著者

Ayane KUSAFUKA Naoki TSUKAMOTO Kohei MIYATA Kazutoshi KUDO

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

pp.23-00220, (Released:2023-11-15)

参考文献数

22

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In human motion capture systems, reflective markers attached to the body have been widely used to track motion using optical cameras. However, when the speed of motion increases, because the brightness and angle of view of the camera are limited, and the markers often fall off, particularly of detailed body parts such as fingers in full-body movements, other parts of the body (palms) have been investigated. This study attempted to acquire finger movements during a high-speed throwing task without attaching markers using automatic image recognition technology based on deep learning (DeepLabCut) and verified its accuracy compared to conventional methods. As a result, the absolute distance between the 3D coordinates obtained from the two motion capture systems was an average of 15.5 to 29.4 mm depending on tracked points, and the correlation coefficients between them ranged from 0.932 to 0.999. Therefore, the shapes of the time-series profiles of the 3D coordinates obtained from the two motion- capture systems were similar. These results suggest that motion measurement using markerless motion capture is possible in environments where conventional motion capture systems are difficult to use.

著者

Jun YOSHIDA Eito MATSUO Yasuyuki TAKATA Masanori MONDE

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.6, no.3, pp.18-00388, 2019 (Released:2019-06-15)

参考文献数

8

被引用文献数

4

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This paper introduces a new hydrogen refueling system with a micro-scale hydrogen turbo-expander that enables us to replace a conventional low temperature refrigerator. From the process simulation of hydrogen refueling to the tank of a typical Fuel Cell Vehicle (FCV), the system is thermodynamically verified to be capable of refueling 5 kg-H2 within 3 minutes by the direct expansion in the micro-scale hydrogen turbo-expander. For the realization of this new concept, a process design approach of a high pressure hydrogen refueling system with the micro-scale hydrogen turbo-expander is described. In this process design, a turbine-compressor type is adopted to the micro-scale hydrogen turbo-expander unit, and an extracted power from the turbine side is consumed as a compressor power which is equipped on the opposite side of the turbine rotor. As a consequence of the thermodynamic analysis and simulation for the proposed system including the turbo-expander with adiabatic efficiency around65 %, it reveals that the new system provides some significant advantages compared with the conventional process. From a feasible investigation of this system, several advantageous features such as 1) high energy conservation, 2) compactness, 3) initial cost and operation cost, and, 4) system expandability (modification for shorter time refueling) are also described when it is compared with the existing system.

著者

Shin-etsu SUGAWARA

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

pp.23-00375, (Released:2023-12-07)

参考文献数

53

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The recent trend of nuclear reactor miniaturization may require reconsideration of the existing framework of safety. This study conceptually explores the safety goals for transportable microreactors (TMRs) by focusing on the differences between large light-water reactors (LLWRs), which contain large amounts of hazardous fission products and TMRs. For LLWRs, the safety goals and surrogate goals representing the integrity of the reactor have played a significant role in reducing the negative health effects of radiation exposure in cases of nuclear disasters. Practitioners, notably the operator, have typically been classified as the main users of these goals. However, the innovative feature of TMRs will lead to the reconsideration of the contents and users of safety goals. The size of the radiological consequences of TMR accidents may highlight the need to capture broader consequences other than direct health effects when formulating the top-level goals. Correspondingly, additional surrogates for representing the interplay between the reactor and surrounding areas may be required. Effectively meeting these new goals only by the efforts of licensees may be a challenge; this indicates a need for the local actors wherein the TMRs are deployed to become the extended users of safety goals. Conceptualizing such new framework of microreactor safety goals as “extended safety goals” as an extension of conventional safety goals for LLWRs, the author discusses their implications and challenges.

