• Title/Summary/Keyword: Multi-body Dynamic

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Design of Power and Load Reduction Controller for a Medium-Capacity Wind Turbine (중형 풍력터빈의 출력 및 타워 하중저감 제어기 설계)

  • Kim, Kwansu;Paek, Insu;Kim, Cheol-Jin;Kim, Hyun-Gyu;Kim, Hyoung-Gil
    • Journal of the Korean Solar Energy Society
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    • v.36 no.6
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    • pp.1-12
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    • 2016
  • A control algorithm for a 100 kW wind turbine is designed in this study. The wind turbine is operating as a variable speed variable pitch (VSVP) status. Also, this wind turbine is a permanent magnet synchronous generator (PMSG) Type. For the medium capacity wind turbine considered in this study, it was found that the optimum tip speed ratios to achieve the maximum power coefficients varied with wind speeds. Therefore a commercial blade element momentum theory and multi-body dynamics based program was implemented to consider the variation of aerodynamic coefficients with respect to Reynolds numbers and to find out the power and thrust coefficients with respect tip speed ratio and blade pitch angles. In the end a basic power controller was designed for below rated, transition and above rated regions, and a load reduction algorithm was designed to reduce tower vibration by the nacelle motion. As a result, damage equivalent Load (DEL) of tower fore-aft has been reduced by 32%. From dynamic simulations in the commercial program, the controller was found to work properly as designed. Experimental validation of the control algorithm will be done in the future.

The Development and Evaluation of the Active Gait Training System for the Patients with Gait Disorder (보행 장애인을 위한 능동형 보행훈련 시스템 개발 및 평가)

  • Hwang, S.J.;Tae, K.S.;Kang, S.J.;Kim, J.Y.;Hwang, S.H.;Kim, H.I.;Park, S.W.;Kim, Y.H.
    • Journal of Biomedical Engineering Research
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    • v.28 no.2
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    • pp.218-228
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    • 2007
  • Modem concepts of gait rehabilitation after stroke favor a task-specific repetitive approach. In practice, the required physical effort of the therapists limits the realization of this approach. Therefore, a mechanized gait trainer enabling nonambulatory patients to have the repetitive practice of a gait-like movement without overstraining therapists was constructed. In this study, we developed an active gait training system for patients with gait disorder. This system provides joint movements to patients who cannot carry out an independent gait. It provides a normal stance-swing ratio of 60:40 using an eccentric configuration of two gears. Joint motions of the knee and the ankle were evaluated with using the 3D motion analysis system and compared with the results from the multi-body dynamics simulation. In addition, clinical investigations were also performed for low stroke patients during the 6-week gait training. Results from the dynamics simulation showed that joint movements of the knee and the ankle were affected by the gear size, the step length and the length of the foot plate, except the radius of curvature of the foot guide plate. Also, the 6-week gait training revealed relevant improvements of the gait ability in all low subjects. Functional ambulation category levels of subjects after training were 2 in three patients and 1 in a patient. The developed active gait trainer seems feasible as an adjunctive tool in gait rehabilitation after stroke.

Development of a Design Support Program for Pivot Points of Working Devices in Construction Equipment using Planar Multi-body Dynamic Analysis (평면 다물체 동역학 해석을 이용한 건설장비 작업장치의 링크 피봇점 설계 지원 프로그램 개발)

  • Park, Hyun-Gyu;Jang, Jin-Seok;Yoo, Wan-Suk;Kim, Min-Seok;Lee, Hee-Jong;Lee, Jae-Wook
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.6
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    • pp.49-56
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    • 2015
  • For designing working devices of construction equipment, it is necessary to consider not only sufficient working ability but also available working range. Therefore, it is important to select the appropriate pivot positions of links. This paper presents a study on selection of pivot points of links used in construction equipment. To analyze the effect of each pivot point, a design program for pivot selection is developed. A conventional pivot design method requires a complicated process because it needs to create a certain working position manually to evaluate its performance. However, the developed program includes an automatic link assembly algorithm; thus, the working device can easily be analyzed by using pivot information of links. The developed program also included a kinematic/static analysis module and characteristic analysis algorithms. Therefore, it is possible to easily analyze a working device model created through the automatic assembly algorithm, whereby users can easily analyze the effect of each link pivot point for the actual product design.

