著者

菅沼 祐介 橘田 聖 野村 浩司 氏家 康成

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.855, pp.17-00352-17-00352, 2017 (Released:2017-11-25)

参考文献数

17

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Microgravity experiments of flame spread along a fuel droplet array were performed to examine the effect of ambient pressure on the flame spread speed. The purpose of this research is to investigate growth mechanism of group combustion of fuel droplets. A fuel droplet array was suspended by SiC fibers of 14 μm in diameter. The number of fuel droplet was varied from 6 to 10 depending on the droplet spacing. Nondimensional droplet spacing and ambient pressure were varied from 2 to 12.5 and from 0.10 to 0.60 MPa, respectively. To simulate flame spread through a 3D fuel-droplet-matrix, a fuel droplet array was placed on the axis of a rectangular optical cell. n-decane was employed as a fuel. The normalized flame spread speed decreased as the ambient pressure increased. For all ambient pressures, the normalized flame spread speed takes the maximum between 3 and 3.75 in the nondimensional droplet spacing. The dependence of the normalized flame spread speed on ambient pressure increases with the increase in the nondimensional droplet spacing. An empirical model equation which expresses the dependence of flame spread speed on the ambient pressure was proposed.

著者

宮田 一司 森 英夫 谷口 隆寛 梅沢 修一 杉田 勝彦

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.855, pp.17-00280-17-00280, 2017 (Released:2017-11-25)

参考文献数

15

被引用文献数

2

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For the development of industrial heat pump systems supplying high-temperature heat source over 130 °C, experiments were carried out on cooling heat transfer of supercritical pressure HFO1234ze(E) flowing in a plate-type heat exchanger (PHE). HFO1234ze(E) with low Global Warming Potential (GWP) is expected as an alternative to refrigerant HFC134a. In the experiment, heat transfer coefficient data were obtained at different pressures including a near-critical pressure condition. To obtain the heat transfer coefficient, an integral method was used for evaluating the mean temperature difference between the refrigerant and cooling water in the PHE. Based on the measurements, characteristics of cooling heat transfer of supercritical pressure HFO1234ze(E) in the PHE were clarified. Generally, heat transfer coefficient showed considerably large values compared with tube flow, attributed to strong turbulence or agitation promoted by corrugated geometry of the PHE plate, and reached a maximum in the vicinity of the pseudocritical point. As the pressure approached the critical pressure, the peak of heat transfer coefficient became higher at lower bulk enthalpy, reflecting the pressure dependence of isobaric specific heat of the refrigerant. These results mean, even in the pseudocritical region where strong temperature dependency of physical properties appears, properties change in the flow cross section was small compared to the tube flow, although not negligible. The correlation developed in the previous study overestimated the measured heat transfer coefficient in the pseudocritical region for the pressure of the reduced pressure 1.01 very close to the critical pressure and also in the enthalpy region near to and lower than the pseudocritical point for the pressures of the reduced pressure about 1.1 or higher. For the better prediction, the necessity to consider the small but non-negligible properties change in the flow channel cross section was recognized.

著者

星野 柊 祖山 均

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.855, pp.17-00400-17-00400, 2017 (Released:2017-11-25)

参考文献数

30

被引用文献数

1

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For hydrodynamic cavitation produced by a Venturi tube, cavitation bubble is collapsed at downstream of a nozzle and its intensity is influenced by upstream pressure and downstream pressure. In order to investigate the effect of the upstream pressure p1 and the downstream pressure p2 on aggressive intensity of hydrodynamic cavitation, an experiment measuring acoustic power by an AE sensor was conducted. Relationship between pressure conditions and acoustic power PA was studied. The higher the upstream pressure p1, the higher the acoustic power PA. Acoustic power had a maximum value at the upstream pressure p1 = 1.6, 2.1, 2.6, 3.1 and 3.6 MPa. At the upstream pressure p1 = 2.6 MPa and the downstream pressure p2 = 0.5 MPa, the aggressive intensity of hydrodynamic cavitation increased to be 36 times larger of the value corresponding to the atmospheric downstream pressure. While the optimum downstream pressure depended on the upstream pressure, the cavitation number was nearly constant for all upstream pressures. It was concluded that increasing the downstream pressure is an effective means to increase the aggressive intensity of the hydrodynamic cavitation without increasing the input energy.

