著者

梅田 綾子 清水 悦郎 南 健悟 三好 登志行

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.84, no.860, pp.17-00464, 2018 (Released:2018-04-25)

参考文献数

20

---

In recent years, engineering technology has become essential for our daily life. We cannot live without civil engineering or information technology even for one day. At the same time, as utilizing technologies sometimes infringe human rights, many laws and regulations exist in our society. In spite of importance to collaborate with legal experts for engineer to realize implementation of their new technologies into society, and a lot of efforts of the Professional Committee of Law and Technology in the Japan Society of Mechanical Engineers, it has not been understood in Japan for a long time. Many issues have been discussed relating to the growing concern about autonomous vehicles, but it seems insufficient from the view of legal and engineering collaboration. In this paper, a case study is introduced that is an example of legal engineering showing countermeasures for legal issues to realize autonomous shipping performed by Robotics Laboratory in Tokyo University of Marine Science and Technology. Furthermore, knowledge obtained by this case study is proposed as legal engineering which presents how engineers may identify legal issues and perform risk assessment of their developing technologies. By communicating with legal experts, engineers might be able to perform technology development with legal risk mitigation and take a role for rulemaking especially in the field of soft-law.

著者

熊谷 正芳 石渡 正人 大谷 眞一

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.84, no.863, pp.18-00139, 2018 (Released:2018-07-25)

参考文献数

18

---

Residual stress measurements on pipe-shaped Ni-alloy, Inconel 625, were conducted. The pipes were made from a thin plate by roll-bend and weld along longitudinal direction of the pipe. Shot peening processes were performed to the outside surface of the pipes. The stresses were measured using X-ray stress measurement method. The residual stresses on the specimen before shot peening process were around 100 MPa toward longitudinal direction and around 250 MPa toward transvers direction to the welding direction. The residual stresses changed to 800 MPa in compressive by shot peening process. After thermal aging at 1173 K for 1 and 10 hour, the residual stresses changed to −100 MPa on the specimens with and without shot peening in both longitudinal and transvers directions. In addition, optical microscopic observation and the analyses of X-ray diffraction peaks were performed to reveal microstructural features due to welding, shot peening, and thermal aging. Equiaxed and columnar dendrites were generated in the center and the outer of fusion zone, respectively. The grains in the heat affected zone, between the fusion zone and base metal became larger. The grains near the surface even in welds became small by shot peening processes according to analyses of X-ray diffraction peaks. Even though induced compressive residual stresses were released during thermal ageing, refined grains had been smaller than before shot peening process.

著者

川那辺 洋 石山 拓二 塩路 昌宏

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.856, pp.17-00294-17-00294, 2017 (Released:2017-12-25)

参考文献数

5

---

Entrainment process of surrounding fluid for a diesel spray is investigated based on the momentum theory and 1-D simple spray model developed by Musculus et. al. Entrained fluid distribution along the spray axis is theoretically estimated. The results show that the absolute value of entrainment velocity depends on axis location and is inversely proportional to the distance from the nozzle. Therefore, the large amount of entrained fluid comes from the upstream region near field of nozzle. 1-D simple spray model is performed for the same target and the effect of the injection rate on entraining process is clarified.

著者

山本 勝太 牧野 一成 石塚 弘道

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.856, pp.17-00337-17-00337, 2017 (Released:2017-12-25)

参考文献数

10

---

The integrity of railway axles is a critical aspect for ensuring the safety of a railway system. Therefore, non-destructive inspections such as ultrasonic testing and magnetic particle testing are conducted periodically. Some railway operators conduct ultrasonic tests directly on axles mounted on the train. However, the axles have to be disassembled for conducting magnetic particle testing. In the present study, the effects of variable amplitude stress acting on cracks and axle bending stress during ultrasonic test on ultrasonic response are discussed. An ultrasonic test was conducted using a full-scale axle specimen that had fatigue cracks and no artificial notches. The ultrasonic response was evaluated for the cracks whose lengths were 10 mm, 16 mm, and 19 mm. Under an unloaded condition, the ultrasonic response for the 16-mm-long and 19-mm-long cracks was approximately 4 or 7 times higher than that for the 10-mm-long crack, although the cross-sectional area of each of these cracks was approximately 2.5 or 3.5 times larger than that of the 10-mm-long crack. The obtained results indicate that the contribution of the reflection area to the ultrasonic response under a variable amplitude stress differs from that under a constant stress condition. Moreover, the influence of axle bending stress ranging between -50 MPa to +47 MPa on the ultrasonic response was investigated. A higher bending stress led to a higher ultrasonic response. However, the decreasing rate of ultrasonic response caused under compressive stress was lower than the increasing rate under tensile stress. For example, the ultrasonic response was approximately 2 dB lower than that under the unloaded condition at a compressive stress of -30 MPa; however, the ultrasonic response showed an increment of approximately 4 dB at a tensile stress of 30 MPa. A similar trend was observed in the crack of each length. The results denote that the crack position influences the precision of crack detection in ultrasonic inspection. However, considering that the maximum static bending stress of axles used in Japan is 30 MPa, its effect on inservice axle inspection is negligible.

