• Journal of KSNVE
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• v.8 no.4
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• pp.683-689
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• 1998

A control algorithm for multi-stage dampers is developed based on the mode skyhook control concept, and implemented on the full vehicle system environment. The test vehicle system is equipped with the real time controller, four-stage variable dampers and sensors. The real time controller is developed using a digital signal processor(DSP), digital I/O, A/D and D/A converters. The dampers are driven by the electromagnetic actuators of less than 20 msec response time. The sensors include accelerometers, relative displacement transducers, and steering wheel rate sensors, etc. Through a series of tests in laboratory and proving ground, the performance of the semi-active suspension system is evaluated and it is shown that the vehicle dynamic characteristics is improved with the developed damping system. Futhermore, the parameter tuning methods to enhance vehicle dynamic performance are propsoed.

• Smart Structures and Systems
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• v.25 no.1
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• pp.65-80
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• 2020

In order to protect a structure over its full life cycle, a novel tuned mass damper (TMD), the so-called semi-active eddy current pendulum tuned mass damper (SAEC-PTMD), which can retune its frequency and damping ratio in real-time, is proposed in this study. The structural instantaneous frequency is identified through a Hilbert-Huang transformation (HHT), and the SAEC-PTMD pendulum is adjusted through an HHT-based control algorithm. The eddy current damping parameters are discussed, and the relationship between effective damping coefficients and air gaps is fitted through a polynomial function. The semi-active eddy current damping can be adjusted in real-time by adjusting the air gap based on the linear-quadratic-Gaussian (LQG)-based control algorithm. To verify the vibration control effect of the SAEC-PTMD, an idealized linear primary structure equipped with an SAEC-PTMD excited by harmonic excitations and near-fault pulse-like earthquake excitations is proposed as one of the two case studies. Under strong earthquakes, structures may go into the nonlinear state, while the Bouc-Wen model has a wild application in simulating the hysteretic characteristic. Therefore, in the other case study, a nonlinear primary structure based on the Bouc-Wen model is proposed. An optimal passive TMD is used for comparison and the detuning effect, which results from the cumulative damage to primary structures, is considered. The maximum and root-mean-square (RMS) values of structural acceleration and displacement time history response, structural acceleration, and displacement response spectra are used as evaluation indices. Power analyses for one earthquake excitation are presented as an example to further study the energy dissipation effect of an SAECPTMD. The results indicate that an SAEC-PTMD performs better than an optimized passive TMD, both before and after damage occurs to the primary structure.

• Structural Engineering and Mechanics
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• v.63 no.3
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• pp.303-315
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• 2017

This paper presents a review on getting a Weighted Multi-Objective Optimization (WMO) of Tuned Mass Damper (TMD) parameters based on Response Surface Methodology (RSM) coupled central composite design and Weighted Desirability Function (WDF) to attenuate the earthquake vibration of a jacket supported Offshore Wind Turbine (OWT). To optimize the parameters (stiffness and damping coefficient) of damper, the frequency ratio and damping ratio were considered as a design variable and the top displacement and frequency response were considered as objective functions. The optimization has been carried out under only El Centro earthquake results and after obtained the optimal parameters, more two earthquakes (California and Northridge) has been performed to investigate the performance of optimal damper. The obtained results also compared with the different conventional TMD's designed by Den Hartog's, Sadek et al.'s and Warburton's method. From the results, it was found that the optimal TMD based on RSM shows better response than the conventional damper. It is concluded that the proposed response model offers an efficient approach regarding the TMD optimization.

• Journal of Drive and Control
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• v.15 no.1
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• pp.38-49
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• 2018

This research describes the development model and testing of a hybrid damper which can be applicable to a vehicle suspension. The hybrid damper is devised to improve the performance of a conventional passive oil damper using a magneto-rheological (MR) accumulator which consists of a gas accumulator and a MR device. The level of damping is continuously variable by the means of control in the applied current in a MR device fitted to a floating piston which separates the gas and the oil chamber. A simple MR device is used to resist the movement of floating piston. At first a mathematical model which describes all flows within the conventional oil damper is formulated, and then a small MR device is also devised and adopted to a mathematical model to characterize the performance of the device.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.331-341
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• 2018

This study proposes an integrated serial spring-damper mechanism as a dual pulse generation system. Compared to the traditional dual pulse generation system, which used multiple springs and a damper to generate a dual pulse critical for impact testing of naval equipments, currently used separated serial spring-damper mechanism is comprised of two components: an air spring, and a damper. The proposed mechanism combines the two components into one integrated system with a unique design that lets simply changing the volume and the pressure of the air tank, and the length of the annular pipe adjust the stiffness and damping constants for testing, eliminating the need to have multiple sets of air springs and dampers. Simulations using MatLab and Simulink were conducted to verify the feasibility of this design. The results show the potential of an integrated serial spring-damper mechanism as a more convenient and flexible mechanism for dual pulse generation system.

