When an elevator rope for a high-rise building is forcibly excited by long-period ground motion, rope displacement becomes large even if the ground acceleration is small. Therefore, detecting the rope sway in real time is important to avoid damage during and after earthquakes. In a previous paper, when elevator cage is moving, a simplified calculation method, based on a single degree of freedom (SDOF) system, for estimating rope displacement during an earthquake by using the building acceleration and ground acceleration is presented. This simplified calculation method is applied to main rope, which resonates only one time with building's sway while the elevator is moving. In the case of the main rope, the results of this simplified calculation method agree with those of the conventional finite difference method (FDM), within the 20% error margin. In this paper, the simplified calculation method is applied to compensating rope, which resonates two times with building's sway while the elevator is moving, by considering the rope tension. Finite difference analyses of rope vibration are also performed to verify the validity of the simplified method. The results of this simplified calculation method agree with those of the conventional finite difference method, within the +20%,-30% error margin.

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A small base isolation system using friction bearings composed of two plates having spherical concave and a ball was developed to prevent overturning small equipment set up inside building during a big earthquake. However it has an amplification problem by resonance. In order to prevent the resonance on this system, the ball of this device is changed to a marble plate or to a ball embedded in a cylindrical sponge. As the results by excitation experiments, the amplification by resonance did not identified, since damping ratio of these systems was increased. The peak acceleration amplitude on these systems has decreased to 42-88 % compared to input waves, and the system using friction bearing with the ball embedded in a cylindrical sponge indicates good reduction in this experiment. And reduction performance of seismic response is evaluated by numerical simulation using SDOF model. Comparing acceleration response waveforms by excitation experiment and by numerical analysis, it was good agreements in case using friction bearing with a ball embedded in a cylindrical sponge. This system is useful for reduction of seismic response.

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In this paper, we propose the seismic response analysis method and investigate the optimal design of the piping system supported by elasto-plastic damper subjected to the random input based on the random vibration theory. The piping system is modeled by simple cantilever beam with weight. The support force is given by bilinear model. The inputs are given by white Gaussian noises. In this optimal design, we can maintain the structural integrities of both the piping systems and the elasto-plastic supporting devices by taking three indexes; dynamic reliability of pipings, accumulated energy of support and dynamic reliability of support into account. Furthermore, the optimal conditions of parameters such as the supporting location, the capacity of the supporting devices are searched. Numerical simulations are performed using a simple piping system model for the random input based on the probabilistic vibration theory. The optimal design proposed here is applicable to the seismic design of piping systems supported by elasto-plastic dampers subjected to the actual earthquake input.

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The final purpose of this paper is to estimate the efficiency of some stochastic floor response spectra in order to easily estimate the dynamic characteristics of secondary system such as piping, equipment and so on, mounted on a structure owing to an earthquake. Because of the increase of uncertainty at earthquake level, the design level for earthquake is tending upward. This is implying that the aseismic design of secondary system based on elastic design becomes more difficult from the viewpoint of economic design. Thus, as a first step, one paper by author has been derived as for the stochastic floor response spectra in consideration of a simple nonlinear design. As a second step, the multi supported secondary system is testified in consideration of correlation between multi components of input. The nonlinear properties of the secondary system are modeled in terms of an equation of motion which linearly involves the auxiliary variable as part of the restoring force and the auxiliary equation which describes a nonlinear relationship. Total equations including the auxiliary equation are linearized using a stochastic linearization technique. Then executing the statistical calculation to obtain the non-stationary variance relating to relative displacement of secondary system, finally the stochastic dynamic characteristics of the multi-supported nonlinear system can be derived analytically. The obtained results are compared with those by Monte Carlo simulation.

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This paper describes the particle damper design, based on the analytical single mass damper model and experiments with smaller size steel balls. The effects of various system parameters - including mass ratio, particle size, cavity dimensions, intensity, and frequency of excitation - were investigated using a SDOF structure under harmonic force excitation when the vertical excitation is applied to the structure. The damper designs call for that the damped motions of the structure equipped with steel ball particle dampers become periodic as well as kept approximately equivalent as predictions by the analytical model. It is shown that the suitable size of steel ball and container dimensions were found to be selected for the combinations of mass ratio and excitation levels in the vicinity of the optimum range of system. Thus, the particle dampers with steel balls, with moderate mass ratios, can be very effective in attenuating the response of lightly damped structures.

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This paper deals with nonlinear transient vibration analysis using finite element method for boxy structures made by six rectangular elastic plates supported by nonlinear springs. The bottom panel in the boxy structure is stiffened by beads. On the bottom plate, a viscoelastic damping material is laminated. The bottom plate is supported by four nonlinear concentrated springs near the four corners of this plate. The shape of the other five elastic plates is flat rectangle. The restoring force of the springs has cubic nonlinear terms and linear hysteresis damping. Finite elements for the nonlinear springs are expressed and are connected to the boxy structure modeled by linear solid finite elements. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled equations using normal coordinate corresponding to linear natural modes. Comparing shares of strain energy of the elastic plates, the damping layer and the springs, we investigate the influences of the bottom panel with/without the beads on modal loss factor. Furthermore, we evaluate the influences of the damping couplings on nonlinear transient responses by the differences of the bottom plate in the boxy structure.