著者

佐野 正利 佐川 貴浩 加藤 琢真

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.855, pp.17-00395-17-00395, 2017 (Released:2017-11-25)

参考文献数

19

被引用文献数

1

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In industrial devices such as heat exchangers, fuel cells, and chemical reactors, the fluid flow enters the inlet manifold and streams into many branch passages. In order to improve the performance of these devices, it is important to obtain a uniform flow rate distribution in each passage. In the present study, an experimental investigation is performed for multiple-passage duct flows. The multiple-passage duct is a reverse flow type and consists of five branch ducts. The duct flows are investigated from the view-point of flow uniformity and pressure loss. Experiments are performed for Reynolds numbers ranging from 6.0 × 102 to 1.5 ×103, based on the bulk velocity and hydraulic diameter at the inlet duct. The aspect ratio (i.e., the ratio between the height and width of the branch duct) is varied as 0.6, 1.0, and 20. The effect of the outlet manifold volume on the flow distribution is investigated. The wall static pressure is measured, and the pressure loss and flow rate are evaluated. The velocity profiles are measured by a PIV system in order to clarify the effect of the increasing the outlet manifold volume. The results reveal that the flow rate changes only slightly with the aspect ratio. As the Reynolds number increases, the uniformity of the flow rate through each branch duct worsens. A uniform flow distribution is realized by increasing the volume of the outlet manifold. The flow uniformity is related to the reduction of the recirculation region at the inlet manifold.

著者

石原 健一 下池 利孝 飯井 俊行

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.855, pp.17-00323-17-00323, 2017 (Released:2017-11-25)

参考文献数

33

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The fracture toughness Jc of the material in the ductile to brittle transition temperature (DBTT) region shows test specimen thickness (TST) effect and temperature dependence, and apparently increases when compressive residual stress is applied. In this paper, as TST effect and temperature dependence, the fact that Jc apparently increases due to compressive residual stress is attributable to the loss in the one-to-one correspondence between J and the crack-tip stress distribution, and then, the fracture prediction of the specimen with compressive residual stress was performed using the T-scaling method proposed by the authors, and its validity was confirmed for high strength steel of 780 MPa class and 0.45 % carbon steel JIS S45C. In addition, it was suggested that the minimum of Jc with compressive residual stress can be predicted by requiring only the tensile test.

著者

細井 厚志 寺内 幹 角田 大 木村 達哉 古挽 彰 川田 宏之

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.855, pp.17-00312-17-00312, 2017 (Released:2017-11-25)

参考文献数

25

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The effects of environment temperature on initiation and multiplication of transverse crack in cross-ply carbon fiber reinforced thermoplastic (CFRTP) laminates have been investigated. Static tensile tests for the cross-ply laminates and the 90° unidirectional laminates were carried out at room temperature, 93 °C and 130 °C, respectively. The transverse cracks were observed by soft X-ray photography. The tensile strength and the failure strain in the cross-ply laminates and the 90° unidirectional laminates at high temperature decreased compared to the values at room temperature. It was also found that the behavior of initiation and multiplication of the transverse cracks in the cross-ply laminates was changed due to the environment temperature. The experimental results under different temperature were analyzed by Weibull distribution on the basis of probabilistic model. Next, the energy release rate was calculated due to formation of a new micro crack based on the Weibull distribution. The predicted transverse crack density by Weibull distribution was compared with the experiment result and the reasonability of using Weibull distribution to CFRTP cross-ply laminates under high temperature was verified. It was found that the critical energy release rate of CFRTP laminates has decreased at high temperature and the experimental results showed that the matrix strength was decreased at high temperature. Also, the fiber-matrix interfacial fracture on the fracture surface of the 90° unidirectional laminates was observed in some areas at high temperature whereas the matrix fracture was observed at room temperature. Therefore, it was suggested that the interface strength between polymer and fiber was decreased at high temperature.

