• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.148-153
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• 2001

Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping hale been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.569-576
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• 2002

A case history is presented pertaining to piping fatigue by vibrations and sustain stresses in the hydraulic oil supply system for control valves in a 200MW thermal power plant that ultimately resulted in pipe rupture. The Piping was designed to supply the hydraulic oil for turbine control valves. Testing and analyses were performed on the system to develop solution to repair work on failures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.60-65
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• 2003

In this study, for estimating responses of a controlled structure and determining the maximum control force of velocity-dependent damping devices, three estimation models such as Fourier envelope convex model, probability model, and Newmark design spectrum are used. For this purpose, a procedure proposed by Gupta (1990) for estimating spectral velocity using pseudo-spectral velocity which is given by the estimation models is used and modified to consider the effects of increased damping ratio by the damping device. Time history results indicate that Newmark design spectrum gives the best estimation of maximum control force for over all period structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.323-328
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• 2002

The control performance of a vehicle installed with an MR(magnetorheological) fluid-based damper is investigated on the basis of Herschel-Bulkley shear model. Generally, most of MR fluid damper has been analyzed based on a simple Bingham-plastic shear model. However, the Bingham-plastic shear model can not well describe the behavior of the damper on the condition of high velocity and high current field input. Therefore, in this study, the Herschel-Bulkley shear model in which the constant post-yield plastic viscosity in Bingham model is replaced with a power law model dependent on shear rate is used to assess control performance of a vehicle with MR fluid damper suspension system. This study deals with a two-degree-of-freedom suspension using the MR fluid damper for a quarter car model. The response for the bump input to identify the fastness of MR fluid damper embedded skyhook controller and requested magnetic field are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.625-629
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• 2014

In this paper, a tile projector for the active control of low-frequency underwater echoes is studied using finite element method. Compared to the existing underwater actuators used for echo reduction, the tile projector is better suited for covering a wide area such as the hull of a submarine. In order to actively match the acoustic impedance at the water-object interface, the projector is driven to radiate a pressure wave that is the inverted replica of the echo at the interface. Finite element simulations demonstrate significant echo reductions due to the active impedance matching by the tile projector.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2225-2227
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• 2002

This paper presents the control and the performances of a $H_2$ controller for active vibration control of a cantilever beam. Electromagnets are used as actuators and a laser sensor is used to measure the position of the bending beam. The transfer function of the beam is obtained via the modal analysis of the free vitiation equation. The performance of the controller are verified by experimental results.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.798-800
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• 1998

In recent years, advances in construction techniques and materials have given rise to flexible light-weight structures. Because these structures extremely susceptib environmental loads, these random loadings u produce large deflection and acceleration on structures. Vibration control system of structur becoming an integral part of the structural syst the next generation of tall building. The proposed control system is applied to s degree of structure with mass damping and com with conventional PID and neural network PID system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.8
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• pp.616-625
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• 2002

In this paper, we drove the filtered-x least mean fourth (FXLMF) algorithm where the error raised to the power of four is minimized and analyzed its convergence behavior for a multiple sinusoidal acoustic noise and Gaussian measurement noise. The application of the FXLMF adaptive filter to active noise control requires to estimate the transfer characteristics of the acoustic path between the output and the error signal of the adaptive controller. The results of the convergence analysis of the FXLMF algorithm indicate that the effects of the parameter estimation inaccuracy on the convergence behavior of the algorithm are characterized by two distinct components phase estimation error and estimated gain. In particular, the convergence is shown to be strongly affected by the accuracy of the phase response estimate. Also, we newly show that the convergence behavior can differ depending on the relative sizes of the Gaussian noise and the convergence constant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.738-741
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• 2003

In general, the essential requirement for cruisers or car ferries is the reduction in noise to ensure high quality and comfort. Recently, the Ro-Ro Passengers Ferry (ROPAX) was built in Hyundai Heavy Industries. In order to minimize the noise levels, careful attention have to De paid by the special committee of experts from the initial design stage to the sea trial. Proper countermeasures, considering the characteristics of sources and receiver spaces, were applied from the noise prediction and various experiment results. Finally, this ship was successfully delivered with excellent noise properties. This paper describes the procedure of noise analysis, the countermeasures of noise control, and the measurement results of the sea trial. Onboard noise analysis had been carried out by statistical energy analysis program and outdoor noise prediction program based on ISO9614. The prediction results are in good agreements with the measurement results. The technology to minimize the noise levels for cruisers or car ferries has been established throughout the construction of this ship.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.709-712
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• 2003

Recently, high noise problem was experienced during the development of 2-pole squirrel cage motor for industrial compressor. In order to firstly identify the noise characteristics, a variety of measurements were carried out. It was found out that high noise was dominated by linear and nonlinear slot noise components. For the development of low noise indusrial motor, the air gap between rotor and stator in the motor was firstly enlarged. Secondly, it was also modified for the cooling housing to have high absorption features. Consequencely, low noise 2-pole motor having the noise level of less 80㏈(A) was developed. In this paper, a series of noise identification and control process for this motor are introduced.