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For the piezoelectric shunt damping technique, active shunt circuits play an essential role for realizing advanced sensor-less piezoelectric vibration control systems. This paper discusses the stability margin of the piezoelectric shunt damping system using the virtual admittance also known as the synthetic admittance. A grounded current amplifier with the drift compensator is developed and its detailed circuit is shown. A physical interpretation of the drift compensator and some remarks are also discussed. From the analysis of the stability-margin of the open-loop transfer function, it is shown that the virtual admittance is suitable for simulating the inductive shunt such as a series LR circuit. The experimental result demonstrates the damping performance of the series LR elements realized by the developed virtual admittance circuit attached to a piezoelectric cantilever.

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Force redistribution method for compensating actuator-breakdown of vibration isolation tables is studied in this paper. The vibration isolation table is supported by eight pneumatic actuators, and has a redundant number of actuators with respect to degrees of freedom of table motion. We propose a force redistributing method which utilizes redundancy of the actuators. When some of the actuators break down, their output forces are re-distributed on the unbroken actuators by the proposed method. We construct a detailed mathematical model of the vibration isolation table supported by a redundant number of pneumatic actuators. Type 1 digital servo system is applied to control the vibration and position of the vibration isolation table. This study performs numerical simulations in which some of the actuators break down and the pressures of the broken actuators decrease at a constant rate. The effectiveness of the proposed method is examined by numerical simulations.

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Recently, ultrasound contrast imaging has been improved greatly, because its application of an approach for therapy is urgently required for area of the heart and abdominal. Sonoporation is also one of the applications using microbubbles that attracts attention in the world. There have been so many studies for understanding the mechanism of sonoporation and improving efficiency of ultrasound contrast agents. Nonspherical oscillation is at a stage before the breakup process of microbubbles. Therefore, consideration of a microbubble's nonspherical oscillation is absolutely imperative for its future development. Thus in this thesis, the author regarded microbubbles as two dimensional air-liquid two-phase flow and calculated their dynamics by using Computational Fluid Dynamics (CFD). Numerical calculation of a microbubble's oscillation and deformation was also carried out, for an air bubble and for a shell-coated bubble in ultrasound field. As a result, it was confirmed that the CFD method developed in this study can be useful for analyzing an insonified microbubble showing nonspherical oscillation.

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The dynamic stability of a flexible plate subjected to a parallel flow is investigated when it moves into a flowing fluid. As the flexible flat plates, the papers in a high speed printing machine, the papers discharged by a paper machine, and the thin plastic film, the fluttering flag and the oscillating doom roof caused by wind are enumerated. The fluid is assumed to be treated as an ideal fluid in a subsonic domain, and the fluid pressure is calculated using the velocity potential theory. The coupled equation of motion of a flexible flat plate which is supported simply at both ends is derived into consideration with the added mass, added damping and added stiffness respectively. In addition, the effects of the tension acting the flexible plate, the moving velocity of a plate and the fluid velocity respectively are also included into the coupled equation of motion. The eigenvalue analysis is performed for the dynamic stability analysis. Changing the velocities of a plate and a fluid, the specifications of a plate as parameters study, the effects of these parameters on the dynamic stability of a plate are investigated. Moreover, it is found this solution shows a good agreement with the already reported experiments in which the flexible flat plate is a paper.

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The stability of nonconservative system of a beam is investigated when an elastic beam is subjected to follower forces. The mathematical formulations for a conservative system and a nonconservative system are established regarding to a uniform cantilever subjected to a concentrated force and a uniform distributed force axially. The displacement of a uniform cantilever is assumed to be obtained by superposing the modal functions which are normal modes in a vacuum, and is estimated by applying the Galerkin method. Changing the forces, the eigenvalue analysis is performed, and the root locus is calculated for the stability analysis. And, the relationships between forces and frequencies for the undamped system and the damped system of the uniform cantilever subjected to a concentrated force and a uniform force are investigated. When the system is subjected to a conservative force, the divergence phenomenon is confirmed to appear first. On the other hand, when the system is subjected to a nonconservative force such as follower force, the flutter phenomenon is confirmed to appear first although the critical force becomes high. And, by changing the structural damping, the destabilized effect due to the structural damping is confirmed when an elastic beam is subjected to follower forces. Moreover, the dynamic behaviors of the higher modes, and the stability of a simply supported beam and a free-free beam are also studied.

