Use Of Magnetorheological Dampers Research Articles

Study on Passive and Semiactive Control Systems in Structures under Near- and Far-Field Earthquakes

The construction demand for irregular structures is increasing due to the population growth of cities, limited construction areas, and the aesthetics of structures. Lack of proper understanding on the dynamic behavior of these structures during seismic events can lead to local and global failures on them. In order to investigate this issue, we used a regular 10-story structure with three different stiffness irregularity cases along the elevation. Irregularities are considered in three positions: the lower half of the structure height, the lowest story, and the middle story. In this study, to reduce the damage and mitigate the seismic response of the structure, three control systems are proposed including a magnetorheological (MR) damper with semiactive fuzzy controller as the semiactive control system, a Tuned Mass Damper (TMD) as the passive control system, and the simultaneous use of them. Based on the numerical analyses under near- and far-field ground motions, the residual plastic deformations are significantly reduced by the simultaneous use of MR damper and TMD, while each of these dampers alone performs poorly in some cases. The results show that if these two dampers are used together, a more promising control system with robust performance against changes in system parameters can be achieved.

A Semi-Active Control Technique through MR Fluid Dampers for Seismic Protection of Single-Story RC Precast Buildings.

The work proposes an innovative solution for the reduction of seismic effects on precast reinforced concrete (RC) structures. It is a semi-active control system based on the use of magnetorheological dampers. The special base restraint is remotely and automatically controlled according to a control algorithm, which modifies the dissipative capability of the structure as a function of an instantaneous dynamic response. The aim is that of reducing the base bending moment demand without a significant increase in the top displacement response. A procedure for the optimal calibration of the parameters involved in the control logic is also proposed. Non-linear modelling of a case-study structure has been performed in the OpenSees environment, also involving the specific detailing of a novel variable base restraint. Non-linear time history analyses against natural earthquakes allowed testing of the optimization procedure for the control algorithm parameters, finally the capability of the proposed technology to mitigate seismic risk of new or existing one-story precast RC structures is highlighted.

Modelling Magnetorheological Dampers in Preyield and Postyield Regions

The use of magnetorheological dampers has rapidly spread to many engineering applications, especially those related to transportation and civil engineering. The problem arises upon modelling their highly nonlinear behaviour: in spite of the huge number of apparently accurate models in the literature, most fail when considering the overall magnetomechanical behaviour. In this study, a brief but broad review of different magnetorheological damper models has been carried out, which includes characterisation, modelling, and comparison. Unlike many other studies, the analyses cover the behaviour from preyield to postyield regions of the MR fluid. The performance of the different models has been assessed by means of numerous experimental tests and by means of simulations in a simple and straightforward semiactive control case study. The results obtained prove that most models usually fail in predicting accurate low‐velocity behaviour (before iron chains yield) and, as a result, may lead to bad estimations when used in control schemes due to modelling errors and chattering.

Magneto-rheological and passive damper combinations for seismic mitigation of building structures

Building structures generally have inherent low damping capability and hence are vulnerable to seismic excitations. Control devices therefore play a useful role in providing safety to building structures subject to seismic events. In recent years semi-active dampers have gained considerable attention as structural control devices in the building construction industry. Magneto-rheological (MR) damper, a type of semi-active damper has proven to be effective in seismic mitigation of building structures. MR dampers contain a controllable MR fluid whose rheological properties vary rapidly with the applied magnetic field. Although some research has been carried out on the use of MR dampers in building structures, optimal design of MR damper and combined use of MR and passive dampers for real scale buildings has hardly been investigated. This paper investigates the use of MR dampers and incorporating MR-passive damper combinations in building structures in order to achieve acceptable levels of seismic performance. In order to do so, it first develops the MR damper model by integrating control algorithms commonly used in MR damper modelling. The developed MR damper is then integrated in to the seismically excited structure as a time domain function. Linear and nonlinear structure models are evaluated in real time scenarios. Analyses are conducted to investigate the influence of location and number of devices on the seismic performance of the building structure. The findings of this paper provide information towards the design and construction of earthquake safe buildings with optimally employed MR dampers and MR-passive damper combinations.

Mitigation of the seismic response of multi-span bridges using MR dampers: Experimental study of a new SMC-based controller

Pounding between adjacent structures has been a concern in multi-span bridges in recent earthquakes. In this paper, a pounding mitigation strategy using magnetorheological dampers is proposed, and its performance is tested for a three-span bridge using a series of shake-table experiments. A new semi-active control algorithm called SMC-OPC is developed that is based on a clipped sliding mode control (SMC) with sliding surfaces designed using an optimal polynomial control (OPC) approach. The control design uses a stochastically linearized model of the nonlinear bridge with passive components of the magnetorheological dampers embedded to achieve a more representative system characterization. Optimal weighting matrices for the optimal polynomial control are found through a genetic algorithm. The proposed method along with uncontrolled, passive-off, and passive-on cases are tested on shake-tables for several scaled near-field Kobe ground motion records. Although no pounding is observed in all control cases for small earthquakes, significant pounding occurs in the uncontrolled and passive-off systems under large earthquakes. For these ground motions, the performance of the semi-active controller converges to that of the passive-on case but with noticeably reduced power consumption. The study shows that the use of magnetorheological dampers between adjacent spans is very effective in mitigating critical bridge responses especially under large earthquakes. In addition, the proposed SMC-OPC semi-active control strategy enables achieving balance among multiple performance objectives with significantly reduced power consumption as compared to passive-on case.

