• Structural Engineering and Mechanics
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• 제55권1호
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• pp.229-244
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• 2015

H-infinity norm relates to the maximum in the frequency response function and H-infinity control method focuses on the case that the vibration is excited at the fundamental frequency, while 2-norm relates to the output energy of systems with the input of pulses or white noises and 2-norm control method weighs the overall vibration performance of systems. The trade-off between the performance in frequency-domain and that in time-domain may be achieved by integrating two indices in the mixed vibration control method. Based on the linear fractional state space representation in the modal space for a piezoelectric flexible structure with uncertain modal parameters and un-modeled residual high-frequency modes, a mixed dynamic output feedback control design method is proposed to suppress the structural vibration. Using the linear matrix inequality (LMI) technique, the initial populations are generated by the designing of robust control laws with different H-infinity performance indices before the robust 2-norm performance index of the closed-loop system is included in the fitness function of optimization. A flexible beam structure with a piezoelectric sensor and a piezoelectric actuator are used as the subject for numerical studies. Compared with the velocity feedback control method, the numerical simulation results show the effectiveness of the proposed method.

• Current Applied Physics
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• 제18권11호
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• pp.1388-1392
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• 2018

Metal thin films are used widely to solve the vibration problem. However, damping mechanism is still not clear, which limits the further improvement of the damping properties for film and the development of multi-functional damping coating. In this paper, Damping microscopic mechanism of porous metal films was investigated at both macroscopically and microscopically mixed levels. Molecular dynamics simulation method was used to model and simulate the loading-unloading numerical experiment on the micro-pore and vacancy model to get the stress-strain curve and the microstructure diagram of different defects. And damping factor was calculated by the stress-strain curve. The results show that dislocations and new vacancies appear in the micro-pores when metal film is stretched. The energetic consumption from the motion of dislocation is the main reason for the damping properties of materials. Micro-mechanism of damping properties is discussed with the results of in-situ experiment.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.213-218
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• 2001

A magnetorheological(MR) engine mount for a passenger vehicle and its vibration control performance is experimentally evaluated. A mixed-mode model for the MR engine is derived by incorporating Herschel-Bulkely model of the MR fluid. After analyzing the field-dependent damping force, a appropriate size of the MR engine mount is manufactured. The field-dependent is displacement transmissibility of the engine mount is evaluated in the frequency domain at various excitation levels. In addition, time-dependant damping force is experimentally investigated by changing the excitation amplitude.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.828-833
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• 2004

The performance of a mixed $H_{\infty}/H_2$ design with pole placement constraints based on robust vibration control for a piezo/beam system is investigated. The governing equation of motion for the piezo/beam system is derived by Hamilton's principle. The assumed mode method is used to discretize the governing equation into a set of ordinary differential equation. A robust controller is designed by $H_{\infty}/H_2$ feedback control law that satisfies additional constraints on the closed-loop pole location in the face of model uncertainties, which are derived for a general class of convex regions of the complex plane. These constraints are expressed in terms of linear matrix inequalities (LMIs) approach for the multiobjective synthesis. The validity and applicability of this approach for vibration suppressions of SMART structural systems are discussed by damping out the multiple vibrational modes of the piezo/beam system.

• 대한기계학회논문집A
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• 제24권2호
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• pp.370-377
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• 2000

This paper presents a mixed-mode type ER(electro-rheological) engine mount, and its vibration control performance for a passenger vehicle is presented. The field-dependent yield stress of a transfo rmer oil-based ER fluid is empirically distilled in both shear and flow modes. This is then incorporated with the governing equation of motion of the proposed mixed-mode(shear mode plus flow mode) type engine mount. The damping force is analyzed with respect to the intensity of the electric field and design parameters such as electrode gap. Subsequently, the ER engine mount which is equivalent to the conventional hydraulic engine mount in terms of the damping level is designed and manufactured. Both computer simulation and experimental test are undertaken in order to evaluate vibration isolation performance. In addition, this performance is compared with that of the conventional hydraulic engine mount.

• 한국소음진동공학회논문집
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• 제15권10호
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• pp.1148-1159
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• 2005

In this paper, the various uncertainties generated in an optical disk drive (ODD) and the robust servo designs considering the uncertainties are studied. First, the brief introduction an ODD and the servo error tolerance of it are discussed. Then, the classifications of uncertainty and the concept of relative stability are introduced. Considering the uncertainty of an ODD, two robust control approaches are applied: (i) mixed sensitivity approach in H$\infty$ control theory for unstructured uncertainty, (ii) QFT for structured uncertainty Finally, the designed controllers are realized by DSP, and these controllers are applied to a commercial DVD-ROM drive. From these experiments, we prove that the designed robust controllers have more good disturbance rejection performance and robustness when it is compared to the conventional lead-lag controller.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2151-2158
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• 2000

This paper presents vibration control performance of a passenger vehicle installed with the mixed-mode type ER engine mounts. The performance is evaluated via hardware-in-the-loop-simulation(HILS) method. As a first step, a dynamic model of a vehicle featuring the ER engine mounts is formulated by taking into account the engine excitation forces. A new type of the fuzzy skyhook controller is then established in order to control both engine and body vibrations. This is accomplished by adopting a weighting parameter between two performance criteria which is to be determined from the fuzzy algorithm. Vertical displacement and acceleration of the engine mount obtained from the HILS method are provided in the frequency domain. In addition, vibration control performance between the conventional hydraulic engine mount and the proposed engine mount is compared in the time and frequency domains.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.481-486
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• 2000

This paper presents vibration control performance of a passenger vehicle installed with olectro-rheological(ER) engine mounts. As a first step, a mixed-mode ER engine mount is modeled and manufactured. After verifying the controllability of the dynamic stiffness by the intensity of the electric field, ER engine mounts are incorporated with a full-car model. The governing equation of motion is then formulated by considering engine excitation force. A skyhook controller to attenuate vibration motions is designed. The controller is implemented through hardware-in-the-loop simulation and control responses are presented in the both frequency and time domains.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.461-468
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• 2005

In this paper, mixed mode magneto-rheological (MR) damper, which is applicable for vibration control of a small scale multi-story structure, is devised. First, the schematic configurations of the shear, flow, and mixed mode MR dampers are described with design constraints and then the analytical models to predict the field-dependent damping forces are derived for each type. Second, an appropriate size of the mixed mode MR damper is manufactured and its field-dependent damping characteristics are evaluated in time domain. Finally, the performance of the manufactured MR damper which is semi-actively applied to a small scale building excited by earthquake load, is numerically evaluated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.37.4-37
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• 2001

This paper presents a vibration-rejection control design for a magnetic suspension system which has strong non-linearity, open-loop unstable characteristics, high-order flexible modes, and parameter variations. The target plant to be controlled consists of a U-core electromagnet and a flexible rail. We describe the test rig and formulate the mathematical model and then we set up a control problem as the mixed sensitivity problem where the augmented plant is constructed with frequency weighting functions and the feedback controller is designed by using the H$\infty$ controller. The effectiveness of the designed controller for the magnetic suspension system with high-order flexible modes is validated and justified using several simulations. These results show that the magnetic suspension system is robustly stable against disturbance and gives the well-damped tracking performance ...