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In a variable speed engine, it is impossible to avoid the resonance during operation. In a constant speed engine, the resonance during start-up or shut-down also cannot be avoided. Therefore, the increase of the acceleration rate passing through the resonance is considered as one of the effective methods for reducing the vibratory stress of the blade and increasing the reliability of the turbo-machinery. In this study, the transient vibration analysis of the mistuned bladed disk passing through the resonance is carried out, using the conventional modal analysis method and the numerical integration. First, the mistuned bladed disk is modeled by the equivalent spring-mass model, and the steady frequency response analysis is carried out by the Monte Carlo simulation, in order to obtain the worst mistuning. Second, for the mistuned bladed disk of the worst mistuning, the transient vibration analysis in passing through the resonance is carried out, and the effect of the acceleration rate and the blade damping on the transient vibration response is examined in detail. From these results, it is concluded that the larger the acceleration rate is, the smaller the mistuning effect is.

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It is well known that asymmetric vane spacing can result in decreased levels of the excitation at specific frequencies. In the previous paper, the resonant response reduction of mistuned bladed disks due to asymmetric vane spacing was studied by use of the equivalent spring-mass model. Although the mistuned bladed disk should be analyzed by FEA to accurately evaluate the resonant response reduction effect of asymmetric vane spacing, it is unrealistic due to enormous computational time. Therefore, in this study, the mistuned bladed disk is modeled by use of FMM (Fundamental Mistuning Model) to evaluate the resonant response reduction effect of asymmetric vane spacing accurately and practically. First, the frequency response analysis of a simple mistuned bladed disk consisting of flat plate blades is carried out for symmetric vane spacing, using both of FMM and the direct FE model, and the calculated results are compared to confirm the validity of FMM. Second, the frequency response analysis of a realistic bladed disk is carried out for asymmetric vane spacing, using FMM, to examine the effect of resonant response reduction effect.

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This study concentrates on torque loss of needle roller bearings used in a planetary gear set. Dynamic analysis is conducted to investigate mechanisms of friction loss by a multibody dynamicss (MBD) model, which is developed to consider dynamic effects on the planetary gear and contact conditions. Contact analysis of needle rollers with other parts utilizes the discrete ball model to obtain the distribution of contact points and to decrease computational cost. The sliding friction coefficient is defined by experimental results that evaluate the relationships between the thrust force and the skew angle of the needle rollers. The MBD analysis evaluates bearing clearances between the needle rollers and other parts in the radial and circumferential directions. It is found that the clearances between the needle rollers and the cage in the circumferential direction are a dominant factor in friction loss. Moreover, numerical results confirm that the skew angle of the needle roller with respect to its rotation axis has the most significant effect on the friction loss of the bearing. The skew of the needle roller causes thrust force that pushes the pinion gear onto the side washer that supports the axial motion of the pinion gear. Finally, this study suggests an appropriate clearance between the needle rollers and the cage to reduce the skew angle of the needle rollers and the friction loss between the pinion gear and the thrust side contact. The circumferential clearance should be desined as small as possible.

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A simple dynamic model will be effective to determine the properties of protection devices because it is useful to understand the essential dynamics of the occupant in car crash. This paper describes an optimal restraint method in frontal car crash by using a reduced-order dynamic model based on human finite element model having age-specific characteristics such as bone stiffness and tolerance of the body. The restraint force is determined so as to minimize the maximum thoracic deflection, which is one of the representing injury criteria in frontal car crash, while the maximum thorax and pelvis displacements are restrained. Simulation results clarify that the optimal restraint force is effective for reducing the maximum thoracic deflection.

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It is necessary to clarify the vibration characteristics of a seated human body for the interpretation of the influence on the seated human body exposure to whole-body vibration. The results of a lot of past studies have informed that the difference of seated postures changes vibration characteristics such as the resonance frequency and the resonance amplitude of a seat-to-head transmissibility and a driving-point apparent mass. However, the seated postures of their subjects in these studies are not necessarily explained in detail. Though the evaluation of human exposure to whole-body vibration are specified by ISO2631, the seated postures at the experiments aren't specified in any ISO standard. In order to make good use of the results of the human vibration experiments, a technical report about the seated postures at the experiments was being discussed. Therefore the purpose of this paper is the expression of the seated postures at the experiments by the index values for seated posture defined by the technical report and the mention of the relation between the seated posture and resonance frequencies of the transmissibility and the apparent mass. The vibration of the experiment was the vertical random vibration whose frequency is from 2 to 30 Hz. The experiments of two different seated postures, an upright posture and a relaxed posture, were performed. In the result, these resonance frequencies in the relaxed posture were lower than those in the upright posture. It is suggested that the lumbar curvature has a relationship with these resonance frequencies.

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This paper proposes an evaluation method for operability of pleasure boats in order to develop an electronic control steering system of those boats. Based on usability as addressed by ISO 9241-11, some evaluation criteria such as effectiveness and efficiency are defined for a task of collision avoidance and course resuming. For safety and repeatability, the simulation with a simplified ship simulator, which is composed a manual hydraulic steering system as hardware in HILS, is performed instead of experiments. As a result of the simulation, it is found that the operability of the manual hydraulic steering system deteriorates in the case of emergency collision avoidance. In particular, the wakes of the course resuming after the emergency collision avoidance are caused to be periodic by wrong estimate of the normal pressure and by time delay in the dynamics of the pleasure boat. Therefore, it is found that the electronic control steering system of pleasure boats should have the functions to support estimation of the normal pressure and to compensate the time delay.

