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Pen comfort is an important factor in selection of pen for handwriting. In handwriting, a pen receives an impact when it contacts to paper placed on a desk. To hold the pen, fingers have to resist the impact. The greater impact, the grater mechanical workload on fingers associated with the grip strength to hold. Therefore, time series data of pen pressure is supposed to indicate the physical workload in handwriting task. As a preliminary step for the pen comfort evaluation, this study aims to evaluate the physical workload in handwriting tasks using time series of pen pressure. To judge whether pen tip contacts with paper, a probabilistic analysis method of time-series pen pressure was built first. Next, several indices of impacts such as average pen pressure and duration per stroke, and number of touchdowns per second were calculated. Finally, the product of the indices was defined as the normalized physical workload. For multiple four-character idioms with different stroke counts, pen pressure was recorded and the indices and the evaluation value were calculated. The results indicate that the normalized physical workload was larger in writing idioms with longer duration per stroke. In holding and moving a pen against the paper, it is considered that keeping pen pressure requires larger workload than resisting fluctuation of the pen pressure.

This paper deals with seismic isolation system with nonlinear characteristics for vertical ground motion. The vertical seismic isolation system consists of a rhombus shaped link mechanism, a tension coil spring, and a leaf spring. The restoring force of the system is obtained by the sum of the restoring force of the buckling deformation of leaf spring and the restoring force of the rhombus shaped link. The purpose of this paper is to create design guidelines for seismic isolation system. Random waves were input to the experimental model with nonlinear restoring force, and the reduction effect was about 0.1 times. In addition, the validity of the analytical model was confirmed by comparing the experimental results with the calculated results. By setting dimensionless parameters and performing analysis, combinations of parameters with high seismic isolation effect were clarified. When the seismic isolation object was determined, a guideline on how to design it was given to make the seismic isolation design easier.

This paper presents a basic study for developing a new adhesion improvement method for railway vehicles, focusing on the tangential force characteristics between wheels and rails. In our previous studies, the following phenomena have been confirmed. First, the tangential force of the wheel/rail is increased by repeated rolling and sliding frictional force, and the tangential force is stabilized by the oxide film covering the contact surface. In addition, the tangential force under the condition where the humidity around the contact surface is low tends to be larger than that under high humidity condition. And finally, these phenomena indicate that the friction coefficient of wheel/rail can be increased by instantaneously reducing the humidity around the contact surface. Therefore, in this paper, we propose a method for improving the frictional force that reflects the above-mentioned results in our previous studies. In the proposed method, assuming that it is applied to re-adhesion control of railway vehicles, the frictional force of the wheel/rail contact is temporarily increased by lowering the humidity around the contact surface by injecting dry nitrogen gas less than 30% humidity. To verify the proposed method, using a pair of the small cylindrical specimen, tangential force was measured under the conditions with different humidity. In addition, in order to confirm the effect on the braking performance of actual railway vehicle, numerical analysis was carried out. As a result, the experimental result showed the frictional force is increased by up to approximately 40% under high humidity condition, and it was confirmed by the numerical analysis that the proposed method has an improvement effect on the reduction of braking distance during dry nitrogen gas injection even if the humidity condition around the contact surface is high.

Recently, in the steering control system based on the steer by wire and the automatic operation, it is possible to flexibly change the relationship between steering input and vehicle response characteristics. In the previous research, robust stabilization by H.inf. Control and model following control Automatic steering by LQG control optimal observer such as vehicle steering system considering uncertainty of vehicle dynamics model, improvement of vehicle performance by robust control rule, and inverted pendulum control by robust model matching Applied research has been applied. Based on such background, we extend the original state variables (yaw rate, transverse slip angle, and steering angle) of an optimal observer and add the disturbance model which models the frequency spectrum of the disturbance as a state variable, and estimate the disturbance value simultaneously with the estimation of the original state quantity. In this paper, we propose a new method of control law, which is based on the estimation of the disturbance value and to obtain the desired response by state feedback. This paper reports the effect of robust steering control law by combination of model matching and optimal observer capable of realizing robustness to input disturbance while realizing steering desired response by proposed steering control system. In the case of the robust control law for an automobile, it is assumed that the disturbance estimation by the optimal observer is suitable to suppress the whole disturbance energy. In this paper, we show the robust control effect of the steering control law on the real vehicle motion in the case where an optimal observer and an H∞filter are observers.

Two phase lubricant has attracted attention as a lubricating oil with little change in viscosity with temperature change. The two phase lubricant consist of the low and high viscosity base oils which are miscible at high temperature but not at lower temperature. For exmaple, Mineral or synthetic base oil are used as a low viscosity lubricant and PAG（polyalkylene glycol）. In the high temperature region, PAG dissolves into mineral or synthetic base oil and the viscosity reduction is relieved. However, the structure and frictional characteristics of the oil film at the sliding part have not been elucidated. In this paper, in-situ analysis of the oil film formed on the friction surface was carried out with a reflection spectroscopic film thickness meter. And, this paper clarified the influence of the oil film structure and oil film thickness of the two phase lubricant and its friction characteristics. As a result, it was suggested that the oil film of the two phase lubricant in the sliding part was a multilayer due to the adsorption layer of PAG. In addition the two phase lubricant showed a friction coefficient lower by about 0.03 to 0.07 at the experimental temperature compared to PAO, and it was clarified that a thick oil film was formed.

This paper introduces a mobile robot system that follows a human target, in particular, a robot system designed to follow a smartphone user. The proposed system integrates a global following method based on Wi-Fi radio intensity maps and a local following method based on matching walking states.“ Global following ”means that the robot follows the global trajectory of the human target. Because it is important to keep following when the target is lost in a crowded environment, we propose a global following system that uses Wi-Fi radio intensity and occupancy grid maps. This paper presents some experimental results for a robot being called to follow a human target using a Wi-Fi radio intensity map. “ Local following ”means that the robot always keeps close to the human target and keeps tracking the target without losing it. The human target is detected by cross-correlating the signals indicating the target ’s walking motion, including vertical acceleration data measured by the target user’s smartphone and the horizontal velocity of the legs measured by an LRF installed in the robot. The results show that the system produces a higher cross-correlation coefficient for the human target than for other pedestrians in the vicinity. The paper introduces a method for calculating the cross-correlation coefficients online and presents experimental results which show that the target can be identified from an online calculation of the cross-correlation coefficients.