• Structural Engineering and Mechanics
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• v.11 no.4
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• pp.341-356
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• 2001

A new class of semi-active tuned mass dampers, named as "Ground Hook Tuned Mass Damper" (GHTMD) is introduced. This TMD uses a continuously variable semi-active damper (so called 'Ground-Hook') in order to achieve more reduction in the vibration level. The ground-hook dampers have been used in the auto-industry as a means of reducing the vibration of primary suspension systems in vehicles. This paper investigates the application of this damper as an element of a tuned damper for the vibration reduction of force-excited single degree of freedom (SDOF) models that can be representative of many structural systems. The optimum design parameters of GHTMDs are obtained based on the minimization of the steady-state displacement response of the main mass. The optimum design parameters which are evaluated in terms of non-dimensional values of the GHTMD are obtained for different mass ratios and main mass damping ratios. Using the frequency responses of the resulting systems, performance of the GHTMD is compared to that of equivalent passive TMD, and it is found that GHTMDs are more efficient. A design methodology to obtain the tuning parameters of GHTMD using the relationships developed in this paper is presented.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.191-194
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• 1997

Passive, semi-active and active dampers have been used to dissipate energy in mechanical systems. Semi-active dampers have higher performance than passive dampers and require lower power to operate than active dampers. Its damping characteristics can be changed appropriately for varying conditions. In this paper, we developed a semi-active damper based on Magnetorheological(MR) fluid. MR fluid has a variable damping characteristics proportional for the magnetic field intensity. It has several advantages such as high strength, low viscosity, robustness in impurities and wide temperature range of operational stability. We designed a constrained rotary MR damper base on valve mode which can dissipate more energy per unit volume. The system with Bingham characteristics is obtained and proved by the experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.151-158
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• 2008

The clutch system is a subcomponent of the transmission that is designed to engage and disengage power flow between the engine and the transmission. Recently, the engine power of automobile has been continuously increased because of customer's demand for the bigger one. As the engine power is increased, the vibration transmitted to the hydraulic clutch operating system has been increased. Therefore the demand for the reduction of clutch pedal vibration during the operation has been increased. This paper describes the pressure pulsation reduction characteristics of the damper cylinder which is applied to the hydraulic clutch operating system. And the purpose of this study is to propose an analysis model and investigate the effect of the design variable variations for the hydraulic clutch system. Especially, we studied the effect of damper cylinder parameter variations on the hydraulic clutch system performance.

• Journal of KSNVE
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• v.10 no.6
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• pp.1029-1034
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• 2000

A new electro-rheological squeeze film damper (ER-SFD) has been sealed with slotted piston rings which have electrodes at the inside of the constant gap. The slotted ER-SFD can prevent the problem of electric discharge which might be occurred in the previous configuration of an ER-SFD. The current paper presents the extraction of linearized dynamic coefficients within small orbit where these coefficients are controlled by the application of electric strength. Test rig has been modified to isolate the damper section for dynamic coefficient extraction. The results show that rotordynamic coefficients, damping and inertia terms, increase with increasing supply voltages, while stiffness coefficients decrease with increasing supply voltages. notating speed of rigid shaft does not affect these coefficients.

• Smart Structures and Systems
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• v.4 no.6
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• pp.741-757
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• 2008

The research field of structural control has evolved from the development of passive devices since 1970s, through the intensive investigation on active systems in 1980s, to the recent studies of semi-active control systems in 1990s. Currently semi-active control is considered most promising in civil engineering applications. However, actual implementation of semi-active devices is still limited due mainly to their system maintenance and associated long-term reliability as a result of power requirement. In this paper, the concept of functionally upgraded passive devices is introduced to streamline some of the state-of-the-art researches and guide the development of new passive devices that can mimic the function of their corresponding semi-active control devices for various applications. The general characteristics of this special group of passive devices are discussed and representative examples are summarized. Their superior performances are illustrated with cyclic and shake table tests of two example devices: mass-variable tuned liquid damper and friction-pendulum bearing with a variable sliding surface curvature.