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Stability of a two-wheeled inverted pendulum vehicle was evaluated by using rider-vehicle modeling, electromyography of leg's muscle of rider, and subjective evaluation. A rider and the vehicle are synthetically modeled as a series-type double inverted pendulum. Utilizing auto-regressive exogenous (ARX) model method, correlative relations were found between control gains and stability of the vehicle that achieves better ride comfort. The experimental result shows that the higher the control gains, the smaller the activities of leg's muscles. However, according to subjective evaluation of ride comfort, higher gains did not always achieve better ride comfort. Moreover, the rider-vehicle model has no unstable poles, even when the vehicle model has an unstable pole. The poles of the rider-vehicle model had tendency to have bigger negative real numbers, which suggests stability of the vehicle can be evaluated by the positions of the poles of the rider-vehicle model. Through identification of the rider-vehicle model, the control gains of the rider's posture were calculated. It was found that the control gain against the rider's posture is dominant, and the higher the control gains of vehicle, the smaller the gain against the rider's posture. The result shows stability of the vehicle can be evaluated by the control gains against the rider's posture.

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A mobile inverted pendulum (MIP) draws attention as a next-generation energy saving vehicle especially for urban life because it is energy-efficient to transport a person and has a small footprint. It is important for the MIP to run safely on various types of roads. However, there are few studies on the MIP considering slopes or steps. We focus on a change of slope angle and aim to improve safety when the MIP runs on such a road. To achieve this goal, a simulation model of the MIP which runs on a road with a change of slope angle is constructed. This simulation model introduces constraint contact formulation to consider change of a contact point between the wheel and the ground. Motion of the MIP is analyzed when it runs up or down the road. The results of the analyses indicate differences of motion caused by running velocity and feedback gains. Based on the results, we show the existence of the feedback gain which has good controlled performance focusing on behavior of pendulum angle, acceleration of human body and running velocity, and the guideline of control system design considering running on a road with a change of slope angle.

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Internal combustion engines are required to use various fuels. A conventional MAP based engine control system is not suitable for achieving stable operation and high thermal efficient operation for various fuels. Authors have been developing the engine control algorithm to realize fuel flexibility by employing experimental rules and a closed loop control using in-cylinder gas pressure. In this study, in order to improve fuel flexibility of engine control algorithm and to confirm the experimental rules, availability of calculation results with elementary reactions for the algorithm is investigated. Availability of instant crank shaft torque for a feedback sensor is also investigated. The result shows that the modified engine control system employing laminar burning velocities calculated from elementary reactions and the torque feedback loop can maintain stable operations when fuel lower heating value varies during engine operation.

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A magnetically levitated motor can realize non-contact support of a rotor using magnetic force. Therefore, it has many advantages over conventional mechanical bearings. In order to accomplish complete magnetic levitation of the rotor, it is necessary to control five degrees of freedom actively. However, this gives rise to major issues such as complicated control system and associated electronics, resulting in enlarged equipment size. The proposed magnetic levitated motor uses a radial bearing-less motor to control both radial translation motion and rotation, and an axial magnetic bearing to control both axial translation and tilt motion. Moreover, stators were installed on the inner side of the rotor, such that the flux path of the axial magnetic bearing and radial bearing-less motor are partially-shared. Therefore, the proposed magnetic levitated motor is small, while achieving five degrees of freedom active control. The prototype device was designed using FEM. According to this analysis, the device had sufficient magnetic force to control the rotor within a designed airgap of ±0.6 mm. An experimental setup was fabricated in order to verify the performance of the proposed device, which demonstrated stable five degrees of freedom active control and fast settling times of 0.0084 sec for radial direction and of 0.026 sec for axial direction control. Levitation experiment showed good capability for an impulse disturbance. In addition, levitated rotation test was carried out. The rotor could run up to 5,000 min^-1 with very low vibration amplitude.

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This paper addresses novel control strategy for 6 salient-pole active magnetic bearings (AMBs). Since 6 salient-pole type AMB has less number of poles as compared with usual 8 salient-pole type AMB, it becomes advantageous to a miniaturization and a low cost. However, since the magnetic circuit has not been independent in x and y direction, bearing forces for coil currents become complicated. Previous research introduced a minimum energy control method which makes the copper loss in coils the minimum. However in the minimum energy control method, the maximum bearing force of specific directions is less than that of the other directions. In order to solve this problem, the maximum bearing force control method is proposed in this paper. Analysis and experiments confirm that the proposed method provides stable rotor levitation and larger bearing force than that of minimum energy control method.