Oil film bearings are often used in large rotating machinery because they have large load capacity and damping coefficients. They, however, generate fluid forces and cause unstable vibrations such as oil whirl and oil whip at high rotational speed. Because the amplitudes of such self-excited vibrations are severe, it is important to predict the stability limit of rotational speed to avoid the unstable vibration problems in rotor systems supported by oil film bearings. This paper describes the vibration analyses of a flexible rotor system supported by oil film bearings and the simplified prediction method for the rotational speed limits of the self-excited vibration induced by the fluid force in oil film bearings. In the vibration analyses, the equations of motion for the rotor system are simplified and modeled as a two-degree-of-freedom system with parallel and flexural modes of vibration. The stability analyses are conducted by introducing the approximation equations instead of complex eigenvalue calculations. The rotational speed limits for the stability of the system obtained by the present method are compared with the calculation results in the references to discuss the validity of the present method. This paper also shows the importance of anisotropic properties of oil film bearings to increase the accuracy of stability prediction when the clearance of the oil film bearing is large.

In order to avoid an obstacle automatically for an automated vehicle, this paper investigated a method to generate a target trajectory using a clothoid curve and to control the vehicle. Although a mathematical constraints or a potential methods are often used to generate the target trajectory for an obstacle avoidance, it requires trial and error and experience, and it is also necessary to consider the vehicle’s drivability. The clothoid curve is often used for a road curve design, therefore, the curve is considered to be suitable for the characteristics of a vehicle driving. Although a clothoid curve passing through a target point is necessary for obstacle avoidance, such clothoid curve is often obtained by trial and error. Therefore, the numerical analyses were executed to obtain the characteristics of the clothoid curve, then, the method was investigated to generate the clothoid curve to pass through the target point. Furthermore, a method to generate a target avoidance trajectory was also investigated expanding the generated clothoid curve based on the traveling characteristics of a vehicle. For driving on the target trajectory satisfactory, both the position and turning angle of the vehicle are controlled by means of a steering manuplation. The controller was constructed using a 1-input 2-output system, therefore, it is very difficult to satisfy both value at the same time. Furthermore, it is also necessary to consider a nonholonomic characteristics of the vehicle. From these point, this paper investigated the optimal control using nonlinear least square probrem sequential quadratic programming(NLSSQP) by means of the time behaviour of input and output in the evaluation value. Well expected results are obtained and shown in the simulation and the experiment.

An effective method for handling turbulent fluctuations in temperature and in partial pressure of infrared-active gas is proposed in order to make a fairly accurate simulation within feasible calculation load in relation to radiative heat transfer in the large-scale hydrocarbon flame formed in industrial furnaces. As for the case of large-scale turbulent hydrogen flame in industrial furnace, an effective method for handling turbulent fluctuations has been proposed and verified in our previous papers. And yet, it’s applicability to large-scale turbulent hydrocarbon flames has not been confirmed. In this paper, the abovementioned method is examined as to the applicability to hydrocarbon flames, and then, an improved method is proposed. In regard to the method proposed in our previous papers to reduce the enormous calculation load contingent on detailed non-gray analysis like line-by-line analysis, it’s validity is easily confirmed not only for hydrogen flames but also for hydrocarbon flames. On the other hand, the method proposed in our previous paper for reducing the calculation load required for tracing turbulent fluctuation in temperature in great detail cannot give satisfactory results in relation to the large-scale hydrocarbon flame. So, in this paper, major attention is concentrated on the improvement of our method for reducing the calculation load associated with detailed trace of turbulent fluctuation. The assumption that temperature fluctuations of arbitrary two positions are independent from each other and the treatment of energy radiation associated with turbulent fluctuation are maintained also for hydrocarbon flames. In contrast, the treatment of fluctuating absorption is changed from the case of hydrogen flames. While the temporal mean amount of absorption is evaluated using the absorption coefficient at temporal mean temperature in the case of hydrogen flames, such value is evaluated using the temporal mean value of instantaneous absorptance. Validity of the improved method is examined on a model optical path imaging the typical course of radiative energy in large-scale industrial furnaces fueled by propane. It is indicated by examination that the error caused by improved method is satisfactorily smaller than that caused by entire disregard of turbulent fluctuation of temperature and gas composition. Moreover, this improvement related to the treatment of turbulent fluctuation is satisfactorily valid even if coupled with our efficient method for treating complicated spectrum of absorption coefficient.

The dynamic stability of rectangular flexible plate often becomes a problem. As the flexible plate, the papers in a high-speed printing machine, the thin plastic, the thin metal, the fluttering flag and the oscillating doom roof are enumerated. In this paper, the dynamic stability of cantilevered rectangular plate is estimated in three-dimensional model. 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. This fluid pressure is determined by using the integral equations for the pressure along the span and the pressure along the chord under the boundary conditions in the Fourier space. The lateral deflection of plate is assumed to be expressed as a product of the cantilevered beam mode in the streamwise direction and the free-free bending beam mode in the spanwise direction. Applying the Galerkin method for the equation of motion of an elastic plate, the three-dimensional coupled equation of motion of a cantilevered rectangular plate is derived. The complex eigenvalue analysis is performed for the stability analysis. Changing the mass ratio and the aspect ratio, the root loci, the vibration modes of the plate and the fluid pressure are investigated. And, the relationship between the critical fluid velocity and the mass ratio taking the aspect ratio as a parameter is investigated.

Rail corrugation that causes the vibration and the noise is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we verify three influence factors of the elastically supported beam model left as subjects in the previous paper. As a result of analyses, it is confirmed that when the track structure is usually used type, the effect of the rail axial force on the growth mechanism of the rail corrugation and the error compared with the analysis results by the model of the moving coordinate system are negligible, and the analysis by the elastically supported beam model is valid including at near the anti-resonance frequency of the elastic support track system.

In this paper, sound absorption properties of poroelastic lattice structure are investigated through numerical simulation and measurement. The lattice structures discussed in this paper are composed of slender beams only (BCC) and beams and shells (BCC-S), and can be fabricated by using the selective laser metal melting machine. In our numerical investigation, the homogenization method is used to calculate a macroscopic elastic tensor for a solid phase, an equivalent density and a bulk modulus for a fluid phase. Also, the sound absorption coefficient for normal incidence can be calculated by using these macroscopic parameters. The obtained numerical result of the sound absorption coefficient agrees qualitatively with the experimental result. In particular, it is found that the dense BCC-S structure attains sufficient sound absorption capacity in comparison with other conventional sound absorption materials.