Optimum semi-active hybrid system for seismic control of the horizontally curved bridge with Magnetorheological damper

Present paper investigates the application of Magnetorheological (MR) damper for a seismic control of the horizontally curved bridge isolated with different passive devices. The main aim of the study is to investigate the effectiveness of hybrid system for the seismic control of curved bridge with variation of important parameters. The selected bridge is a three span continuous concrete box girder supported on pier and rigid abutment. The bridge deck is model as a single spine beam, which is made with number of small straight two node beam elements and supporting pier model as linear lumped mass system. The MR dampers are located between the deck and abutments or piers in chord and radial direction. The bridge is excited with four different ground motions having different ground motion characteristics with all three-ground motion components (horizontal as well as vertical). The analysis results confirm use of MR damper with different isolator effective in controlling the response of the curved bridge and MR damper also effective in controlling the bearing displacement. The combination of MR and Lead rubber bearing (LRB) can provide an effective way for overall seismic control of curved bridge structure.

Anti-windup linear parameter varying control of structural systems with magneto-rheological dampers

Magneto-rheological (MR) dampers are a family of semi-active devices widely used for vibration attenuation in space and civil engineering structures. In this paper, we study the use of MR dampers for seismic protection of a model two-story structure in the presence of actuation saturation. A modified Bingham model is considered for linear parameter varying (LPV) modeling and control of the system. The main contribution of the paper is the design and experimental validation of a LPV anti-windup compensator to tackle the effect of actuator saturation on the control design performance. The designed LPV anti-windup control scheme is advantageous from the implementation standpoint because it can be considered as an addition to the existing control system. Experimental results demonstrate the ability of the design method to attenuate the effects of seismic excitation by controlling the MR damper and simultaneously avoid the adverse effects of actuator saturation by taking advantage of the designed anti-windup compensator and leading to savings in power consumption.

Semiactive Control Methodologies for Suspension Control With Magnetorheological Dampers

Suspension systems are one of the most critical components of transportation vehicles. They are designed to provide comfort to the passengers to protect the chassis and the freight. Suspension systems are normally provided with dampers that mitigate these harmful and uncomfortable vibrations. In this paper, we explore two control methodologies (in time and frequency domain) used to design semiactive controllers for suspension systems that make use of magnetorheological dampers. These dampers are known because of their nonlinear dynamics, which requires the use of nonlinear control methodologies for an appropriate performance. The first methodology is based on the backstepping technique, which is applied with adaptation terms and H∞ constraints. The other methodology to be studied is the quantitative feedback theory (QFT). Despite QFT is intended for linear systems, it can still be applied to nonlinear systems. This can be achieved by representing the nonlinear dynamics as a linear system with uncertainties that approximately represents the true behavior of the plant to be controlled. The semiactive controllers are simulated in MATLAB/Simulink for performance evaluation.

Numerical Investigation of the Effects of MR Damper Characteristic Parameters on Vibration Isolation of SDOF Systems Under Harmonic Excitations

Magnetorheological (MR) damper has recently received considerable attention particularly for vibration isolation applications. However, the relationship between the current and damping force of MR dampers is extremely non-linear. Although it is possible to directly control the current of MR dampers to reduce the vibration of a system, this direct use of MR dampers often cannot achieve a desired system performance. As a result, researchers normally develop a feedback control system to accommodate the non-linearity associated with MR dampers. This technique, however, results in a significant increase in the system cost and complexity. This article applies the concept of the output frequency response function derived recently by the authors to analyze the effects of the damping characteristic parameters and current in an MR damper on the output frequency response of single-degree-of-freedom vibrating system. The results gained from this work are of great significance as they can facilitate the analysis of the effects of MR damper characteristic parameters on output response of the system and potentially allow engineers to directly control the current of a commercially available MR damper to achieve a desired system response without the need to develop a feedback control system, thereby reducing the system cost and complexity.

GA-optimized FLC-driven semi-active control for phase-II smart nonlinear base-isolated benchmark building

An optimized fuzzy logic control (FLC) algorithm is developed for the phase-II smart base-isolated benchmark building with nonlinear isolation system. A restart genetic algorithm-based optimization strategy has been used to change the fuzzy system properties like the fuzzy rule base, pre-scale gains, membership function type and parameters at every simulation step. Acceleration and relative velocity responses at the damper location have been taken as inputs to the FLC system. Voltage required by the magneto-rheological (MR) damper is obtained as an output from the FLC. The use of MR dampers in the benchmark study as a control device along with isolation bearings in the building renders the overall system nonlinear. The advantage of using a fuzzy rule base is its inherent ability to handle nonlinearities and uncertainties in structural behavior, input excitation, sensor, and actuator dynamics. As a consequence, FLC provides robustness to the control mechanism. Moreover, FLC-driven MR damper voltage monitoring provides a gradual and smooth change of voltage. In the present study, the number of sensors and actuators and their locations have been kept unchanged as in the sample controller provided in the benchmark study. Simulation results for FLC, the adaptive rule and fixed rule base type, and results from the sample controller provided have been tabulated and compared. Results obtained indicate improvement using the proposed control approach without considering a multi-objective nondominated solution, where the weight of objective functions can be varied. A stability test for the proposed adaptive rule base FLC has been shown.