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Flux-path control magnetic suspension using flux concentration is proposed and studied both analytically and experimentally. The proposed system used control plates made of permanent magnet instead of ferromagnetic material. It was shown that flux-concentrated type can produce larger suspension force than the conventional flux-interrupted type. However, it was difficult to achieve stable suspension since the control (variable) force was not so large. In this paper, to solve such a problem, the characteristics of the suspension system are studied by finite element analysis. The effects of the direction of motion, the operating positions and the shape of the control plates are investigated. An experimental apparatus with a variable flux-path unit using flux concentration is developed based on the analytical result. A single-axis stable suspension is achieved by applying PD control in the developed apparatus.

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This paper proposes a method improving precision of sound source identification by inverse acoustic analysis. The inverse acoustic analysis identifies a vibrational state for mechanical structures by measuring the radiated sound in many points and solving the inverse problem. In this analysis, the uniqueness of solution is not always guaranteed, and the problem is to avoid the instability of the inverse matrix in sound source identification. A numerical simulation is performed about a plate model, on which many point sources are assumed that radiate sound pressure by their vibration. Sound pressures are measured by many microphones and the inverse matrix is calculated from acoustic transfer functions. This paper presents two kinds of methods for changing the coordinates of measurement points in order to decrease the instability of the inverse matrix. One is the singular value sensitivity analysis and the other is the statistic approach by using normal distribution. Both methods are applied for the noise source identification of the plate, and the results are compared, and their features are discussed.

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In this study, target level setting method for reference signal of operational TPA was considered using principal component regression method. A principal component having high contribution to the response signal was selected and target levels of the reference signals were calculated using the principal component by principal component sensitivity analysis. In addition, a useful information obtaining procedure for countermeasure was proposed using analysis of principal component behavior. Principal component behavior analysis shows the vibration behavior at a principal component having high contribution to the response signal. By referring to the behavior, the vibration behavior that should be measured to reduce response signal vibration could be obtained. To verify the effectiveness of these methods, operational TPA with the new methods were applied to a small model vehicle. In the experiment, floor vibration was set as the response signal and nine measurement points such as motor attachment point were used as the reference signals.The reduction target levels of each reference signal were calculated by principal component sensitive analysis and the countermeasure was considered by the principal component behavior analysis. By referring to the analytical result, a countermeasure was performed actually. As a result, the floor vibration level was reduced almost same as the target level. Through these consideration and experiment, operational TPA could have more function in which the method could set the target of reference signals and suggest the countermeasure guideline in addition to performing contribution separation.

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The dispersion curve of an extensional wave of a curved beam has negative slope at a restricted frequency region. A wave packet which is synthesized by more than two extensional waves at the region of negative slope has negative group velocity. This paper addresses an issue of engineering application of the negative group velocity. Firstly, the horizontal axis of dispersion curve was normalized as a dimensionless frequency to specify the frequency region of negative slope. Then, a structure to allow negative group velocity was designed as a U-shaped beam based on the normalized dispersion curve, and waves on the beam was verified using transient response analysis of a finite element model. Validation was carried out from the standpoint of both negative group velocity and backward movement of structural intensity. The results show that wave energy in a curved beam does not propagate in the positive direction along the axial direction.

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Recent years, it has been required accurate and agile attitude control of satellites. For this purpose, the necessity of Control Moment Gyros (CMGs) has been increasing, which can generate much higher torque than Reaction Wheel which is used for a conventional spacecraft actuator. CMGs have singularity problem that they cannot output a desired torque. Several singularity avoidance methods have been proposed, but they can fail to output the desired torque through the mission because of their singularity avoidance action. In this paper, we focus on singularity and CMGs' angular momentum and propose a singularity avoidance method by planning path in angular momentum space. Because output torque from CMGs depends on path of angular momentum, we plan the angular momentum path that avoids singularity and its length is short as possible by application of A* algorithm. It is shown from the simulations that the proposed method can realize desired output torque and assured singularity avoidance.

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This paper proposes a relative position and attitude control method by using only magnetic force with multi-dipole for formation-flying spacecrafts. The control method can be widely applied to re-configurable space structures that architect large structure or reconstruct themselves by assembling basic structural units. One remarkable benefit of the method is that it does not require reaction wheels for relative attitude controls and then fuels for unloading. This paper focuses on current control of dipoles which produce strong nonlinear magnetic forces and suggests a way of linearization by using a corresponding linear reference system. A feasibility of this method and controllability of the strong nonlinear system is discussed, and then the series of position and attitude control simulation are shown, and the future works are suggested in the paper.

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With our society rapidly aging, it is worried that the burden on families who have members in need of nursing care increase. The elderly people sometimes have come to require nursing care caused by falling. To reduce the risk of fallings in elderly, gait training is conducted in community health activities. In order to evaluate the effect of gait training, the measurement system of gait performance is performed. With conventional gait measurement systems using a force plate or a 3-dimensional motion measuring device, it is difficult to introduce in community health activities because of its scale and cost. Therefore, a gait measurement system with easy to use and low cost is needed. In this study, a gait measurement system using a laser range finder (LRF) is proposed. In the proposed system, legs of the subject are detected based on pattern recognition for the range data of LRF. Then, the system obtains the human motions in the horizontal plane and extracts the particular kinematic parameters during walking. To verify the validity of the extracted parameters, the proposed system was applied to the walking test. The subjects walk on the predesignated targets in a verification test. From the results, it was confirmed that the proposed system can measure foot contact time, position and velocity of both legs with accuracy.