著者

Motomu NAKASHIMA Yohei CHIDA

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.8, no.5, pp.21-00230, 2021 (Released:2021-10-15)

参考文献数

10

被引用文献数

2

---

In skateboarding as a sports event, the riders compete in difficulty and completeness of acrobatic motions called “tricks”. As a basic trick, Ollie is performed popularly. However, the basic mechanical principle of the Ollie has not been discussed to date, especially for the Ollie jump (the jumping phase of Ollie). The objective of this study was to elucidate the mechanism of Ollie jump in skateboarding. A simulation model was firstly constructed on a multibody dynamics analysis platform. Next, an experiment using an actual rider was conducted to acquire the motion of the feet during the Ollie jump. By inputting the acquired motion of the feet into the model, a simulation of Ollie jump was carried out. In addition, a parameter study with respect to the geometry of the skateboard and the motion of the rider’s feet was conducted. It was found that the simulated Ollie jump was successful since the skateboard reached a sufficient height and became sufficiently horizontal at the peak height. It was also found that the Ollie jump can be divided into five stages from the mechanical point of view. From the parameter study, it was found that large kick angle of the deck or large distance between two trucks of the deck might cause difficulty in the contact of the tail and the ground, while small kick angle or small distance between two trucks might result in excessive rotating angle of the deck. In addition, three important points for a successful Ollie jump were found to be, to produce sufficiently fast rotational movement of the skateboard around the rear wheels, to separate both feet from the deck before the tail of the deck hits the ground, and to separate the rear foot from the deck at the final stage.

著者

Mai NONOGAWA Seigo NAKAYA Masashi ISOBE Kenzen TAKEUCHI Hideyuki AZEGAMI

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

pp.21-00200, (Released:2021-09-05)

参考文献数

29

---

This study presents methods to develop a three-dimensional numerical foot model and to identify the loading condition that is used to design a stable sole for running shoes. In a previous study, the authors proposed a method to optimize the shape of the sole to increase stability while maintaining the cushioning property. In the problem formulation, the loading condition was given as a boundary force distributed on the top surface of the sole. The aim of this study is to replace the loading condition with the force and moment at the origin of the ankle joint coordinate (AJC) system by modeling a foot with a finite element model. A finite element model of a foot is constructed using X-ray CT image data, and consists of bony structures, soft tissue, and plantar fascia. The plantar fascia is set at the bottom of the bony structures. The force and moment used in the finite element analysis are identified by inverse dynamic analysis using an experimental measurement in the practical operation of the ground reaction force (GRF) when the GRF in the direction of the foot length becomes minimum. In the finite element analysis, the finite deformation containing the contact condition between the bottom surface of the foot and the ground representing a sole made of resin is considered. For an index of the shoe stability, we define a heel eversion angle (HEA) by the rotational angle of the heel with respect to an axis in the foot length direction and evaluate it by finite element analysis. The validity of the finite element foot model as well as the force and moment obtained in this study are confirmed based on the agreement in the HEA results between the experiment and finite element analysis.

著者

Shinichiro UESAWA Susumu YAMASHITA Mitsuhiko SHIBATA Hiroyuki YOSHIDA

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.5, no.4, pp.18-00115, 2018 (Released:2018-08-15)

参考文献数

17

被引用文献数

2

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A dry method is one of fuel debris retrieval methods for decommissioning of TEPCO’s Fukushima Daiichi nuclear power station. However, the cooling of fuel debris must be fully maintained without water. Japan Atomic Energy Agency (JAEA) has evaluated the air-cooling performance of the fuel debris in the dry method by using JUPITER. Because JUPITER can represent the relocation of the corium, the unknown parameters, such as the composition and the position of the fuel debris at the RPV pedestal, can be reduced. By calculating the heat transfer of the fuel debris based on the corium relocation obtained with JUPITER, more accurate analysis of the air-cooling performance of the fuel debris in the dry method is expected. In order to evaluate the air-cooling performance of fuel debris in the dry method by using JUPITER, the validation of the free-convective heat transfer analysis of JUPITER were performed in this paper. In order to qualitatively evaluate results of JUPITER for configurations closer to experimental conditions and to decide physical values and positions to be measured in the validation, JUPITER was compared with OpenFOAM for the simple cuboid configuration which has the heating and cooling surfaces at the floor and the ceiling, respectively. The comparison proved that JUPITER can calculate the vertical temperature distribution as well as OpenFOAM on the condition of the lower heating amount. In the validation, JUPITER was compared with the heat transfer experiments of free convection in air adjacent to an upward-facing horizontal heating surface. The comparison proved that JUPITER was in good agreement with the experiment on the condition of the lower heating-surface temperature. The result indicated that JUPITER is a helpful numerical method to evaluate the free-convective heat transfer of the fuel debris in the dry method.

