著者

南後 淳 宮原 洋平 高山 将歩 宮田 和揮 鈴木 貴史 佐藤 潤

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00171-17-00171, 2017 (Released:2017-10-25)

参考文献数

15

被引用文献数

1

---

In recent years, many assist devices have been developing to enable the users to walk by an electric control system. However, introducing an electric control system makes the price rise of the device. It is difficult for users to purchase an expensive device, even if it is easy to use. In order to spread an assist device in daily life, a development with a low price and a simple device is expected. The device driven by external power sources disturbs users' independent action, there is a risk that it could be make users' physiologic function decline and users disincentive to do daily actions. An appropriate control system should be constructed in order to avoid an interference between a user's motion and a device's output motion. In case that the control system has the problem, an appropriate assisting motion can not be obtained, and it is in danger of harming to the user's body. So the design of devices is needed to consider for safety. The purpose of this research is the design and the development of a simple device for assisting walking motion which is driven by users' self, considering users' own physical condition. The assist device is designed by using a planar 6-link mechanism which transforms a rotational motion into an oscillating motion. The respective lengths of the links are determined by comparing the movement of the link, which the user's foot is put on, with the movement of the human leg in the action of walking. We optimize the device by using the Genetic algorithm while we consider the max value of input-torque to drive the device. In this study, the device assisting the user's legs are driven by the user's arm. Authors evaluate the device's supporting performance by the method of measuring the leg motion and the EMG of the leg. The transmissibility is also evaluated by the method of measuring the output force with load cells. The results are verified by comparing the values derived from the static analysis. From these results, authors investigated that the driving arm motion interlocked with the assisting leg motion, even though it had only one degree-of -freedom. The measurement result of the transmissibility shows that the output is enough to support the walking motion in the swing phase.

著者

森安 竜大 松森 唯益 永岡 真

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00144-17-00144, 2017 (Released:2017-10-25)

参考文献数

26

---

A topology optimization method is proposed for the design of shallow-flow channels based on quasi-three-dimensional flow models of laminar and turbulent flows. The models for laminar flow and turbulent flow are derived from the Navier-Stokes equations and the Reynolds-Averaged Navier-Stokes (RANS) equations, respectively, by integrating along the direction of channel thickness. The thickness is employed as the design variable in the topology optimization. The design variables are updated using a time-dependent diffusion equation with a design sensitivity which is calculated by a discrete adjoint approach. Numerical examples for minimizing dissipation energy or variance of flow velocity magnitude using the topology optimization demonstrates that the proposed method is capable of finding optimal solutions that satisfy the KKT conditions. In the former example, the design domain was clearly divided into domains where the thickness was either near the upper limit or near the lower limit. However, in the latter example, the thickness was at an intermediate level in almost the whole the design domain. The distribution of the thickness varied depending on the Reynolds number in both examples.

著者

佐藤 皓明 遊佐 泰紀 岡田 裕

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00300-17-00300, 2017 (Released:2017-10-25)

参考文献数

20

被引用文献数

3

---

In this paper, formulations and some computational results of cycle jump method based on the nonlinear finite element method are presented. Problems, involving nonlinear cyclic deformation, such as low cycle fatigue problems can be solved by the proposed cycle jump method. To solve the problems of nonlinear cyclic deformation of structure by the nonlinear finite element method with a cycle-by-cycle approach, a large amount of computational time is generally required. Thus a cycle jump method is presented from a view point of temporal multi-scale analysis. Then, an alternative analytical procedure consisting of three steps is proposed. They are a few cycles of nonlinear analysis in a cycle-by-cycle fashion, computations of jumps of strain history dependent quantities (extrapolations) based on the results of the cycle-by-cycle analysis and a cycle jump for several dozen to several hundred cycles using the results of the extrapolations. The results of cycle jump analyses are presented and their accuracies are critically examined. It was found that the results of several load cycles at the beginning of each cycle-by-cycle analysis step should be excluded from the computations of the extrapolation step.

