Multiple Magnetorheological Research Articles

Numerical Simulation and Torsional Vibration Mitigation of Spatial Eccentric Structures with Multiple Magnetorheological Dampers

Eccentric structures will have torsional vibrations subjected to earthquakes, which can accelerate the damage of structures, and even become the main cause of building collapse. Semi-active control systems equipped with multiple magnetorheological (MR) dampers have been widely applied in structural vibration control. In this study, numerical models of spatial eccentric structures with multiple MR dampers were established, and time history analysis was conducted to mitigate torsional vibrations of eccentric structures. Firstly, a full-scale spatial eccentric structure model with both plan asymmetry and vertical irregularity was established in OpenSEES, and the accuracy of the structure model was verified by comparisons with model results from SAP2000. Then, the mathematical model of MR dampers was introduced to the structure model using the ‘Truss’ element and self-defined material in OpenSEES, and damping forces obtained from the MR damper model were compared with experimental data. Finally, modal analysis and nonlinear time history analysis of the eccentric structure model equipped with multiple MR dampers subjected to different seismic excitations were performed. Comparisons between the seismic responses of the uncontrolled structure and the structure with multiple MR dampers were carried out to demonstrate the effectiveness of the MR control system. Numerical results show that the control system with multiple MR dampers can significantly attenuate the torsional vibrations of eccentric structures, and thus possess significant engineering application prospects.

Semi-Active Control for a Helicopter with Multiple Landing Gears Equipped with Magnetorheological Dampers

Due to their extensive use in various applications, helicopters need to be able to land in a variety of conditions. Typically, a helicopter landing gear system with skids or passive wheel-dampers is designed based on only one critical touchdown condition. Thus, this helicopter landing gear system may not perform well in different landing conditions. A landing gear system with magnetorheological (MR) dampers would be a promising candidate to solve this problem. However, a semi-active controller must be designed to determine the electrical current applied to the MR damper to directly manage the damping force. This paper presents a new skyhook controller, called the skyhook extended controller, for a helicopter with multiple landing gears equipped with MR dampers to reduce the helicopter’s acceleration at the center of gravity in off-normal landing attitude conditions. A 9-DOF simulation model of a helicopter with multiple MR landing gears was built using RECURDYN. To verify the effectiveness of the proposed controller, co-simulations were executed with RECURDYN and MATLAB in different initial pitch and roll angles at touchdown. The main simulation results show that the proposed controller can greatly decrease the peak and rms acceleration of the helicopter’s center of gravity compared to a traditional skyhook controller and passive damper.

Adaptive neuro-fuzzy and simple adaptive control methods for full three-dimensional coupled buildings subjected to bi-directional seismic excitations

Attenuation of three-dimensional coupled buildings under bi-directional seismic excitations using semi-active control devices is pursued in this paper. Multiple magneto-rheological (MR) dampers are employed to connect two adjacent buildings at multiple levels for real-time control of the structural responses. The MR dampers are managed by adaptive neuro-fuzzy inference systems (ANFIS) and simple adaptive control (SAC) methods so a comparison between the performance of both controllers can be made. The displacement feedback type is used for both control methods to design the closed-loop action. The structural system modeled as two three-dimensional buildings connected by frame elements in which the MR dampers are implemented. The equations of motions of the three-dimensional model are formulated by assuming that each floor diaphragm is rigid in its own plane but flexible in the vertical coordinate. Each link is assumed to have three degrees-of-freedom two translational and one rotational at its ends. The adaptive neuro-fuzzy inference system is designed based on Sugeno-type model. Seven triangular membership functions are chosen to fuzzify the input crisp data in the fuzzy logic controller. The training data for ANFIS are generated by the Linear Quadratic Regulator (LQR) under white-noise disturbance. For the simple adaptive controller, LQR is also used to generate the desired trajectories of the reference-model. Numerical simulations are carried out for both symmetrical and asymmetrical coupled buildings under eleven pairs of major earthquakes. The results show that both ANFIS and SAC can deal very successfully with modeling complexities associated with full three-dimensional models subjected to multi-excitations. In terms of seismic responses reduction, both methods have shown a great potential in enhancing the structural performance under seismic activities.