著者

Yutaka OKAMOTO Masafumi OKADA

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.10, no.6, pp.23-00200, 2023 (Released:2023-12-15)

参考文献数

17

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In excavation by hydraulic excavators, automation of excavation is effective in reducing the burden on operators and improving work efficiency. This paper focuses on automatic control of the weight of excavated soil. To control the weight of excavated soil, a soil dynamic model is required. However, the interaction between soil and bucket is complex and computationally expensive, making it unsuitable for real-time control. In this paper, we propose a dynamic model of excavation based on the experimental data of the weight of excavated soil and the workload done by the bucket. In addition, a differential equation that expresses the relationship between the data is derived. Based on the proposed model, a control method is also proposed to achieve the reference weight of excavated soil by changing the dragging length, assuming that the power done by the bucket during excavation is equivalent to the swept volume. Furthermore, we evaluate the effectiveness of the proposed method by excavating under several soil conditions using the proposed method.

著者

Katsuhiko SANDO Takeshi YAMAMOTO Kenji SAWADA Tomoyuki TANIGUCHI Nobuyuki SOWA Hiroki MORI Takahiro KONDO

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.8, no.2, pp.20-00497, 2021 (Released:2021-04-15)

参考文献数

11

被引用文献数

1

---

This paper describes a design method of a friction reducer device using a loading cam to suppress unstable vibration. Nonlinear simulation and energy analysis of numerical solutions demonstrates that destabilization is caused by the large phase difference between the slipping velocity in the translation direction and that in the rotation direction. It was found that similarly unstable vibration occurs in various structures using wedge rollers with translational and rotational motion. The analytical equation could be simplified by focusing on the motion factor that affects the slip velocity of the power transmission surface, which is the factor of vibration. Consequently, the design method for suppressing vibration could be expressed by a mathematical formula. This equation is validated by using the results of experiments conducted in the previous work of the current authors. Furthermore, from this equation, we proposed that vibration could be suppressed by the parameter balance of the power transmission device without using damping. The power transmission surface slips when a quick torque is input and damping is used. The proposed design can handle a quick torque response and reduce the weight of the reducer. Specifically, the shape of the wedge roller is made lighter, so that the moment of inertia of the roller is not lowered, or the wedge roller is set as a small roller.

著者

Shugo MIYAMOTO Seiichi KOSHIZUKA

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.10, no.5, pp.23-00127, 2023 (Released:2023-10-15)

参考文献数

18

---

Computational fluid dynamics has been widely used in the design and analysis of various fluid systems. The proper treatment of boundary conditions is crucial for the accurate simulation of fluid flow. However, in particle methods, such as smoothed particle hydrodynamics method and moving particle semi-implicit method, the treatment of boundary conditions has been a challenging problem. In this paper, starting from the incompressibility condition, we present a new theory for the unified treatment of both rigid bodies and wall boundaries, which allows the strong coupling of rigid bodies and incompressible fluids. Because the boundary models are based on signed distance functions and do not use particles, these models can avoid several problems, such as resolution dependence of particle representations, and unavoidable unevenness of surfaces. We also provide a way to efficiently handle rigid-body boundaries and wall boundaries without particles by finding the fundamental boundary weight function that does not change with time. Several numerical examples are presented to demonstrate the capability of our models and to compare them with theoretical and experimental results.