著者

中川 健一 長谷川 裕晃 村上 正秀 大林 茂

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.856, pp.17-00165-17-00165, 2017 (Released:2017-12-25)

参考文献数

13

被引用文献数

1

---

Badminton is one of the most popular sports in the world and is famous as the sport having the fastest initial velocity of a batted ball among all ball games. Initial velocity immediately after smashing may reach up to 408 km/h (113 m/s) at maximum. A badminton shuttlecock generates significant aerodynamic drag and it was confirmed that the high deceleration characteristics was related to the slots located at the leg portion of a shuttlecock in the previous study. Turnover refers to the flipping experienced by a shuttlecock when undergoing heading change from nose pointing against the flight path at the moment of impact and a shuttlecock indicates the aerodynamically stable feature for the flip movement just after impact. The purpose of this study is to investigate the effect of gaps on the aerodynamic stability (turnover stability) of a badminton shuttlecock during the flip phenomenon. In the present study, the flow field around the shuttlecock during impulsive change of an angle of attack (flip movement) was measured by using the smoke flow visualization and the behavior of the shuttlecock during the flip movement was evaluated in comparison with that of the conic model (with no gaps). The turnover stability of a badminton shuttlecock is affected by gaps of the shuttlecock skirt.

著者

鈴木 明宏 茂庭 優貴 石井 賢治 藤原 誠助 永富 良一

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.849, pp.16-00450-16-00450, 2017 (Released:2017-05-25)

参考文献数

10

---

Amount of daily physical activity is strongly associated with the prevalence of lifestyle-associated diseases, and thus maintaining a certain level of physical activity is recommended. Amount of physical activity, namely energy expenditure, is commonly estimated from linear regression analysis of oxygen uptake during steady-state exercise of different intensities. Short-duration exercise, mainly walking lasting less than 3 minutes, has been reported to account for over 90% of the daily energy expenditure of healthy adults. The estimation of energy expenditure by ACSM Metabolic Equations used well, however, is based on steady-state exercise of more than 5 minutes, and energy consumption of shorter duration exercise is not commonly considered. Oxygen consumption remains elevated for some period of time after exercise. Then, the estimation of energy expenditure for short duration exercise must include excess post-exercise oxygen consumption (EPOC). The amount of EPOC change in duration exercise. Therefore, we attempted to elucidate the energy expenditure for VO2 kinetics. Ten healthy participants aged 19-54 y walked and ran for 1, 3 and 5 minutes on a treadmill at constant speed. Oxygen consumption during and post-exercise was measured using a portable gas analyzer in breath-by-breath mode. A best-fit exponential equation to estimate oxygen consumption from exercise duration and walking speed was generated. The root mean square (RMS) of estimate equations was calculated using Leave-one-out cross validation. The RMS(1.44~2.14 ml/kg/min) was lower, and the results of the Bland-Altman analysis revealed neither fixed nor proportional bias with the exception of the decent walking and running. An equation for the estimation of oxygen consumption at shorter durations of exercise was successfully generated. Accumulation of additional data may further improve the equation.