A Study on the Durability and Running Stability Evaluation of the Korean PRT (한국형 소형궤도차량(PRT)의 내구성 및 주행안정성 평가 연구)

  • Cho, Jeonggil;Kim, Junwoo;Kim, Hyuntae;Koo, Jeongseo;Kang, Seokwon;Jeong, Raggyo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.5
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    • pp.50-58
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    • 2014
  • The PRT(Personal Rapid Transit) system is highly interested to meet a need for demand-responsive transport service and increasing demands of traffic in Korea recently. And it is being spotlighted as an eco-friendly transportation system. For these reasons, researches on the PRT system are actively undergoing in Korea. In this study, we evaluated the static structural and fatigue strengths based on ASCE-APM standards and ERRI B 12/RP 17 by means of FE simulation. We also evaluate the running stability by multi-body dynamic analyses and the rollover safety by a theoretical static stability factor according to the road modeling scenarios for the PRT system. From the results of this study, we confirmed the durability and running stability of the Korean PRT under development.

The Effect Spiral Way Movement of a Trunk Exerts on the Movement Ability (체간의 나선방향운동이 운동능력에 미치는 효과)

  • Lee, In-Hak;Nam, Taek-Gil
    • Journal of the Korean Academy of Clinical Electrophysiology
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    • v.5 no.2
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    • pp.35-45
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    • 2007
  • The purpose of this study was to examine spiral way movement of a trunk exerts on the movement ability. The details established to achieve for this article. This examination confirmed the weight, weight/height2 index, ratio of lumbar to pelvic, musculoskeletal quantity, push up for 2 minute, pitch a ball and voluntary isometric contraction with flexion and extension of knee joint of the subjects with spiral direct movement. Healthy eighteen subjects who understand fully the significance of procedure, consented to a plan, without neuromuscular disease were participated in two groups of experiment. The group were a spiral movement(9), rectilinear movement(9). Trunk movement tested 2 sessions of a spiral movement and rectilinear movement with a push up for 2 minute, 5days per a week, for the 4 weeks. This experiment tested 3 times with a sufficient rest for fatigue limitation. An analysis of the results used a paired samples t-test for difference from before and after experiment. The following results were obtained; At an internal change of the body, the musculoskeletal quantity was increased significantly to spiral movement group, but the weight was increased significantly, the musculoskeletal quantity was not significant to rectilinear movement. The movement ability evaluation for a external change was increased significantly in a push up for 2 minute, pitch a ball, isometric contraction with extension of knee joint of a spiral movement group, but a push up for 2 minute was increased significantly in a push up for 2 minute on the abdominal muscle training of a rectilinear movement group. As compared with a rectilinear movement, a spiral movement was more effect by cooperation with nerve and musculoskeletal system and an increase in movement ability was caused by learning acknowledgment, muscular reeducation. These results lead us to the conclusion that a spiral movement of trunk was more effect than a rectilinear movement, the coordination of nerve and musculoskeletal system was of importance of Multi-direction movement. Therefore, A further studies concerning the therapeutic exercise intervention and active-dynamic analysis could enhance the development of the most effect on the trunk.

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Comparative Study on the Several Types of Double-Acting Oleo-Pneumatic Shock Absorbers of Aircraft Part II. Numerical Analysis and Comparison (항공기 올레오식 2중 완충기 종류에 따른 특성 비교 연구 Part II. 수치해석 및 비교)

  • Jeong, Seon Ho;Lee, Cheol Soon;Kim, Jeong Ho;Cho, Jin Yeon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.45 no.11
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    • pp.951-966
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    • 2017
  • In this work, numerical analyses are carried out and the behaviors are investigated for three types of double-acting oleo-pneumatic shock absorbers along with the mathematical models proposed in the part I of this work. After presenting each numerical algorithm corresponding to each model, the numerical algorithms are implemented as user-subroutines in MSC/ADAMS commercial multi-body dynamic software. By using the developed user-subroutines, numerical studies are carried out for compression/stretch test as well as drop test. From the comparative studies, we investigated the salient feature of each double-acting oleo-pneumatic shock absorber. Results identifies that it is possible to increase the absorbing efficiency in accordance with the requirements for aircraft landing conditions.