著者

Haoran GENG Masafumi MIYATAKE Qingyuan WANG Pengfei SUN Bo JIN

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

pp.22-00360, (Released:2023-05-23)

参考文献数

16

---

The timetable of urban rail greatly affects its daily energy consumption. To improve the utilization of renewable energy between trains using timetabling has become an effective way to reduce energy consumption. Previous studies ignore or simplify the modelling of traction power supply network, which failed to accurately describe the flow of energy between trains through the power network. This paper proposed an optimisation method of energy efficiency timetabling considering the power flow of traction power supply network. First, an urban rail transit DC traction network model is established, and the current-vector iterative method is used to characterize the energy consumption. Then, a train timetable optimisation model is proposed to minimize the total energy consumption of the traction network system by adjusting the dwell time and section running time. The genetic algorithm is used to solve the optimisation problem. Finally, simulation result shows that the proposed method can accurately characterize the energy flow and effectively reduce the total energy consumption of the urban rail transit.

著者

Soichiro TAKATA

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.10, no.1, pp.22-00002, 2023 (Released:2023-02-15)

参考文献数

12

---

This paper discusses a new identification method for a linear single-degree-of-freedom system that uses a Gaussian random response and is based on the maximum likelihood estimation (MLE) method. The likelihood function of the proposed method consists of the analytical solution of the Fokker–Planck equation. We have already published a paper on theoretical and numerical considerations. However, in that study, the experimental verification of the proposed identification method was not performed. Therefore, in this study, we conduct an experimental verification of the proposed identification method. First, the identification algorithm is formulated in a spring-mass-damper system subjected to white noise excitation by a moving foundation to correspond to the actual experimental setup. A preliminary experiment in terms of the excitation source is conducted using a vibration speaker. In addition, the experimental modal analysis is performed to confirm the validity of the vibratory system. The fundamental operation test of the identification method is performed using the actual experimental random response data, and a dependency survey of the number of samples is conducted. From the results, the convergence behaviors of the estimation value are observed with an increasing number of samples in the spring constant and the ratio between the diffusion coefficient and the damping constant. In addition, benchmark tests are conducted using the half–power method (HPM) based on spectral analysis and the auto-regressive method (ARM) based on time–series analysis. In the case of spring constant estimation, the behaviors of the estimation value that converge to the true value are observed in all identification methods. In the ratio between the diffusion coefficient and damping constant, the behavior of the estimation value that converges to the true value is observed only in the proposed identification method.

著者

Hikaru AONO Satoshi SEKIMOTO Makoto SATO Aiko YAKENO Taku NONOMURA Kozo FUJII

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.2, no.4, pp.15-00233, 2015 (Released:2015-08-15)

参考文献数

42

被引用文献数

23 32

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Characteristics of flow fields produced by a dielectric barrier discharge plasma actuator in quiescent air are numerically investigated. A time-dependent localized body-force distribution is utilized to mimic the effect of the plasma actuator with modulated bursts. The computed time-averaged and instantaneous flow fields are compared with the experimental results by using high-speed schlieren photography and particle image velocimetry. The computed flow fields are in good agreement with the experimental results when the nondimensional parameter (Dc) is within the appropriate range. With an appropriate choice of Dc, the location and size of the induced flow structures, computed with respect to the maximum flow velocity parallel to the wall, are quantitatively in agreement with the experimental results. Also considered are the effects of the burst frequency (non-dimensionalized by the chord length and the free-stream velocity of assumed separated flow control experiment) on the induced flow. The results show that changes in the burst frequency cause insignificant changes in the magnitude of the time-averaged flow parallel to the wall, but they cause significant fluctuations in the amplitude and power spectral densities of that flow.