著者

久野 翔太郎 石川 諭 雉本 信哉 木庭 洋介

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00305-17-00305, 2017 (Released:2017-10-25)

参考文献数

13

---

Several adaptive feedforward control methods have been proposed in previous research on active noise control. In those methods, noise control is achieved by adding in a reverse-phase control sound of the same amplitude to noise near an error microphone. Because this method is aimed at controlling only noise near the error microphone, the control area is inherently narrow. Here, we propose an alternative method of noise control for an entire closed space. The proposed method is based on state feedback control and modeling of the acoustic space by the concentrated-mass model. The acoustic space is modeled as masses, connecting springs, and connecting dampers. Further, a loudspeaker as control source is also modeled as a mass-spring-damper system. We previously reported a method for simple one-dimensional acoustic space control. In this paper, we show the design of a control system for two-dimensional acoustic spaces. The acoustic space and loudspeakers are modeled in a concentrated-mass model, and the state feedback control system is realized as a Kalman filter with pole placement. The number of degrees of freedom is reduced by using modal analysis, which reduces the computation time of the controller. Experiments and numerical simulation of the coupled system were conducted to confirm the validity of the analysis model. Noise in the acoustic space was experimentally controlled, with the finding that noise in the entire acoustic space was reduced around the resonance frequencies. Furthermore, the limit of the control effect are considered within the proposed system.

著者

松岡 太一

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00292-17-00292, 2017 (Released:2017-10-25)

参考文献数

22

被引用文献数

3

---

In this paper author proposed a unique vibration suppression device that has variable inertia mass using continuously variable transmission (CVT) in order to obtain vibration isolation when a harmonic frequency was coincided with an anti-resonance frequency of 1DOF system. The device complies a ball screw mechanism, a flywheel, servo motors and CVT. The CVT is composed of toroidal wheels and power transmission wheels. The device has a small inertia force when an attitude angle of the power transmission is low by the servo motor as depending on a contact radius between two half toroidal wheels, on the other hand the large inertia force under high angle, so variable inertia force which acts as series inertia mass can be controlled continuously. The trial device was manufactured and the resisting force characteristics were measured. Theory of the variable inertia force was introduced, and compared with the experimental results. In order to confirm vibration control, an optimized inertia mass which always adjusts to anti-resonance frequency was determined in case of 1DOF system with the device, frequency response tests were carried out by using a shaking table, and experimental results were compared with calculated ones. Finally, the theory of resisting force and effects of vibration suppression were confirmed.

著者

松田 聡一郎 松浦 大輔 菅原 雄介 武田 行生

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00282-17-00282, 2017 (Released:2017-10-25)

参考文献数

17

被引用文献数

2

---

In order to improve living space for stable walks by elderly people, this paper discussed assessment of living space with unique-shaped support objects. Four evaluation indices expressing capability of balance recovery corresponding to the support object were derived based on directionality of generative force by human's upper extremity and directionality of reaction force depending on surface shapes of the objects. Experiments were carried out to (1) obtain the parameters necessary to calculate the proposed indices and (2) carry out organoleptic evaluation of the support objects. Compared to the results obtained in these experiments (1) and (2), effects of the proposed indices were discussed, and an effective index among the four for evaluating the effect of the support objects was clarified. Assessment of a support object using the index was shown as an example.

著者

田井 浩一 佐藤 邦彦 前田 栄一

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00259-17-00259, 2017 (Released:2017-10-25)

参考文献数

9

被引用文献数

1

---

Response spectrum analysis method is widely used for the seismic design of equipment and piping systems of nuclear power plant, or other industrial facilities. Some of the equipment and piping systems are multiply supported with plural floors, or several different points. In these cases, conservative design methods, such as uniform response spectrum (URS) method that envelopes all of the individual response spectra, or independent support motion (ISM) method are commonly accepted. These design methods are not practical, but often mislead to design with unnecessary conservatism. This paper presents the practical seismic analysis methodologies considering the correlation coefficients of seismic responses with multi-directional excitations, which is extended to apply the correlations between modal responses and between support motions, called cross-oscillator, cross-floor response spectrum by Asfura, A. and Kiureghian, A,D., and numerical examples are also presented to examine the validity for the seismic analysis method of multiply supported secondary systems, with simultaneous three directional excitations of each X, Y, Z axis.

