共查询到20条相似文献,搜索用时 15 毫秒
1.
Michele Dilena Antonino Morassi 《Mechanical Systems and Signal Processing》2011,25(5):1485-1507
In this paper the results of a campaign of dynamic tests carried out on an existing reinforced concrete single-span bridge subjected to increasing levels of damage are presented. The deck structure consists of a slab and three simply supported beams. The damage is represented by a series of notches made on a lateral beam to simulate the effect of incremental concentrated damage. The modal parameters of the lower vibration modes were estimated from frequency response measurements obtained under harmonic excitation. The variation of natural frequencies shows an anomalous increase in the transition from one intermediate configuration to the next damage configurations. Changes in vibration modes are appreciable from the earliest level of damage. In particular, changes in modal curvature of lower modes do provide indication on the damage location. 相似文献
2.
Vibration control of smart hull structure with optimally placed piezoelectric composite actuators 总被引:1,自引:0,他引:1
Active vibration control to suppress structural vibration of the smart hull structure was investigated based on optimized actuator configurations. Advanced anisotropic piezoelectric composite actuator, Macro-Fiber Composite (MFC), was used for the vibration control. Governing equations of motion of the smart hull structure including MFC actuators were obtained using the Donnell-Mushtari shell theory and Lagrange's equation. The Rayleigh-Ritz method was used to obtain the dynamic characteristics of the smart hull structure. Experimental modal tests were conducted to verify the proposed mathematical model. In order to achieve high control performance, optimal locations and directions of the MFC actuators were determined by genetic algorithm. Optimal control algorithm was then synthesized to suppress structural vibration of the proposed smart hull structure and experimentally implemented to the system. Active vibration control performances were evaluated under various modes excitations. Vibration tests revealed that optimal configurations of MFC actuators improved the control performance of the smart hull structure in case of the limited number of actuators available. 相似文献
3.
Sung-Ryong Hong Seung-Bok Choi Moon-Shik Han 《International Journal of Mechanical Sciences》2002,44(10):2027-2045
A squeeze-mode electro-rheological (ER) mount has been designed, manufactured, and applied to the vibration control of a frame structure subjected to external excitations. After verifying that the damping force of the ER mount can be controlled by controlling the applied voltage, a frame structure system supported by spring mounts and the proposed ER mounts has been assembled. The governing equation of the structural system is derived in the modal coordinate and is rewritten as a state-space control model. An optimal controller, which consists of the velocity feedback signal of the frame structure and the force feedback signal transmitted from the exciting point to the mount position, is formulated in order to attenuate the imposed excitations. The controller has been optimized experimentally and control responses such as the acceleration of the frame structure and the transmitted force at each mount position are presented in both time and frequency domains. 相似文献
4.
A new matrix on the covariance of covariance is formed from the auto/cross-correlation function of acceleration responses of a structure under white noise ambient excitation. The components of the covariance matrix are proved to be function of the modal parameters (modal frequency, mode shape, and damping parameter) of the structure. Information from all the vibration modes of the structure limited by the sampling frequency contributes to these components. The formulated covariance matrix contains more information on the vibration modes of the structure that cannot be obtained by the general methods for extracting modal parameters. When the component of the covariance matrix is used for damage detection, it is found more sensitive to local stiffness reduction than the first few modal frequencies and mode shapes obtained from ambient excitation. A simply supported 31 bar plane truss structure is studied numerically where a multiple damage scenario with different noise levels is identified with satisfactory results. 相似文献
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Jin-Young Jeon 《Journal of Mechanical Science and Technology》2009,23(5):1435-1445
Piezoelectric materials can be used for structural damping because of their ability to efficiently transform mechanical energy
to electrical energy and vice versa. The electrical energy may be dissipated through a connected load resistance. In this
paper, a new optimization technique for the optimal piezoelectric shunt damping system is investigated in order to search
for the optimal shunt electrical components of the shunt damping circuit connected to the piezoelectric patch on a vibrating
structure for the structural vibration suppression of several modes. The vibration suppression optimization technique is based
on the idea of using the piezoelectric shunt damping system, the integrated p-version finite element method (p-version FEM),
and the particle swarm optimization algorithm (PSOA). The optimal shunt electrical components for the piezoelectric shunt
damping system are then determined by wholly minimizing the objective function, which is defined as the sum of the average
vibration velocity over a frequency range of interest. Moreover, the optimization technique is performed by also taking into
account the inherent mechanical damping of the controlled structure with the piezoelectric patch. To numerically evaluate
the multiple-mode damping capability by the optimal shunting damper, an integrated p-version FEM for the beam with the shunt
damping system is modeled and developed by MATLAB. Finally, the structural damping performance of the optimal shunt damping
system is demonstrated numerically and experimentally with respect to the beam. The simulated result shows a good agreement
with that of the experimental result.