著者

橋本 博文 今井 栄一 矢野 創 渡辺 英幸 横堀 伸一 山岸 明彦

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

2016

被引用文献数

1

---

The mechanical thermometer using a bimetallic strip coil was developed for the Tanpopo mission. The Tanpopo mission is a multi-year passive exposure experiment for astrobiology exposure and micrometeoroid capture onboard the Exposed Experiment Handrail Attachment Mechanism (ExHAM) at the Japanese Experiment Module 'Kibo' (JEM) Exposed Facility (EF) on the International Space Station (ISS). The Tanpopo mission apparatuses were launched by the SpaceX-6 Dragon CRS-6 on April 14 2015, from the Cape Canaveral Air Force Station in the U.S.A. Since its microbial exposure experiment requires recording the maximum temperature that the Tanpopo exposure panel experiences, we have developed a mechanical thermometer with no electric power supplied from the ExHAM. At a given time and orbital position of the ISS, the thermometer indicator was video-imaged by the extravehicular video camera attached to the Kibo-EF and controlled from the ground. With these images analyzed, we were able to derive the maximum temperature of the Tanpopo exposure panels on the space pointing face of the ExHAM as 23.9±5 °C. Now this passive and mechanical thermometer is available to other space missions with no electric supplies required and thus highly expands the possibility of new extravehicular experiments and explorations for both human and robotic missions.

著者

松本 浩乃 窪田 佳寛 大石 正行 望月 修

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.833, pp.15-00389-15-00389, 2016 (Released:2016-01-25)

参考文献数

13

---

The typhoon often causes a serious damage of the apple before harvest. Many apples fall from trees by the strong wind. These apples are bagged to protect them from insects and control sun light for the apples coloring while they are ripening on the tree. We conceive that the wind-force acting on the bagging apple exceeds one without bag. Thus, we investigate the drag coefficient CD of the bagging apple by measuring drag force acting on an apple model experimentally. The shear stress on a stem under the typhoon is estimated for understanding one of mechanism for dropping apple due to the strong wind. The shear stress of a stem whose apple encounters the maximum velocity recorded at the past typhoon is estimated by the obtained CD. The drag force of the bagging apple becomes bigger than that of the apple without the bag. The bagging apple is not a rotational symmetry so that the CD is different with the different wind direction. The angle against the flow of model with the bag is changed from 0 deg. to 90 deg. to understand the influence of shape, since CD depends on the geometry. The shear force acting on the stem depends on the drag. Thus, the shear stress is larger if the drag is larger. The obtained shear stress is compared with allowable shear stress of a real tree. We suggest that there is possibility to decrease damage if we can decrease the drag of the bagging.

著者

円山 重直

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.80, no.820, pp.TEP0377-TEP0377, 2014 (Released:2014-12-25)

参考文献数

30

被引用文献数

1

---

In order to investigate the process of accident of Fukushima Nuclear Power Plants, an accident scenario of Fukushima Daiichi Nuclear Power Plant, Unit 1 is analyzed from the data open to the public. Phase equilibrium process model and adiabatic expansion model were introduced. Original data reported in the first stage of the accident were examined to clarify the behavior of the isolation condensers (ICs) which are generally believed unfunctional after the arrival of Tsunami and station blackout. The original data and observation reports verified that the so called “fail safe” system to close the valves in IC did not work properly due to the shutdown of AC power. The reports also showed the evidence that the operators injected water to the storage tank of IC. We proposed a scenario that IC was operational until approximately at 3/12 3:00, small leakage occurred at the reactor pressure vessel (RPV) at the initial stage of the accident, the RPV ruptured at 3/12 6:20, and it ruptured again in approximately at 3/12 16:00. We assumed that PCV ruptured at 3/12 3:00, and the area of rupture did not change after the hydrogen explosion occurred at 3/12 15:36. The present analysis model describes the data measured at the accident, and many evidences and witnesses reported at the early stage of the accident. We also simulated according to the scenario of Tokyo Electric Power Company (TEPCO) that the ICs did not work after the Tsunami arrival. The estimation by the present analysis agrees with the TEPCO's one, however, there are many discrepancies that cannot explain the behavior of the reactor accident.

著者

水野 湧太 熊谷 正芳 田邉 晃弘 新部 純三

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

pp.23-00242, (Released:2024-01-11)

参考文献数

11

---

Since it is known that tensile strength and hardness are roughly proportional, a hardness test is often used as a simple and substitute test. However, it has been reported that the proportional relationship between tensile strength and hardness is broken above 595 HV (≈55 HRC). Besides, there are few examples of mechanical properties determined by compression tests despite the fact that high-hardness and high-strength materials subjected to significant compressive stress are used in machine element parts, e.g. bearings. Tensile strength is used instead of compressive strength for the design. Thus, the relationship between hardness and compressive strength in hard materials, quenched medium carbon steel, was revealed. The compressive strength at 8% plastic strain (compressive strength) was almost the same as the maximum compressive strength. The compressive strength and hardness were at their maximum in the as-quenched specimen and decreased with the increase in tempering temperature. The compressive strength and hardness had a linear relationship up to 2000 MPa similar to the relationship of tensile tests. However, the compressive strength increased slightly in relation to the hardness above 2000 MPa in contrast to tensile tests. Thus, the work-hardening index was introduced as a variation parameter to the function that expresses the relationship between compressive strength and hardness to obtain better estimation. The estimated compressive strengths using the work-hardening index are agreed well to the experimental results.