The in-situ blocked force approach is suitable for estimating noise radiation from a mechanical system by component tests of its active subsystem because blocked force is a specific characteristic of the active subsystem and independent from the passive subsystem or supporting structure of the component test bench for the active subsystem. However, it is reported that the in-situ blocked force approach is a methodology for estimating structure borne noise and cannot be applied to airborne noise. In this research it was found that the in-situ blocked force approach can be approximately applied to airborne noise in eigenfrequencies of the mechanical system. Therefore it was proposed to employ the in-situ blocked force approach to estimate airborne noise as an approximate method at eigenfrequencies of the mechanical system in the previous paper. In this paper the proposed estimation method was verified by numerical analysis of noise radiation from a cantilever rectangular plate. Eigenfrequencies and vibration responses of the cantilever rectangular plate were obtained by FEM and sound pressures at an observed point were calculated on the assumption that point sound sources are distributed at the all FE nodes on the whole plate surface. Furthermore, a means based on discarding small singular values in the inverse matrix method was proposed in order to reduce the estimation error which is increased in the peak frequencies of blocked forces.

This paper is concerned with the demonstration of scallop-like swimming with the aid of robot toy; using jet propulsion by clapping the shells quickly. Previous works from biological approach have indicated what structures contributes to generate the jet propulsion. This paper tries to perform quick underwater locomotion by mimicking the structures of scallop based on constructive approach: development of scallop-like robot with autonomous generation of jet propulsion. After designing the structure and actuation mechanism by mimicking the scallop, we focus on the effect of the mantle property on swimming. Firstly we confirm that developed robot can perform scallop-like swimming. Secondly we also compare the swimming speed by changing the property of designed mantles.

A design method of a strongly coupled vibration system is required for improving noise and vibration performance of machinery. One of the authors proposed that analysis of the self-compliance matrix at interface degrees of freedom between two systems, called as kernel compliance matrix, gives the insight to work out satisfactory countermeasures for resonance frequency control of a strongly coupled vibration system. The approach, however, is only feasible for a two by two kernel compliance matrix. To expand this approach to an N by N kernel compliance matrix, a coordinate transform is available to reduce the matrix dimensions. However, the selection of the basis vector is not so easy. This paper presents a practical approach for the analysis of an N by N kernel compliance matrix. In this paper, it is shown that structural modification for resonance control can be derived using the Wedderburn’s rank-one perturbation of a kernel compliance matrix. Finally, this approach was verified by a numerical case study.

The author proposed the identification method of symmetric nonlinear system based on the Auto-Regressive analysis and the method of averaging in a previous paper. However, there is a problem that conventional methods including the one in the previous paper cannot address the identification of asymmetric vibrating systems. In this paper, the system identification in asymmetric nonlinear system is investigated. At first, formulation of identification problem is conducted. The identification problem is described using the method of Krilov-Bogoliubov-Metropolsky is considered the two-order approximation. The description contains the amplitude dependency however coefficient of the sign cannot discriminate. Therefore, this paper proposes a new system identification method to solve these problems by identifying appropriate sign of nonlinear parameters based on movement of center-of-vibration. Identification experiment is conducted using numerical investigation, Runge-Kutta method. A nonlinear coefficient is considered in two cases: positive number and negative number. In both cases, the proposed method gives good estimated results which show good agreement with the true values. Moreover, identification experiment is conducted using the cantilever system subjected to the magnetic force. The proposed method gives estimated results which shows good agreement with the true experiment values.

This paper describes basic study of sheet attitude during accelerated delivery of the nip transport mechanism. The nip transport mechanism with a pair of rollers is widely used in many devices, such as automated teller machines (ATMs), printing machines, etc. In these machines, a sheet is sometimes nipped by two pairs of rollers rotating unequal speed. There are two kinds of the conveyance between rollers with unequal speed, namely, accelerated delivery and decelerated delivery. The sheet attitude during the accelerated delivery and the decelerated delivery can be changed. In this paper, we presumed the parameters that affect the sheet attitude during accelerated delivery. Furthermore, we clarified the influence by observing the sheet attitude in actual transport. As a result, we have found a method to stabilize the sheet attitude during accelerated delivery.

In this paper, a formulation and some computational results of cycle jump method for finite strain elastic-plastic problems subject to cyclic loads are presented. The cycle jump method is to shorten the total computational time. An analysis using the cycle jump method is carried out such that a combination of a few cycles of cycle-by-cycle analysis and the cycle jump by extrapolating physical quantities such as the plastic strains for many cycles based on the results of preceding cycle-by-cycle analysis. The cycle-by-cycle analysis and the cycle jump are repeated until the desired load cycle is achieved. When the method is applied to the finite strain elastic-plastic problem, it involves the finite rotation and the finite stretch. Then, both of them are decomposed into the elastic and the plastic components. This paper presents appropriate treatments on the rotation and the stretch under the multiplicative decomposition of the deformation into the plastic and the elastic parts. Then, some numerical examples are shown. It is concluded that the proposed cycle jump approach performs well under a certain conditions. Such conditions are also described in the paper.

This paper describes a newly invented loading cam that provides a contact force for a planetary roller. A high-speed electric motor with a small reducer and high-power transmission efficiency realizes a powertrain system with a high power density because electric motors can be miniaturized to increase the rotational speed. Planetary traction drive roller reducers are suitable for high-speed driving to avoid meshing vibration as in gears; however, it is difficult to provide a sufficient loading force on the rollers to transmit power. A previously proposed planetary reducer with conical rollers could generate a contact force; however, it lost spin power at the point of contact. The pinion of a planetary roller contacts both a sun roller and a ring so that the pinion must exert a force in opposite directions, inside and outside, at the same time. The new loading mechanism has a pair of cams acting in opposing directions to generate a moment force during contact. This paper presents analytic equations for force and displacement on a pinion that was constructed to agree well with simulations and experimental results. The paper also describes how the analytical equations were used to design the cam and rollers. The cam causes skewing on a pinion because of its asymmetrical profile, which reduces the transmission efficiency. This skewing can be reduced to adjust the rigidity balance of contact points and components. The proposed cam achieves a loading system that provides a contact force to planetary rollers, which is the most important requirement for achieving a planetary roller reducer.