Seismic Performance Evaluation of a Recently Developed Magnetorheological Damper: Experimental Investigation

Magnetorheological (MR) dampers have the ability to mitigate natural hazards for structures due to their high energy dissipation features with low power demand. This feature has made the MR damper one of the most popular semiactive damping devices. The present work validates the performance of a single-story reinforced concrete (RC) frame using a reduced scale 10 kN capacity multiple coil MR damper that has recently been developed by the authors. To conduct this test, MR fluid is synthesized and the proposed multicoil MR damper was designed and fabricated. Three RC frames were cast and tested using a loading frame with a capacity of 50 kN. This frame was subjected to earthquake excitation with MR damper placed diagonally at 0 A current, 3 A current, and without MR damper for a better comparison. The comparative performance indicated the reductions in displacements, increase of forces, and changes in crack patterns. The proposed semiactive damper can, therefore, be used effectively as a seismic resilient device in reducing the structural responses in the regions of moderate to high seismicity.

A Takagi-Sugeno Fuzzy Model-Based Control Strategy for Variable Stiffness and Variable Damping Suspension

As the concept of variable stiffness and variable damping (VSVD) has increasingly drawn attention, suspensions applied with magnetorheological (MR) dampers to achieve varying stiffness and damping have been an attractive method to improve vehicle performance and driver comfort further. As highly nonlinearity of MR damper dynamics and coupled interconnections in the case of multi-output control, to build a direct control system for VSVD suspension based on multiple MR dampers is difficult. Applying Takagi-Sugeno (T-S) fuzzy model on the VSVD system enables the linear control theory to be directly utilized to build the multi-output controller for multi-MR dampers. In this paper, a T-S fuzzy model is established to describe an MR VSVD suspension model, and then an H ∞ controller that considers the multi-input/multi-output (MIMO) coupled interconnections characteristic and multi-object optimization is designed. To estimate state information for the T-S fuzzy model in real-time, a state observer is designed and integrated in the controller. Then, the performance of the VSVD control algorithm was evaluated by numerical simulation. The results demonstrate that the T-S fuzzy model-based H ∞ controller outperforms the independent control method for a VSVD suspension system with multi-MR dampers.

Structure Optimization and Performance Analysis of a Multiple Radial Magnetorheological Valve

Due to the controllable and reversible properties of the smart magnetorheological (MR) fluid, a novel multiple radial MR valve was developed. The fluid flow channels of the proposed MR valve were mainly composed of two annular fluid flow channels, four radial fluid flow channels and three centric pipe fluid flow channels. The working principle of the multiple radial MR valve was introduced in detail, and the structure optimization design was carried out using ANSYS software to obtain the optimal structure parameters. Moreover, the optimized MR valve was compared with pre-optimized MR valve in terms of their magnetic flux density of radial fluid resistance gap and performance of pressure drop. The experimental test rig was set up to investigate the performance of pressure drop of the proposed MR valve under different currents applied and different loading cases. The results show that the pressure drop between the inlet and outlet port could reach 5.77 MPa at the applied current of 0.8 A. Furthermore, the experimental results also indicate that the loading cases had no effect on the performance of pressure drop.

Comparative Studies of Semiactive Control Strategies for MR Dampers: Pure Simulation and Real-Time Hybrid Tests

This paper presents comparisons of the performances of three semiactive control algorithms for use with multiple magnetorheological (MR) dampers. The three controllers are (1) the clipped-optimal controller, (2) the decentralized output feedback polynomial controller, and (3) the simple passive controller. These controllers use different types of inputs to calculate control signals for the MR dampers, based on different control mechanisms. To investigate the advantages of each controller, a three-degree-of-freedom steel moment-resisting frame, designed using a performance-based design methodology, was developed. The performance was investigated by using four different earthquakes utilized during the design of the building frame. Comparisons of the controllers’ performance were carried out in terms of reduction in the maximum interstory drifts, displacements, absolute accelerations, and control forces. Real-time hybrid tests were carried out to validate these comparisons.