Optimization of the Operating Stiffness of a Two-Axis Parallel Robot (2축 병렬로봇의 작동강성 최적설계)

  • Lee, Jae-Wook;Jang, Jin-Seok;Lee, Sang-Kon;Jeong, Myeong-Sik;Cho, Yong-Jae;Kim, Kun-Woo;Yoo, Wan-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.6
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    • pp.561-566
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    • 2015
  • In this paper, the operating stiffness of a parallel robot used to handle heavy packages is optimized. Because the studied model, called a "pick and place robot," is applied for packaging logistics, it is important for the robot to be lightweight so that it may respond rapidly and have high stiffness to allow sufficient operating precision. However, these two requirements of low weight and high stiffness are mutually exclusive. Thus, the dynamic characteristics of the robot are analyzed through multibody dynamics analysis, and topology optimization is conducted to achieve this exclusive performance. Lastly, the reliability of the topology optimization is verified by applying the optimized design to the parallel robot.

Analysis on the Lateral Stiffness of Coil Spring for Railway Vehicle (철도차량용 코일스프링 횡강성 해석)

  • Hur, Hyun-Moo;Ahn, Da-Hoon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.9
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    • pp.84-90
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    • 2018
  • In constructing the multi-body dynamics model to analyze the behavior of the railway vehicle, it is very important to understand the properties of the suspension elements that constitute the suspension system. Among them, coil springs, which are mainly used in primary and secondary suspension systems, clearly show the axial stiffness in the drawings, but the lateral properties of the coil springs are not specified clearly, making it difficult to construct a dynamic analysis model. Therefore, in this paper, the model for analyzing the lateral stiffness of the coil spring is examined. A finite element method was applied to analyze the lateral stiffness of the coil spring and numerical analysis was performed by applying the coil spring lateral stiffness analysis model proposed by Krettek and Sobczak. And the test to analyze the lateral stiffness of coil spring was conducted. As a result of comparing with the test results, it was found that the results obtained by applying the lateral stiffness analysis model of Krettek and Sobczak and correcting the correction coefficient are similar to those of the test results.

Numerical Analysis of Rarefied Hypersonic Flows Using Generalized Hydrodynamic Models for Diatomic Gases (이원자 기체 일반유체역학 모델을 이용한 극초음속 희박 유동장 해석)

  • Myong, Rho-Shin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.5
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    • pp.32-40
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    • 2002
  • The study of nonlinear gas transport in rarefied condition or associated with the microscale length of the geometry has emerged as an interesting topic in recent years. Along with the DSMC method, several fluid dynamic models that come under the general category of the moment method or the Chapman-Enskog method have been used for this type of problem. In the present study, on the basis of Eu's generalized hydrodynamics, computational models for diatomic gases are developed. The rotational nonequilibrium effect is included by introducing excess normal stress associated with the bulk viscosity of the gas. The new models are applied to study the one-dimensional shock structure and the multi-dimensional rarefied hypersonic flow about a blunt body. The results indicate that the bulk viscosity plays a considerable role in fundamental flow problems such as the shock structure and shear flow. An excellent agreement with experiment is observed for the inverse shock density thickness.

Friction Power Loss Reduction for a Marine Diesel Engine Piston (박용엔진 피스톤 스커트 프로파일 변경에 의한 마찰손실(FMEP) 저감 연구)

  • An, Sung Chan;Lee, Sang Don;Son, Jung Ho;Cho, Yong Joo
    • Tribology and Lubricants
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    • v.32 no.4
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    • pp.132-139
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    • 2016
  • The piston of a marine diesel engine works under severe conditions, including a combustion pressure of over 180 bar, high thermal load, and high speed. Therefore, the analyses of the fatigue strength, thermal load, clamping (bolting) system and lubrication performance are important in achieving a robust piston design. Designing the surface profile and the skirt ovality carefully is important to prevent severe wear and reduce frictional loss for engine efficiency. This study performs flexible multi-body dynamic and elasto-hydrodynamic (EHD) analyses using AVL/EXCITE/PU are performed to evaluate tribological characteristics. The numerical techniques employed to perform the EHD analysis are as follows: (1) averaged Reynolds equation considering the surface roughness; (2) Greenwood_Tripp model considering the solid_to_solid contact using the statistical values of the summit roughness; and (3) flow factor considering the surface topology. This study also compares two cases of skirt shapes with minimum oil film thickness, peak oil film pressure, asperity contact pressure, wear rate using the Archard model and friction power loss (i.e., frictional loss mean effective pressure (FMEP)). Accordingly, the study compares the calculated wear pattern with the field test result of the piston operating for 12,000h to verify the quantitative integrity of the numerical analysis. The results show that the selected profile and the piston skirt ovality reduce friction power loss and peak oil film pressure by 7% and 57%, respectively. They also increase the minimum oil film thickness by 34%.