Showing papers on "Magnetorheological damper published in 2008"

Semi-Active Magnetorheological Helicopter Crew Seat Suspension for Vibration Isolation

Abstract: 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.

Vibration control of magnetorheological damper system subjected to parameter variations

Abstract: This paper presents vibration control of a semi-active magnetorhological (MR) suspension system subjected to parameter variations. After manufacturing the cylindrical MR damper, the field-dependent damping force and its controllability are experimentally evaluated. The full vehicle model is then derived by considering vertical, pitch and roll motions. A robust H∞ controller is formulated by treating the sprung mass as parameter variation. This is accomplished by adopting the loop shaping design procedure. In order to demonstrate the effectiveness and robustness of the proposed control system, the Hardware-In-The-Loop Simulation (HILS) methodology is adopted by integrating the suspension model with the proposed MR damper. Vibration control responses of the vehicle suspension system such as vertical acceleration are evaluated under both bump and random road conditions.

Nondimensional Herschel—Bulkley Analysis of Magnetorheological and Electrorheological Dampers:

Abstract: Quasisteady modeling of linear stroke flow mode magnetorheological (MR) (or electrorheological (ER)) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the variable yield stress of the fluid, τ y , is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a pre-yield condition where the local shear stress is less than the yield stress, τ Ty, so that the material flows with a constant post-yield viscosity. The objective of this study is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits post-yield shear thinning or thickening behavior, that is, the post-yield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results - velocity profile, pre-yield thickness, and damping coefficient - are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.

Effect of an electromagnetically optimized magnetorheological damper on vehicle suspension control performance

Abstract: This paper examines the effect of an electromagnetically optimized magnetorheological (MR) damper for vehicle suspension on vibration control performance. In order to achieve this goal, a cylindrical MR damper that satisfies design specifications for a middle-sized commercial passenger vehicle is designed using an optimization methodology. The optimization problem is to find the optimal geometric dimensions of the electromagnetic circuit for the MR damper in order to maximize the damping force. A first-order optimization method using commercial finite element method (FEM) software is adopted for the constrained optimization algorithm. After manufacturing the MR damper with optimally obtained design parameters, its field-dependent characteristics are experimentally evaluated. The effect of the optimal MR damper on suspension control is then investigated using a quarter-vehicle test facility. Control performances such as vertical acceleration, suspension travel, and power consumption are evaluated a...

Study on semi-active control of mega-sub controlled structure by MR damper subject to random wind loads

Abstract: The recently proposed mega-sub controlled structure (MSCS), a new type of structure associated with the design and construction of super-tall buildings, has attracted the attention of designers for use in enhancing the control effectiveness in mega-frame buildings. In this paper, a dynamic equation and method to assemble parameter matrixes for a mega-sub controlled structure under random wind loads is presented. Semi-active control using magnetorheological dampers for the MSCS under random wind loads is investigated, and is compared with a corresponding system without dampers. A parametric study of the relative stiffness ratio and relative mass ratio between the mega-frame and the substructures, as well as the additional column stiffness ratio that influences the response control effectiveness of the MSCS, is discussed. The studies reveal, for the first time, that different control mechanisms exist. The results indicate that the proposed structure employing semi-active control can offer an effective control mechanism. Guidelines for selecting parameters are provided based on the analytical study.

Modeling and Verification of an Innovative Active Pneumatic Vibration Isolation System

Abstract: This paper presents a novel concept in active pneumatic vibration isolation. The novelty in the concept is in utilizing an air-spring-orifice-accumulator combination to vary the natural frequency as well as inject damping into the system per requirement, thereby eliminating the need for a hydraulic cylinder or a magnetorheological damper. This continuously variable natural frequency and damping (CVNFD) technology is aimed at achieving active vibration isolation. For analysis purposes, a particular application in the form of pneumatic seat suspension for off-road vehicles is chosen. A mathematical model representing the system is derived rigorously from inertial dynamics and first principles in thermodynamics. Empirical corelations are also used to include nonlinearities such as friction that cannot be accounted for in the thermodynamic equations. An exhaustive computational study is undertaken to help understand the physics of the system. The computational study clearly depicts the CVNFD capability of the vibration isolation system. An experimental test rig is built to experimentally validate analytical and simulation modeling of the system. Experimental verification corroborated the variable natural frequency and damping characteristic of the system observed through computational simulations.

