• 동력기계공학회지
• /
• 제15권2호
• /
• pp.19-24
• /
• 2011

In this study, a control method of MR(magneto-rheological) damper for a cruise bus is investigated. A virtual dynamic damper and a sky-hook algorithm are employed to control the damping characteristics of MR damper. Coefficients for a virtual dynamic damper are determined through the parameter identification. A quarter car model of a cruise bus is established by using ADAMS/Car program for the computer simulation. Sine wave excitation and random excitation are used to compare the controlled MR damper with the passive damper. From the simulation results, the performance of MR damper with a virtual dynamic damper is better than that of the passive damper.

• 한국소음진동공학회논문집
• /
• 제12권6호
• /
• pp.469-477
• /
• 2002

An orificed fluid damper(OFD) having the capacity of about 2 tons was designed and fabricated, and series of tests were performed to grasp the fundamental performance characteristics of it. Several important findings were observed and introduced in this paper. It was applied to a 6-story steel structure under random excitation and seismic excitation for the confirmation of its validity on structural vibration absolution. The experimental results demonstrated that the addition of an OFD to the test structure is very effective in reduction of vibration level of the higher modes as well as the fundamental mode. Maxwell model was adopted to describe the frequency-dependent characteristics of the fabricated OFD and the numerical simulation was carried for the test structure. It was confirmed that the experimentally and numerically simulated results agree well.

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

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.817-824
• /
• 2000

It is essential to analyze structural vibrations due to turbulent wall pressure fluctuations over a body surface which moves through a fluid, because the vibrations can be a severe source of noise affecting to passengers in airplanes and SONAR performance. Generally, this kind of problems have been solved for very simplified models, e.g. plates, which can be applied to the wavenumber domain analysis. In this paper, a finite element modeling of the wall pressure fluctuations over arbitrary smooth surfaces is investigated. It is found that the modeled wall pressure fluctuation at nodes becomes uncorrelated at higher frequencies and at lower flow speeds, and the response is over-estimated due to the aliased power. Finally, the frequency range available for uncorrelated loading model and two power correction schemes are presented.

• 전기학회논문지
• /
• 제61권3호
• /
• pp.451-458
• /
• 2012

This paper addresses the problem that policy iteration (PI) for continuous-time (CT) systems requires explorations of the state space which is known as persistency of excitation in adaptive control community, and as a result, proposes a PI scheme explorized by an additional probing signal to solve the addressed problem. The proposed PI method efficiently finds in online fashion the related CT linear quadratic (LQ) optimal control without knowing the system matrix A, and guarantees the stability and convergence to the LQ optimal control, which is proven in this paper in the presence of the probing signal. A design method for the probing signal is also presented to balance the exploration of the state space and the control performance. Finally, several simulation results are provided to verify the effectiveness of the proposed explorized PI method.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1995년도 제12회 음성통신 및 신호처리 워크샵 논문집 (SCAS 12권 1호)
• /
• pp.146-149
• /
• 1995

This paper proposes a SM-CELP speech coder which applies different excitation signal according to the characteristic of speech segment at bit-rate below 4 kbps. Speech signal is divided with 2 modes such as stationary voice and etc. using the parameters of average energy of the short-time speech and the residual signal after long term prediction. Structured multi-pulse method is used for the excitation of mode-A and gaussian or pulse-like codebook for mode-B. 4.8kbps DoD-CELP are used to evaluate the performance of the proposed coder. As a result, the propose method shows 1~2 dB higher segmental signal to noise ratio and better subjectional quality without increasing the computational amount.

• 한국소음진동공학회논문집
• /
• 제17권9호
• /
• pp.785-796
• /
• 2007

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigates the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a potential energy loss ratio of cable vibration, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, three types of multi-mode patterns such as ambient vibration, support excitation and rain-wind induced vibration are assumed. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5 and in case of support excitation or rain-wind induced vibration it is between 0.5 and 1.0.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.602-603
• /
• 2014

A gearbox can be regarded as a self-exciting dynamic system, which has a vibration source. Transmission error (TE) is considered to be an main excitation source for gear noise and vibration. The TE excitation is transmitted through the gears, shafts, bearings, and housings. Thus, an experimental approach to each mechanical parts is useful in order to understand and evaluate the dynamic behaviour of a gearbox. This study is focused on the transmission and vibration characteristics of a helical gear system in development stage. In addition, by considering the tolerance factors and resonance characteristics, the vibration response of actual dynamic system is analysed.

• 한국소음진동공학회논문집
• /
• 제14권8호
• /
• pp.767-773
• /
• 2004

Semi-active control systems have attracted a great deal of attention in recent years, because they offer the adaptability of active devices without requiring large Power sources. One of the most Promising semi-active devices proposed for structural control is magneto-rheological fluid dampers (MR damper). In this paper, an MR damper having the capacity of about 1 ton was designed and fabricated. and series of tests were performed to grasp the fundamental Performance characteristics of it. It was also applied to a 6-story steel structure under random excitation and 3-different seismic excitations for the confirmation of its validity on structural vibration absorption. Through this study, the techniques and know-hows for MR damper production were acquired.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.393-396
• /
• 2001

According to the development of power electronic element(GTO, IGBT) and material for electrical machines(permanent magnet, super conductor), the technology for electrical machines is nowaday rapidly developing. Here with, a novel electrical machine, based on the new conception of transverse flux configuration leads to a considerable Increase in power density and enables simultaneously high efficiency. The transverse flux machine with PM excitation will be applied to gearless direct drives for railway traction system and magnetic levitation system. The designed and measured performance of transverse machine for railway traction system and magnetic levitation system revealed a great potential of system improvements to reduce linear motor mass and increase efficiency.