Effects of multiple MR dampers controlled by fuzzy-based strategies on structural vibration reduction

Fuzzy logic based control has recently been proposed for regulating the properties of magnetorheological (MR) dampers in an effort to reduce vibrations of structures subjected to seismic excitations. So far, most studies showing the effectiveness of these algorithms have focused on the use of a single MR damper. Because multiple dampers would be needed in practical applications, this study aims to evaluate the effects of multiple individually tuned fuzzy-controlled MR dampers in reducing responses of a multi-degree-of-freedom structure subjected to seismic motions. Two different fuzzy-control algorithms are considered, a traditional controller where all parameters are kept constant, and a gain-scheduling control strategy. Different damper placement configurations are also considered, as are different numbers of MR dampers. To determine the robustness of the fuzzy controllers developed to changes in ground excitation, the structure selected is subjected to different earthquake records. Responses analyzed include peak and root mean square displacements, accelerations, and interstory drifts. Results obtained with the fuzzy-based control schemes are compared to passive control strategies.

Semi-active control of a torsionally-responsive structure

The mitigation of torsional responses in structures using semi-active devices is pursued in the current study. Multiple magnetorheological (MR) dampers are employed for real-time control of the response of a benchmark structure to earthquake excitations. MR damper resistance levels are intelligently managed by a global fuzzy logic controller (FLC). The FLC is generated using a controlled-elitist genetic algorithm (GA). Development of an optimal FLC is expedited by a discretized search space of fuzzy logic membership functions. To enable robust control an excitation is created for training by a GA using the RSPMatch2005 algorithm that modifies historic ground records in the time-domain by wavelet operations. Both numerical and large-scale experimental efforts are undertaken to validate the proposed control system. Results show that the GA-optimized FLC control provides a favorable balance in reduction of inter-story drift and absolute acceleration levels.

Decentralized sliding mode control of a building using MR dampers

This paper presents the structural control results of shaking table tests for a steel framestructure in order to evaluate the performance of a number of proposed semi-active controlalgorithms using multiple magnetorheological (MR) dampers. The test structure is asix-story steel frame equipped with MR dampers. Four different cases of damperarrangement in the structure are selected for the control study. In experimental tests, theEl Centro earthquake and Kobe earthquake ground motion data are used as excitations.Further, several decentralized sliding mode control algorithms are developed in this paperspecifically for applications of MR dampers in building structures. Various controlalgorithms are used for the semi-active control studies, including the proposeddecentralized sliding mode control (DSMC), LQR control, and passive-on andpassive-off control. Each control algorithm is formulated specifically for the use ofMR dampers installed in building structures. Additionally, each algorithm usesmeasurements of the device velocity and device drift for the determination of the controlaction to ensure that the algorithm can be implemented in a physical structure.The performance of each algorithm is evaluated based on the results of shakingtable tests, and the advantages of each algorithm are compared and discussed.The reduction of story drifts and floor accelerations throughout the structure isexamined.

Large-Scale Experimental Verification of Semiactive Control through Real-Time Hybrid Simulation

Magneto-rheological (MR) fluid dampers have been identified as a particularly promising type of semiactive control device for hazard mitigation in civil engineering structures. Large-scale experimental testing is important to verify the performance of MR fluid dampers for seismic protection of civil structures. Real-time hybrid testing, where only the critical components of the system are physically tested while the rest of the structure is simulated, can provide a cost-effective means for large-scale testing of semiactive controlled structures. This paper describes the real-time hybrid simulation experimental setup for multiple large-scale MR fluid dampers and demonstrates the capability at the University of Colorado at Boulder shared-use Fast Hybrid Test facility to conduct real-time hybrid testing within the Network for Earthquake Engineering Simulation.