著者

水野 毅 Asief JAVED 石野 裕二 髙﨑 正也

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00217-17-00217, 2017 (Released:2017-10-25)

参考文献数

19

被引用文献数

2

---

A switching stiffness control and a modified variable stiffness control were applied to reduce vibration in the lateral directions in active magnetic suspension system with electromagnets operated in the differential mode. The magnetic suspension system using the attractive force between magnetized bodies is inherently unstable in the normal direction so that feedback control is necessary to achieve stable suspension. In contrast, it is usually stable in the lateral directions because of the edge effects in the magnetic circuits. However, damping in the lateral directions is poor so that vibration is easily induced. In this work, a switching stiffness control was applied to attenuate such vibration. The effectiveness of the switching stiffness control was confirmed experimentally. In addition, a modified control method that varies stiffness continuously was proposed to overcome problems occurring in switching. The efficacy of the modified control method was also confirmed experimentally.

著者

福田 拓生 坂口 聡範 滝本 隆 潮 俊光

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00207-17-00207, 2017 (Released:2017-10-25)

参考文献数

22

---

The quadrotors are useful for periodic inspections of tunnels and bridges. However, the conventional quadrotor has a problem such that it is impossible to control the rotational motion and the translational motion independently. Therefore, if the camera is attached on the bottom of the quadrotor, it is difficult to observe its upward direction. In this paper, we develop a novel quadrotor that has a parallel link to tilt itself. By increasing one degree of freedom of the quadrotor, we resolve the problems described above. And we derive a model of the developed quadrotor. Then, we consider a PID controller for the stabilization of the quadrotor at a specified hovering state. We derive gain parameters of the PID controller by which the controlled quadrotor is stabilized.

著者

柏崎 翔 涌井 伸二

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00189-17-00189, 2017 (Released:2017-10-25)

参考文献数

24

被引用文献数

7

---

Pneumatic anti-vibration apparatus (AVA) has been used for suppressing the vibration from the floor. Compressed air produced by the air compressor is supplied to air spring, which is used as an actuator in AVA. This paper considers the suppression of flow disturbance, which is caused by pressure variation of compressed air. Based on the internal model principle, the suppression of vibration of AVA due to flow disturbance has been confirmed by using Central Pattern Generator (CPG) in parallel with a displacement controller. In biological study, CPG in bodies playing a significant role in the walking have been learned. Moreover, mathematical models of CPG have been reported, and some researchers have been studying about walking of biped-robots by using CPG to generate desired value. On the other hand, this paper proposes asymmetric CPG as new model for further vibration suppression, compared with the symmetric CPG which is the conventional model. This new model introduces asymmetry by changing its parameters into different values in order to improve reproducibility of waveform which shows the variation of supplied air pressure. Validity of the proposed model is presented by experimental result of AVA. The effectiveness is shown by analyzing and comparing the results of experiment and simulation of symmetric and asymmetric CPGs.

著者

吉武 裕 安部 晃 村上 心 梶原 修平 古川 隼人 坂本 竜二郎

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00164-17-00164, 2017 (Released:2017-10-25)

参考文献数

9

被引用文献数

1

---

This paper deals with the vibration quenching problem of the one-degree-of-freedom system with a limited power supply. This system is forced by centrifugal force of rotating unbalance, and the system is quenched using a Hula-Hoop and a motor to assist the rotation of Hula-Hoop. The entrainment region, the amount of vibration quenching, and the energy consumptions of the system are studied from the approximate analysis using the averaging method, the numerical integration analysis, and the experiment. Following was made clear: (1) When the unbalance is large, the entrainment region of the voltage of the assistant motor is large. On the other hand, when the unbalance is small, the entrainment region becomes narrow. (2) When the unbalance is large, by setting the voltage of the assist motor to a value smaller than the optimum value for vibration control, within the range that satisfies the allowable vibration amplitude level, the increase amount of the energy consumption becomes low. (3) The approximate solutions obtained by the averaging method are in good agreement with those obtained by the numerical integration method, and the characteristics of these results coincide with those of the results obtained by experiment.

