• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문집
• /
• pp.914-920
• /
• 2002

Nonlinear flow-induced vibration characteristics of a generic missile wing (or control surface) are investigated in this study. The wing model has freeplay structural nonlinearity at its pitch axis. Nonlinear aerodynamic flows with unsteady shock waves are considered in the transonic flow region. To practically consider the effects of freeplay structural nonlinearity, the fictitious mass method (FMM) is applied to structural vibration analysis based on a finite element method (FEM). A computational fluid dynamics (CFD) technique is used for computing the nonlinear unsteady aerodynamics of all-movable wings. The aerodynamic analysis is based on the efficient transonic small-disturbance aerodynamic equations of motion using the potential-flow theory. To solve the nonlinear aeroelastic governing equations including the freeplay effect, a modal-based computational structural dynamic (CSD) analysis technique based on fictitious mass method (FMM) is used in time-domain. In addition, CSD and unsteady CFD techniques are simultaneously coupled to give accurate computational results. Various aeroelastic computations have been performed for a generic missile wing model. Linear and nonlinear aeroelastic computations have been conducted and the characteristics of flow-induced vibration are introduced.

• Smart Structures and Systems
• /
• 제19권6호
• /
• pp.633-641
• /
• 2017

The complexity of macro-fiber composite (MFC) materials increasing the difficulty in simulation and analysis of MFC integrated structures. To give an accurate prediction of MFC bonded smart structures for the simulation of shape and vibration control, the paper develops a linear electro-mechanically coupled static and dynamic finite element (FE) models based on the first-order shear deformation (FOSD) hypothesis. Two different types of MFCs are modeled and analyzed, namely MFC-d31 and MFC-d33, in which the former one is dominated by the $d_{31}$ effect, while the latter one by the $d_{33}$ effect. The present model is first applied to an MFC-d33 bonded composite plate, and then is used to analyze both active shape and vibration control for MFC-d31/-d33 bonded plate with various piezoelectric fiber orientations.

• 한국소음진동공학회논문집
• /
• 제18권5호
• /
• pp.533-540
• /
• 2008

In this study, a new slab system where a part of precast slab is connected each other by viscoelastic material is proposed and numerical analysis is performed to evaluate the effect of the connection between the material and PC slab on the vibration and noise control. Substructuring is introduced to develop the equation of motion for the slab system. In addition, the optimal properties of viscoelastic material are investigated. For the performance evaluation of the new slab system, the sound power and acceleration responses of the slab are compared with those of two way slab and one way slab, respectively. Numerical analysis results show that the sound power of the new slab system can be reduced by viscoelastic material significantly.

• Smart Structures and Systems
• /
• 제18권2호
• /
• pp.335-354
• /
• 2016

This contribution presents an extended one-dimensional theory for piezoelectric beam-type structures with non-ideal electrodes. For these types of electrodes the equipotential area condition is not satisfied. The main motivation of our research is originated from passive vibration control: when an elastic structure is covered by several piezoelectric patches that are linked via resistances and inductances, vibrational energy is efficiently dissipated if the electric network is properly designed. Assuming infinitely small piezoelectric patches that are connected by an infinite number of electrical, in particular resistive and inductive elements, one obtains the Telegrapher's equation for the voltage across the piezoelectric transducer. Embedding this outcome into the framework of Bernoulli-Euler, the final equations are coupled to the wave equations for the longitudinal motion of a bar and to the partial differential equations for the lateral motion of the beam. We present results for the wave propagation of a longitudinal bar for several types of electrode properties. The frequency spectra are computed (phase angle, wave number, wave speed), which point out the effect of resistive and inductive electrodes on wave characteristics. Our results show that electrical damping due to the resistivity of the electrodes is different from internal (=strain velocity dependent) or external (=velocity dependent) mechanical damping. Finally, results are presented, when the structure is excited by a harmonic single force, yielding that resistive-inductive electrodes are suitable candidates for passive vibration control that might be of great interest for practical applications in the future.