著者

酒井 忍 保富 大輔 史 金星 浦上 晃 溝口 正人

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.85, no.877, pp.19-00118, 2019 (Released:2019-09-25)

参考文献数

19

---

In rubber baseball games, when the rubber ball is hit by a baseball bat, the rubber ball is deformed greatly comparing to an official baseball ball, and the batted ball speed decreases due to the energy loss during the deformation. Since the new rubber ball has been applied in games from 2018, the material properties and the restitution characteristics of the new rubber ball attract plenty of attention among scholars. In this study, the difference of the material properties and the restitution characteristics between the new and old rubber balls is investigated deeply by the static compression and collision tests. According to the static compression test, we find that the new rubber ball is harder and more difficult to generate deformation than the old one. In the collision test, the rebound ball speeds of both of the new and the old balls become faster when using a smaller diameter of steel cylinder instead of baseball bat, and the rebound ball speed of the new ball is slower than that of the old one under the same experimental conditions. Furthermore, to develop high performance baseball bats adapting to the new rubber baseball, the diameter of the baseball bat is studied by the impact simulation based on the finite element analysis. In the simulation, the batted ball speed under the analytical conditions of different offset heights and different barrel diameters of the bat are evaluated considering the initial spin. As a result, the batted ball speed generated by the bat with diameter φ55 mm is faster than generated by the bat with diameter φ70 mm when the offset height range is smaller than 14.6 mm, so that the bat diameter φ55 mm is recommended according to the present work.

著者

山藤 勝彦 山本 建 澤田 賢治

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.852, pp.16-00553-16-00553, 2017 (Released:2017-08-25)

参考文献数

11

被引用文献数

1

---

This paper describes self-excited oscillation caused by coulomb friction of electromagnetic proportional valve. Especially, this research focuses on a hydraulic system in which electromagnetic proportional and pressure proportional valves are located tandem. In the system, the coulomb frictional force effects on the displacement direction of the spool of the former valve and the piston is established in the downstream region of the latter valve. Each valve is stable, but, the connection of them causes instability. This paper analyzes the mechanism of this unstable vibration and then investigates an anti-vibration design method. In analysis, this paper clarifies that the vibration is caused by an elastic deformation delay of the oil in the piston. This delay increases the phase delay of the spool due to the coulomb frictional force. After replacing the coulomb frictional force with hysteresis, the proposed method uses the describing function method to express phase delay phenomenon due to the coulomb frictional force. The describing function is the complex function which expresses an amplitude ratio and phase difference with the input and output of nonlinear element. The delay of a vibration factor is linearized by converting coulomb friction into hysteresis. The effectiveness of the proposed method is demonstrated via practical experiment and non-linear simulation results.

著者

多田 海斗 平塚 将起 伊藤 慎一郎 瀬尾 和哉

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.89, no.924, pp.23-00045, 2023 (Released:2023-08-25)

参考文献数

15

---

The paper describes the critical Reynolds number of soccer balls as a function of the total groove volume on the ball surface. In this study, the aerodynamic drag and separation point of 6 soccer balls with different panel orientations were measured in a wind tunnel. Moreover, the total volume of grooves on the ball’s surface was measured by One shot 3D measuring machine. It was found that the drag coefficient in the supercritical region and the critical Reynolds number depend on the design of the ball surface (shape, number of panels, surface roughness). A negative correlation exists between the total groove volume on the surface and the critical Reynolds number. When the total groove volume is large, the drag in the supercritical region increases. The position of the separation point does not change in the subcritical and supercritical regions even if the orientation of the panel is changed. However, when the groove width is wider, the panel orientation dependence becomes significant in the supercritical region. In the transition region, the position of the separation point differs depending on the panel's orientation.

