A novel modified analytical method and finite element method for vibration analysis of cable-driven parallel robots

Sy Nguyen-Van,Kwan-Woong Gwak,Duc-Hai Nguyen,이순걸,Byoung Hun Kang 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9

Cable-driven parallel robots (CDPRs) are vulnerable to vibration due to the inevitable flexible properties of the cables. Thus, vibration analysis is critical for CDPR’s operation in which highly accurate motion is required. However, most of the current methods related to vibration analysis of CDPRs rely on simple spring models which have limitations in their performance and complexity that are not general to analyze the vibration of various CDPRs. Hence, accurate, simple and general approaches for vibration analysis in CDPRs are need. To solve this problem, this paper presents the finite element method (FEM) and the modified analytical method to analyze the vibration of CDPRs. To validate these methods, free vibration analysis was conducted using the proposed methods for the planar and spatial cable-driven parallel robots. The natural frequencies of these two CDPRs were computed by the proposed two methods and compared with those of the commercial software, SAP2000. The solutions obtained by the FEM and the modified analytical models turned out to be close to SAP2000’s results, thereby verifying the validity of the proposed methods.

저진동 파일시공법에 따른 지반진동 응답 예측을 위한 실험적 연구

강성후(Kang, Sung-Hoo),정석규(Jeoung, Sug-Kyu),박선준(Park, Sun-Joon) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.4

This study investigated the SIP-method as a low-vibration, low-noise engineering method. The ground vibrations caused by the SIP-method were measured and analyzed in each step. From the analysis results, quantitative ground vibration values and reliable vibration estimation equations were proposed. Furthermore, the ground vibrations caused by the SIP-method were compared with the ground vibrations caused by other methods presented by existing studies. Based on the vibration estimation equation with 50 % reliability, the ground vibration values by the SIP-method at the distance of 10~150 m corresponded to 17~57 % of the ground vibration values by the equation proposed by Attewell & Famer, and 14~96 % of the ground vibration values by the equation proposed by Prof. Park in his study using a diesel drop hammer. These results showed that the ground vibration reduction effect of the SIP-method was higher those of other general engineering methods. Finally, the permissible scope of work using the SIP-method which meets the domestic vibration standards was presented.

철도터널과 인접한 흙막이 가시설의 진동 수준을 고려한 열차진동 평가방법의 적정성 평가

우동희,이영진,송용재,이강일 한국지반환경공학회 2023 한국지반환경공학회논문집 Vol.24 No.10

최근 도심지를 중심으로 개발사업이 증가함에 따라 도시철도 운행구간 인접지역에서 건축 구조물의 시공이 증가하고 있다. 이러한 경우 운행 중인 열차에 의해 지반진동이 발생하여 인접 구조물에 영향을 미치므로 건축 구조물은 설계단계부터 인접한 위치에서 발생하는 열차진동에 대한 적절한 방진대책이 필요하다. 그러나, 열차진동 평가방법에 따라 산정된 진동 수준은 서로 상이하며, 이는 열차진동 평가방법별로 방진대책 실시여부가 달라질 수 있음을 의미한다. 따라서, 본 연구는 수치해석과 열차진동 평가방법을 이용하여 지반조건, 터널깊이, 가진원과 인접 구조물 간의 이격거리에 따른 진동 수준을 산정하고, 이를 설계사례와 비교하여 적용성이 높은 열차진동 평가방법을 제시하였다. 그리고, 진동 수준과 허용규제기준과의 비교를 통해 터널과 인접 구조물 간 적정 이격거리를 평가하였다. 연구결과, 열차진동 평가방법 중 Ungar and Bender 평가방법이 가장 적정성이 높은 것으로 평가되었으며, 터널과 인접 구조물 간의 적정 이격거리는 4.5D 이상인 것으로 평가되었다. With the recent increase in development projects centered on urban areas, the construction of building structures is increasing in areas adjacent to the urban railway operation section. In this case, since ground vibration is generated by the train in operation and affects the adjacent structure, the building structure needs appropriate vibration reduction against train vibration generated at the adjacent location from the desing phase. However, the vibration levels calculated vary depending on the train vibration evaluation method, which means that the implementation of vibration reduction may vary depending on the train vibration evaluation method. Therefore, this study calculated the vibration level according to ground conditions, tunnel depth and separation distance between vibration sources and adjacent structures using numerical analysis and train vibration evaluation methods, and compared them to designning phase. And the appropriate separation distance between the tunnel and the adjacent structure was evaluated by comparing the vibration level with the allowable standards. As a result of the study, the Ungar and Bender evaluation method is evaluated as the most appropriate among the train vibration evaluation methods, and the appropriate separation distance between the tunnel and the adjacent structure is evaluated to be more than 4.5D.