This paper was recommended for publication in revised form by Associate Editor Eung-Soo Shin
Jin-Young Jeon received his Ph.D. degree in Mechanical and Aerospace Engineering from Tokyo Institute of Technology in 2005. Dr. Jeon is
currently a senior engineer at Digital Printing Division, Digital Media & Communications Business at Samsung Electronics Co.,
Ltd., Korea. His research interests are the areas of structural-acoustic optimization, sound quality, motion quality, and
vibration control. 相似文献
7.
This paper introduces a vibration control method for a flexible beam subjected to arbitrary, unmeasurable disturbance forces. The concept of independent modal space control is adopted. Here, we choose the modal filters as the state estimator to obtain the modal coordinates and modal velocities for the modal space control. Because of the existence of the disturbance forces, applying only the state feedback to suppress the vibration usually cannot achieve the desired control performance. The modal space feedforward control is then introduced to cancel out the disturbance forces. In this paper, the feedforward and feedback control method is implemented to reduce the beam vibration. The disturbance force observer is established to observe the disturbance modal forces for the feedforward control. The control gains are derived from the extended optimal control algorithm, where the disturbance modal forces are treated as exogenous state variables. By combining the feedback, feedforward control laws and the disturbance force observer together, the vibration control performances are discussed. 相似文献
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CHEN Xuedong YU Xianzhong HE Xueming YAN Tianhong 《机械工程学报(英文版)》2008,21(2):17-22
Dynamic characteristic is presented by identifying the model and the dynamic parameters of a precise long stroke linear motor (PLSLM) with the air-bearing in optical lithography. The PLSLM is supported by air-bearing on the stator, and is driven by on-board two large linear motors in a cross-configuration. Firstly, a model of the PLSLM is established by finite element method (FEM). Secondly, based on the model, the natural frequencies and model shapes are discusse& And the contribution of each active mode is evaluated by computing the modal participation factors (MPF), which indicates the major vibration direction. Furthermore, by the experimental modal analysis, the experimental results are in agreement with simulation results, which it is sure that the FEM is reasonable. What's more, comparing with the effects on the frequency due to the air-bearing stiffness, the relations of the natural frequencies with the air-bearing stiffness are found. It is found that the frequency response curve is fluctuant with the air-bearing stiffness in each direction. Finally, it is conclusion that the natural frequency of the PLSLM is largely affected by the air-bearing stiffness variety. This research is contributed to the dynamic characteristics resulted from the air-beating stiffness. Further work will include better optimization on the dynamic parameter in the controller design through the control algorithm for the precise long stroke motor. 相似文献
10.
Fook Choon Choi Jianchun Li Bijan Samali Keith Crews 《Journal of Mechanical Science and Technology》2007,21(6):903-907
Using vibration methods for the damage detection and structural health monitoring in bridge structures is rapidly developing.
However, very little work has so far been reported on timber bridges. This paper intends to address such shortcomings by experimental
investigation on a timber beam using a vibration based method to detect damage. A promising damage detection algorithm based
on modal strain energy was adopted and modified to locate/evaluate damage. A laboratory investigation was conducted on a timber
beam inflicted with various damage scenarios using modal tests. The modal parameters obtained from the undamaged and damaged
state of the test beam were used in the computation of damage index, were then applied using a damage detection algorithm
utilising modal strain energy and a statistical approach to detect location of damage. A mode shape reconstruction technique
was used to enhance the capability of the damage detection algorithm with limited number of sensors. The test results and
analysis show that location of damage can be accurately identified with limited sensors. The modified method is less dependent
on the number of modes selected and can detect damage with a higher degree of confidence. 相似文献
11.
使用有限元软件MSC/NASTRAN对动调陀螺组合体进行了模态分析与研究,并给出了陀螺组合体的15阶模态频率和振型。分析结果表明,陀螺组合体前6阶模态频率对其整体振动有很大的影响,同时验证了陀螺组合体的固有频率将远离外界激振频率,不会因为受到外界频率的激振而发生工作失效。 相似文献
12.
