• Structural Engineering and Mechanics
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• v.62 no.2
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• pp.197-208
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• 2017

Among various retrofitting strategies, use of semi-active control for retrofitting a building structure has gained momentum in recent years. One of the techniques for such retrofitting is to connect a weaker building to an adjacent stronger building by semi-active devices, so that performances of a weaker building are significantly improved for seismic forces. In this paper, a ten storey weaker building is connected to an adjacent stronger building using magneto-rheological (MR) dampers, for primarily improving the performance of the weaker building in terms of displacement, drift and base shear. For this, a fuzzy logic controller is specifically developed by fuzzyfying the responses of the coupled system. The performance of the control strategy is compared with the passive-on and passive-off controls. Pounding Mitigation between the two buildings is also investigated using all three control strategies. The results show that there exists a fundamental frequency ratio between the two buildings for which maximum control of the weaker building response takes place with no penalty on the stronger building. There exists also a fundamental frequency ratio where control of the weaker building response is achieved at the expense of the amplification of the stronger building. However, coupling strategy always improves the possibility of pounding mitigation.

• Smart Structures and Systems
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• v.16 no.2
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• pp.329-345
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• 2015

As commonly known, sensor errors and faulty signals may potentially lead structures in vibration to catastrophic failures. This paper presents a new approach to deal with sensor errors/faults in vibration control of structures by using the Fault detection and isolation (FDI) technique. To demonstrate the effectiveness of the approach, a space truss structure with semi-active devices such as Magneto-Rheological (MR) damper is used as an example. To address the problem, a Linear Matrix Inequality (LMI) based fixed-order $H_{\infty}$ FDI filter is introduced and designed. Modeling errors are treated as uncertainties in the FDI filter design to verify the robustness of the proposed FDI filter. Furthermore, an innovative Fuzzy Fault Tolerant Controller (FFTC) has been developed for this space truss structure model to preserve the pre-specified performance in the presence of sensor errors or faults. Simulation results have demonstrated that the proposed FDI filter is capable of detecting and isolating sensor errors/faults and actuator faults e.g., accelerometers and MR dampers, and the proposed FFTC can maintain the structural vibration suppression in faulty conditions.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.6
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• pp.582-587
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• 2012

This paper presents a solution of the vibration reduction in the hollow shafts by using magentorehological( MR) elastomer. Proposed active damping structure is built by embedding the MR elastomers whose elastic modulus is controllable by an applied magnetic field. MR elastomers consist of synthetic rubber filled with micron-sized magnetizable particles. For reduction of vibration, dynamic damper of hollow shaft is designed by using MR elastomer and equipped in the hollow shaft for the application to drive shaft. Experiment results are shown through the experiments to confirm the effect of MR elastomer dynamic damper for vibration reduction. Thus, the designed damping structure can be applied to vibration absorber used in drive shafts as well as the propeller shafts.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.26-32
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• 2009

This study is about roll characteristics evaluation to show the advantage of using MR(magneto-rheological) dampers for steering of a SUV(sports utility vehicle). Roll characteristics is very important to observe the roll-propensity of the SUV. ADAMS/Car program was used to simulate the basic steering motion, using 63 D.O.F. vehicle model. Sky-Hook and Ground-Hook control algorithms were used as a semi-active suspension system controller. The roll characteristics from the steering motion were compared between the simulation results from the semi-active suspension system and the passive suspension system.

• Earthquakes and Structures
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• v.20 no.3
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• pp.353-364
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• 2021

Natural hazards like earthquakes, high winds, and tsunami are a threat all the time for multi-story structures. The environmental forces cannot be clogged but the structures can be prevented from these natural hazards by using protective systems. The structural control can be achieved by using protective systems like the passive, active, semi-active, and hybrid protective systems; but the semi-active protective system has gained importance because of its adaptability to the active systems and reliability of the passive systems. Therefore, a semi-active protective system for the earthquake forces has been adopted in this work. Magneto-Rheological (MR) damper is used in the structure as a semi-active protective system; which is connected to the current driver and proposed controller. The Proportional Integral Derivative (PID) controller and reliable PID controller are two proposed controllers, which will actuate the MR damper and the desired force is generated to mitigate the vibration of the structural response subjected to the earthquake. PID controller and reliable PID controller are designed and tuned using Ziegler-Nichols tuning technique along with the MR damper simulated in Simulink toolbox and MATLAB to obtain the reduced vibration in a three-story benchmark structure. The earthquake is considered to be uncertain; where the proposed control algorithm works well during the presence of earthquake; this paper considers robustness to provide satisfactory resilience against this uncertainty. In this work, two different earthquakes are considered like El-Centro and Northridge earthquakes for simulation with different controllers. In this paper performances of the structure with and without two controllers are compared and results are discussed.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.112-121
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• 1999

