Showing papers on "Magnetorheological damper published in 2002"

Vibration Control of a Suspension System via a Magnetorheological Fluid Damper

Abstract: Semi-active control systems are becoming more popular because they offer both the reliability of passive systems and the versatility of active control without imposing heavy power demands. It has been found that magneto-rheological (MR) fluids can be designed to be very effective vibration control actuators. The MR fluid damper is a semi-active control device that uses MR fluids to produce a controllable damping force. The objective of this paper is to study a single-degree-of-freedom suspension system with an MR fluid damper for the purpose of vibration control. A mathematical model for the MR fluid damper is adopted. The model is compared with experimental results for a prototype damper through finding suitable model parameters. In this study, a sliding mode controller is developed by considering loading uncertainty to result in a robust control system. Two kinds of excitations are inputted in order to investigate the performance of the suspension system. The vibration responses are evaluated in both ti...

Neural network emulation of inverse dynamics for a magnetorheological damper

Abstract: The dynamic behavior of a magnetorheological (MR) damper is well portrayed using a Bouc–Wen hysteresis model. This model estimates damper forces based on the inputs of displacement, velocity, and voltage. In some control applications, it is necessary to command the damper so that it produces desirable control forces calculated based on some optimal control algorithms. In such cases, it is beneficial to develop an inverse dynamic model that estimates the required voltage to be input to the damper so that a desirable damper force can be produced. In this study, we explore such a possibility via the neural network (NN) technique. Recurrent NN models will be constructed to emulate the inverse dynamics of the MR damper. To illustrate the use of these NN models, two control applications will be studied: one is the optimal prediction control of a single-degree-of-freedom system and the other is the linear quadratic regulator control of a multiple-degree-of-freedom system. Numerical results indicate that, using t...

Harmonic analysis of a magnetorheological damper for vibration control

Abstract: Semi-active control systems are becoming more popular because they offer both the reliability of passive systems and the versatility of active control systems without imposing heavy power demands. In particular, it has been found that magnetorheological (MR) fluids can be designed to be very effective vibration control actuators, which use MR fluids to produce controllable damping force. The objective of this paper is to study a single-degree-of-freedom (SDOF) isolation system with an MR fluid damper under harmonic excitations. A mathematical model of the MR fluid damper with experimental verification is adopted. The motion characteristics of the SDOF system with the MR damper are studied and compared with those of the system with a conventional viscous damper. The energy dissipated and equivalent damping coefficient of the MR damper in terms of input voltage, displacement amplitude and frequency are investigated. The relative displacement with respect to the base excitation is also quantified and compared with that of the conventional viscous damper through updating the equivalent damping coefficient with changing driving frequency. In addition, the transmissibility of the MR damper system with semi-active control is also discussed. The results of this study are valuable for understanding the characteristics of the MR damper to provide effective damping for the purpose of vibration isolation or suppression.

Two mechanic models for magnetorheological damper and corresponding test verification

Abstract: In this paper two mechanic models are proposed to describe the dynamic performance of magnetorheological (MR) damper according to the experiment results. One is the modified Bingham model which consists of Bingham model (a frictional element in parallel with a dashpot) in series with a spring element. The spring element stiffness is related to pre yield shear modulus of MR fluid and accumulator stiffness. The other is the modified Dahl model that adopts Dahl model instead of Bouc Wen model to simulate Coulomb friction force to avoid the determination of too many parameters. To make the proposed model valid under fluctuating current or magnetic field, an intrinsic variable is introduced to determine the function dependence of the parameters on the input current. By comparison between numerical and experimental results, the proposed two mechanic models are proved to be accurate enough to portray the dynamic performance of most MR dampers under fluctuating current or magnetic field.

Magnetorheological damper with piston bypass

Abstract: A magnetorheological damper includes a cylinder and a magnetorheological piston. The magnetorheological piston is located within and slideably engages the cylinder. The magnetorheological piston includes a magnetically energizable passageway and a magnetically non-energizable passageway spaced apart from the magnetically energizable passageway. The magnetorheological piston also includes a pressure and flow control valve disposed to allow pressure-dependent fluid flow in the magnetically non-energizable passageway when the magnetorheological piston slides towards the first end of the cylinder.