著者

金生 翔太 橋本 雅文 余田 侑仁 高橋 和彦

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00138-17-00138, 2017 (Released:2017-10-25)

参考文献数

26

---

This paper presents a laser-based tracking (estimation of pose and size) of moving objects using multiple mobile robots in Global-navigation-satellite-system (GNSS)-denied environments. Each robot is equipped with a multilayer laser scanner and detects moving objects, such as people, cars, and bicycles, in its own laser-scanned images by applying an occupancy-grid-based method. It then sends measurement information related to the moving objects to a central server. The central server estimates the objects’ poses (positions and velocities) and sizes from the measurement information using Bayesian filter. In this cooperative-tracking method, the nearby robots always share their tracking information, allowing tracking of invisible or partially visible objects. To perform a reliable cooperative tracking, robots have to correctly identify their relative pose. To do so in GNSS-denied environments, the relative pose is estimated by scan matching using laser measurements captured by both sensor nodes. Such cooperative scan matching is performed by 4-points-congruent-sets (4PCS)-matching-based coarse registration and Iterative-closest-point (ICP)-based fine registration methods. The experimental results of tracking a car, a motorcycle, and a pedestrian with two robots in an outdoor GNSS-denied environment validate the proposed method.

著者

古性 裕之 毛利 宏

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00095-17-00095, 2017 (Released:2017-10-25)

参考文献数

14

---

We propose image processing method for road white-line detection using brightness gradient direction of edges. Many methods for white-line detection have been proposed for standardized roads. These methods use model fitting for the detection of edges on white-line contour. So it is difficult to apply these methods to non-standardized roads for which modeling is difficult. To expand the scope of white-line detection to common roads in the future, it is necessary to achieve processing without models. Clustering based on position proximity of edges is one approach. However, there is concern about degrading noise reduction that has so far been done by model fitting. In this study, we developed an edge clustering method that utilizes the characteristics of edges on white-line contours; proximity of position as well as proximity of brightness gradient direction. In the proposed method, edges are first clustered based on proximity of gradient direction. And for each cluster, edges are again clustered based on proximity of position. Edge filter bank is specially designed for the first clustering and the effectiveness compared to conventional filter bank is explained. By applying the method to the images taken by on-board camera, we demonstrate that white-line detection that can apply to diverse road environments but is hardly affected by noise can be realized.

著者

早坂 良 大村 高弘

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00180-17-00180, 2017 (Released:2017-10-25)

参考文献数

9

---

We have investigated the sedimentation phenomenon in a colloidal dispersion composed of spherical ferromagnetic particles using Brownian dynamics simulations. We have attempted to clarify the conditions under which all particles settle down and a thin film is formed, by varying the applied magnetic field, magnetic force between particles, mass density, and temperature of the solution. The particle concentration was set so that the average inter-particle distance was 2.5 times the particle diameter. The main results obtained are summarized as follows. When the mass density is increased, the sedimentation rate increases due to the influence of gravity. The sediment is deposited at the bottom layer immediately after being dropped, and the particles display a stronger tendency to settle down at the bottom layer. However, as the magnetic force between the particles increases, the bonding between the particles becomes strong and clusters are formed, which makes it difficult to obtain the desired thin film in which all particles precipitate at the bottom layer and exist separately. Even in such a situation where the influence of the applied magnetic field is dominant, a thin film can be obtained if the magnetic moment of the particle is strongly restrained in the direction of the magnetic field, thus preventing the formation of clusters. In addition, when the density ratio is as large as 30 as is in this case, a planar cluster may be formed in the lowermost layer even when all the particles have settled down. On the other hand, if the temperature of the liquid is too low, the clusters remain intact without collapsing because of the low random force. As a result, the desired thin film cannot be obtained. However, there is a limitation where in the number of conditions under which the thin film formation occurs does not increase when the random force value exceeds a certain level.