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This paper presents a new method using conformal transformation to obtain crease patterns of foldable circular membranes by wrapping around a center. This method enables to design complex structures systematically and efficiently from simple structures, controlling angles among fold lines for maintaining significant advantages of origami foldable and developable at will. It is shown that not only existing designs of foldable circular membranes, which are wrapped up and shaped as regular polygons, and also new designs, which are shaped as polygons with different sides or angles like a rectangle or a diamond shape, are successfully produced by the method. For foldable membranes to radial direction, the new method is more flexible to the designing of zigzag fold lines than the previous method by mirror image, since zigzag fold lines can be generated close to the center of membranes without geometrical constraint. Properties of the produced membranes are discussed in the paper.

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This study deals with the rebound vibration characteristics of a SLR camera's internal mirror model. The mechanism of the mirror rebound phenomena is considered by using six types of rectangle metal plate models. In the experiment, the behavior of vibration during the rebound phenomena is observed. The mirror models are supported with rotational axis at long axis of the model. The mirror models swing down freely from the horizontal plane and then hit with a stopper. Amount of rebound is measured by a laser displacement meter. The results indicate that the rebound amount depends on the stopper position. The vibration behavior after the collision varies by stopper position. The vibration after the collision depends on the deformation while in contact with the stopper at the time of collision. We observed that when the amount of rebound is small, there is a tendency that the vibration after the collision becomes large.

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Spot welds are widely used to join plate structures such as an automotive body and the vibration characteristics of the whole structure are affected by the spot welded joints. For the spot welded structure, the actual spot welding location is often misaligned from the design specific location. In this paper, we investigate the effect of welding location variability on the vibration characteristics of plate structures based on Fuzzy finite element method (FFEM) with Monte Carlo simulation. From the membership functions of the natural frequencies from the FFEM and the histograms of the natural frequencies from the interval analysis in the FFEM, we examine the modes that are strongly affected by welding location variability and the locations that strongly affect the vibration characteristics. As an example structure, the structure consisting of hat section steel plates joined together by 20 spot welds at the flanges is used.

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This paper concerns the estimation method of damage location based on the nonlinear wave modulation demodulation which has attracted much attention in the field of structural health monitoring. When a structure containing a contact-type damage is subjected to a low-frequency vibration, a high-frequency wave which propagates through the damage may undergo amplitude and phase modulation at the damage location because the scatter characteristics of high-frequency waves in the vicinity of the damage may fluctuate in synchronization with the low-frequency vibration because of the contact acoustic nonlinearity. Since this modulation propagates through the structure with the group velocity, it may be possible to estimte damage location by measuring the modulation and performing an inverse analysis based on the wave propagation model. In this paper, a mathematical model of the modulation propagation on a Timoshenko beam is constructed, and by considering the damage as a source of the modulation, an estimation algorithm of damage location which utilizes the time difference between the modulated waves measured by sensor arrays located at both sides of the damage is proposed, and examined experimentally.

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The budget assigned to construction of infrastructures is reduced in our country in recent years. The tendency continues, and the importance of maintenance for the life prolongation of existence structures becomes more important. As for freeways, the maintenance for comfort securement as well as safety is important from the view of users' needs. The smoothness of the pavement surface plays a key role for the comfort evaluation of the freeway under a vehicle running condition. IRI (International Roughness Index) is defined as the index to estimate the ride quality of the vehicle running by evaluating the smoothness of the road surface. Authors have developed the IRI instrumentation system by which the road surface profile can be estimated even when the vehicle velocity changes while running. The sequential processing algorithm is presented for real time processing for non-stationary data analysis, which includes time and spatial analysis.

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An integrated active-passive control for structural and electrical coupled systems is presented to achieve an effective vibration attenuation of vibrating structures. The transition of relative phase between displacement and voltage is focused on. The cooperative combined system is composed of both tuned electrical resonance and bang-bang active methods. Switching logics are devised for the integrated control based on the interactive relations between mechanical and electrical vibrations. Furthermore, this paper presents quite an interesting phenomenon, i.e., the relative phase-transition of electrical resonance in transient response, which cannot be found in steady-state condition. This phase-transition has been ignored in spite of an essential factor for integrated systems. Experiments on a 10-bay truss structure demonstrate that the integrated active-passive control enhances vibration attenuation of conventional bang-bang active systems

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In this paper we carried out the simulation for controlling the resonance frequency of a Helmholtz resonator, which is used for the reduction of noise. The resonance frequency is designed to the desired value by PID control of the acoustical boundary condition of the Helmholtz resonator. The resonator like this is called Smart Helmholtz Resonator. At first the gains of PID controller is changed to several values and it is confirmed that the resonance frequency is varied. In order to realize the desired resonance frequency, the gains of PID controller are determined by the response surface method. By using the response surface method the determination of the optimal gains are possible for a lower frequency region accurately. It is shown that this method is effective for designing the resonance frequency of Smart Helmholtz Resonator.

