-filter controller, which compensates the phase delay of the wire-driven positioning system, was designed. Positioning experiment was confirmed that the controller effectively improved the following performance regarding the target trajectory without the need for an additional sensor.

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This paper proposes a modified linear model for the snake motion in the hot strip rolling, and the tail crash control based on the model is considered. First, an improved linear model for the snake motion is provided by introducing some parameters to conventional equations. Next, the state-space model is derived from the obtained linear model, and the state feedback control system is designed. The dynamic simulation based on the rapid version of the generalized 2-dimensional theory is used for adjusting parameters and for checking behaviours of the control system, instead of the experiment using an actual plant. The effectiveness of the proposed method is demonstrated by numerical experiments of the hot strip rolling by a six-high mill.

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In previous study, H-infinity control theory was applied in order to establish high reliability of a torque converter lock-up clutch slip control system, so that it was confirmed that robust stalility against large characteristic variation of the plant was ensured. There is, however, a problem of requiring much time to perform the procedure from the modeling to the designing of the control system because of many experimental data under various conditions to obtain practicable models. We propose new design method that shortens the design time by representing the plant model by interpolation of vertex characteristics, which represent boundary of model set made from the data and knowledge accumulated in the past, and can construct the control system on an onboard ECU. In this paper we aim at modeling in the above method, and show that the time for modeling has been shortened greatly as compared with the conventional method.

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Nuclear power plants have a large number of pipes. These small-diameter pipe branches in particular are often damaged due to high-cycle fatigue. In order to ensure the reliability of a plant it is important to detect fatigue damages in pipe branches at an early stage and to develop the technology to predict and diagnose the advancement of fatigue. Further, in order to carry out the diagnosis of the piping system effectively during operation, non-contact evaluation is useful. Hence, we have developed a “high-cycle fatigue diagnostic system with non-contact vibration sensing”, which measures the vibration of the pipe branch using a non-contact sensor.

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When a snail is crawling on a ground, dark transverse bands appear on the sole of the snail and propagate from the posterior end of the foot to the anterior end. The dark bands are essentially the regions of longitudinal muscle contraction of the surface of foot, which form pedal waves. We paid attention to the manner of formation and propagation of the pedal wave. A pedal-like locomotion mechanism is developed of which moves forward by a pedal crawling like the snail. The pedal mechanism consists of eight units of the contraction mechanism which performs such a series of contraction motions as longitudinal contraction of the sole, lifting the sole surface and propagation of pedal wave by the use of a link mechanism and a SMA as actuator. As a result of the experiment on locomotion of the pedal mechanism, it was found that the locomotion velocity of the pedal mechanism was in proportion to both the propagation velocity of a pedal wave and the number of a pedal wave past on the sole per unit time, but an increase of the frequency of a pedal wave caused a decrease in traction of the pedal mechanism.

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The performance of the knee component of above-knee prosthesis greatly affects the gait of the user. Recently, the intelligent knee joint that can adapt itself to the change of walking speed has been developed. The purpose of this study is to develop above-knee prosthesis that is able to be automatically adapted to various gates by using simple and passive control units at the knee joint. In this paper, control of the knee joint in swing phase of the gate cycle is analytically investigated by using a simplified dynamic model of a lower limb. As the result, it was clarified that the control of viscosity of the knee was more effective to change the pace than the control of inertia of the shank and the friction force. In addition, it was also clarified that extension torque was required at the knee joint in the latter half of the swing phase under the condition of instructed step size and pace.

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This paper describes a method of muscles assist at start walking using human leg model. We analyzed the walking motion and measured the surface EMG, and discovered there are 2 joint angle are needed for start walking, also discovered Gluteus maximus, Iliopsoas, Gastrocnemius, Soleus muscles were main components of beginning of walking. We produced the human leg model and installed the actuators instead of the muscles. And we used leg model to obtain the condition when the leg model beginning to walk from leg open position. It was confirmed that action timing of the actuator matched with the muscles work in the surface EMG. As the result, the start walking was able to be confirmed by the operation of 2 actuators in moving sequence of Gluteus maximus to Gastrocnemius muscle. Based on this discovery, we obtained basic data for the development of the wearable assisting equipment for walking in this study.

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Fixed and orbiting scrolls of scroll compressor components have spiral grooves known as scroll wraps. High precision contour milling using end mills is the best method to produce these scrolls. The aim of our present work is to recognize the mechanism of tool wear on end mills in end face machining and to reduce tool wear in highly efficient milling. The paper describes an effective coolant supply system to the cutting point and an appropriate tool geometry developed in the study. The following conclusions can be drawn : (1) The wear rate of the flank wear can be reduced to approximately 1/50 by supplying coolant to the cutting edge through the center hole of the tool at a cutting speed of 230 m/min (V=230 m/min). (2) The optimal back clearance angle is 5 degrees for abrasive resistance in the turning operation. (3) The wear rate of the corner edge can be reduced to 1/6 when the back clearance angle is changed from 15 degrees to 5 degrees.