著者

Mai NONOGAWA Seigo NAKAYA Masashi ISOBE Kenzen TAKEUCHI Hideyuki AZEGAMI

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.8, no.5, pp.21-00200, 2021 (Released:2021-10-15)

参考文献数

29

---

This study presents methods to develop a three-dimensional numerical foot model and to identify the loading condition that is used to design a stable sole for running shoes. In a previous study, the authors proposed a method to optimize the shape of the sole to increase stability while maintaining the cushioning property. In the problem formulation, the loading condition was given as a boundary force distributed on the top surface of the sole. The aim of this study is to replace the loading condition with the force and moment at the origin of the ankle joint coordinate (AJC) system by modeling a foot with a finite element model. A finite element model of a foot is constructed using X-ray CT image data, and consists of bony structures, soft tissue, and plantar fascia. The plantar fascia is set at the bottom of the bony structures. The force and moment used in the finite element analysis are identified by inverse dynamic analysis using an experimental measurement in the practical operation of the ground reaction force (GRF) when the GRF in the direction of the foot length becomes minimum. In the finite element analysis, the finite deformation containing the contact condition between the bottom surface of the foot and the ground representing a sole made of resin is considered. For an index of the shoe stability, we define a heel eversion angle (HEA) by the rotational angle of the heel with respect to an axis in the foot length direction and evaluate it by finite element analysis. The validity of the finite element foot model as well as the force and moment obtained in this study are confirmed based on the agreement in the HEA results between the experiment and finite element analysis.

著者

Katsuhiko SANDO Takeshi YAMAMOTO Kenji SAWADA Tomoyuki TANIGUCHI Nobuyuki SOWA Haruki MORI Takahiro KONDO

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

pp.20-00497, (Released:2021-03-03)

参考文献数

11

被引用文献数

1

---

This paper describes a design method of a friction reducer device using a loading cam to suppress unstable vibration. Nonlinear simulation and energy analysis of numerical solutions demonstrates that destabilization is caused by the large phase difference between the slipping velocity in the translation direction and that in the rotation direction. It was found that similarly unstable vibration occurs in various structures using wedge rollers with translational and rotational motion. The analytical equation could be simplified by focusing on the motion factor that affects the slip velocity of the power transmission surface, which is the factor of vibration. Consequently, the design method for suppressing vibration could be expressed by a mathematical formula. This equation is validated by using the results of experiments conducted in the previous work of the current authors. Furthermore, from this equation, we proposed that vibration could be suppressed by the parameter balance of the power transmission device without using damping. The power transmission surface slips when a quick torque is input and damping is used. The proposed design can handle a quick torque response and reduce the weight of the reducer. Specifically, the shape of the wedge roller is made lighter, so that the moment of inertia of the roller is not lowered, or the wedge roller is set as a small roller.

著者

Shigenobu KUBO Yoshitaka CHIKAZAWA Hiroyuki OHSHIMA Masato UCHITA Takayuki MIYAGAWA Masao ETO Tetsuji SUZUNO Ichiyo MATOBA Junji ENDO Osamu WATANABE Koichi HIGURASHI

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.7, no.3, pp.19-00489, 2020 (Released:2020-06-15)

参考文献数

17

被引用文献数

5

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The authors are developing the design concept of the pool-type sodium-cooled fast reactor (SFR) that addresses Japan’s specific siting conditions such as earthquakes and meets safety design criteria (SDC) and safety design guidelines (SDG) for Generation IV SFRs. The development of this concept will broaden not only options for reactor types in Japan but also the range and depth of international cooperation. A design concept of 1,500 MWt (650 MWe) class pool-type SFR was thought up by applying design technology obtained from the design of advanced loop-type SFR, named JSFR, equipped with safety measures that reflect results from the feasibility study on commercialized fast reactor cycle systems and fast reactor cycle technology development, improved maintainability and repairability, and lessons learned from the Fukushima Daiichi Nuclear Power Plants accident. The design concepts of a reactor vessel (RV) and its internal structures have been investigated whether they could withstand severe seismic conditions in Japan and thermal loads. The design adopted enhanced RV support structure, enhanced conical-shaped core support structure, a thickened knuckle part of the RV, and a flat plenum separator with ribs. A three-dimensional steady-state thermal hydraulic analysis of the RV revealed that the temperature difference of the upper and lower surfaces of the flat plenum separator could be effectively reduced by installing layers of thermal insulation plates. The authors have also conducted a transient analysis of loss of flow type anticipated transients without scram events to evaluate the feasibility of a self-actuated shutdown system. Moreover, the configuration of the decay heat removal system has been investigated considering sufficient utilization of natural circulation capability of sodium coolant, heat removal capacity of each cooling system, conformance with design requirements, and recommendations of SDC and SDG such as diversity and redundancy of components.