著者

森重 直樹 TRIAWAN Farid 因幡 和晃 岸本 喜久雄

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.855, pp.17-00304-17-00304, 2017 (Released:2017-11-25)

参考文献数

13

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A zirconium alloy cylindrical tube exhibited fracture under high-velocity axial impact load when high yield strength pellets were inserted as reported by Morishige et al., 2016. The fracture occurred after a crack was initiated at the tensile side of the bending tube. In this paper, FE analyses were conducted to clarify the fracture mechanism as well as the deformation behavior. At first, axial tensile tests using tubes with four slit-holes located at the center were performed in order to evaluate the fracture behavior of the tube. Then, digital image correlation (DIC) method was utilized to measure the local strain near the slit-holes. The results showed that the fracture displacement became smaller with smaller slit-holes’ radius. Also, the strain was concentrated at the slit-holes’ tips where cracks were generated before fracture. Subsequently, FE analyses of the tensile tests were conducted by LS-DYNA using the implicit method to obtain the fracture criterion. The load-displacement curve agreed well with the experiment. Then, the relationship between stress triaxiality and equivalent plastic strain near the slit-holes’ area were evaluated to define the fracture criterion. Finally, FE analyses of the axial impact tests using the dynamic explicit method were conducted to compare with the fracture criterion defined by the axial tensile tests. The results indicated that a localized stress and strain might occur at the tube boundary adjacent to pellets. This was caused by the interaction between tube and pellets’ edge which generated a tensile stress condition at the tube boundary when high yield strength pellet was applied. Under this condition, both stress triaxiality and effective plastic strain could increase and eventually lead to the fracture criterion.

著者

皮籠石 紀雄 仮屋 孝二 中村 祐三 永野 茂憲 岩本 竜一

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.855, pp.17-00274-17-00274, 2017 (Released:2017-11-25)

参考文献数

23

被引用文献数

2

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Fatigue cracks in some aluminum alloys propagate not in a typical tensile mode with striations but in a macroscopic shear direction with ductile facets under specific conditions. In the previous paper, it was shown that this unique propagation of a shear mode crack occurred in high humidity under rotating bending fatigue and under ultrasonic loading fatigue irrespective of humidity. Two types of mechanism for the shear mode crack were proposed: one is a case that a slip deformation to one direction in cross slip in formation process of striation was enhanced by hydrogen generated in corrosion process of Al alloy in high humidity and the other is that a slip deformation of one direction was inhibited by the re-welding of crack faces in vacuum condition. In the present study, fatigue tests of Al alloys of extruded and drawn 2017-T4 and extruded 7075-T6 were conducted under rotating bending and ultrasonic loading conditions in relative humidity environments of 25% and 85% and in nitrogen gas, to verify the proposed mechanism experimentally and investigate influencing factors on the shear mode propagation. In addition, the effect of change in the testing condition on the propagation behavior of a crack was investigated. Although the microscopic shear mode propagation occurred within grains in both of the extruded and the drawn alloys, the crack propagated to a specific shear direction macroscopically in the extruded alloy related to the strong texture, and the crack propagated in a tensile mode macroscopically in the drawn alloy possessing no texture. These differences in macroscopic crack propagation mode, thus, were caused by the degree of texture. The proposed mechanism was verified by some experiments in various environments. Furthermore the effect of change in testing conditions influencing on the shear mode crack was explained by the results under the constant conditions.

著者

皮籠石 紀雄 中村 祐三 仮屋 孝二 永野 茂憲 岩本 竜一

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.855, pp.17-00273-17-00273, 2017 (Released:2017-11-25)

参考文献数

21

被引用文献数

1

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There are many studies reported that a fatigue crack propagated in a tensile mode macroscopically and the fracture surface was mainly occupied by striations in many metals. Whereas, a unique fracture in which a crack propagated in a macroscopic shear direction accompanied by ductile facets was observed in some aluminum alloys under specific conditions. In the present study, fatigue tests of age-hardened Al alloys of extruded 2017-T4 and 7075-T6 were conducted in relative humidity environments of 25% and 85% under rotating bending and ultrasonic loading conditions to clarify the crystallographic feature of a shear mode crack and propose its growth mechanism. Many facets showing a feature of shear mode crack propagation with an equivalent size to the grain size were observed at the fracture surface under both conditions of rotating bending in high humidity and ultrasonic loading irrespective of humidity. In addition, it was confirmed that the angle between the loading axis and the growth direction of the shear mode crack composed a constant value, ~35°, relating to the marked texture in the propagation process of the macroscopic shear mode crack. However, a crack growth rate was lower in the ultrasonic loading than in the rotating bending in high humidity. Based on their differences in occurrence conditions of the shear mode crack, two mechanisms for this unique propagation were proposed as follows; that is, one was a shear mode crack occurred by the promotion of the slip deformation to one direction due to hydrogen generated by reaction of Al alloy with water vapor in high humidity, and the other was a crack by the suppression of the deformation to one direction due to re-welding of crack faces under ultrasonic loading.