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The main purpose of the current study is to model and identify vibrations in mechanical systems subject to arbitrary external excitations. In this paper, we propose a method based on infinite impulse response digital filter technology - termed time-frequency analysis - to analyze transient and steady-state vibrations. Firstly, we introduce the time-frequency analysis procedure and the algorithm to implement this procedure. Secondly, we analyze typical discrete signal inputs such as impulse, sinusoidal and swept sine signals, and present time-frequency characteristics for transient and steady-state signals. Thirdly, we apply our analysis method to the mechanical vibration behavior of a single-degree-of-freedom system subjected to various types of external excitations. The results of our analysis for steady-state vibration are verified as being equivalent to those from a fast Fourier transform (FFT) analysis. Moreover, the proposed analysis has the advantage over FFT analysis that we can also analyze transient vibration phenomena.

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This study investigates the circumferential modes of a thin cylindrical shell partially filled with liquid. Here two harmonic numbers appeared; one is above the liquid surface and the other one is below the surface. To clarify this phenomenon, we developed FEM code which can consider non-axisymmetric additional mass, additional stiffness, initial imperfection, and can express the above mentioned circumferential modes as its natural modes, too. We also carried out the vibration test with a small liquid shell by measuring vibrational modes in total tridimensional entire view. As a result, those modes are clarified to be the natural modes in the case that a cylindrical liquid shell has a non-axisymmetric additional mass, additional stiffness or initial imperfection. Analysis results by our original code could show good agreement with the experiment results, too.

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In case the rubber tube is squeezed like an orifice, the orifice opening changes according to the pressure variations near the orifice. Under the given supply pressure, there is a maximum point on the flow rate, dependent on the downstream pressure. In the region of positive dQ/dP, the flow vibrations are excited, mostly, in the downstream side of the squeezed portion in the tube. The frequency is close to the natural one of the tube, with the one end open at the water tank, and the other end closed at the squeezed point. The frequency of rubber-metal connected tube can be estimated by the addition of the concentrated mass of the fluid in the metal tube to the distributed system of the rubber tube. The characteristics of the flow rate, the variation propagation, and the excitation conditions are explained.

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This paper deals with a seismic isolation system having nonlinear characteristics mechanism for a vertical seismic oscillation. The seismic isolation system consists of a rhombus shape link, horizontal coil springs and vertical coil springs. Restoring force of the system can be calculated by the geometric calculation. This paper proposes a design principle of the system, using that the natural period of the seismic isolation system can be calculated from its restoring force characteristics. An experimental model of the seismic isolator having nonlinear characteristics was actually made, and its restoring force characteristics were measured by static loading test. Frequency response function of the seismic isolation device was measured using shaking equipment. From these experimental results, it was revealed that the characteristics of the seismic isolation device can be accurately estimated from the proposed design principle.

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This paper discusses lead time constant of yaw angular velocity based on equations of motion of automobiles in planar motion. However, the equations of motion are too complex to be interpreted because the steering angle input generates two variables, lateral and yaw angular accelerations simultaneously. Under reasonable assumption, I derive an equivalent transformation models that generates only one acceleration value from the equations of motion. To generate only one variable against steering input, rigid body of an automobile is replaced by two particles located at the front and rear axles. The equations of motion of the equivalent transformation models imply a mechanism of automobiles transient behavior as follows. Steering angle input causes a yaw angular acceleration around the rear axle. This acceleration changes into a yaw angular velocity by time integration. The yaw angular velocity causes an attitude angular velocity of the rear axle. The velocity changes into an attitude angle at the rear axle by time integration. This attitude angle generates a yaw angular acceleration as restoring yaw moment. In this equivalent transformation models, lead time constant of the yaw angular velocity implies time difference between the yaw angular velocity and attitude angle at the rear axle. Therefore the lead time constant is suitable for criteria of behavior of the automobile at the rear axle. Furthermore the equations of motion will introduce a control law to improve automobile dynamic behaviors.

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Autonomous four-wheeled robots have been widely studied and developed for various purposes over several decades. We have developed an All Terrain Vehicle(ATV)-based, four-wheeled, car-like robot to support the environmental field survey of landfills. Navigating the robot toward an observation spot must have feedback control of the vehicle. We propose a path-generating regulator (PGR) for car-like robots and show the properties of its control performance. Originally, the PGR was a control method for two-wheeled mobile robots to converge at the origin of a coordinate frame, of which the heading angle is controlled so as to align the tangential angle of one of the path among the path function group. Unlike other control methods of the nonholonomic system, neither a coordinate transformation nor an input transformation is needed in this method. In this paper, the PGR is extended to car-like robots. We take care of the singular points, due to both of the mechanism of a car-like robot and the control method. First we show that the origin of the control system is stable in the sense of Lyapunov in accordance with Lyapunov's theory. Next, we discuss initial state convergence at the origin. We examine the performance of the control method via simulations, and apply the method to the ATV-based, car-like robot. As a result, we show the property of convergence to the origin in the car-like robot using the proposed control method.