Vehicle ride performance with semi-active suspension system using modified skyhook algorithm and current generator model

Abstract: This paper presents the simulation of a semi-active suspension system by using designed parameter model of magnetorheological (MR) damper. The design is based on the performance of the original equipment shock absorber of a passenger vehicle. A 7DOF of vehicle ride model was developed and validated in order to study the performance of a passive suspension system and the designed semi active suspension system. A controller known as modified skyhook algorithm and current generator model was used in the semi-active suspension system. The simulation results show that the semi active suspension system give significant improvement on vehicle's ride comfort.

Modeling and Control for a Semi-active Suspension with a Magnetorheological Damper Including the Actuator Dynamics

Abstract: Reported researches on semi-active suspension neglect the actuador dynamics, missing important information that can deteriorate the suspension's performance. The present research proposes a new semi-active suspension model with a magnetorheological damper, including its dynamics. Three control approaches are applied to this suspension model to improve passenger comfort and vehicle stability. The well known control strategies: skyhook, groundhook and hybrid, are adequated for the model and simulated using Matlab. Exhaustive simulation results compare comfort and stability between an average city car passive suspension and the proposed semi-active suspension. The suspension with hybrid control shows the best performance complying, at the same time, with vehicle stability and passenger comfort.

An experimental electromagnetic induction device for a magnetorheological damper

Abstract: The work presents an experimental electromagnetic induction device consisting of permanent magnets and a coil which produces electric energy for an attached magnetorheological (MR) damper. The study covers design considerations and calculations of magnetic fields, description of the engineered device, and results of experimental tests on the dynamic testing machine.

Semi-active control of a passenger vehicle for improved ride and handling

Abstract: A theoretical model is developed for the semi-active control of the suspension of a full passenger car using a variable-structure-type algorithm. Skyhook control and variants of balance control (cancelling or adding the dynamic spring forces) are applied via a magnetorheological damper at the front and rear wheels to improve the vehicle ride and handling. The magnetorheological damper is modelled via a Bouc—Wen approach.The semi-active vehicle response is compared with a passive response. The robustness of control is established by adding noise to the computed sensor inputs, and the loose-wire scenario is also considered. The results show that balance control is a robust algorithm. The magnitude of acceleration reduction (for the human body and head—neck complex) using semi-active control varies with the semi-active approach and vehicle speed (a simulated random road was assumed). At 30m/s the human body acceleration reduction was found to be 70 per cent with skyhook control and 40 per cent with b...

Non-parametric linearised data driven modelling and force tracking control of a magnetorheological damper

Abstract: This paper presents a Non-Parametric Linearised Data Driven (NPLDD) approach to model the dynamic performance of Magnetorheological (MR) damper. The proposed model is developed based on experimental data and consists of a pair of subsystems, namely, positive and negative relative acceleration of the damper. In each subsystem, the hard points of experimental data are mapped into look-up table for a set of applied voltage signals. The results of the study show that the proposed model is able to describe the behaviour of the damper adequately and the force tracking controller has the ability to track the desired force well.

Stochastic change detection in uncertain nonlinear systems using reduced-order models: system identification

Abstract: The reliable detection of relatively small changes in the characteristics of monitored systems, which simultaneously involve nonlinear phenomena as well as uncertain parameters, is a challenging problem whose resolution is crucial to the development of practical structural health monitoring methodologies slated for use with complex physical systems. This paper reports the results of a comprehensive experimental study involving an adaptive nonlinear component (an actively controlled magnetorheological damper) that was used to investigate the representation and propagation of uncertainties in a probabilistic format that provides a convenient means for reliable detection of small changes in uncertain nonlinear systems. In experimental studies of the MR damper, the uncertainty of the system characteristics was precisely controlled with known input-current statistics. A total of 4000 tests were performed, and the MR damper was identified using the restoring force method with both orthogonal and non-orthogonal basis functions. The identification results show that the identified coefficients involving orthogonal basis functions have several desirable features that are ideal for condition assessment purposes when dealing with complex nonlinear systems whose underlying physics is not amenable to easy modeling: (1) no a priori knowledge of the systems characteristics is required; (2) the orthogonal coefficients are statistically unbiased with respect to model complexity; and (3) the distributions of the orthogonal coefficients can be reliably used to detect changes in uncertain nonlinear systems, even if a reduced-order model is used in the identification process.