In this paper, heat transfer characteristics and the pressure drop response of sandwich structures containing open-cell core were studied by using numerical simulation. The effect of micro-architecture and cell size of the unit cell on these characteristics were investigated by changing relative density of the models. In this paper, three types of open-cell were analyzed. There is a trade-off relationship between the heat transfer characteristics and the pressure drop response. These factors are the direction of thermal paths, surface area size and internal flow state. Also, these factors can be controlled without changing the relative density when the cell size is changed and the aspect ratio is equal. In order to clarify the characteristics of the open-cell, the open-cell were compared with two types of closed-cell as representative of other cores in terms of two dimensionless numbers (Nusselt number and friction factor). As a result, it was confirmed that the open-cell has high superiority in applications requiring light weight and high heat transfer characteristics.

This paper describes the novel on-machine measurement method of tool edge shape by using fluorescence emitted from cutting fluid. Tool wear and chipping are a major factor of decreasing machining accuracy. Therefore, on-machine measurement methods of tool edge shape with high accuracy are the subject of intensive study. Especially, considering the machining process, a robust measurement method with water-soluble cutting fluid is required for precise machining. For these reasons, the purpose of this research is to develop the technique that enables to measure tool edge shape precisely by using a confocal microscope. In order to achieve it, we have proposed the measurement method of tool edge shape by detecting fluorescence of cutting fluid adhering to the tool edge. Previous research has shown that it is possible to measure tool edge shape precisely by using oily cutting fluid. However, the applicability to water soluble cutting fluid is still remained. In particular, since water-soluble cutting fluid is used with dilution, it is worried that its fluorescence emission efficiency is lower than oily cutting fluid and the fluorescence detection is difficult. In this paper, it is shown that fluorescence could be detected from water-soluble cutting fluid. Then, the cutting tool edge shape adhering water-soluble cutting fluid is measured. These results show that the proposed method has high applicability to an on-machine measurement.

In recent years, environmental concerns have led to a demand for sustainable materials, and natural rubber (NR) reinforced with cellulose nanofibers (CNFs) has been attracting attention as one such material. When CNFs are added to NR, the elastic modulus is greatly improved. This is considered to be caused by deformation constraint of NR by reinforcing CNFs. On the other hand, it is known that there exists a region around reinforcing fibers where the rubber is tightly connected to the surface of fibers, which is called bound rubber. The volume fraction of the bound rubber is usually measured by swelling tests using organic solvent. In this paper, we focused on the relationship between the tensile properties of NR reinforced with CNFs and the volume fraction of bound rubber. Firstly, cyclic tensile tests were performed using plate specimens of CNF-reinforced NR and the effect of reinforcing CNFs on the tensile properties of CNF-reinforced NR and their change with loading cycles were investigated. Then, the swelling tests were conducted for similar specimens and the volume fraction of the bound rubber was evaluated. It was found from a series of experimental results that tensile deformation resistance of NR increased largely by adding 5 phr (4.8 mass%, 3.2 vol.%) of CNFs but that this increase decreased from the second loading cycle. Moreover, a clear relationship was found between the tensile deformation resistance of CNF-reinforced NR and the volume fraction of bound rubber. These results suggest that the tensile deformation resistance of CNF-reinforced NR can be evaluated by swelling tests.

This paper discusses the design of the mechanism for an artificial mastication device that reproduces the formation of the food bolus by humans. A novel mechanism, the enclosure area expansion and reduction mechanism, that can gather fragments of food is proposed. In the proposed mechanism, multiple movable walls with common shape and sizes form a symmetrical enclosure area that contains the food fragments. Driven by a single actuator, all walls move coordinately so that the enclosure area reduces and expands for gathering the fragments. We first show the mathematical formulation of the geometrical conditions of the movable walls. We then design the movable walls and power transmission system for a prototype installed in the artificial mastication device. Finally, we present the experimental results, which validate the proposed method.

Condition monitoring technology has advanced remarkably in recent years in various areas, including railways. Since the overhead catenary system and the pantograph in railway does not have enough redundancy, failures of the overhead catenary system or the pantograph will result in long downtime in railway operations. For preventing such failures efficiently, it is effective to apply condition monitoring methods to detect the pantograph failure on the overhead catenary system. To Achieve stable current collection, although the lift characteristic of the pantograph must be maintained within an appropriate range, the monitoring method of lift of pantograph in actual use has been not established so far. Therefore, the authors developed a method to measure the lift of pantographs with sensors on the overhead catenary system. According to this method, the lift is obtained from the sum of hanger forces and vertical components of the tensile force of contact wire. However, this method has some problems to solve in terms of measurement error and easiness of implementation. Therefore, in this paper, the authors focus on the wave equation for each wire of the overhead catenary system to propose new four measurement methods of the pantograph lift. The proposed methods will solve the problems of the previous methods. The methods are verified using dynamic simulation of the overhead catenary system and the pantograph. It also reports that the proposed method is effective even when two pantographs pass continuously.

This paper addresses a method for devising an undamped periodic structure that suppresses energy propagation due to a specific wave mode based on the Wave and Finite Element (WFE) method. Then, structural modifications to reduce the active transmitted power are derived by solving an inverse eigenvalue problem of the WFE method. In solving the inverse problem, it is important that the solution is feasible in the sense that it is low-cost and easy to fabricate as an actual mechanical structure. Therefore, in the proposed method, the designer specifies the regions in which structural modifications may be made before solving the inverse problem. As a result, the solution of the inverse problem is approximated within these regions. Finally, the method allows us to suggest feasible structural modifications necessary to reduce the amount of active transmitted power for a given wave mode and a given frequency. However, this method cannot consider the changes in wave numbers due to structural modification. It should therefore be noted that this method cannot be used to achieve significant reductions in active transmitted power due to large-scale structural modification.

As the number of elderly people increases, the demand for electric wheelchairs is increasing. Among them is a joystick-type 6-wheel electric wheelchair. It has three wheels, the central wheel of which is the driving wheel in side view. This structure allows the left and right drive wheels to rotate in the opposite direction, resulting in an extremely small turning radius compared to other types. On the other hand, it is difficult to ensure the grounding performance of the wheels, including the drive wheels, due to changes in the road surface outdoors because it has 6 wheels, so it is mainly intended for indoor use. In this paper, I studied how to improve the grounding performance of the drive wheels and other wheels by using a newly devised passive link. I devised a parallel double rocker link mechanism that connects six wheels with four sets of rocker links. I found a way to improve it. As a result, it was confirmed that the prototype vehicle using the parallel double rocker link satisfies the JIS requirements.

