Showing papers on "Damper published in 2006"
TL;DR: Computationally-tractable algebraic expressions are suggested here in contrast to the commonly-used Bouc–Wen model, which involves internal dynamics represented by a non-linear differential equation.
Abstract: Non-linear hysteresis is a complicated phenomenon associated with magnetorheological (MR) fluid dampers. A new model for MR dampers is proposed in this paper. For this, computationally-tractable algebraic expressions are suggested here in contrast to the commonly-used Bouc–Wen model, which involves internal dynamics represented by a non-linear differential equation. In addition, the model parameters can be explicitly related to the hysteretic phenomenon. To identify the model parameters, a particle swarm optimization (PSO) algorithm is employed using experimental force–velocity data obtained from various operating conditions. In our algorithm, it is possible to relax the need for a priori knowledge on the parameters and to reduce the algorithmic complexity. Here, the PSO algorithm is enhanced by introducing a termination criterion, based on the statistical hypothesis testing to guarantee a user-specified confidence level in stopping the algorithm. Parameter identification results are included to demonstrate the accuracy of the model and the effectiveness of the identification process.
282 citations
TL;DR: Based on theoretical analysis and experiments, a new model for a magnetorheological (MR) damper was proposed in this article, which can interpret the bi-viscous and hysteretic behaviors of the MR damper very well.
Abstract: Based on theoretical analysis and experiments, this article proposes a new model for a magnetorheological (MR) damper. The proposed model with a smooth and concise form can interpret the bi-viscous and hysteretic behaviors of the MR damper very well. The parameters in the model have definite physical meanings. The bi-viscous and hysteretic behaviors can be characterized by two parameters � 0 and A3. The proposed model makes it convenient to study the effects of the bi-viscous and hysteretic behaviors on the performance of a system with a MR damper. As one application of the model, a vibration isolation system with a MR damper is investigated, and the effects of bi-viscous and hysteretic behaviors on system performances are studied by numerical methods and theoretical analysis.
178 citations
TL;DR: In this article, an improved theoretical model of the previously developed system was formulated using the image method, thus allowing the eddy current density to be more accurately computed in addition to the development, modeled, and tested.
Abstract: When a conductive material experiences a time-varying magnetic field, eddy currents are generated in the conductor These eddy currents circulate such that they generate a magnetic field of their own, however the field generated is of opposite polarity, causing a repulsive force The time-varying magnetic field needed to produce such currents can be induced either by movement of the conductor in the field or by changing the strength or position of the source of the magnetic field In the case of a dynamic system the conductor is moving relative to the magnetic source, thus generating eddy currents that will dissipate into heat due to the resistivity of the conductor This process of the generation and dissipation of eddy current causes the system to function as a viscous damper In a previous study, the concept and theoretical model was developed for one eddy current damping system that was shown to be effective in the suppression of transverse beam vibrations The mathematical model developed to predict the amount of damping induced on the structure was shown to be accurate when the magnet was far from the beam but was less accurate for the case that the gap between the magnet and beam was small In the present study, an improved theoretical model of the previously developed system will be formulated using the image method, thus allowing the eddy current density to be more accurately computed In addition to the development of an improved model, an improved concept of the eddy current damper configuration is developed, modeled, and tested The new damper configuration adds significantly more damping to the structure than the previously implemented design and has the capability to critically damp the beam 's first bending mode The eddy current damper is a noncontacting system, thus allowing it to be easily applied and able to add significant damping to the structure without changing dynamic response Furthermore, the previous model and the improved model will lie applied to the new damper design and the enhanced accuracy of this new theoretical model will he proven
155 citations
TL;DR: In this paper, the authors provide a comprehensive review on the response time of magnetorheological (MR) dampers and investigate the effect of operating current, piston velocity, and system compliance.
