• Title/Summary/Keyword: multi-degree-of-freedom model

Search Result 84, Processing Time 0.023 seconds

Dynamic Stability Analysis of Flexible Media (유연 매체의 동적 안정성 해석)

  • Jee, Jung-Geun;Hong, Sung-Kwon;Jang, Yong-Hoon;Park, No-Cheol;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2004.11a
    • /
    • pp.596-599
    • /
    • 2004
  • The media transport systems, such as printers, copiers, facsimile, ATMs, cameras, etc., have been widely used and being developed rapidly. In the development of those systems, the media feeding mechanism is an important key technology for the design and development of the media transport systems. In this paper, a multi-degree of freedom sheet model with dynamic contact conditions is presented to understand the mechanism of sticking and jamming. A sheet is modelled as a cantilever beam and the feeding velocity is assumed to be constant. The relation between the feeding velocity and the coefficient of friction for guaranteeing stable feeding is presented. Simulations are performed for a horizontal linear guide and a oblique linear guide, calculating the contact force and contact states of mass points.

  • PDF

A novel nonlinear gas-spring TMD for the seismic vibration control of a MDOF structure

  • Rong, Kunjie;Lu, Zheng
    • Structural Engineering and Mechanics
    • /
    • v.83 no.1
    • /
    • pp.31-43
    • /
    • 2022
  • A nonlinear gas-spring tuned mass damper is proposed to mitigate the seismic responses of the multi-degree-of-freedom (MDOF) structure, in which the nine-story benchmark model is selected as the controlled object. The nonlinear mechanical properties of the gas-spring are investigated through theoretical analysis and experiments, and the damper's control parameters are designed. The control performance and damping mechanism of the proposed damper attached to the MDOF structure are systematically studied, and its reliability is also explored by parameter sensitivity analysis. The results illustrate that the nonlinear gas-spring TMD can transfer the primary structure's vibration energy from the lower to the higher modes, and consume energy through its own relative movement. The proposed damper has excellent "Reconciling Control Performance", which not only has a comparable control effect as the linear TMD, but also has certain advantages in working stroke. Furthermore, the control parameters of the gas-spring TMD can be determined according to the external excitation amplitude and the gas-spring's initial volume.

The Identification of Vibration Sources in Optical Disk Drive Using PCF Method (PCF 기법을 이용한 광디스크 드라이브의 진동원 규명)

  • 함경훈;장영배;박노철;박영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.05a
    • /
    • pp.127-133
    • /
    • 2002
  • After the vibration source is searched in optical disk drive as an information storage device broadly used the influence of it against FES(Focusing Error Signal) which is a kind of positioning error of pick up from the circuit is carefully examined. For that Purpose, partial coherence function method is applied on a simple multi-degree of freedom model made for the theoretical verification and it is practically introduced in optical disk drive for analyzing the effect of vibration source. Finally, partial coherence output spectrum is attentively observed in order to know which vibration source is a great influence on FES.

  • PDF

Constraint-Based Modeling of Human Hands (구속조건 기반의 손 모델)

  • Choi, Haeock;Song, Mankyun;Jun, Byoungmin
    • Journal of the Korea Computer Graphics Society
    • /
    • v.3 no.1
    • /
    • pp.1-7
    • /
    • 1997
  • Technology for the realistic model and the motion control of human is applied to many areas of computer graphics, virtual reality and computer simulations. Human body is a multi-articular body. Generally, to create a human model and motions. articulated body models are generated and their motions are controlled based upon kinematics. The hand of the human consists of many small articulations and each articulations have a various degree of freedom. This paper presents a model of human hand which is based on the two kinds of constraints to control the motions of the hand realistically. To build a hand model, we experimented the anatomy of the human hand, and the diverse motions of the hand are tested.

  • PDF

A new method for optimal selection of sensor location on a high-rise building using simplified finite element model

  • Yi, Ting-Hua;Li, Hong-Nan;Gu, Ming
    • Structural Engineering and Mechanics
    • /
    • v.37 no.6
    • /
    • pp.671-684
    • /
    • 2011
  • Deciding on an optimal sensor placement (OSP) is a common problem encountered in many engineering applications and is also a critical issue in the construction and implementation of an effective structural health monitoring (SHM) system. The present study focuses with techniques for selecting optimal sensor locations in a sensor network designed to monitor the health condition of Dalian World Trade Building which is the tallest in the northeast of China. Since the number of degree-of-freedom (DOF) of the building structure is too large, multi-modes should be selected to describe the dynamic behavior of a structural system with sufficient accuracy to allow its health state to be determined effectively. However, it's difficult to accurately distinguish the translational and rotational modes for the flexible structures with closely spaced modes by the modal participation mass ratios. In this paper, a new method of the OSP that computing the mode shape matrix in the weak axis of structure by the simplified multi-DOF system was presented based on the equivalent rigidity parameter identification method. The initial sensor assignment was obtained by the QR-factorization of the structural mode shape matrix. Taking the maximum off-diagonal element of the modal assurance criterion (MAC) matrix as a target function, one more sensor was added each time until the maximum off-diagonal element of the MAC reaches the threshold. Considering the economic factors, the final plan of sensor placement was determined. The numerical example demonstrated the feasibility and effectiveness of the proposed scheme.