From the machining center (MC) user’s point of view, this paper, as the second report of a systematic study, proposes a practical approach to estimate the trajectory error of a circular arc interpolation cutter path produced by the NC linear acceleration/deceleration (Acc/Dec) processing to interpolation segment and the feed axis servo control for a target MC. A simple and convenient motion model is established for describing the behavior of the servo axes corresponding to a circular arc segment of any length processed by the linear Acc/Dec operation. Based on the model and a linearity assumption on the dynamics of servo system, an efficient simulation method is developed to precisely calculate the cutter path trajectory and the servo axis speed from the motion parameters commanded in NC program. The verification experiments have been performed on the target MC, in which the specially designed cutter paths were inspected by a cross grid measuring device, and the measured motion trajectories were compared and discussed with the ones simulated by using the same motion parameters, from different perspectives. The examination results sufficiently demonstrate the effectiveness of the proposed model and simulation method if the adopted feed rate is within the commonly used range at the production site. Therefore, as a useful tool, the approach provides a potential application possibility, i.e. beforehand estimating the influence of the NC Acc/Dec processing and the servo control on cutter path accuracy or judging the motion conditions for the machining purpose without performing an actual machining with the target MC. Moreover, a reverse compensation principle of the cutter path motion error based on the simulation results is presented and examined through an actual example. The result has proved the possibility of practical application of the principle and suggested the direction of future effort.

This paper proposes a method for machining a miniature Gaudi-screw and nut for a miniature differential drive mechanism with an ultra-small diameter and ultra-long lead based on a square cross-section. A miniature Gaudi-screw with a square cross-section of 2 mm on one side, a 10 mm lead (57.9 degrees slope angle), a total length of 40 mm (aspect ratio 20), and a square cross-section of right and left helix nuts are developed. First, the geometry of the proposed Gaudi-screw and the reasons why it is suitable for miniaturization are explained. Then, the configuration and kinematics of the mechanism using the Gaudi-screw as a two-input, two-output differential screw mechanism are described in preparation for the operation verification experiment. Next, the minimum radii of curvature of the Gaudi-screw and nut surfaces are derived using three-dimensional surface geometry, and the ball end mill tip diameters for cutting the miniature Gaudi-screw and nut are calculated. For the machining of long miniature Gaudi screws with small diameters, a machining method that suppresses deformation during machining due to machining reaction forces are proposed, and the results of actual machining using a 5-axis NC machine are shown. In addition, a parting and assembling method for miniature nuts are proposed, and the results of actual machining are shown. A prototype of an experimental device to motorize the miniature Gaudi differential screw mechanism was fabricated, and its operations were verified.

The purpose of this paper is to construct a methodology which can produce a lightweight panel structure while being satisfied with more than one constraint by using some simple model. In this study, we chose a problem including bending stiffness and the 1st order eigen frequency as constraints and volume minimization as objective function among basic performances which a vehicle requires. So far, we have been trying to solve the problem by using a method consisting of Fully Stressed Design (FSD) and Genetic Algorithm (GA). FSD is an optimization which evaluates only stiffness of a structure based on relationship between thickness and stress, while GA, a broad array method, can have various number of objective functions and constraints. Prior to this study, the authors found a process was effective that stresses on the elements were to be equalized in the 1st step by applying FSD that made an individual superior on static stiffness. In this study, proposed method, which includes a process of equalization on normalized stresses on eigen vibrations, are added to that of static stresses in the 1st step. In the 2nd step, GA is selected. GA conducts operations, such as select, crossing, and mutation repeatedly until this attains a final solution. As for the model, we chose a sandwich panel which is equipped with top and bottom plates and interlayer lattice stiffeners. The reason for this selection is that the sandwich panel is lightweight and superior to stiffness, dumping, and strength. As a result, the obtained model presents a lightweight structure while being satisfied with the requirements of both stiffness and eigen frequency. Moreover, the proposed method attains optimized results earlier than GA without using FSD.

High-speed and high-precision actuator control is required for industrial manufacturing equipment. In such systems, the control operation cycle needs to be shortened to 100 μs or less. Recently, the quantity of sensors and actuators is increasing because new control methods have been developed. Therefore, the amount of information input/output to/from sensors and actuators is also increasing. Any electromagnetic noise occurring inside the equipment due to using high-voltage power or various actuators affects the system performance. The authors are thus developing a network communication system for high-speed and high-precision mechatronics control considering electromagnetic noise. The network communication adopts an original protocol operating in the 40-MHz band with 8B10B coding for SerDes logic implemented on an FPGA. In this paper, a method for the K-code usage of 8B10B coding to reduce packet transmission overhead is proposed, as well as a data transfer scheduling method that can reduce communication delay by setting a communication period for each data and distributing the amount of data transfer per communication cycle. Evaluation results show that the cycle-to-cycle jitter in sampling between the main controller and the control device was 260 ns. In addition, the data transfer scheduling reduced communication delay by 36% compared to the case without the scheduling.

The drum cable engines with DO/HBs (Draw off hold back gear) have been indispensable equipments to lay and recover the optical submarine cables and the optical submarine repeaters. When use them, the back tensions by the DO/HB have been set at relative high tensions because of the empirical knowledge to pass repeaters and cable couplings safely through the drum. However there had been no papers on the minimum back tensions for the DO/HB. If we could know them for the various kind of repeaters, the preparation and operations of the drum cable engines and DO/HBs would be improved and get security. Therefore the author solved forces and moments acting on the repeaters and the cable couplings on the rotated drum cable engines using the linear system of equations. And found that there were the negative longitudinal axial forces acting on the repeaters when the repeaters passed around 85 to 100 degrees from the top of the drum of the first turn in the lay, and around 80 to 110 degrees from the top of the drum of the last turn in the recovery if the back tensions by DO/HB were set below specific values. If there were the negative longitudinal forces, the repeaters would not face the drum and not be wound correctly on the drum. Then here the author clarified the minimum DO/HB back tensions for the drum cable engines based upon more than zero longitudinal axial forces acting on the optical submarine repeaters during lay and recover. These calculations can apply to almost all kind of repeaters if they are connected to the cable coupling with the gimbals joints.