Abstract: The primary purpose of this paper is to provide a comprehensive review on the response time of magnetorheological (MR) dampers. Rapid response time is desired for all real-time control applications. In reviewing the literature, a detailed description of the response time of semi-active dampers is seldom given. Furthermore, the methods of computing the response time are not discussed in detail. The authors intend to develop a method for the definition and the experimental determination of the response time of MR dampers. Furthermore, parameters affecting the response time of MR dampers are investigated. Specifically, the effect of operating current, piston velocity, and system compliance are addressed. Because the response time is often limited, not by the response of the fluid itself, but by the limitations of the driving electronics and the inductance of the electromagnet, the response time of the driving electronics is considered as well. The authors define the response time as the time required to transition from the initial state to 95% of the final state. Using a triangle wave to maintain constant velocity across the damper, various operating currents ranging from 0.5 to 2 A were applied and the resulting force was recorded. The results show that, for a given velocity, the response time decreases as the operating current increases. Results for the driving electronics show the opposite trend: as current increases, response time increases. To evaluate the effect of piston velocity on response time, velocities ranging from 0.1 to 4 in s−1 were tested. The results show that the response time decreases exponentially as the velocity increases, converging on some final value. Further analysis revealed that this result is an artifact of the compliance in the system. To confirm this, a series of tests was conducted in which the compliance of the system was artificially altered. The results of the compliance study indicate that compliance has a significant effect on the response time of the damper.
149 citations
TL;DR: In this article, two numerical models of friction dampers are proposed for single-degree-of-freedom (SDOF) structures and validated with the results obtained from the analytical model considering an example of SDOF structures.
141 citations
TL;DR: In this article, a semi-active independently variable stiffness (SAIVS) device is proposed to reduce seismic response of isolated buildings under near fault earthquakes, which can vary stiffness continuously and smoothly between minimum and maximum stiffness.
Abstract: Effectiveness of a new semiactive independently variable stiffness (SAIVS) device in reducing seismic response of sliding base isolated buildings is evaluated analytically and experimentally. Through analytical and experimental study of force—displacement behaviour of the SAIVS device, it is shown that the device can vary stiffness continuously and smoothly between minimum and maximum stiffness. Passive sliding base isolation systems reduce interstorey drifts and superstructure accelerations, but with increased base displacements, which is undesirable, under large velocity near fault pulse type earthquakes. It is a common practice to incorporate non-linear passive dampers into the isolation system to reduce bearing displacements. Incorporation of passive dampers, however, may result in increased superstructure accelerations and drifts; while, properly designed passive dampers can be beneficial. A viable alternative is to use semiactive variable stiffness systems, which can vary the period of the sliding base isolated buildings in real time, to simultaneously reduce bearing displacements and superstructure responses further than the passive systems, which deserves investigation. This study investigates the performance of a 1:5 scaled smart sliding base isolated building model equipped with the SAIVS device analytically and experimentally, under near fault earthquakes, by developing a new moving average non-linear tangential stiffness control algorithm for control of the SAIVS device. The SAIVS device reduces bearing displacements further than the passive cases, while maintaining isolation level forces and superstructure responses at the same level as the passive minimum stiffness case, indicating the significant potential of the SAIVS system. Copyright © 2005 John Wiley & Sons, Ltd.
139 citations
TL;DR: In this paper, a new hysteresis model based on the Bouc-Wen model has been developed to better characterize the hystresis phenomenon of the MR damper.
Abstract: Semi-actively controlled magnetorheological (MR) fluid dampers offer rapid variation in damping properties in a reliable fail-safe manner using very low power requirements. Their characteristics make them ideal for semi-active control in structures and vehicle applications in order to efficiently suppress vibration. To take advantage of their exceptional characteristics, a high fidelity model is required for control design and analysis. Perfect understanding of the dynamic characteristics of such dampers is necessary when implementing MR struts in applications. Different models have been proposed to simulate the hysteresis phenomenon of MR dampers. The Bouc–Wen model has been extensively used to simulate the hysteresis behavior of MR dampers. However, considerable differences still exist between the simulation and experimental results. Moreover, the characteristic parameters in the traditional Bouc–Wen model are not functions of the frequency, amplitude and current excitations; therefore, the estimated parameters can characterize the behavior of the tested MR damper under specific excitation conditions and must be re-evaluated if a different combination of excitation parameters is desired. This can be extremely cumbersome and computationally expensive. In this work, a new hysteresis model based on the Bouc–Wen model has been developed to better characterize the hysteresis phenomenon of the MR damper. The proposed model incorporates the frequency, amplitude and current excitation as variables and thus enables us to predict efficiently and accurately the hysteresis force for changing excitation conditions. The proposed modified Bouc–Wen model has been validated against the experimental results through graphical and quantitative analysis in time, displacement and velocity domains and an excellent correlation has been found.