Magnetorheological piston and damper

Abstract: A magnetorheological piston includes a body having a substantially magnetically energizable passageway and a substantially magnetically non-energizable passageway. The substantially magnetically non-energizable passageway has a valveless passageway throat and has a flow cross-sectional area which has a minimum at the passageway throat and which is larger away from the passageway throat. A magnetorheological damper includes a cylinder and the above-described magnetorheological piston, wherein the piston is positioned in, and slideably engages, the cylinder.

Magnetorheological fluid damper

Abstract: A radial magnetorheological damper is provided which includes a plurality of alternating inner and outer sleeves, a magnetorheological fluid interspersed between them, a return path to return magnetic flux, and a wire coil to produce magnetic flux in the circuit.

Magnetorheological damper with bypass valving

Abstract: An adjustable vehicle suspension damper (10) configured to be arranged between a wheel assembly and a body of a vehicle, the adjustable damper including a tube (12). A piston (14) is slidably carried in the tube. A coil (52) is carried on the piston adjacent a first flow passageway (79) in the piston to produce a magnetic field thereacross and a control valve (65) is carried on the piston controlling fluid flow through a second flow passageway (80) in the piston.

Single-stage magnetorheological damper parameter estimation

Abstract: This work describes a new technique for parameter estimation for magnetorheological dampers which relies on rearrangement of the constitutive equations for the modified Bouc–Wen model to obtain a cost function using only predetermined time series values. Advantages of the new method include reliable convergence under low-noise conditions with only broad constraints and single-stage estimation of seven damper parameters.

Twin-tube magnetorheological damper

Abstract: A magnetorheological damper (10) includes an inner tube (12), a magnetorheological piston (14), and an outer tube (16). The magnetorheological piston (14) is located within and slideably engages the inner tube (12). The outer tube (16) surrounds the inner tube (12). The outer tube (16) is in fluid communication with the inner tube (12).

MR power free ball screw magnetorheological damper

Abstract: PURPOSE: A power-free MR(magnetorheological) damper combined with a ball screw is provided to absorb shock and to restrict vibration by forming torque from rotation of the MR brake and back electromotive force from a motor with the ball screw in applying impact or vibration. CONSTITUTION: A power-free ball screw MR damper is composed of a motor(1) supplying current to the MR unit; a rotary MR damper/ brake(2) for semi-active control; a ball screw(3) converting linear motion into rotation or rotation into the linear motion efficiently and actively; telescoping mechanisms(5,6) assembling the ball screw, a ball nut(4) or an acme screw; and a control circuit(7) connected to the motor and the rotary MR damper or the rotary MR brake. Current is adjusted with varying resistance of the control circuit according to intensity of vibration, and the rotary MR damper or brake is operated with real-time control. Vibration is absorbed with adjusting the ball screw lead individually.

Harmonic Analysis of Semi-Active Control with MR Dampers

Abstract: Semi-active control systems are becoming more popular because they offer both the reliability of passive systems and the versatility of active control systems without imposing heavy power demands. In particular, it has been found that magnetorheological (MR) fluids can be designed to be very effective vibration control actuators, which use MR fluids to produce controllable damping force. The objective of this paper is to study a single-degree-of-freedom (SDOF) isolation system with a MR fluid damper under harmonic excitations. A mathematical model of the MR fluid damper with experimental verification is adopted. The motion characteristics of the SDOF system with the MR damper are studied and compared with those of the system with a conventional viscous damper. The energy dissipated and equivalent damping coefficient of the MR damper in terms of input voltage, displacement amplitude, and frequency are investigated. The relative displacement with respect to the base excitation is also quantified and compared with that of the conventional viscous damper through updating equivalent damping coefficient with changing driving frequency. In addition, the transmissibility of the MR damper system with semi-active control is also discussed. The results of this study are valuable for understanding the characteristics of the MR damper to provide effective damping for the purpose of vibration isolation or suppression.