Jinjun Jiang Weijin Gao Liang Wang Zhaohua Teng Yongguang Liu 《Journal of Mechanical Science and Technology》2018,32(8):3515-3521
Active vibration control to suppress structural vibration of the flexible structure is investigated based on a new control strategy considering structure-actuator interaction. The experimental system consists of a clamped-free rectangular plate, a controller based on modal control switching, and a magnetostrictive actuator utilized for suppressing the vibrations induced by external excitation. For the flexible structure, its deformation caused by the external actuator will affect the active control effect. Thus interaction between structure and actuator is considered, and the interaction model based on magnetomechanical coupling is incorporated into the control system. Vibration reduction strategy has been performed resorting to the actuator in optimal position to suppress the specified modes using LQR (linear quadratic regulator) based on modal control switching. The experimental results demonstrate the effectiveness of the proposed methodology. Considering structure-actuator interaction (SAI) is a key procedure in controller design especially for flexible structures. 相似文献
13.
《Mechanical Systems and Signal Processing》2007,21(1):334-347
This study deals with active robust modal vibration control of rotor systems supported by magnetic bearings. The inherent divergent rigid body modes are suppressed by using a dual-level control approach. Finite element method is applied to formulate the rotor model. The Timoshenko beam theory, including the effects of shearing deformations and rotary inertia, is considered in this work. Because practical control systems are often limited by its sensing, hardware, and computation speed capabilities, the reduced order approach is often used for a control system design. This study applies the independent modal space control (IMSC) approach to extract the accurate lower modes from the complex rotor systems with the gyroscopic effect considered. In practice, it is extremely difficult to model the complete dynamic characteristics of a rotor system. The model may contain unmodelled dynamics and parameter changes, which can be viewed as uncertainties of a system. As opposed to the conventional control approach, which requires fixed and accurate system parameters, this study considers robust control approach to design a controller capable of tolerating external disturbance and model uncertainties. It is demonstrated that the proposed approach is effective for vibration suppression when the system is subjected to impulsive or step loading, speed variation, and sudden loss of disk mass. 相似文献
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为对木结构构件局部缺陷进行 有效检测,结合试验模态分析和有限元模拟方法,对含不同位置、大小和数量孔洞缺陷的木梁 进行研究,计算其第1阶位移模态振型和曲率模态,分析木梁损伤前后的曲率模态变化,探讨 模态分析方法在木材缺陷检测中的适用性。研究结果表明:曲率模态是一个对木梁损伤比较 敏感的参数,可用于对孔洞位置、大小及数量进行定量的估计;通过降低有限元模型局部单 元的弹性模量能够较好地模拟木梁损伤,有限元模态分析和试验模态分析得到的位移模态振 型及曲率模态吻合均较好,验证了模态分析对木梁无损检测是一种有效的方法。 相似文献
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The residual vibrations of highly resonant flexible structures can be usually composed of sinusoidal signals. The identification of the frequencies, amplitudes and/or phases of these sinusoidal signals may be of interest for health monitoring or to update controller parameters in active vibration control systems. This work considers a previously developed algebraic estimator of the frequencies, amplitudes and phases of two sinusoidal signals in order to identify the first two natural frequencies of flexible-beam-like structures. The influence of the unconsidered vibration modes on the estimation accuracy is studied by simulating a residual vibration formed by four sinusoidal components. It has been shown that the velocity and accuracy in the estimation of the first two natural frequencies depend on the distance between frequencies and the amplitudes of the first three vibration components. Finally, the beam parameters are related to the estimation performance. 相似文献
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航天器上悬臂板型挠性附件在扰动作用下将引起包括弯曲和扭转模态的振动,这将影响系统的稳定性和控制精度,尤其是在平衡点附近低频模态频率上的小幅值残余振动很难快速抑制。为了快速抑制压电智能挠性悬臂板系统,包括弯曲和扭转模态的振动,提出采用基于特征模型的非线性黄金分割自适应控制,组合非线性切换逻辑积分阻尼器算法。首先,优化配置压电传感器和驱动器实现了悬臂板的弯曲和扭转模态在检测和驱动上的解耦;其次,设计并建立压电挠性悬臂板试验平台,进行试验模态辨识并获得了悬臂板系统弯曲和扭转振动的模态频率和频响特性;最后,进行压电智能悬臂板的弯曲和扭转振动模态主动振动几种方法试验的比较研究。试验结果表明,采用的控制方法能够快速地抑制压电智能挠性悬臂板的振动。 相似文献
20.
基于灵敏度分析的机械系统损伤识别方法 总被引:7,自引:0,他引:7
提出了一种基于振动灵敏度分析的机械系统损伤识别方法。该方法同时考虑了固有频率灵敏度和固有模态灵敏度 ,既可用于损伤定位 ,也能用于确定损伤大小 ,且对单个损伤和多个损伤情况都适用。为了提高识别的精度 ,考虑了二阶灵敏度。针对工程实际的需要 ,分析了不完备模态和模态测量误差对该方法识别精度的影响。算例表明 :本方法合理可靠 ,具有足够的精度。 相似文献