著者

小川 渉 鞍谷 文保 吉田 達哉 小出 俊雄 水田 泰次

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.86, no.881, pp.19-00237, 2020 (Released:2020-01-25)

参考文献数

10

被引用文献数

2 2

---

Cymbals are percussion instruments that vibrate and radiate sounds when hit with a stick. A bell is the raised section in the middle of the cymbal and its size produces different sounds. In this study, we investigate the effect of bell size on the sound characteristics of cymbals. The radiated sounds and vibrations for cymbals with two different bell sizes are measured. In addition, the natural frequency and mode shape are obtained by finite element analysis and the sound radiation efficiency is calculated for each mode. The measured results indicate that the sound frequency characteristics for the large bell show three peaks with large sound pressure within the range of 1000 to 3000 Hz and the sound pressure for the small bell is larger than that for the large bell within the range of 4000 to 5000 Hz. The vibration frequency characteristics show there is no remarkable difference between the large and small bells. The sound radiation efficiencies indicate that the large bell has many modes with high radiation efficiency within the range of 1000 to 3000 Hz and their modes have a small number of nodal diameters and a large deformation at the bell. The small bell has many modes with high efficiency within the range of 4000 to 5000 Hz. This is reason for the difference in sound characteristics between the large and small bells.

著者

鞍谷 文保 北林 研人 小川 渉 吉田 達哉 長村 光造 小出 俊雄 文珠 義之 水田 泰次

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.851, pp.17-00110, 2017 (Released:2017-07-25)

参考文献数

13

---

Cymbals are percussion instruments that vibrate and radiate sounds when hit with a stick or when used in pairs. The sound radiated from a cymbal depends on its vibration characteristics. Cymbals are made through spin forming, hammering and lathing processes. The spin forming creates the domed shape of cymbals, determining the basic vibration characteristics. The hammering and lathing make specific sound quality adjustments by changing the vibration characteristics. In this paper, we focus on how the hammering affects the cymbal's vibration characteristics. The hammering produces many shallow dents over the cymbal's surface, generating residual stresses in it. These residual stresses change the vibration characteristics. We perform finite element analysis of the hammered cymbal to obtain its vibration characteristics. In the analysis, we use thermal stress analysis to reproduce the stress distribution and then with this stress distribution we perform vibration analysis. The results show that the effects of thermal load (i.e., hammering) vary depending on the mode: an increase or decrease in the natural frequency. As a result, the peak frequencies and their peak values in the frequency response function change.

著者

西川 友弘 綿貫 啓一 楓 和憲 村松 慶一 増子 直也

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.86, no.890, pp.20-00034, 2020 (Released:2020-10-25)

参考文献数

46

---

This study aims to examine the benefit of visual fatigue evaluation based on prefrontal cortex (PFC) measurement by near infrared spectroscopy (NIRS), and to evaluate fatigue on various colored LED backlit text. In our method, eight adult participants read a LED backlit text 10 minutes in a dark room. Before and after task, subjective fatigue questionnaire “Jikaku-sho shirabe”, subjective visual fatigue questionnaire (SVF), and the critical flicker-fusion frequency (CFF) were measured. The time-course of oxy-Hb in the PFC was measured using a 22-channel NIRS. Heart rate variability (HRV) was measured to access an autonomic nervous system balance. Six types of white LEDs were used for backlighting: general white as a control (W), high color-rendering white (WH), bluish white (WB), reddish white (WR), greenish white (WG), and yellowish white (WY). In our results, correlation analysis suggested that the development of central fatigue is related to deactivated condition in the mPFC, and the development of subjective visual fatigue is related to deactivated condition in the LPFC. In comparison between LED treatments, in WH condition, high subjective central fatigue, CFF decay and LF/HF were revealed, and the PFC inactivated. In WG condition, low subjective central fatigue and CFF decay revealed. Our findings suggested that participants get tired on high color-rendering white LED backlit text, and were less tired in greenish white LED backlit text. Also, NIRS provides benefits in the evaluation of visual fatigue.