131 citations
TL;DR: In this paper, three semi-active control methods are investigated for use in a suspension system using a commer- cial magnetorheological damper, including the limited relative displacement method, the modified skyhook method, and the modified Rakheja-Sankar method.
Abstract: Three semi-active control methods are investigated for use in a suspension system using a commer- cial magnetorheological damper. The three control methods are the limited relative displacement method, the modified skyhook method, and the modified Rakheja-Sankar method. The method of averaging has been adopted to provide an analytical platform for analyzing the performance of the different control methods. The analytical results are verified using numerical simulation, and further are used to assess the efficiency of dif- ferent control methods. An experimental test bed has been developed to examine the three control methods under sinusoidal and random excitations. Both analytical and experimental results confirm that the Rakheja- Sankar control and modified skyhook control methods significantly reduce the root-mean-square response of both the acceleration and relative displacement of the sprung mass, while the limited relative displacement controller can only control the relative displacement of the suspension system.
116 citations
TL;DR: In this paper, the effect of installing viscoelastic dampers (VEDs) in places such as seismic joints or building-sky-bridge connections to reduce earthquake-induced structural responses was investigated.
110 citations
TL;DR: In this paper, a two-DOF absorber with a negative damper in one of its two connections to the primary system was proposed to suppress single-mode vibration of a primary system.
Abstract: Whenever a tuned-mass damper is attached to a primary system, motion of the absorber body in more than one degree of freedom (DOF) relative to the primary system can be used to attenuate vibration of the primary system. In this paper, we propose that more than one mode of vibration of an absorber body relative to a primary system be tuned to suppress single-mode vibration of a primary system. We cast the problem of optimization of the multi-degree-of-freedom connection between the absorber body and primary structure as a decentralized control problem and develop optimization algorithms based on the H2 and H-infinity norms to minimize the response to random and harmonic excitations, respectively. We find that a two-DOF absorber can attain better performance than the optimal SDOF absorber, even for the case where the rotary inertia of the absorber tends to zero. With properly chosen connection locations, the two-DOF absorber achieves better vibration suppression than two separate absorbers of optimized mass distribution. A two-DOF absorber with a negative damper in one of its two connections to the primary system yields significantly better performance than absorbers with only positive dampers.
102 citations
TL;DR: In this article, a methodology for the optimal design of supplemental viscous dampers for framed structures is presented, which addresses the problem of minimizing the added damping subject to a constraint on the maximal inter-storey angular drift for an ensemble of realistic ground motion records while assuming linear behaviour of the damped structure.
Abstract: A methodology for the optimal design of supplemental viscous dampers for framed structures is presented. It addresses the problem of minimizing the added damping subject to a constraint on the maximal interstorey angular drift for an ensemble of realistic ground motion records while assuming linear behaviour of the damped structure. The solution is achieved by actually solving an equivalent optimization problem of minimizing the added damping subject to a constraint on a maximal weighted integral on the squared angular drift. The computational effort is appreciably reduced by first using one 'active' ground motion record. If the resulting optimal design fails to satisfy the constraints for other ground motions from the original ensemble, additional ground motions (loading conditions) are added one by one to the 'active' set until the optimum is reached. An efficient selecting process which is presented herein will usually require one or two records to attain an optimum design. Examples of optimal designs of supplemental dampers are presented for a 2-storey shear frame and a 10-storey industrial frame. The 2-storey shear frame is required to withstand one given ground motion whereas the 10-storey frame is required to withstand an ensemble of twenty ground motions. The resulting viscously damped structures have envelope values of interstorey drifts equal or less than the target drifts.
