• Coupled systems mechanics
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• 제7권6호
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• pp.707-729
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• 2018

The semi-active optimal vibration control of nonlinear torsion-bar suspension vehicle systems under random road excitations is an important research subject, and the boundedness of MR dampers and the uncertainty of vehicle systems are necessary to consider. In this paper, the differential equations of motion of the coupling torsion-bar suspension vehicle system with MR damper under random road excitation are derived and then transformed into strongly nonlinear stochastic coupling vibration equations. The dynamical programming equation is derived based on the stochastic dynamical programming principle firstly for the nonlinear stochastic system. The semi-active bounded parametric optimal control law is determined by the programming equation and MR damper dynamics. Then for the uncertain nonlinear stochastic system, the minimax dynamical programming equation is derived based on the minimax stochastic dynamical programming principle. The worst-case disturbances and corresponding semi-active bounded parametric optimal control are obtained from the programming equation under the bounded disturbance constraints and MR damper dynamics. The control strategy for the nonlinear stochastic vibration of the uncertain torsion-bar suspension vehicle system is developed. The good effectiveness of the proposed control is illustrated with numerical results. The control performances for the vehicle system with different bounds of MR damper under different vehicle speeds and random road excitations are discussed.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.302-310
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• 2001

In order to lessen cable vibration, new cable damper system with high damping rubber was developed using the basis of the LRB design scheme. The analysis model of cable damper system incorporate voigt-kelvin damper model into the nonlinear cable analysis model. To achieve maximum damping capacity both reducing damper stiffness and developing high damping rubber were performed. As a result of verification test, the high damping rubber damper shows its effectiveness in improving cable damping capacity.

• 동력기계공학회지
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• 제17권2호
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• pp.63-69
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• 2013

Most washing machines are now produced as a drum-type, where a washing drum mounted on a suspension system with springs and dampers, to minimize the transmittance of the vibration from the drum to the frame. A low-cost MR damper, using magneto-rheological fluids, can produce variable damping forces by changing the current values in the magnetic coil. Experimental results show the comparison of the vibration attenuation performances between two different dampers. One test set-up uses a passive damper and another one uses a MR fluid damper. The test results showed that the vibration amplitude of the washing machine with the MR damper is much smaller than the case with the passive damper.

• 동력기계공학회지
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• 제3권3호
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• pp.91-96
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• 1999

This study is about the design and analysis ot a suspension damper for truck driver's seat to improve the ride comfort. Trucks are usually subjected to hostile driving environments. Therefore, many truck driver's seat have suspension seats to isolate the vibration from the cab floor panel. Because the vehicle suspension system can reduce the primary vibration from the ground, only low frequency vibration can be transmitted to the driver's seat. But, this low frequency vibration can be harmful to the driver. The seat damper is very critical element to improve the ride comfort for the driver. In this study, a four-stage damper is designed and analyzed for the vibration capability. The damping coefficient of this damper can lie manually controlled in response to the road and driving environment.

• Structural Engineering and Mechanics
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• 제64권2호
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• pp.195-204
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• 2017

Analytical and experimental studies of the innovative pipe in pipe damper have been recently investigated by the authors. In this paper, by adding lead or zinc infill or slit diaphragm inside the inner pipe, it is tried to increase the equivalent viscous damping ratio improving the cyclic performance of the recently proposed multi-level control system. The damper consists of three main parts including the outer pipe, inner pipe and added complementary damping part. At first plastic deformations of the external pipe, then the internal pipe and particularly the added core and friction between them make the excellent multi-level damper act as an improved energy dissipation system. Several kinds of added lead or zinc infill and also different shapes of slit diaphragms are modeled inside the inner pipe and their effectiveness on hysteresis curves are investigated with nonlinear static analyses using finite element method by ABAQUS software. Results show that adding lead infill has no major effect on the damper stiffness while zinc infill and slit diaphragm increase damper stiffness sharply up to more than 10 times depending on the plate thickness and pipe diameter. Besides, metal infill increases the viscous damping ratio of dual damper ranging 6-9%. In addition, obtained hysteresis curves show that the multi-level control system as expected can reliably dissipate energy in different imposed energy levels.

• Smart Structures and Systems
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• 제9권1호
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• pp.35-53
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• 2012

Mechanical dampers have been proved to be one of the most effective countermeasures for vibration mitigation of stay cables in various cable-stayed bridges over the world. However, for long stay cables, as the installation height of the damper is restricted due to the aesthetic concern, using passive dampers alone may not satisfy the control requirement of the stay cables. In this connection, semi-active MR dampers have been proposed for the vibration mitigation of long stay cables. Although various studies have been carried out on the implementation of MR dampers on stay cables, the optimal damping performance of the cable-MR damper system has yet to be evaluated. Therefore, this paper aims to investigate the effectiveness of MR damper as a semi-active control device for the vibration mitigation of stay cable. The mathematical model of the MR damper will first be established through a performance test. Then, an efficient semi-active control strategy will be derived, where the damping of MR damper will be tuned according to the dynamic characteristics of stay cable, in order to achieve optimal damping of cable-damper system. Simulation study will be carried out to verify the proposed semi-active control algorithm for suppressing the cable vibrations induced by different loading patterns using optimally tuned MR damper. Finally, the effectiveness of MR damper in mitigating multi modes of cable vibration will be examined theoretically.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.344-349
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological (MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, The proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1121-1127
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• 2012

This paper presents a new small-sized damper featuring magneto-rheological(MR) fluid which can be applied to vibration control system. The proposed MR damper consists of cylinder, piston, a couple of bearings, oil-seals and magnetic circuit which has two coils. In this damper, approximately 5cc of MR fluid is used. The damping force of the MR damper is designed to be followed by linear shear-mode Bingham-plastic model. In order to verify the performance of the MR damper, an experimental apparatus is established. In the experimental test, the damping force of the MR damper is measured with respect to time, displacement and velocity. In addition, the time response of MR damper is measured when 1A of step current is applied. Finally, the proposed small MR damper is applied to vibration control. In this process, a simple 1-DOF system is modeled and controlled using PID controller.

• 대한기계학회논문집A
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• 제24권2호
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• pp.355-361
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• 2000

In this study, active control magnetic actuator for reducing vibration of rotor system is performed. Identification, modeling, simulation, control system design, and evaluation of active magnetic damper system have been researched. Power amplifier modeling, connected magnetic actuator and augmented by system identification, is included to establish a magnetic damper simulation which provides close performance correspondence to the physical plant. A magnetic actuator, digital controller using DSP(Digital Signal Processor), and bipolar operational power supply/amplifiers are developed to show the effectiveness of reducing rotor vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent components is developed. Two kinds of test are executed as sliding and oil bearing. Results presented in this paper will provide a well-defined technical parameters in designing magnetic damper system for the proposed rotor.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.463-471
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• 2013

This paper presents design and control of electronic control suspension(ECS) equipped with controllable magnetorheological(MR) damper for passenger vehicle. In order to achieve this goal, a cylindrical type MR fluid damper that satisfies design specification of a middle-sized commercial passenger vehicle is proposed. After manufacturing the MR damper with design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of a conventional damper. A quarter-vehicle MR ECS system consisting of sprung mass, spring, tire, controller and the MR damper is established in order to investigate the ride comfort performances. On the basis of the governing equation of motion of the suspension system, five control strategies(soft, hard, comfort, sport and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle MR ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in frequency domains on random road condition. In addition, performance comparison of WRMS(weighted root mean square) of the quarter-vehicle MR ECS system on random road are undertaken in order to investigate ride comfort characteristics.