Seismic response control of a complex structure using multiple MR dampers: experimental investigation

This paper presents an experimental investigation on semi-active seismic response control of a multistory building with a podium structure using multiple magnetorheological (MR) dampers manipulated by a logic control algorithm. The experiments are performed in three phases on a seismic simulator with a slender 12-story building model representing a multi-story building and a relatively stiff 3-story building model typifying a podium structure. The first phase of the investigation is to assess control performance of using three MR dampers to link the 3-story building to the 12-story building, in which seismic responses of the controlled two buildings are compared with those of the two buildings without any connection and with rigid connection. The second phase is to investigate reliability of the semi-active control system and robustness of the logic control algorithm when 2 out of 3 MR dampers fail and when the electricity supply to MR dampers is completely stopped. The last phase is to examine sensitivity of semi-active control performance of two buildings to change in ground excitation. The experimental results show that multiple MR dampers with the logic control algorithm can achieve a significant reduction in seismic responses of both buildings. The proposed semi-active control system is of high reliability and good robustness.

Innovative Technology for Seismic Response Reduction of Tall Buildings with Podium Structures

Structural controf technology offers many new ways to proted structures from naturol hazards. A comprehensive experimental Investigation was carried out in The Hong Kong Polytechnic University to apply multiple magnetorheological (MR) dampers to connect podium structures to tall buildingsfar preventing seismic damage due to sudden change of lateral stiffness and mass. A slender 12-storey building madel and a relatively stiff 3-storey bUilding model were construded to represent a tall building and a podium strudure respectively. MR dampers were used to link the 3-storey building to the 12storey building at each of the bottom three storeys. The two buildings without any connedlon and with a rigid connedian weref/rst tested under scaled EI Centro 1940 N-S ground motion. A test was then performed on the two buildings connected by MR dampers manipulated by a semi-adive logic control algorithm. Finally, reliability of the seml-adive cantrol system and robustness of the semi-adive logic control algorithm were ex...

Experimental Verification of Multiinput Seismic Control Strategies for Smart Dampers

This paper documents the results of an experimental study conducted to demonstrate the capabilities of multiple magnetorheological (MR) devices for seismic control of civil engineering structures. A six-story test structure in the Washington University Structural Control and Earthquake Engineering Lab is considered, and four parallel-plate, shear-mode MR dampers are used to control this test structure. Two control devices are installed in the test structure between the base and first floor, and two are installed between the first floor and second floor. A phenomenological model of the shear mode MR damper is proposed and verified. A nonlinear system identification method, appropriate for multi-input/multi-output systems, is used to develop a model of the integrated structural system. Experimental transfer function data corresponding to one system input are used to update the eigenvalues of an analytical model. Two semiactive control algorithms, including a Lyapunov algorithm and a clipped-optimal algorithm, are considered. An El Centro earthquake example is used to disturb the system at three amplitude levels. The results indicate that high performance levels can be achieved, and the responses of the semiactive system are significantly better than that of comparable passive systems.

Semiactive Control Strategies for MR Dampers: Comparative Study

This paper presents the results of a study to evaluate the performance of a number of recently proposed semiactive control algorithms for use with multiple magnetorheological (MR) dampers. Various control algorithms used in recent semiactive control studies are considered including the Lyapunov controller, decentralized bang-bang controller, modulated homogeneous friction algorithm, and a clipped optimal controller. Each algorithm is formulated for use with the MR damper. Additionally, each algorithm uses measurements of the absolute acceleration and device displacements for determining the control action to ensure that the algorithms could be implemented on a physical structure. The performance of the algorithms is compared through a numerical example, and the advantages of each algorithm are discussed. The numerical example considers a six-story structure controlled with MR dampers on the lower two floors. In simulation, an El Centro earthquake is used to excite the system, and the reduction in the drifts, accelerations, and relative displacements throughout the structure is examined.