Seismic Response of Structures with Buckling-Restrained Braces (좌굴방지 가새가 설치된 건물의 지진응답)

  • 김진구;최현훈
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.15 no.2
    • /
    • pp.197-207
    • /
    • 2002
  • Energy dissipation capacity and earthquake responses of steel structures installed with unbonded braces(UB) were investigated. Parametric studies were performed for a single-degree-of-freedom structure under harmonic loads, and optimum yield strength of unbonded braces were derived. Nonlinear dynamic time history analyses were carried out to investigate the seismic response of multi-story model structures with UB having various size and strength. Various techniques were applied to determine proper story-wise distribution of UB in multi-story structures. The analysis results show that the maximum displacements of structures generally decrease as the stiffness of UB increases. However for some natural frequencies and seismic loads the maximum displacement and accumulated damage increases as the stiffness of UB increases.

An Enhancement of Multi-Dof Frequency Response Spectrum From Impact Hammer Testing (충격햄머 실험에서 다자유도 주파수 응답스팩트럼의 개선)

  • Ahn, Se-Jin;Jeong, Weui-Bong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.11b
    • /
    • pp.623-629
    • /
    • 2002
  • The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function(FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

  • PDF

The Improvement of Multi-dof Impulse Response Spectrum by Using Optimization Technique (최적화 기법을 이용한 다자유도 충격응답스펙트럼의 오차 개선)

  • 안세진;정의봉
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.12 no.10
    • /
    • pp.792-798
    • /
    • 2002
  • The spectrum of impulse response signal from an impulse hammer testing is widely used to obtain frequency response function (FRF) of the structure. However the FRFs obtained from impact hammer testing have not only leakage errors but also finite record length errors when the record length for the signal processing is not sufficiently long. The errors cannot be removed with the conventional signal analyzer which treats the signals as if they are always steady and periodic. Since the response signals generated by the impact hammer are transient and have damping, they are undoubtedly non-periodic. It is inevitable that the signals be acquired for limited recording time, which causes the finite record length error and the leakage error. In this paper, the errors in the frequency response function of multi degree of freedom system are formulated theoretically. And the method to remove these errors is also suggested. This method is based on the optimization technique. A numerical example of 3-dof model shows the validity of the proposed method.

A study on the characteristics of torsional vibration for 4*4 vehicles drivetrain (4륜구동 차량구동계의 비틀림진동 특성에 관한 연구)

  • Choi, Eun-O;Kim, Hei-Song;Hong, Dong-Pyo
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.21 no.11
    • /
    • pp.1957-1964
    • /
    • 1997
  • Torsional vibration is to vibrate strongly when the ignition pulses of the engine is excited with natural frequency of driveline. Torsional vibration like this can cause various noises as rattle and booming. For this study multi-degree of freedom analysis model of torsional vibration, which is combined with mass moment of inertia and torsional spring, was developed toward two wheel drive, four wheel drive and torsional vibration characteristics were compared and analyzed through the natural frequences, mode shapes and frequency response characteristics which was acquired by the simulation of it. The pertinence of that model was proved by the field test and the outcome of the simulations coincided with feeling test. Therefore, four wheel drive simulation model is considered to be useful thing for reducing torsional vibration of driveline and developing full-time four wheel drive vehicles.

Derivation of Dynamic Characteristic Values for Multi-degree-of-freedom Frame Structures based on Frequency Response Function(FRF) (주파수응답함수 기반 다자유도 골조 구조물의 동특성치 도출 및 구조모델링 적용 )

  • So-Yeon Kim;Min-Young Kim;Seung-Jae Lee;Kyoung-Kyu Choi
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.27 no.4
    • /
    • pp.1-10
    • /
    • 2023
  • In the seismic design of structures, seismic forces are calculated based on structural models and analysis. In order to accurately address the dynamic characteristics of the actual structure in the structural model, calibration based on actual measurements is required. In this study, a 4-story frame test specimen was manufactured to simulate frame building, accelerometers were attached at each floor, and 1-axis shaking table test was performed. The natural period of the specimen was similar to that of the actual 4 story frame building, and the columns were designed to behave with double-curvature having the infinite stiffness of the horizontal members. To investigate the effects seismic waves characteristics, historical and artificial excitations with various frequencies and acceleration magnitudes were applied. The natural frequencies, damping ratios, and mode shapes were obtained using frequency response functions obtained from dynamic response signals, and the mode vector deviations according to the input seismic waves were verified using the Mode assurance criterion (MAC). In addition, the damping ratios obtained from the vibration tests were applied to the structural model, and the method with refined dynamic characteristics was validated by comparing the analysis results with the experimental data.