著者

小川 登志男 小田 哲郎 酒井 潤一

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.855, pp.17-00005-17-00005, 2017 (Released:2017-11-25)

参考文献数

20

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We investigated differences in the hydrogen thermal desorption mechanism for Ni-Ti superelastic alloys following hydrogen charging by cathodic charging in a 0.9% NaCl aqueous solution and by immersion testing in a 0.2% APF aqueous solution. For the immersed specimen, the presence of corrosion products on the surface resulted in an upward shift of the hydrogen desorption peak by approximately 100 °C. When the total amount of desorbed hydrogen was almost the same for both specimens, a higher fraction was desorbed at temperatures below 200 °C for the cathodically charged specimen. Furthermore, a larger amount of hydride was formed for the cathodically charged specimen. These results indicate that the hydrogen thermal desorption mechanism depends on the presence of corrosion products on the surface and the amount of hydride formed.

著者

西山 修二

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.855, pp.17-00228-17-00228, 2017 (Released:2017-11-25)

参考文献数

18

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This paper descries theoretical and experimental research on mechanical behavior of a cylindrical container which is divided into multiple space of an equal size into which one cylindrical rod of the same diameter and material is enclosed. It is clarified that an explanatory variable and a criterion variable which are governed rolling movement characteristics of the cylindrical container. A rotary dumping number that is a dimensionless parameter is defined. Theoretical formulas are introduced for the cylindrical container in which one, two and numerous cylindrical rods are enclosed in none divided space of the cylindrical container. Unfixed coefficients in the theoretical formula are properly identified from experimental results practiced more than one. As a result of investigation, we have found that initial velocity from which a rotary dumping number becomes maximum value exists for the cylindrical container in which numerous cylindrical rods are enclosed in none divided space. Some results are presented in the form of parametric tables and graphs.

著者

高梨 宏之 阿部 勝哉 道辻 洋平 小竹 元基 ポンサトーン ラクシンチャラーンサク 林 隆三

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.855, pp.17-00224-17-00224, 2017 (Released:2017-11-25)

参考文献数

16

被引用文献数

2

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This paper describes a modeling method for predicting a walking route of a pedestrian in a stochastic manner. We consider one of the most typical situations where a pedestrian walks along to a sidewalk, and then some obstacle exists in front of the pedestrian. To represent the walking route of the pedestrian during the avoidance action, a stochastic model is suitable than deterministic one. The stochastic model is derived from the walking experiment where a pedestrian avoids some obstacle in natural walking. Based on the loci obtained from the experiment, the pedestrians walking speed and walking direction at any local area was approximated by Gaussian and Beta distribution function, respectively. As a result the walking route of a pedestrian can be represented in a stochastic manner. The estimated output of the model is examined by comparing with two real walking loci that were obtained from near-miss incident database. One examination scene is avoidance of a parked vehicle, and the other is of parked bicycle on the roadside. By the numerical simulation, we obtained the results that the both real walking routes are included within the 3-sigma ranges of the estimated output of 500 trials.

著者

萬 礼応 青山 朋樹 福本 貴彦 森口 智規 高橋 正樹

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.855, pp.17-00223-17-00223, 2017 (Released:2017-11-25)