著者

中出 孝次 佐久間 豊 梶島 岳夫

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.87, no.893, pp.20-00366, 2021 (Released:2021-01-25)

参考文献数

11

被引用文献数

1 1

---

To clarify the mechanisms underlying airflow-induced vibrations of high-speed trains running through tunnels, large-eddy simulation of a large-scale flow structure around a simplified 6-car train model was conducted. Since actual trains run on one of the double track lines, the position of the train model was made to deviate from the tunnel center and hence the gap between one of the sides of the train and the tunnel wall is narrower than that of the other side. A train running in the open air was also calculated for comparison. The results of this study shed light on the generation mechanism of the pressure fluctuations acting on the side of high-speed trains as follows. Firstly, in the open air, the air velocity in the space between the underbody and the ground gradually decreases from the head toward the tail of the train. Thus, the air velocity is slower than that on both sides of the train, which generates shear flows near the bottom edges of both sides of the train. The shear flows cause large Karman vortex-like vortices (staggered Karman vortex street), which in turn lead to a meandering airflow beneath the underbody of the train. Secondly, in the tunnel, the air velocity not only in the gap between the underbody and the ground but also in the narrower gap between the side of the train and the tunnel wall gradually decreases from the head toward the tail of the train. In the same mechanism as the open air, a meandering airflow is generated throughout the side and underbody of the train and causes pressure fluctuations along the side of the train. Finally, it is demonstrated that the wavelength of pressure fluctuations along the side of the actual train can be estimated from the present LES results.

著者

佐藤 優也 原田 研介 酒田 信親 万 偉偉 ラミレス イクシェル

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.84, no.861, pp.17-00546-17-00546, 2018 (Released:2018-05-25)

参考文献数

19

被引用文献数

1

---

In this paper, we propose a novel two-stage approach on picking an object from randomly stacked pile. We especially consider a situation where it is difficult for a 3D depth sensor to identify the pose of objects such as shinny ones and black ones. For such objects, our method first roughly grasps some of the objects from the pile without using the visual information and roughly place them onto a working table. After some of the objects are placed on a working table, a robot picks one of them by detecting the 2D position of objects placed on a working table by using the 2D RGB image. We performed experiments for several objects with different shape and weight. Through experimental study, we confirmed that a robot can identify the position of one of the objects after the objects are placed on a working table and that one of the objects can be successfully picked up by a robot.

著者

鈴木 栄司

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

pp.21-00336, (Released:2022-06-23)

参考文献数

7

---

Jitter Ring is the popular toy which has another name called as “Chatter Ring” or “Gyro Ring”. This toy is composed of a circular ring and the washer inserted into the ring. Just after supplying the washer with an initial angular velocity, the player of this toy has only need to wheel the ring in the vertical state by handling each hand alternately. Then, the washer will continue to rotate with fluctuation by this operation. Further the player will feel the oscillating response through the driving hands. This rotatory motion of the washer is somewhat complicated and the analyses tried up to now concerning this motion don’t almost appear in public. Consequently the author thought that there were the significant meanings in the dynamic analysis for this motion of the washer. Considering the friction between the ring and the washer, he performed the three-dimensional analysis by regarding the washer as the rigid body without a fixed point and adopting Eulerian angles in this research. As a result, the actual behavior with fluctuating rotation of the washer was confirmed by the numerical analysis. Furthermore, he investigated the influence on the motion of the washer by varying each value of parameters in this system.

著者

金子 友暁 横山 博史 佐藤 充 西川原 理仁 柳田 秀記

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

pp.22-00044, (Released:2022-05-25)

参考文献数

16

---

For a small axial fan in a duct, the effects of acoustic resonance occurring in the duct on the flow around the fan are focused on. To clarify the condition for the intense acoustic resonance, the effects of the rotational speed and duct width on the flow and acoustic fields around the fan were investigated by compressible flow simulations with a volume penalization method. The computational methods were validated by comparing the predicted static pressure rise and aerodynamic sound by the fan with those measured. The sound pressure level became most intense for a specific rotational speed, where the acoustic resonance occurs at the blade passing frequency in the upstream duct. Although the overall tendency of the increase in the static pressure coefficient was found for a higher rotational speed with the thinner momentum thickness around the blade surface, the static pressure coefficient drops at the rotational speed for the acoustic resonance. Moreover, the acoustic resonance became more intense for a narrower duct width. In this condition, flow disturbances occur near the wall of the bell-mouthed inlet of upstream duct due to the acoustic resonance, which prompts the inflow turbulence to the fan. To clarify the effects of the acoustic resonance on the flow around the fan, the computation with the artificially suppressed acoustic resonance was also performed and the predicted flow fields were compared with those with intense acoustic resonance for the same rotational speed and duct width. The incoming flow to the fan is confirmed to become more turbulent when the acoustic resonance occurs, which promotes the spreading of the tip vortices between rotor blades. As a result, the blade loading decreases and the turbulence in the blade wake leading to mixing loss becomes intense, causing the static pressure rise by the fan to decrease.