• International Journal of Control, Automation, and Systems
• /
• 제6권6호
• /
• pp.836-844
• /
• 2008

This paper presents an approach to order reduction of linear parameter varying controller for polytopic model. Feasible solutions which satisfy relevant linear matrix inequalities for constructing full-order parameter varying controller evaluated at each polytopic vertices are first found. Next, sufficient conditions are derived for the existence of a right coprime factorization of parameter varying controller. Furthermore, a singular perturbation approximation for time invariant systems is generalized to reduce full-order parameter varying controller via parameter varying right coprime factorization. This generalization is based on solutions of the parameter varying Lyapunov inequalities. The closed loop performance caused by using the reduced order controller is developed. To examine the performance of the reduced-order parameter varying controller, the proposed method is applied to reduce vibration of flexible structures having the transverse-torsional coupled vibration modes.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.1204-1209
• /
• 2000

Many analytical and experimental studies on the active suppression of nonlinear panel flutter by using piezoceramic patch have been carried out. However, these active control methods have a few important problems; a large amount of power is required to operate actuators, and additional apparatuses such as sensor systems and controller are needed. In this study passive suppression schemes for nonlinear flutter of composite panel, which is believed to be more robust suppression system than active control in practical operation, are proposed by using piezoelectric inductor-resistor series shunt circuit. Toward the end, a finite element equation of motion for an electromechanically coupled system is proposed using the Hamilton's principle. To achieve the best damping effect, optimal shape and location of the piezoceramic(PZT) patches are determined by using genetic algorithms. The results clearly demonstrate that the passive damping scheme by using piezoelectric shunt circuit can effectively attenuate the flutter.

• 한국소음진동공학회논문집
• /
• 제22권11호
• /
• pp.1042-1048
• /
• 2012

A 2-axis gimbal system is one of main disturbance sources affecting image jitter response of a satellite. The gimbal system comprises azimuth stage and elevation stage, and these pointing mechanism can be rotated by stepping motors about its azimuth and elevation axes simultaneously. Because of the complex and coupled dynamic motion of the gimbal system, its moment of inertia and structural modes can be changed according to the system configuration, and thus the gimbal system generates complicated and non-linear disturbance characteristics. In order to improve the jitter response of a spacecraft, it is an indispensable process to reduce the micro-vibration disturbance level of the antenna system. In the present research, a 2-axis gimbal system was manufactured and then its micro-vibration test was performed in terms of two types of stepping motors(2-phase and 5-phase). The test results show that the disturbance level of the gimbal system can be reduced by replacing the 2-phase stepping motor with the 5-phase one, and the average disturbance attenuation ratio is 56 % in peak level and 48 % in standard deviation level. The experimental results confirm that it is an efficient jitter reduction method to adopt a high-phase stepping motor.

• Steel and Composite Structures
• /
• 제27권4호
• /
• pp.465-477
• /
• 2018

In this research, vibration and smart control analysis of a concrete foundation reinforced by $SiO_2$ nanoparticles and covered by piezoelectric layer on soil medium is investigated. The soil medium is simulated with spring constants and the Mori-Tanaka low is used for obtaining the material properties of nano-composite structure and considering agglomeration effects. With considering first order shear deformation theory, the total potential energy of system is calculated and by means of Hamilton's principle in three displacement directions and electric potential, the six coupled equilibrium equations are obtained. Also, based an analytical method, the frequency of system is calculated. The effects of applied voltage, volume percent and agglomeration of $SiO_2$ nanoparticles, soil medium and geometrical parameters of structure are shown on the frequency of system. Results show that with applying negative voltage, the frequency of structure is increased.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.556-560
• /
• 2007

In this paper, the research results for the improvement of tracking performance of a hydraulic shaking table are presented. A servo-hydraulic shaking table is not only highly nonlinear but also has a lot of time delay. In addition, the shaking table, which consists of multi axial hydraulic actuators, is a MIMO system coupled by kinematics and dynamics of each other's actuators. And it is demanded for the shaking table to track arbitrary trajectories up to high frequency even at the extreme situations such as substantial external loads and large disturbances. For this purpose, an iterative feed-forward control based on the inverse of a measured frequency response function is used for the shaking table. To solve the dynamic coupling, a pressure feedback control as numerical damping is used. It is shown through numerical simulations that the tracking performance of shaking table is improved up to 100Hz.

• International Journal of Control, Automation, and Systems
• /
• 제3권4호
• /
• pp.601-611
• /
• 2005

In this paper, an active vibration control of a tensioned, elastic, axially moving string is investigated. The dynamics of the translating string are described with a non-linear partial differential equation coupled with an ordinary differential equation. A right boundary control to suppress the transverse vibrations of the translating continuum is proposed. The control law is derived via the Lyapunov second method. The exponential stability of the closed-loop system is verified. The effectiveness of the proposed control law is simulated.