Experimental investigation into magnetorheological damper subjected to impact loads

Abstract: A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation But at present, the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads In this paper, a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied experimentally in order to investigate its isolation performance under the impact loads A new mechanical model of MRD was proposed according to the data obtained by impact test A good agreement between the numerical results and test data was observed, which showed that the model was good to simulate the dynamic properties of MRD under impact loads It is also demonstrated that MRD can improve the acceleration and displacement response of the structure obviously under impact loads

Integrated intelligent control analysis on semi-active structures by using magnetorheological dampers

Abstract: The control strategy is very important for semi-active control or active control systems. An integrated intelligent control strategy for building structures incorporated with magnetorheological (MR) dampers subjected to earthquake excitation is proposed. In this strategy, the time-delay problem is solved by a neural network and the control currents of the MR dampers are determined quickly by a fuzzy controller. Through a numerical example of a three-storey structure with one MR damper installed in the first floor, the seismic responses of the uncontrolled, the intelligently controlled, the passive-on controlled, and the passive-off controlled structures under different earthquake excitations are analyzed. Based on the numerical results, it can be found that the time domain and the frequency domain responses are reduced effectively when the MR damper is added in the structure, and the integrated intelligent control strategy has a better earthquake mitigation effect.

Fuzzy control of the semi-active suspension with MR damper based on μGA

Abstract: A fuzzy control strategy is presented for the semi-active control of a quarter-car suspension system model based on a magnetorheological (MR) damper. The improved Bouc-wen model is used to describe the mechanical model of MR damper. We choose the modified genes of the fuzzy rules, the scale genes of the input variables and the scale gene of the output variables as the variables, and the weight values of the fuzzy control are found by the micro genetic algorithms (muGA). Numerical simulations demonstrate that with micro genetic algorithms the semi-active suspension can improve both the ride comfort and handing stability.

Supervisory semiactive nonlinear control of a building-magnetorheological damper system

Abstract: This paper proposes a supervisory semiactive nonlinear control of a building structure equipped with magnetorheological dampers. First, three sets of multi-input-single-output (MISO) linear controllers that are operated in local linear operating regions are designed such that the closed loop system is globally asymptotically stable and the performance on transient responses is also satisfied. Among them, two sets of the MISO linear controllers are blended into two lower level nonlinear controllers via a fuzzy interpolation method, while a set of the linear controllers are blended into a higher level nonlinear controller. Then, a supervisory semiactive nonlinear control system is developed through integration of the lower level nonlinear controllers with the high level controller. To demonstrate the effectiveness of the proposed methodology, the performance of the proposed supervisory control approach is compared with that of a fully decentralized semiactive nonlinear controller; while uncontrolled responses are used as the baseline.

Semi-active control of torsionally responsive structures

Abstract: 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 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 a training excitation is created using the RSPMatch2005 algorithm which 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 the GA-optimized FLC performs superior to passive operation in 42% of considered cases.

Temperature sensitive stability of feedback controllers for MR dampers

Abstract: Smart fluid dampers can undergo large temperature changes due to the heating associated with energy dissipation. Such heating will alter the fluid's properties and could degrade control system performance. For example, previous work by the authors has shown that the stability of an MR damper under feedback control is dependent on the fluid's compressibility and viscosity. In the present study, a temperature dependent model of a magnetorheological damper is developed from experimental data, and it is shown that the fluid's yield stress, viscosity and compressibility parameters vary significantly. An experimental and numerical control study is then performed to investigate the resulting effects of temperature on the stability of two feedback controllers - a PID controller, and a proportional controller. Experimental results indicate that both controllers can exhibit a reduction in stability with increasing temperature, particularly if the controller gains are not suitably chosen. The temperature dependent MR damper model predicts this behaviour well, and it is shown that the change in viscosity has the most significant effect on stability. Future work could focus on the resulting effect on a complete vibration system, devices with different modes of operation, and alternative controllers.