The interior noise characteristics of railway vehicles vary depending on the position of the cabin. In general, interior noises are louder in the area directly above bogies (ends of the cabin) than in the center of the cabin. It has been known that structure-borne sounds from bogies contribute greatly to the interior noises directly above bogies. This paper describes, using measured data obtained with the rolling stock test plant at Railway Technical Research Institute (RTRI), the application of the operational transfer path analysis (OTPA) to determine the contribution ratio of each transmission path of vibration from bogies to cabin floors. It is considered that structure-borne sounds from bogies propagate mainly through the parts connecting the bogie and car body such as single-link-type traction devices (traction links), yaw dampers, and air springs. As a result of applying the OTPA and determining the contribution ratios, it has been confirmed that the contribution ratios varied depending on the position of the floor and the frequency band. In addition, the validity of the contribution has been verified by examining the linearity of input/output data and the correlations of input data using multiple coherence functions and partial coherence functions. Although a bogie vibrates rigidly in the low frequency range with the very high correlation between the vibrations of the bogie and the parts connecting the bogie and car body, the correlation becomes low in the high frequency region. Therefore, it is expected that the contribution of each transfer path can be well estimated by applying the OTPA in the high frequency range for structure-borne sounds from bogies.

This paper addresses a plant that includes different time delays dependent on the polarity of control inputs. An example of such a system is a pneumatic isolation table, which consists of two valves of different lengths. For this plant, a switching control method depending on the control input polarity has been employed. Each polarity is considered as a separate single input system. Alternatively, this plant can also be considered as a two-input system by using both control inputs simultaneously. Thus, the conventional method might have restricted the control performance. Moreover, the switching control method determines an input value by considering the next step input beforehand. To improve control performance, a method comprising several steps in advance is proposed. It is a model predictive control (MPC). However, this method is difficult to apply to the switched system as it results in a problem of hybrid control. In the present paper, we consider this plant as a two-input system, and thus, improvement of control performance is expected. Moreover, the proposed view of the plant is not considered as a switched system. It enables MPC to be applied to the plant by solving a linearly constrained quadratic optimization problem. Finally, the control performance achieved by the proposed method is verified through numerical simulations.

The passive mechanical element that can change the stiffness by using particle jamming has been used for soft robots. The mechanical element can keep the shape by decreasing the internal air pressure, however, is not able to transform the shape by itself. Therefore, it has been used in combination with other actuators to transform the shape actively for the use of robots, which increases the complexity of the system. In this study, we developed a novel mechanical element that contains sponges inside the conventional mechanical element. Evacuating the inside air of the element increases the rigidity, same as the conventional one. At the same time, it compresses the sponges and transforms the shape of the element so that it can wrap the element around an object automatically. This novel mechanical element can be used for fixing or grasping objects or a body. The element requires only a vacuum pressure source; therefore, the system is simpler than conventional robots. This paper firstly shows the structure of the mechanical element and the optimization method from the viewpoint of deformability. Secondly, this paper shows the ability of wrapping various objects and that the contact pressure was constant regardless of the shape of the object. Finally, this paper discusses future applications and problems of the element.

Although bladed disks are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all the blades on a disk are slightly different due to the manufacturing tolerance, deviations in the material properties, and wear during operation. These small variations break the cyclic symmetry. Bladed disks with small variations are referred to as a mistuned system. In the forced response of a mistuned bladed disk, the responses of all the blades become different, and the response of a certain blade may become extremely large due to splitting of the duplicated eigenvalues and distortion of the vibration modes. On the other hand, mistuning suppresses blade flutter, because the complete traveling wave mode is not formed in a disk. Although such mistuning phenomena of bladed disks have been studied since 1980s, almost all studies focused on the amplification factor of the displacement response, and few studies researched the amplification factor of the vibratory stress response. In the previous paper, authors studied the amplification factor expressed by the vibratory stress for bladed disks with the continuous ring-blade structure, using the reduced order model SNM (Subset of Nominal Modes), and pointed out that the amplification factor of the displacement and the vibratory stress is different. This work is a follow-up study on the previous paper. The amplification factor of the vibratory stress for bladed disks with the free-standing blade structure is studied, using the reduced order model SNM. Comparing the mistuning phenomena of bladed disks of the continuous ring-blade structure and the free-standing blade structure, the reason why the amplification factor of the displacement and the vibratory stress is different is clarified.

This paper presents a new type of energy balance equation for a seismic isolation system, which consists of a restoring force element, a damping element and a bearing element, to improve the accuracy of seismic response predictions. The proposed energy balance equation has advantages that it can be taken into account the yield displacement and the bilinear factor for the damping element and the friction force for the bearing element as compared the previous energy balance equation. These advantages will lead to the seismic responses corresponding to the maximum shear force coefficient and the maximum response displacement for the seismic isolation system obtained from the time-history response analysis. This paper demonstrates that the proposed energy balance equation can capture the seismic responses obtained from the time-history response analysis taken into account the various ground motions. Additionally, the optimal damping force that leads to the reducing between the shear force coefficient and the response displacement is presented on the basis of the proposed energy balance equation.

The purpose of this paper is to show a new gravity compensator which allows for the passive vertical weightless motion. The conventional zero gravity simulators could not simulate the vertical balance and weightless motion passively at the same time. For example, the simulator using the counter weight of the same mass can only simulate half the acceleration of the weightless motion because an external force acts on both the object and the counter weight. On the other hand, the simulator using the low stiffness spring is difficult to balance. Firstly in this paper for such a trade-off, a new concept which is named degree of zero gravity (DOZ for short) is introduced. By using DOZ we can estimate how similarly the system simulates the acceleration in zero gravity. Secondly, a new gravity compensator which uses a heavy counter weight and a pantograph mechanism is introduced and evaluated by means of DOZ. When an external force acts on the object of the gravity compensator, most of the energy acts on the relatively lightweight object by using the heavy counter weight. It follows the passive vertical weightless motion of the object. Finally, numerical results show the effectiveness for the passive vertical weightless motion. The main results obtained are 0.86 times the acceleration in zero gravity when an external force is applied and the disturbance acceleration of 2.3 × 10−4g or less when an external force is not applied.