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The center of the finger pulp in 3 men was deformed 8 mm proximal to the distal end of the finger by compression using a φ4 hemisphere, φ5 cylinder, and flat plate at compressive loads of 1N and 3N. The angle between the object and the central axis of the fingertip was 30°. With or without a compressive load, magnetic resonance imaging (MRI) scans of the transverse section were performed beginning from the distal end of the finger to a 22-mm point proximal to the distal end at a slice spacing of 1 mm. Three extraction parameters (cross-sectional area, pulp cross-sectional area, and thickness of the central fingertip) were measured from the MRI scans. For each extraction parameter, the maximum compression strain with and without a compressive load was calculated from the MRI scans. The cross-sectional area measurements of the fingertip revealed a local displacement, which spread radially from a center of concentrated load. The pulp cross-sectional area values revealed that the fat present in the deformed pulp was displaced to other compartments. The maximum compression strain of the finger achieved with the plate tended to be lower than that achieved with the sphere or cylinder. This observation may be attributed to the fact that the load with the sphere or cylinder was supported locally.

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In this paper, we discuss some phenomena of obstacle clustering by distributed autonomous robots, in the light of space-discretization (or cellular automata) approach. This work was motivated by Swiss Robots which collect scattered obstacles into some clusters without any global information nor intelligent concentrated controller. Then we define fundamental event rules in this cellular world, and introduce two types of local rules for robot action: one is the Push & Turn rule, which can collect obstacles, the other is Pull & Turn rule, which can scatter obstacles. By defining several indices (ratio of immobile obstacles, ratio of moved obstacles), we investigate the dynamic equilibrium of obstacle clustering by heterogeneous agents. And, this paper also presents a control method of ratio of immobile obstacles from the estimation of each robot's local information even if all the states of obstacles cannot be measured.

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This paper describes fish's intelligent strategies for survival observed in the hostile situation between robot and fish. The robot pursues catching fish by a net attached at robot's hand through visual servoing of hand-eye manipulator, whose real-time tracking method utilizes an optimization technique of a genetic algorithm (GA) in order to track swimming fish hastily and precisely. Through catching/releasing experiments conducted consecutively, it has been shown the fact that the fish possess an ability to produce avoiding behaviors by their own intelligence against a robot that constantly tracks the fish to try to catch them by net. This means that the fish have come up with ideas to escape from the exhaustless robot while saving their limited energy. In this paper we propose a method to measure fish's learning speed by comparing the behavior of fish with that of robots taking consistent hostile action of catching fish.

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Recently, tissue engineering therapy, culturing autologous chondrocytes in vitro to create three dimensional tissue for the replacement of damaged tissue, has been developed. Although the tissue engineering is a useful approach to reconstruct cartilage in vitro, the mechanical property of the engineered cartilage is not sufficient to replace natural cartilage. Within the natural cartilage, cells and collagen fibers, which are main components of the cartilage, align in response to the direction of cyclic deformations induced by daily walking or other activities. Due to this collagen fiber alignment, the cartilage has mechanical anisotropy. In this study, we focus on the beneficial effect of dynamic compressive loading on tissue regeneration for articular cartilage. The purpose of this study is to create mechanically anisotropic cartilage by compressive stimuli during the culture.

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In this paper, we newly propose a microarm which has a bionic joint for medical application, especially for minimally invasive surgery. The novel design of bionic joint has a characteristic of the stiffness anisotropy of insect legs, and comprised of several materials which have different stiffness characteristics. The advantages of proposed joint are as follows: (1) small, (2) flexible, (3) simple mechanism fabricated by stacking microassembly process, and (4) biocompatible. First of all, we designed the microarm based on analytical approach and confirmed that the joint structure can be realized by using materials with wide range (10⁴ times different) of stiffness. Considering the material properties and machining accuracy, we determine the using of SU-8 (negative photoresist) and PDMS (polydimethylsiloxane) as materials of designed microarm. The structure of the microarm was fabricated by stacking layers with the micropattern by using photolithography techniques. By using this structure, we confirmed that the movement of the fabricated joint was successfully performed as designed and the developed joint has a potential for application of endoscopic surgery such as endoscopic sub-mucosal dissection (ESD).

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In the paper, we construct a decision model for determining the behavior of pedestrians encountering at a L-shaped corner taking into consideration the dynamics of judgment characteristics caused by interplays with each other. First, we formulate parameters that characterize the behavioral judgment of pedestrians according to the model, based on the game theory. Further, we extend the decision model to exhibit dynamic behaviors of changing their judgment characteristics using evolutionary game theory and reinforcement learning. Then, the extended model was experimented to verify the effectiveness by simulation. Based on such a model as to take human judgment characteristics into account, robot navigation control is expected to realize the safe operations even at indoor blind corners that contain a high risk of collision.

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