著者

Shohei TAKAOKA Tsutomu KAIZUKA Bo YANG Kimihiko NAKANO

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.7, no.2, pp.19-00572, 2020 (Released:2020-04-15)

参考文献数

28

被引用文献数

1

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Methods for presenting information by utilizing a visual field (such as driver peripheral vision) are attracting increased attention in association with an increase in the amount of information required for driver assistance. However, studies on interfaces utilizing such a visual field are currently insufficient. In addition, to avoid information overload, it is important to evaluate different interfaces in terms of the amount of information presented. The authors researched those interfaces from the viewpoint of ergonomics with the purpose that the result is possible to be applied to various researches mainly in the field of automobiles. Through an in-house experiment, participants viewed video clips presenting dot patterns within their peripheral vision or effective visual field (which is nearer to the gazing point than peripheral vision), and then answered questions regarding the positions and moving directions of the dots and the mental workload they experienced. The authors prepared two types of dotted patterns (fixed and moving) based on the perceptive characteristics of peripheral vision. The number of dots varied from one to six. The rate of misperception and participant mental workload were calculated. The results showed a tendency for the effect of the visual fields to depend on the type of dot pattern. It appears that the interface for peripheral vision may have resulted in a lower accuracy when fixed objects were presented, whereas fewer differences occurred when moving dots were shown. This implies that information with motion can be more suitable for interfaces utilizing peripheral vision. A larger amount of information and number of tasks resulted in lower accuracy and higher workload. Moreover, the relation between the number of dots and the rate of misperception (estimated based on percentage) suggests that the rate of misperception may increase significantly when either four or more fixed objects, or three or more moving objects, are presented.

著者

Kazuki KIMURA Kenichiro NONAKA Kazuma SEKIGUCHI

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.2, no.3, pp.14-00568, 2015 (Released:2015-06-15)

参考文献数

22

被引用文献数

3 4

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This paper focuses on a real-time obstacle avoidance control method for vehicles using model predictive control (MPC). MPC can optimize the motion of the vehicle over a finite time horizon while satisfying various constraints such as vehicle dynamics, the road width and the steering range. However, the computational cost is too large for conducting real-time control. In this paper, a collision avoidance is realized by MPC with constraints for avoiding prohibited regions represented as circles. We approximate this region into a half plane separated by the tangent of the prohibited region. By handling approximated regions as constraints of the road width of MPC, we can implement the collision avoidance algorithm into the controller without increasing the computational cost. Moreover, in order to reduce the computational effort, we transform the nonlinear vehicle dynamics into reduced order and linearizable subsystems called time-state control form (TSCF). The effectiveness of the proposed method is proved by comparative simulations with conventional method where artificial potential method is applied to MPC. In addition, we conduct two experiments using a 1/10 scale vehicle which is equipped with a laser range finder to execute obstacle detection and localization. We show that real-time control can be realized even if we use an on-board embedded CPU which runs at the frequency of 500MHz.