Reproduction of vibration patterns of elastic structures by block-wise modal expansion method (BMEM)

B.K. Jung,조진래,정의봉 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.4

The quality of vibration pattern reproduction of elastic structures by the modal expansion method is influenced by the modal expansion method and the sensor placement as well as the accuracy of measured natural modes and the total number of vibration sensors. In this context, this paper presents an improved numerical method for reproducing the vibration patterns by introducing a block-wise modal expansion method (BMEM), together with the genetic algorithm (GA). For a given number of vibration sensors, the sensor positions are determined by an evolutionary optimization using GA and the modal assurance criterion (MAC). Meanwhile, for the proposed block-wise modal expansion, a whole frequency range of interest is divided into several overlapped frequency blocks and the vibration field reproduction is made block by block with different natural modes and different modal participation factors. A hollow cylindrical tank is taken to illustrate the proposed improved modal expansion method. Through the numerical experiments, the proposed method is compared with several conventional methods to justify that the proposed method provides the improved results.

사장재 케이블 형태를 이용하여 케이블 장력을 추정하는 영상기반 방법

김진수,박재봉,이덕근,박동욱,김성완 한국구조물진단유지관리공학회 2024 한국구조물진단유지관리공학회 논문집 Vol.28 No.1

건설 기술과 해석 도구의 발전으로 인해 최근에는 점점 더 많은 사장교가 설계되고 건설되었다. 케이블은 사장교의 주요한 하중을전달하는 부재이며 일반적으로 전체 교량 시스템의 상태를 반영하는 데 가장 중요한 역할을 한다. 이 연구에서는 원거리에 위치한 사장재 케이블의 장력을 추정하기 위하여 영상기반 방법을 적용하였다. 영상기반 방법을 이용하여 케이블의 응답을 측정하기 위해서는 케이블에 특이점또는 타겟의 설치가 필요하다. 그러나 측정하고자 하는 지점의 위치에 따라 케이블에 특이점이 존재하지 않을 수 있으며 또한 케이블에 타겟의설치가 어려울 수 있는 한계가 존재한다. 따라서 기존의 영상기반 방법의 한계를 극복하여 케이블 응답을 측정하는 방법이 필요하다. 이 연구에서는 케이블 형태의 특징을 이용하여 케이블 응답을 측정하는 방법을 제시하였다. 제시된 방법은 획득된 이미지에서 케이블 형태를 추출하였으며 추출된 케이블 형태의 중심을 산정하여 케이블 응답을 측정하였다. 측정된 응답을 이용하여 진동모드에 대한 고유진동수들을 추출하였으며 진동법에 적용하여 장력을 추정하였다. 영상기반 방법의 신뢰성을 확인하기 위해 공용 중인 화태대교에서 케이블 이미지를 상시진동조건에서 획득하였다. 영상기반 방법을 이용하여 진동법에 적용하여 추정된 장력은 가속도 센서를 이용하여 추정된 장력과 1% 이내의 오차로이 연구에서 제시된 방법의 신뢰성을 확인할 수 있었다. Due to advancements in construction technology and analytical tools, an increasing number of cable-stayed bridges have been designed and constructed in recent years. A cable is a structural element that primarily transmits the main load of a cable-stayed bridge and plays the most crucial role in reflecting the overall condition of the entire bridge system. In this study, a vision-based method was applied to estimate the tension of the stay cables located at a long distance. To measure the response of a cable using a vision-based method, it is necessary to install feature points or targets on the cable. However, depending on the location of the point to be measured, there may be no feature points in the cable, and there may also be limitations in installing the target on the cable. Hence, it is necessary to find a way to measure cable response that overcomes the limitations of existing vision-based methods. This study proposes a method for measuring cable responses by utilizing the characteristics of cable shape. The proposed method involved extracting the cable shape from the acquired image and determining the center of the extracted cable shape to measure the cable response. The extracted natural frequencies of the vibration mode were obtained using the measured responses, and the tension was estimated by applying them to the vibration method. To verify the reliability of the vision-based method, cable images were obtained from the Hwatae Bridge in service under ambient vibration conditions. The reliability of the method proposed in this study was confirmed by applying it to the vibration method using a vision-based approach, resulting in estimated tensions with an error of less than 1% compared to tensions estimated using an accelerometer.