Patent•
02 Nov 2006
TL;DR: In this paper, an amount of time that air has been delivered from an air handler to a space is tracked, and based on the tracked amount of air, at least one turn-on time or one turnoff time of the delivery of air from the handler to the space is controlled.
Abstract: An amount of time that air has been delivered from an air handler to a space is tracked, and based on the tracked amount of time, at least one turn-on time or one turn-off time of the delivery of air from the air handler to the space is controlled. Other features relate, among other things, to controlling a replacement air vent, and to user interfaces.
TL;DR: This study presents a design strategy based on genetic algorithms (GA) for semi-active fuzzy control of structures that have magnetorheological dampers installed to prevent damage from severe dynamic loads such as earthquakes.
TL;DR: In this paper, a nonlinear multidegree-of-freedom (mdof) model of bladed disk system is analyzed in frequency domain by applying a quasi-linearization technique, which transforms the nonlinear differential equations into a set of nonlinear algebraic equations.
TL;DR: In this paper, a full-scale wind catcher was connected to a test room and positioned centrally in an open boundary wind tunnel to investigate the effect of air flow control mechanism and heat source inside rooms on wind catcher performance.
TL;DR: In this article, structural dynamic models for both wedge and split underplatform dampers have been developed, taking into account inertia forces and the effects of normal load variation on stick-slip transitions at the contact interfaces.
Abstract: Advanced structural dynamic models for both wedge and split underplatform dampers have been developed. The new damper models take into account inertia forces and the effects of normal load variation on stick-slip transitions at the contact interfaces. The damper models are formulated for the general case of multiharmonic forced response analysis. An approach for using the new damper models in the dynamic analysis of large-scale finite element models of bladed disks is proposed and realized. Numerical investigations of bladed disks are performed to demonstrate the capabilities of the new models and an analysis of the influence of the damper parameters on the forced response of bladed disks is made
TL;DR: In this article, the conventional steering damper is replaced with a network of interconnected mechanical components comprised of springs, dampers and inerters that retain the virtue of the damper, while improving the weave-mode performance.
Abstract: The establishment of damper settings that provide an optimal compromise between wobble- and weave-mode damping is discussed. The conventional steering damper is replaced with a network of interconnected mechanical components comprised of springs, dampers and inerters - that retain the virtue of the damper, while improving the weave-mode performance. The improved performance is due to the fact that the network introduces phase compensation between the relative angular velocity of the steering system and the resulting steering technique
TL;DR: In this article, a semi-active vibration control of an inclined sag cable with discrete magnetorheological (MR) dampers is investigated using the finite difference method (FDM).
TL;DR: The simulation results show that properly controlled MR dampers are effective means for vibration suppression for passenger cars.
Abstract: Magnetorheological dampers, which are semi-active devices that use MR fluids to produce controllable forces, can be used as smart actuators to reduce the vibrations of mechanical systems. The advantage of these actuators is the low power input requirements and the high output force they produce. An analytical study is performed in this article to examine the effectiveness of this type of actuator in suppressing the vibrations of a passenger car suspension system. A half-car model including passenger dynamics subjected to road disturbance is used. Two MR dampers attached to the front and back axles are used as actuators. An optimal control scheme is used to control the overall suspension system such that the vibrations of the passenger seats as well as the chassis of the car are greatly reduced or eliminated. The simulation results show that properly controlled MR dampers are effective means for vibration suppression for passenger cars.
TL;DR: In this paper, a generalized nonlinear model is formulated for the dynamic analysis of suspension seats with passive, semi-active and active dampers, while the contribution due to biodynamics of the human operator is considered to be negligible.
TL;DR: In this paper, a magnetorheological (MR) damper model is established and linearized based on theory analyses and real testing, and a model-free fuzzy control algorithm is employed to design a controller for achieving vibration isolation.