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In order to investigate the influence of shot peening on the surface durability of sintered powder metal gears, the plasma case-hardened sintered powder metal gears shot-peened with different shot diameter and shot hardness were fatigue-tested using a gear testing machine. The hardness, the compressive residual stress and the surface roughness of the gears increased by the shot peening. The pores near the tooth surface of the shot-peened gears were obviously deformed excect for those of the lightest shot-peened gear in this study. The failure mode of the unpeened gear was pitting, and those of the shot-peened gears was mainly spalling. The failure depth agreed almost with the depth where the amplitude A (τ_yz/HV) of the ratio of orthogonal shear stress to Vickers hardness became peak near the tooth surface. In these experiments the surface durability of the lightest shot-peened gear was highest comparing with those of the other gears. Therefore, it can be proposed that the light shot peening, which does not cause too large surface roughness and the deformed sharp pore, has to be selected in order to improve the surface durability of sintered powder metal gears.

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Weld metal yield strength mismatch may increase the structural integrity of welded components providing that a certain level of weld metal toughness is maintained. Based on this fact, the objective of this paper is to investigate the effect of filler wire selection on the fracture behavior of welded mild steel plates from the perspective of application temperature. Two types of flux-cored wire were used to buttweld mild steel base plates by semi-automatic CO₂ gas shielded arc welding. Rectangular test specimens were extracted from the welded plates and a through-the-thickness center crack was fabricated along the weld line in each specimen. A uniaxial tensile load was applied perpendicular to the crack plane over a range of ambient temperatures and the fracture behavior was investigated using a combination of experimental techniques and elastic-plastic finite element analysis. The advantages offered by each weld metal were found to be temperature dependent, thus limiting their suitability to certain applications.

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Austempered Ductile Iron (ADI), which has much the same strength and toughness as usual steels, has been developed. ADI has many advantages in physical properties and manufacturing, such as weight reduction, good properties of vibration and noise, low cost in machining and heat treatment of blanks due to near-net-shape casting. Using these advantages, it has been reported that ADI can be sufficiently applied as a medium hardness gear material. In addition, it is important to reduce the amount of the lubricant when many problems, i.e. global environment, resource conservation and cost reduction, etc., are considered. So it is necessary to examine the perfarmance of ADI under oil-free condition or Minimal Quantity Lubrication (MQL) condition. In this paper, the surface failure strength of ADI rollers is investigated using a disk machine which simulates the rolling and sliding action of gears. In particular, the surface failure strength under the MQL conditions is examined in comparison with the steel which has almost the same hardness of ADI. As the results of experiments, the surface failure strength of ADI rollers under MQL conditions is as same as that of SCM 435 rollers under usual lubricated condition.

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It has long been believed that the tip of a knife-edge has a single small radius and the radius becomes larger with abrasion during daily use. Recently, for the most popular knife made of SUS 420J2, the authors have found that the tip has two micro-blades (the secondary blades) with a groove between them along the knife-edge and the groove grows and thus its width becomes larger with cutting operations. In this paper, this evidence is confirmed to be true even for the knife of a heat resisting alloy-SUH3 and a high-hardness Zirconia Ceramics, and thus it is concluded that the formation of such groove and its growth is a general phenomenon for almost all knife-edges. For each tested blade, the relationship between the cut piece number of paper (NCP ; the cutting performance) and the repetition number of abrading operation (Nt) is approximately expressed as an exponential relation. Ideas to express the durability of cutting performance (Nt*), the total cutting performance (TNP) and the feeling of cutting paper (ACP) through the service period are proposed and quantitatively evaluated for the tested materials. It is surprisingly found that even for the brittle Ceramics, the relationship between the groove spread and Nt is almost the same as those for SUS420J2 and SUH3. In comparison with SUH3 and SUS420J2, Zirconia Ceramics has the highest durability Nt*, the best total cutting performance (TNP) and the best feeling of cutting (ACP). The ratio of the durability, total performance and the feeling of cutting to those of SUS420J2 are 28, 40 and 1.4 for SUH3, and 48, 71 and 1.5 for Zirconia Ceramics, respectively.

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We aim to develop an intelligent prosthetic foot that has the braking system of ankle joint. Magnetorheological (MR) fluids is material that changes their rheological behavior by an applied magnetic field. A brake using MR fluid can change the braking force according to the strength of applied magnetic field. In this paper, we develop the linear brake using MR fluid for the intelligent prosthetic foot, and carry out the virtual walking experiment by the use of that brake.

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A concept of effectively global search is introduced and used for setting an adaptive stopping criterion for local search heuristics. By applying this criterion to the detection of equilibrium, a new adaptive cooling schedule is developed for the simulated annealing algorithm. To examine the function and optimization performance of the presented method, it is numerically tested on the Euclidean traveling salesman problem. The proposed strategy realizes an adaptive search to the global landscape structure of the cost function. As a result, the present adaptive cooling shows good ability in yielding better solutions stably than the conventional non-adaptive one.

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