저진동 파일시공법에 따른 지반진동 응답 예측을 위한 실험적 연구

강성후(Park, Sun Joon),박선준(Kang, Sung Hoo),정석규(Jung, Seug Gyu) 한국소음진동공학회 2010 한국소음진동공학회 학술대회논문집 Vol.2010 No.10

In this study, the SIP (Soil-cement Injected precast Pile) method among the Low-vibration & Low-noise pile driving methods was decided into study compensation. Ground vibrations by the SIP methods step by step divide and were analyzed. Quantitative response values and ground vibration equations with reliability were presented from findings of this study. Also, vibration responses that are occurred by the SIP method of construction were compared as quantitative with vibration responses by general method of construction that are presented in existent study. Ground vibration values by the SIP method correspond to level of 17 ~ 57% of values that are assumed by the Attewell & Famer`s equation, respectively, and these result compares in reliability 50% and separated distance 10 ~ 50 m. Also, those values were analyzed that correspond to level of 14 ~ 96% of ground vibration values by the Prof. Parks equation, respectively. Construction limit extents, separation distances from vibration occurs position, were presented that can satisfy domestic criteria for vibration control for the SIP methods. Those presented in this paper were divided newly according to reliability.

Free vibration analysis of straight-line beam regarded as distributed system by combining Wittrick-Williams algorithm and transfer dynamic stiffness coefficient method

Myung-Soo Choi,Takahiro Kondou,Yasuhiro Bonkobara,Kyong-Uk Yang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

We developed a method for analyzing the free vibration of a structure regarded as a distributed system, by combining the WittrickWilliams algorithm and the transfer dynamic stiffness coefficient method. A computational algorithm was formulated for analyzing the free vibration of a straight-line beam regarded as a distributed system, to explain the concept of the developed method. To verify the effectiveness of the developed method, the natural frequencies of straight-line beams were computed using the finite element method, transfer matrix method, transfer dynamic stiffness coefficient method, the exact solution, and the developed method. By comparing the computational results of the developed method with those of the other methods, we confirmed that the developed method exhibited superior performance over the other methods in terms of computational accuracy, cost and user convenience.

Dynamic Substructuring 기법을 이용한 APR 1400 원자로 내부구조물의 동적 거동 고찰

이상정(Sang-Jeong Lee),박노철(No-Cheol Park),최영인(Youngin Choi),박영필(Young-Pil Park),김진성(Jinsung Kim),박찬일(Chanil Park),노우진(Woo-Jin Roh) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.4

In order to identify dynamic behavior of complex structure as nuclear reactor, vibration analysis is mostly conducted as using finite element method (FEM). If the structure is complicated, high computational cost and time is demanded at vibration analysis using FEM. After model reduction is fulfilled with using dynamic substructuring method, it is objective to decrease the computational cost and time at vibration analysis of complex structures in this study. With applying selecting method of mater degree of freedom (MDOF) whose validity was identified in previous study, accuracy of vibration analysis is guaranteed. We apply the method to APR 1400 nuclear reactor internals which are one of complex structures. Because the result of application shows that vibration analysis data from dynamic substructuring method are well matched with original method, we confirm the effect of Vibration analysis using dynamic substructuring method.

The Non-gradient-based Reliability Method in Equivalent Linear Systems for Nonlinear Random Vibration

Saeid Pourzeynali,Hossein Abbaszadeh 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2

A conventional approach for nonlinear random vibration analysis is using equivalent linearization method. Tail-Equivalent Linearization Method (TELM) is one the best proposed methods in the recent decade for determination of equivalent linear model. In TELM, the design point is obtained using first-order reliability method. In the current research, a non-gradient-based method is applied for determination of the design point. One of the main advantages of this method is non-application of limit-state function gradient for calculation of the design point. In the implemented method, n arbitrary points in n-dimension standard normal space are selected and limit-state function in these points is estimated. Then, these points converge to the design point using a convergent algorithm. Since many random variables are produced in TELM for discretization of seismic excitation, iterative algorithms for determination of design point numerical instability would be encountered. By modification of step length for each iteration and application of a magnification coefficient for each step, an appropriate non-gradient method is proposed for analysis of the problems with many random variables. The efficiency of this method was investigated by solving numerical examples. Moreover, the convergence of this method for finding the design point was presented. It was also indicated that results obtained using this method are in good agreement with results obtained by gradient methods.

Development of free vibration analysis algorithm for beam structures by combining Sylvester’s inertia theorem and transfer stiffness coefficient method

최명수,Takahiro Kondou,Yasuhiro Bonkobara 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1

A new free vibration analysis method, which is called the Sylvester-transfer stiffness coefficient method (S-TSCM), is developed by combining Sylvester’s inertia theorem and the transfer stiffness coefficient method. In this paper, the free vibration analysis algorithm of a straight-line beam structure is formulated by S-TSCM. From the computation results of the free vibration analysis for the three types of beam structures, we confirm that S-TSCM is a very effective method. In particular, S-TSCM is superior to both the transfer stiffness coefficient method and the transfer matrix method in terms of computational accuracy and time. In the free vibration analysis for the beam structure with a large number of degrees-of-freedom, S-TSCM is superior to the finite element method in terms of computational time and storage.