Abstract: A magnetorheological (MR) damper model is established and linearized based on theory analyses and real testing. Since the mathematical model of the suspension system is nonlinear and complicated, a model-free fuzzy control algorithm is employed to design a controller for achieving vibration isolation. As a pilot study, two MR dampers are used to replace the passive ones of the front half-car. A quarter-car fuzzy intelligent controller is employed to control the two MR independent suspension systems, respectively. The performance of the MR suspension system is evaluated by road testing. The test results indicate that the vibration of the vehicle body and unsprung mass are both reduced significantly.
TL;DR: In this paper, a tuned mass damper with a viscoelastic damping element applied to a single-degree-of-freedom system excited by white noise is considered and the effect of the damper is modelled as a force proportional to the fractional derivative of the relative displacement between the structure and the secondary mass.
TL;DR: In this paper, a simplified inverse dynamics (SID) model has been developed for both the Bingham plasticity model and the Bouc-Wen hysteresis model.
TL;DR: In this paper, an analytical and numerical study has been carried out to evaluate the dynamic behavior of the damped rotor as a function of the current supplied to the adjustable device, and a linear model that depicts the main characteristics of the system was developed as a useful tool in damper and control design.
Abstract: Magneto-rheological (MR) fluids react to magnetic fields undergoing changes in their mechanical characteristics, viscosity in particular. After an analytical and numerical study, an MR squeeze-film damper has been designed and set up on a reduced scale rotor test-rig. Numerical simulations were carried out in order to evaluate the dynamic behaviour of the damped rotor as a function of the current supplied to the adjustable device. A linear model that depicts the main characteristics of the system has been developed as a useful tool in damper and control design. By testing different fluids, an optimal fluid has been singled out. Tests conducted on the selected fluid show that it is possible to have the optimum conditions for each steady rotational speed.
TL;DR: In this article, a total of 312 semi-active magnetorheological dampers (RD-1005, Lord Corporation) have been installed for rain-wind-induced cable vibration control on the cable-stayed Dongting Lake Bridge, China.
Abstract: As the world's first implementation of magnetorheological (MR) smart damping technique in bridge structures, a total of 312 semi-active MR dampers (RD-1005, Lord Corporation) have recently been installed for rain-wind-induced cable vibration control on the cable-stayed Dongting Lake Bridge, China. This project has undergone several stages of in situ experiments and tests: (i) modal tests of undamped cables, (ii) forced vibration tests of MR-damped trial cables, (iii) monitoring of MR-damped and undamped cable responses under rain-wind excitations, (iv) comparative tests using different damper setups, (v) full installation, and (vi) field measurements and real-time control tests after the installation. After outlining the above six stages of the whole project and addressing the experience and lessons learned from both open-loop control and closed-loop control practices, this study focuses on the design considerations of implementing MR dampers for cable vibration control, taking into account the effects of the damper stiffness, damper mass, stiffness of damper support, nonlinearity of the damper, and sag and inclination of the cable. The research efforts make it possible to develop elaborate MR dampers specific for application to bridge stay cables.
TL;DR: In this paper, the effectiveness of MR damper-based control systems for seismic protection of base-isolated building structures employing some semi-active control algorithms, such as the modified clipped-optimal control, the maximum energy dissipation, the modulated homogeneous friction, and fuzzy logic based control algorithms was investigated.
Abstract: This paper investigates the effectiveness of the MR damper-based control systems for seismic protection of base-isolated building structures employing some semi-active control algorithms, such as the modified clipped-optimal control, the maximum energy dissipation, the modulated homogeneous friction, and fuzzy logic-based control algorithms, by examining the Phase I smart base-isolated benchmark building problem. The results of the numerical simulations showed that most of the control systems considered herein could be beneficial in reducing seismic responses, especially the base displacement or the isolator deformation, of the base-isolated building. If the base displacement is to be primarily reduced without regard to variation of the floor acceleration, the original clipped-optimal control algorithm could be recommended. On the other hand, if it may be required to reduce the base displacement without increasing the floor acceleration, the modified clipped-optimal control algorithm proposed in this study could be considered as one promising candidate for the linear benchmark base-isolated system. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: In this paper, a sealed liquid column damper (TLCD) is used to counteract steady-state vibrations in a base-isolated building with a TLCD in the basement.