参考文献数

17

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Gait measurements and physical fitness tests are carried out in the community health activities for health promotion and care prevention services in the growing elderly population. In particular, the timed up and go test (TUG) is the clinical test most often used to evaluate functional mobility in many clinical institutions or local communities. To evaluate the functional mobility during the TUG, a gait measurement system (Laser-TUG system) using a laser range sensor (LRS) has been proposed. The system tracks both legs and measures the foot contact positions to obtain walking parameters such as stride length and step length. To reduce the false tracking and improve the measurement accuracy during the turning phase of the TUG, a data association considering gait phase and a spline-based interpolation have been proposed. However, the false tracking is likely to be occurred in the elderly and the measurement accuracy during the turning phase is still deteriorated because of occlusion and inaccurate observation of legs. Therefore, this paper presents a high-accuracy gait measurement system using multiple LRSs. Using multiple LRSs is able to reduce the situation of leg occlusion. However, the measurement accuracy of leg position depends on the distance from the LRS. To improve the measurement accuracy, an integrated leg detection method by a weighted mean of the observation candidates from each LRS data based on the distance from the LRS is proposed. We confirm that the proposed leg detection method can improve the success rate of leg tracking in the elderly and measurement accuracy of the leg trajectory and walking parameters.

著者

黒山 喬允

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.855, pp.17-00222-17-00222, 2017 (Released:2017-11-25)

参考文献数

14

被引用文献数

1

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A reduction method of engine sound disturbance for on-board power spectral measurement of tire sound is proposed and its validity is evaluated. The proposed method employs two microphones; one is mounted in the engine compartment, and the other in the wheel well of the vehicle. At first, the sound propagation characteristics between the two microphones are discussed. It is shown that the complex coherence between the engine sounds obtained with two microphones are very low. On the other hand, the power coherence takes about 0.4 within the frequency range from 0 to 15 kHz. These imply that the sound does not propagate linearly between the two microphones, but the power spectra of microphones correlate each other. Next, the power spectra of the sound measured with each microphone are calculated and the power spectrum of the tire sound is extracted by the calculation with the two spectra based on a pre-identified transfer function between the two microphones. The calculated power spectrum of the tire sound depends on the driving conditions of the engine and its large variance is not acceptable. This may be caused by the error of the pre-identified transfer function. Then, the modified transfer function is determined and the power spectra are calculated again. As a result, the variance of the power spectra becames lower than previous results and thus, the validity of the proposed method is confirmed.

著者

木下 俊 呉 魏 廣垣 俊樹 青山 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.81, no.822, pp.14-00486-14-00486, 2015 (Released:2015-02-25)

参考文献数

13

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Nowadays, industrial dual-arm robots have gained attention as novel tools in the factory automation field for anext generation. We therefore focus on them to flexibly control both the linear motion and the rotational motion of a working plate. However, there has been one problem that it is difficult to measure the synchronous accuracy of two rotary axes without high accuracy gyro sensor. Thus, we proposed a novel method to measure the synchronous accuracy of two rotary axes of working plate with a ball, which keeps a ball rolling around a circular path on it by dual-arm cooperative control and demonstrated that a proposed method is effective to estimate its motion of frequency response. In present report, for widening the range of applications, we tried to keep a ball rolling around rhomboid path which is one of polygonal path on working plate by dual-arm cooperative control and to investigate its characteristic.

著者

西田 勇 前田 正登 川野 常夫 白瀬 敬一

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.82, no.840, pp.16-00006-16-00006, 2016 (Released:2016-08-25)

参考文献数

11

被引用文献数

1

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For several decades, factory automation or unmanned factory productivity has been progressed to realize much higher productivity in manufacturing. However, human centered manufacturing system is getting attention to realize much more flexibility for manufacturing of wide product variety and volume. So it is necessary to provide the safe and efficient environment to workers considering their own physical properties. This study investigated a mechanism of muscle fatigue and proposed a muscular fatigue model to evaluate muscle fatigue progress under several muscular force patterns. Previous studies have already proposed a muscular fatigue model. However, these previous studies discussed about the condition of maximum voluntary contraction. The new point of this study is considering several muscular force patterns including muscle recovery progress. This study proposed the method to estimate the endurance times for keeping constant forces considering the physical characteristics. This study also proposed the method to estimate the iteration numbers for keeping constant forces with interval. To validate the effectiveness of the proposed method, experimental verifications were conducted. The experimental results had a good agreement with the evaluation of muscle fatigue progress using the proposed method although it is necessary to consider the method to raise the precision of determining the physical parameters and the method to decrease the dispersion of experiments derived from the subjective judgement of participants. Success of resolving these issues will provide ergonomically safe and efficient working environments considering the physical properties of each worker.

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

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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

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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

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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

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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.