著者

松岡 三郎 松永 久生 山辺 純一郎 濱田 繁 飯島 高志

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00264-17-00264, 2017 (Released:2017-10-25)

参考文献数

29

被引用文献数

19

---

Considering in design by analysis, four types of tests, slow-strain-rate tensile (SSRT), fatigue life, fatigue crack-growth (FCG), and elasto-plastic fracture toughness (JIC) tests, were conducted with low-alloy steels, JIS-SCM435 and JIS-SNCM439, in 115 MPa hydrogen gas and air at room temperature (RT). In addition to above tests at RT, the SSRT tests were also conducted in 115 MPa hydrogen gas and air at 120 oC and in 106 MPa hydrogen gas and 0.1 MPa nitrogen gas at -45 oC. The low-alloy steels used in this study had tensile strengths (σB) ranging from 824 to 1201 MPa with fine and coarse tempered-martensitic microstructures. In the SSRT and fatigue life tests, the tensile strength and fatigue limit were not degraded in hydrogen gas. The FCG tests revealed that the FCG rate (da/dN) was accelerated in hydrogen gas; however, there existed an upper bound of the FCG acceleration, showing the FCG rate in hydrogen gas was about 30 times larger than that in air, when σB was lower than 900 MPa. The JIC tests demonstrated that the fracture toughness (KIC) in air was 207 MPa·m1/2 at σB = 900 MPa, whereas the hydrogen-induced crack-growth threshold (KI,H) was 57 MPa·m1/2 at σB = 900 MPa. Based on these results, we proposed advanced guidelines on the use and design for SCM435 and SNCM439 on design by analysis in 115 MPa hydrogen gas, which enable to design the storage cylinders used in 70 MPa hydrogen station with lower cost without compromising safety.

著者

円谷 悠 毛利 宏

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00114-17-00114, 2017 (Released:2017-10-25)

参考文献数

8

被引用文献数

1

---

This paper describes an investigation on the nonlinear filter that can realize its gain and phase characteristics independently. In the driver-vehicle closed loop system, it is reported that there is an optimal value in vehicle phase delay, i.e., excessive large or small delay deteriorates vehicle maneuverability. However, there is a strict relationship between the gain and phase delay in linear system. It is difficult to evaluate the gain and phase delay of vehicle response independently. In this investigation, we tried to design a non-linear filter that can set the relationship between gain and phase delay arbitrarily by using neural network. We investigate the effect of the gain and phase delay corresponding to the steering angle input on the ease of driving by using driving simulator, and evaluate the control performance on the lane change task. We verified that the ease of driving is improved by reducing a phase delay and decreasing a high frequency gain.

著者

石倉 嵩也 鈴木 宏典

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00111-17-00111, 2017 (Released:2017-10-25)