Abstract: Sealed liquid column damper (TLCD) are tuned in the low-frequency range of application (say below 5 Hz) with respect to a selected natural frequency of the main structure by means of a geometrical transformation in analogy to the classical tuned mass damper (TMD). To improve the performance in MDOF buildings even further, the influence of neighboring modes is taken into account by fine-tuning in state space, rendering the optimal parameters modified. Final adjustments are easily made in the course of in situ testing. The passive sealed TLCD making use of the gas-spring effect and, since turbulent damping of assigned strength is present, is perfectly suited to counteract steady-state vibrations. Reduction of transient vibration peaks, observed within the initial period of the strong motion phase of earthquakes, requires active control, realized by controlled pressure input into the gas volume. The TLCD is commonly sufficiently damped and the vertical component of the seismic excitation does not cause parametric resonance. A sufficient condition based on the cut-off damping must be checked. Computer simulations and small scale experimental testing under time-harmonic-, single seismogram- and random- forcing confirmed the excellent performance and robustness of the TLCD. Optimal solutions for benchmark MDOF structures with multiple TLCD are presented when excited either by wind gusts or by earthquakes. A base-isolated structure is considered with the effective damping supplied by a TLCD in the basement. Copyright © 2005 John Wiley & Sons, Ltd.
TL;DR: It is shown that the proposed method can find optimal fuzzy rules and that the NSGA‐II‐optimized FLC outperforms not only a passive control strategy but also a human‐designed FLC and a conventional semiactive control algorithm.
Abstract: Smart base-isolation strategies are being widely investigated as a way to reduce structural damage caused by severe loads. This study uses a friction pendulum system (FPS) as the isolator and a magnetorheological (MR) damper as the supplemental damping device of a smart base-isolation system. Neuro-fuzzy models are used to represent dynamic behavior of the MR damper and FPS. A fuzzy logic controller (FLC) is used to modulate the MR damper so as to minimize structural acceleration while maintaining acceptable base displacement levels. To this end, a multi-objective optimization scheme that uses a nondominated multi-objective genetic algorithm (NSGA-II) is used to optimize parameters of membership functions and find appropriate fuzzy rules. To demonstrate the effectiveness of the proposed multi-objective genetic algorithm for FLC, a numerical study of a smart base-isolation system is conducted using several historical earthquakes. The findings show that the proposed method can find optimal fuzzy rules and that the NSGA-II-optimized FLC outperformed a passive control strategy, a conventional semiactive control algorithm and a human-designed FLC.
TL;DR: In this article, a tuned mass damper with a nonlinear power law viscous damper excited by white noise is considered and the system is analyzed by statistical linearization and stochastic simulation with the objective of minimizing the standard deviation of the response.
Abstract: A tuned mass damper with a nonlinear power law viscous damper excited by white noise is considered. The system is analyzed by statistical linearization and stochastic simulation with the objective of minimizing the standard deviation of the response. It is shown that the optimal parameters for the tuned mass damper are unaffected by the magnitude of the structural damping in the linear case. However, in the nonlinear case the structural damping influences the equivalent parameters obtained by statistical linearization and thereby indirectly the optimal values for the damper parameters. Results from stochastic simulation show good agreement with results from statistical linearization in terms of the standard deviation of the response. It is shown that the optimal damping, which can be obtained by the passive device, is the same for the linear and nonlinear damper. However, for the nonlinear tuned mass damper the optimal parameters will depend on both structural damping and excitation intensity (or vibration amplitude). The results are presented in such a way that they can be used directly for the design of a tuned mass damper with damping governed by a nonlinear viscous power law.
TL;DR: In this paper, a combination of four friction pendulum system (FPS) bearings and an adjustable magnetorheological (MR) damper was used to provide robust control of vibration for a large full-scale structure undergoing a wide variety of seismic loads.