Rail corrugation is such phenomenon that roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and cause the vibration and the noise. In the previous papers of ours, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we report the results of simulation analyses of the characteristics of each step of formation, growth and saturation of the rail corrugation using a discrete elastic support model close to the actual track. As a result of the simulation, the following are confirmed : (1) at the formation step, by providing a minute and irregular wheel load fluctuation, rail surface roughnesses are formed with such wavelengths that their amplification factor of roughness amplitude is maximal and greater than 1.0. (2) at the growth step, as the contact length of the wheel / rail becomes longer, growth of roughness of the short wavelength is suppressed. (3) at the saturation step, when the roughness amplitude increases and the wheel loses the contact with the rail, the growth is suppressed and the roughness amplitude saturates. Based on these results, we present the progress process of the rail corrugation and the ways to approach the countermeasures.

In this paper, the equations of in-plane and out-of-plane displacements, in-plane stress distributions, and Mises stress of the rectangular plate after buckling are composed using the well-known buckling deflection shape, based on the plane stress state and the effective width theory by Karman. Equations of in-plane displacement and stress distributions are obtained from the large deflection theory, and the maximum value of out-of- plane displacement is derived by use of Karman’s theory. The composed equations are compared with results of the finite element method (FEM) with shell elements. The boundary condition used in FEM is that the in-plane displacement of both long side edges is unconstrained. As a result, the following conclusions were obtained. Among the composed equations, the out-of-plane displacement amplitude and the in-plane compressive displacement are close enough to FEM computation results. Three in-plane stresses near the both long sides show slightly different distributions between composed equations and FEM results. The normal stress distribution of the FEM result fluctuates near the both long side edges, although that distribution by the composed equation indicates the intermediate value of the FEM result, and it was found that the maximum compressive stress appearing at both sides is lower than the one by the FEM result. On the other hand, the Mises stress distribution and its maximum value were close to the FEM results. As factors of these differences, it is considered that the in-plane deflection of the both sides and the out-of-plane displacement shape at larger load are different from the shape used in this paper.

This paper proposes a method that fuses two kinds of stereo measurements using a fisheye stereo camera. A stereo measurement method can be divided into two types: binocular and motion stereo. Generally, the accuracy of long range depends on the baseline of the camera. In case of the binocular stereo, the direction of the baseline is horizontal. Its size is small due to the convenience of installation conditions. By contrast, in the case of the motion stereo, the direction of the baseline changes depending on the direction of the camera motion. For example, the direction of the baseline is the optical axis when a stereo camera is mounted on a vehicle or a mobile robot that drives in the forward direction. When the speed is high such as in driving, its baseline becomes larger as it becomes the moving distance between frames. Therefore, between the two stereo measurements there are differences in the magnitude of the baseline and the uncertainty of the position in the image. In addition, the area-based approach is used for binocular stereo and the feature-based approach is used for motion stereo at the time of corresponding point search. So, robustness against false matching is different. In this paper, we try to fuse the two stereo measurements in order to realize more accurate range image generation. A method, which restricts the disparity search range using the reference disparity map and a bilateral-like filter, which is a weighted averaging are proposed for fusing the two stereo measurements. The proposed methods are verified by experiments in indoor and outdoor environments.

This paper introduces a novel robotic joint mechanism composed of antagonistically twisted round-belt actuator, which has multiple small-diameter round-belts in antagonistic location around the joint. This joint mechanism is developed by emulating muscle structure of human upper limbs, and can be activated by twisting each round-belt that is made of polyurethane materials. Especially, this paper shows position and force control by means of the proposed twisted round-belt actuators with traditional P/PI controllers. We clearly demonstrate that contact force on tip of the robot is able to follow desired sinusoidal trajectory with no errors by means of straightforward algorithm on the basis of voltage-controlled robot hardware. Through these experiments, we explain intrinsic characteristics of twisted round-belt actuator system and advantages of the structure in control performance.

In the field of regenerative medicine, cell processing is currently done manually. The process is labor intensive and expensive, and its efficiency must be improved. Automatic cell culture apparatuses equipped with a vertical articulated robot have been proposed recently. However, automating all tasks of cell processing complicates the system constitution. The present study aims to develop a simple and rational cell processing system by combining the tasks performed by a robot with those performed by a human. Herein, we first analyze each task in the cell processing operation, verify whether a task can be efficiently performed by a robot and automated equipment, and decide the combination of the tasks. In a previous paper, we improved the efficiency of the task of discarding spent culture media in a flask by using a robot arm in the media change process. In the present paper, by focusing on the media change process, we examine the efficiency improvement of the task of injecting culture media by using a robot. We propose the configuration of an inspiration/injection port and an algorithm to estimate the start time of injection end motion from the flow rate and conduct a verification experiment. Our results show that a robot can perform the injecting task more efficiently than a human. Moreover, the risk of dripping can be reduced by using a robot.

In this paper, a flexible morphing wing with piezoelectric materials for morphing actuation is studied. The objectives of this paper are 1) to develop an integrated geometrically nonlinear electro-aeroelastic framework, which allows evaluating performances of flexible morphing wings with piezoelectric actuators, 2) to validate the developed analysis framework, and 3) to demonstrate the capability of the framework and explore the performance. This paper provides a description of the electro-aeroelastic equations of morphing wings taking into account piezoelectric effects, which can be used to actuate morphing wings. The electro-mechanical model is validated by comparing with experimental results. The validation with a single macro fiber composite showed a very good agreement between the experimental result and the simulation. The result of an actuation test with an integrated corrugated structure and macro fiber composite also reasonably agreed with the solution from the present code. Aeroelastic behaviors of a corrugated wing with the piezoelectric actuator are then explored. The camber morphing wing with the corrugated structure actuated by the piezoelectric actuator could provide a larger lift in the vicinity of the trailing edge. Such a camber morphing has a good potential to control aeroelastic response by wing morphing with piezoelectric actuation.