Semi-Active Magnetorheological Helicopter Crew Seat Suspension for Vibration Isolation

This study explores the use of magnetorheological dampers in a semi-active seat suspension system for helicopter crew seats to enhance occupant comfort. Key concepts in designing a magnetorheological seat suspension system to isolate the occupant from rotorcraft vibration are identified. Using these design concepts, a magnetorheological damper is designed, fabricated, and retrofitted into a tactical SH-60 Seahawk crew seat. This magnetorheological damper is implemented in series with the existing fixed load energy absorbers such that the crashworthiness capability of the seat is not impaired. Semi-active control is implemented and performance is evaluated both analytically and experimentally. Experimental test results have shown that this system reduced the dominant rotor-induced vertical vibration (4 per rev) transmitted to a 50th percentile male aviator by 76%, which is a 61-70% improvement over the unmodified SH-60 crew seat depending upon whether a soft seat cushion is used. Furthermore, these experimental tests also show that this system significantly reduces vertically induced seat rocking that occurs as a result of an offset center of gravity in the crew seat design.

MR 감쇠기를 이용한 구조물의 변형된 슬라이딩 모드 제어

Semi-active control devices have received significant attention in recent Years because they offer the adaptability of active-control devices without requiring the associated large power sources. Magnetorheological(MR) dampers are semiactive control devices that use MR fluids to produce controllable dampers. This paper applies sliding mode control method using target variation rate of Lyapunov function for the control of structures by use of MR dampers. The three-story building model under earthquake excitation is analyzed by installing a MR damper in the first-story. The performance of semi-active controllers designed by clipped-optimal algorithm and modified sliding mode control algorithm is compared to the performance of passive-type MR dampers. The results indicate that semi-active controllers achieve a greater reduction of responses than passive-type system and especially the controller by modified sliding mode control method shows a good applicability in the view of response control and control force.

An Analytical and Experimental Evaluation of Magneto Rheological Suspensions for Heavy Trucks

SUMMARYThis study provides an analytical and experimental evaluation of the performance of magneto rheological (MR) primary suspensions for a heavy truck. The analytical aspect of the study includes the development of a roll-plane simulation model that is used for evaluating the effect of various control strategies for MR primary suspensions for improving both the ride comfort and roll stability of the vehicle. The simulation results are used in determining the most promising control approaches for a series of tests that are conducted on a heavy (class 8) truck. The tests include the use of four controllable MR dampers, which are installed on a Volvo VN series heavy truck. A real-time embedded controller is used to independently vary the damping force in each of the four dampers according to a skyhook control policy. The performance of the truck with the experimental dampers is compared with the truck with stock dampers for two distinct test conditions, a transient and a steady state driving condition. The results of a series of transient and steady state dynamic tests indicate that MR dampers with skyhook control policy can be more effective than passive stock dampers in lowering the RMS accelerations at most locations on the truck. This would lead to the conclusion that the use of MR dampers could increase operator comfort and reduce vehicle wear, over an extended period of time. The same data, however, shows an increase in the peak intensity of the measured acceleration in four frequency bands in the range of 1–19 Hz. Further study of the MR dampers, however, has shown that proper tuning of the semiactive controller on substantially reduce the acceleration peak intensity and the potential ride harshness.

Neuro-control of cable vibration using semi-active magneto-rheological dampers

A neuro-control method is proposed for semi-active vibration control of stay cables using magneto-rheological (MR) dampers. A finite element model with multiple degrees-of-freedom is formulated for the hybrid system of a sagged stay cable incorporated with MR dampers. Two neural network control strategies are developed by using the full-order system model directly and introducing a reduced-order modal model, respectively. In the first strategy, which eschews a model reduction process, the neural network controller is designed and trained to have the dual functions of controller and observer, so that the resulting neuro-controller is able to perform the clipped linear quadratic Gaussian (LQG) control with incomplete state observation. In the second strategy, with the aid of a reduced-order modal model, the neural network controller is designed to consist of a control network and a state estimator network. The resulting neuro-controller performs the clipped LQG control using only a few observed states. The control effectiveness of the proposed neural network control strategies is verified numerically by application to a 12 m long scale-model cable prototype transversely connected with an MR damper near the lower anchorage. The response mitigation ability of the proposed control strategies using incomplete output observation is compared with that of the clipped LQG control with full state observation. The adaptive capability of the configured neuro-controllers under dynamic excitation distinct from training loading is examined. The analysis results show that the proposed control strategies can effectively implement semi-active vibration control of stay cables with the use of MR dampers.