参考文献数

13

被引用文献数

1

---

This paper proposes mathematical models to predict preceding car's deceleration intent and evaluates its effect on the following car driver in terms of the mitigation of risk of rear-end collision. Assuming a four-vehicle convoy, an unscented Kalman filter (UKF) integrated with a conventional car-following model attempt to estimate the headway and velocity of the 1st to 3rd vehicles in the platoon. The car following model used in this research is the conventional Gazis-Herman-Rothery model (GHR model). Then, another GHR model is used to predict the deceleration intent of the 3rd vehicle, which is expected to occur 1.5 seconds later based on the estimates of headways and velocities. In addition, this study proposes an interface to inform the predicted intention to the following vehicle by using a windshield display (WSD). Numerical analyses showed that the UKF integrated with the GHR model succeeded in estimating the vehicle platooning states and predicting the deceleration intent accurately. However, the prediction does not always shows the perfect match with the actual observation due to the uncertainty of driver's behavior. Although it is not completely accurate, it is a quite useful information to mitigate the collision risk so that we decided to design the interface by the WSD to inform the predicted deceleration intent to the following car driver. A driving simulator experiment was carried out to present the 3rd vehicle deceleration intent expected to occur 1.5 seconds later to the 4th ego car. It was found that the maximum deceleration rate of the 4th vehicle was suppressed and the value of the Time-To-Collision was increased not only in an ordinal deceleration case but also in a situation where the collision risk became significant.

著者

川勝 俊輝 毛利 宏

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00099-17-00099, 2017 (Released:2017-10-25)

参考文献数

8

---

Many articles have reported that the white lines painted on both sides of highways are used by automatically driven vehicles to control their lateral movement when driving. They are detected by stereo cameras or radars. And GPS is used as an additional information for improving its robustness and reliability. However, when we think about an urban area, the stereo cameras and radars cannot recognize any white lines because white lines do not exist at intersection. Therefore, a method for controlling a vehicle without environmental recognition becomes necessary. In our method, the steering angle is controlled by using simple map information comprising nodes and links of roads, which are widely used in navigation systems, and the data of the vehicle's position, which is obtained continuously. In addition, by using two front gaze points to solve the problem associated with one front gaze point, we propose a method that allows a vehicle to steer smoothly when turning at intersection. We performed an experiment using an actual vehicle under the same conditions as those used in the simulation. The results confirmed the validity of our proposed method because the target steering angles at each corner and the driving trajectory of the actual vehicle were almost the same as those obtained using the simulation.

著者

藤原 大悟 塩川 貴之

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00087-17-00087, 2017 (Released:2017-10-25)

参考文献数

12

---

Aiming at the realization of agile autonomous flight for the extension of the flying range of single-rotor helicopters in the limited flight time, the flight control system design and the control performance verification for the high-speed turn flight are conducted. To achieve the reference following control for large attitude angles and the rotor thrust, the control system is composed of the main-rotor thrust and body torque centralized controller based on the MIMO (Multiple-Input, Multiple-Output) helicopter model including the blade motion dynamics, rotor speed proportional-integral controller, the attitude controller designed via the backstepping method based on the quaternion attitude model, and the guidance controller based on translational motion model. Simulation results show that the hovering and 10-m/s straight cruise flight followed by over 45-degree bank turn is feasible by using the proposed control system. In addition, flight tests have been conducted using the experimental small unmanned electric helicopter equipped with the flight control computer, and the high speed turn agile autonomous flight was successful in the real environment.

著者

酒井 英樹

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.854, pp.17-00064-17-00064, 2017 (Released:2017-10-25)

参考文献数

10

---

This paper considers ways to increase stability of wheelset hunting. The aim of this study is to introduce formulas which represent the damped natural frequency and its damping. This has been done by analytical and not by numerical calculation. These formulas are functions of mass, creep coefficient and other wheelset parameters. These formulas are obtained with a 2 degree of freedom wheelset model whose radius of gyration of yaw equals to a half of gauge and whose creep coefficient is isotropic, in the first part of this paper. In the second part, based on one of these formulas, ways to increase damping of wheelset hunting are discussed. First, it is shown that a longer wavelength of geometrical hunting is effective in reducing hunting at all vehicle speeds. Secondly, it is shown that at speeds slower than a certain speed, the damping is increased when the ratio of the wheelset mass to the creep coefficient is larger. Further, a symbolic formula for this boundary speed is obtained. Thirdly, if it is assumed that the wheelset mass is proportional to the square of the wheel radius, then at speeds higher than a certain speed, the damping is increased when the wheel radius is larger. Moreover a symbolic formula for this boundary speed is also obtained.