An MR(Magneto-Rheological) fluids damper is designed and applied to vibration suppression of a 1/4 car model. The damping constant of MR damper changes according to input current which is controlled in a semi-active way. Several control algorithms are compared in simulations and experiments. The advantage of the proposed Frequency shaped LQ control is that passenger comfort is emphasized in the range of 4~8Hz and driving safety is emphasized around the resonance frequency of unsprung mass.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.33-41
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• 2020

The landing gear of an aircraft is a device that absorbs and dissipates shock energy transmitted from the ground to the fuselage. Among the landing gears, the semi-active MR damper landing gear is supposed to show high-shock absorption efficiency under various landing conditions and secure the stability when out of control. In the case of the MR damper landing gear using an annular channel rather than orifice, Amesim, a commercial multi-physics program, is considered as more useful than the conventional two-degree-of-freedom model because the damping force generated by the pressure drop through the flow annular path can cause cavitation in the low-pressure chamber of the MR damper with a specific internal structure. In this paper, the main dynamic characteristics of the MR damper landing gear with an annular type flow path structure has been analyzed under the condition of cavitation. Based on the analysis results using Amesim, a design guideline for the MR damper flow path that prevents cavitation has been proposed based on the modification of the arrangement of internal components of the damper. The guideline was verified through a drop simulation.

• Smart Structures and Systems
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• v.15 no.6
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• pp.1481-1501
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• 2015

MR-TLCD (Magneto-Rheological Tuned Liquid Column Damper) is a new developed vibration control device, which combines the traditional passive control property with active controllability advantage. Based on traditional TLCD governing equation, this study further considers MR-fluid viscosity in the equation and by transforming the non-linear damping term into an equivalent linear damping, a solution can be obtained. In order to find a countable set of parameters for the design of the MR-TLCD system and also to realize its applicability to structures, a series of experimental test were designed and carried out. The testing programs include the basic material properties of the MR-fluid, the damping ratio of a MR-TLCD and the dynamic responses for a frame structure equipped with the MR-TLCD system subjected to strong ground excitations. In both the analytical and experimental results of this study, it is found that the accurately tuned MR-TLCD system could effectively reduce the dynamic response of a structural system.

• Smart Structures and Systems
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• v.5 no.3
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• pp.261-277
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• 2009

A fuzzy-sliding mode controller is presented to control the dynamics of semi-active suspension systems of vehicles using magneto-rheological (MR) fluid dampers. A full car model is used to design and evaluate the performance of the proposed semi-active controlled suspension system. Four mixed mode MR dampers are designed, manufactured, and integrated with four independent sliding mode controllers. The siding mode controller is designed to decrease the energy consumption and maintain robustness. In order to overcome the chattering of the sliding mode controllers, a fuzzy logic control strategy is merged into the sliding mode controller. The proposed fuzzy-sliding mode controller is designed and fabricated. The performance of the semi-active suspensions is evaluated in both the time and frequency domains. The obtained results demonstrate that the proposed fuzzy-sliding mode controller can effectively suppress the vibration of vehicles and improve their ride comfort and handling stability. Furthermore, it is shown that the "chattering" of the sliding mode controller is smoothed when it is integrated with a fuzzy logic control strategy. Although the cost function of the fuzzy-sliding mode control is a slightly higher than that of a classical LQR controller, the control effectiveness and robustness are enhanced considerably.

• Smart Structures and Systems
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• v.10 no.6
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• pp.557-572
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• 2012

This paper focuses on the vibration control of long-span reticulated steel structures under multi-dimensional earthquake excitation. The control system and strategy are constructed based on Magneto-Rheological (MR) dampers. The LQR and Hrovat controlling algorithm is adopted to determine optimal MR damping force, while the modified Bingham model (MBM) and inverse neural network (INN) is proposed to solve the real-time controlling current. Three typical long-span reticulated structural systems are detailedly analyzed, including the double-layer cylindrical reticulated shell, single-layer spherical reticulated shell, and cable suspended arch-truss structure. Results show that the proposed control strategy can reduce the displacement and acceleration effectively for three typical structural systems. The displacement control effect under the earthquake excitation with different PGA is similar, while for the cable suspended arch-truss, the acceleration control effect increase distinctly with the earthquake excitation intensity. Moreover, for the cable suspended arch-truss, the strand stress variation can also be effectively reduced by the MR dampers, which is very important for this kind of structure to ensure that the cable would not be destroyed or relaxed.