著者

Hisayoshi NAKA Hiromu HASHIMOTO

出版者

The Japan Society of Mechanical Engineers

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.2, no.1, pp.14-00262-14-00262, 2015 (Released:2015-02-15)

参考文献数

14

被引用文献数

5 5

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The dragonfly wing is passively deformed under flapping and has the strength to withstand high flapping frequency simultaneously. These characteristics of deformation and vibration of the wing are important for flapping flight. However, the effect of these characteristics on flapping flight has not been well understood. The purpose of this study is to investigate deformation and vibration characteristics of the dragonfly wing, and then to develop an artificial wing suitable for flapping flight on the basis of the dragonfly wing. In this study, natural frequency and deformation of the dragonfly wing are measured, and the artificial wing is fabricated on the basis of the results. From the measured results, the dragonfly wing has the high natural frequency of about 120 Hz, and thereby, it does not resonate with flapping. Although base-side of the wing is hardly deformed, the tip-side of the wing is greatly deformed because of the torsional deformation from the nodus of dragonfly wing. On the basis of characteristics of the dragonfly wing, the deformable artificial wing that can deform in the same manner of dragonfly wings was fabricated. Then, aerodynamic force and power consumption under flapping when using the deformable artificial wing was measured. As a result, the power efficiency of aerodynamic force using the deformable artificial wing is five times greater than the power efficiency using a non-deformable wing.

著者

Makoto IWAMURA Yoshiko YAMAGUCHI Ittou TANAKA Hiroyuki FUJISHIMA

出版者

一般社団法人日本機械学会

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.4, no.4, pp.17-00028-17-00028, 2017 (Released:2017-08-15)

参考文献数

8

被引用文献数

1

---

Recently, several types of nursing care equipment to aid the lifting and transfer of aged persons have been developed. Especially, rotational boom-type care lifts are used widely because of their simplicity and usefulness. However, such lifts sometimes provide a feeling of uneasiness because during lift-up, the center of the human body moves backward relative to the position of the heel. Hence, in this paper, we first propose a telescopic boom-type care lift to approximate the trajectory of the lift-up motion of a human standing up naturally. By using a multibody dynamics approach, we show that the proposed mechanism can achieve nearly natural standing-up motion and requires a smaller force for lift-up than that required by the conventional-type lift. Next, we develop a prototype telescopic boom-type care lift and verify experimentally that the proposed lift can reduce mental and physical burden compared with the conventional lift. To compare mental burden, we conduct a sensory evaluation by administering a questionnaire. To compare physical burden, we estimate muscle activation based on users' electromyographic signals. These results show the effectiveness of the proposed telescopic boom-type lift. Finally, we consider the optimal design of the proposed care lift structure. We propose an algorithm to seek optimal design parameters that minimize the error between the tip trajectory of the lift and the human chest trajectory measured using a motion capture system.

著者

Kazuma HIROSAKA Katsumasa MIYAZAKI Motoki NAKANE Satoshi SAIGO Norihide TOHYAMA

出版者

一般社団法人日本機械学会

雑誌

Mechanical Engineering Journal (ISSN:21879745)

巻号頁・発行日

vol.3, no.3, pp.15-00683-15-00683, 2016 (Released:2016-06-15)

参考文献数

18

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A safety assessment needs to be conducted to analyze the damage caused by an aircraft impacting into a concrete structure at a nuclear power plant. One of the analytical methods used for this issue is a numerical impact simulation conducted after aircraft and reinforced concrete (RC) models are determined. We established the RC model and aircraft model in this study and confirmed the applicability of an impact simulation. Validation of our RC model was confirmed by conducting impact simulations of an F4 Phantom engine (GE-J79) crashing into three different wall thicknesses of 900, 1150, and 1600 mm. The damages to the wall in the simulations agreed with the test results conducted at Sandia National Laboratory around 1990. We also conducted parametric impact simulations of a rigid missile crashing into a concrete wall, changing the impact speed, mass of the missile, and the wall thickness. The wall thickness required to prevent perforation in the simulations was close to that estimated by the empirical formulae, although the residual speeds of the missile after the perforation in simulation did not agree very well to the values obtained by empirical formulae. One of the reasons of the difference in the residual speed is that the speed of the ejected concrete was not considered in our RC model. An impact simulation of an F4 Phantom crashing into a RC wall was conducted for the validation of our aircraft model. The shape of the impact load and the state of the frames of F4 Phantom on impact were almost the same as those in the test results conducted at Sandia, which showed that the F4 Phantom model was valid.