This paper presents theoretical research on an optimum transition curve with a smoothly changing curvature using a multiple clothoid curve for improving the occupant ride comfort of automobiles when vehicle changes a lane from a traveling lane to a passing lane. In the first report, a three dimensional vehicle occupant model was developed, and the multiple clothoid curve was proposed as a new transition curve. In the second paper, application of a newly-developed multiple clothoid curve for the vehicle turning at an intersection was reported. In this paper, application of the multiple clothoid curve for the vehicle lane change is presented. The traveling path from a slow lane to a fast lane consists of the combination of a straight line and an arc of circle. At the connecting points between an inlet straight line and a circular arc, or between a circular arc and an outlet straight line, vehicles cannot run smoothly owing to the discontinuity of curvature. The discontinuity of curvature at connecting points makes highly precise control of apparatus difficult. Then, the smoothly changed curvature of multiple clothoid curve is applied as a transition curve at connecting points. Four sorts of lane change which consists of various combination of a straight line and a circular arc are investigated, and the validity of the application of a multiple clothoid curve as a transition curve at connecting points is explained. According to the prescribed analysis method, a three-dimensional vehicle passenger model is applied and the validity of applying to a multiple clothoid curve is quantitatively demonstrated as compared with the case where a connecting point is not interpolated. It was found that the influence of multiple clothoid curve on the vehicle movement and a ride comfort is superior to those of the non-interpolation. Some results are presented in the form of parametric plots.

This paper proposes a novel topology optimization method for unsteady state incompressible Navier-Stokes flow. Many methods of topology optimization for steady state flow have been proposed, whereas most fluid flow problems should be considered as unsteady state. Therefore, a topology optimization method focusing on unsteady state fluid flow governed by the incompressible Navier-Stokes equation is considered in this paper. In addition, the defined boundary condition on the wall of an optimized structure should be precisely evaluated because it describes the specific fluid flow profile, such as velocity and pressure, on the wall that the fluid contacts. In order to solve flow profile near walls, an immersed boundary method is applied in the proposed method. The finite volume method is adopted to discretize primal and adjoint problems. These problems are solved using the Pressure-Implicit with Splitting of Operators (PISO) method. In this study, sensitivity analysis based on a topological derivative is applied. The update scheme for the design variable uses a reaction-diffusion equation. Some examples are shown and the effectiveness of our method is discussed in this paper.

This paper presents experiments and an analysis of the self-excited vibration of a floating plate and a support structure. The system in which a floating plate and a support structure vibrate, the elasticity of the support structure influences the stability of the system. Therefore, in this paper, the influence of the elasticity of the support structure on the vibration characteristics and occurrence conditions of the self-excited vibration is examined. In the analysis, the unsteady fluid force is calculated based on the basic equation of a two-dimensional leakage-flow between the plate and the support structure surface. The basic equation of leakage-flow considers the effect of air compressibility. Moreover, the equation of continuous air flow in the chamber includes the effect of air compressibility. The characteristic equation on the stability of the system is derived from the plate and the support structure motion coupled with the unsteady fluid force. The experiment consists of a floating plate and a support structure, where the vibration characteristics are examined. The influence of elasticity of the support structure on the vibration characteristics and occurrence conditions of the self-excited vibration are clarified comparing the analysis with experiments. Lastly, the local work done by the unsteady fluid force acting on the plate surface and the support structure surface is shown, and the instability mechanism is discussed.

The present paper proposes a shape optimization of the adhesive interface to improve the strength of adhesive structure under a multiaxial stress state. Its strength was evaluated by the failure function based on the first invariant of stress tensor I1 and the second invariant of deviatoric stress tensor J2, which has been discussed in the related previous paper. We defined a sum of squares of the failure function as an objective function in the optimization. Two types of the adhesive material properties, which put the major weights on only I1 and J2, respectively, were numerically examined. As a multi-material structure model bonded by the adhesive, a thin-walled butt-jointed cylinder was employed to avoid stress concentration at free edges in the adhesive layer. Three kinds of loadings were applied: only tension, only torsion, and a tension-torsion combined load. The shape of optimal adhesive layer according to each condition was in good agreement with the simplified theoretical solution. The kinked part of the optimal adhesive interface necessary for the pipe configuration was also reasonable to diminish the stress concentration around the corner. The obtained optimal shapes for the two typical adhesive material properties suggest that the present optimization method would be applicable dependent to the adhesive material parameters under multiaxial stress states.

This paper addresses the cascading design method of NVH (Noise, Vibration and Harshness) performance between an OEM (Original Equipment Manufacturer) and suppliers. The increasing trend toward electric vehicles requires the exploring of cascading design method, because of the easiness of the assembly of the electric vehicles. However, there are difficulties for the cascading design of NVH performance to overcome the coupling problem among each subsystem. It is generally difficult to divide key evaluation characteristics of a whole structure to individual characteristics of each subsystem because of the coupling resonance. In this paper, cascading design method which utilizes the MMC (Mutual Mean Compliance) was proposed. The MMC is used as an index to meet the final NVH target levels of a whole structure. Then, the MMC is cascaded to each subsystem or component. Finally, the cascaded MMC is achieved by improving individual MMCs of each separate subsystem, while being careful about the resonance of a whole structure caused by strong coupling. In the paper, it is shown that the recalculation of MMCs after subsystem’s structural modification is feasible using FBS (Frequency response function Based Sub-structuring). In addition, MMC based cascading design method using FBS was defined and organized as a procedure. The method was also verified by a numerical case study.

Purpose of this paper is to reduce the response of rocking vibration mode of vertically isolated equipment. The rocking vibration is the motion that the top of equipment vibrates as the fulcrum in a bottom end. According to the low vertical stiffness of vertically isolated equipment, the rocking vibration is largely excited by horizontal earthquake motion. In this paper, a dynamic absorber is developed in order to apply to the rocking vibration of the vertically isolated equipment. The proposed system is a rolling pendulum type dynamic absorber using magnetic damper, which is composed of circular rails, a rolling body including magnets and a conductor plate. The design method for the dynamic absorber and the evaluation method for vibration reduction effect are showed in this paper. The dynamic characteristics are also examined by vibration test. It is confirmed from the vibration tests using a rocking model apparatus that the proposed dynamic absorber is effective for rocking vibration reduction.

This paper considers the positive real property of the impedance matching controller for double cascade-connected damped mass-spring systems, whose mass is connected to beyond the adjacent masses. The system can be regarded as a linearized model of a tensegrity beam, one of the basic structures in tensegrity systems corresponding to a cantilevered beam in continuum case. In our previous work, we considered wave analysis and control of the systems, and showed that the impedance matching controller is effective for vibration suppression of the tensegrity beam. However, in the paper, analytical property of the impedance matching controller, i.e., positive real property, was not investigated; and thus the closed loop stability is not guaranteed from the theoretical point of view. This paper addresses this issue, and shows that the impedance matching controller is actually a positive real function.