Rate-Dependent Elastoslide Model for Magnetorheological Damper

Abstract: A rate-dependent elastoslide model is developed to study the quasi-steady and dynamic behavior of a magnetorheological damper. This time-domain model uses a rate-dependent slide and a parallel viscous damping to describe the practical yield behavior demonstrated by field-activated magnetorheological fluids, and it uses a stiff spring in series with the slide to represent the preyield stiffness of the damper. A method of determination of the model parameters is developed using single-frequency hysteresis data of the magnetorheological damper. The model parameters are determined using virtual loading curves identified from the force-displacement and force-velocity hysteretic diagrams. A relationship between current controllable parameters and current input is established. The fidelity of the model is justified by a good correlation between modeling results and experimental steady-state data over a broad amplitude and moderate-frequency range. Significantly, this model captures nonlinear amplitude- and frequency-dependent behavior of magnetorheological dampers using constant model parameters and trivial computational effort.

Research on the hardware-in-the-loop simulation of magnetorheological damper subjected to impact load

Abstract: With the rapid development of structure design and the applications of high and new technology, more and more impact issues have occurred in engineering applications, especially in weapon system. This paper was explored and aimed at its dynamic character and vibration control of magnetorheological damper subjected to impact load. In order to evaluate its controllability of the designed long-stroke gun recoil MR damper in reducing the recoil displacement and damping force, a suit of hardware in the loop simulation platform based on dSPACE system and MR damper under impact load excitation is designed and developed. Based on the fluid mechanics theory, an amendment dynamic model of magnetorheological damper subjected to impact load is derived. Considering the impact load character and its strong nonlinear and uncertainty of a magnet-rheological damper, a fuzzy controller is designed and applied into the electromagnetic coil to achieve a control of active variable damping. The experimental results proved the derived dynamic modelpsilas correctness for magnet-rheological damper under impact load, and indicated that the designed large-scale single-ended MR damper and fuzzy controller could reduce off 40% its recoil displacement and pressure peak value of MR damper, which will further establish the basis of engineering application for a magnet-rheological damper under impact load.

Driver of magnetic current damper

Abstract: The invention discloses a driver of a magnetorheological damper, comprising a voltage-current conversion unit which converts control voltage to control current, and a power amplification unit which performs power amplification on the control current to drive the magnetorheological damper, wherein, the voltage-current conversion unit comprises an instrumentation amplifier, an operational amplifier and a converting resistor, wherein, an input end of the instrumentation amplifier receives the control voltage, while an output end of the instrumentation amplifier is connected to an input end of the power amplification unit; an inverse input end of the operational amplifier is connected with an output end of the operational amplifier, while the output end of the operational amplifier is connected with a reference voltage end of the instrumentation amplifier; one end of the converting resistor is connected with an output end of the power amplification unit, while a non inverting input end of the operational amplifier and the magnetorheological damper are respectively connected with an output end of the power amplification unit. In the invention, the control voltage is converted into the control current by the driver of the magnetorheological damper realized through integrated circuit components, and the control current is subject to the power amplification to drive the magnetorheological damper. The driver of the magnetorheological damper has the advantages of low cost, high precision, good linearity, simple debugging and quick response.

Response Control Performance Evaluation of MR Damper by Shaking Table Tests and Real-Time Hybrid Tests

Abstract: Magnetorheological damper (MR damper) has been expected to control the response of civil and building structures in recent years, because of its large force capacity and variable force characteristics. In this paper, a series of real-time hybrid test was conducted and the results of real time hybrid tests were compared to those of shaking table tests. To determine the control force of the MR damper, skyhook control and sliding mode control theory were employed. As the results, the validity of real-time hybrid test was verified. This paper describes the capability of MR damper to control the structural response.