Magnetorheological fluid

About: Magnetorheological fluid is a research topic. Over the lifetime, 8538 publications have been published within this topic receiving 131502 citations. The topic is also known as: MRF & MR fluid.

Frequency and damping adaptation of a TMD with controlled MR damper

Abstract: This paper describes the new concept of a semi-active tuned mass damper with magnetorheological damper (MR-STMD). The real-time controlled MR damper force emulates controlled damping and a superimposed controllable stiffness force to augment or diminish the force of the passive spring stiffness which enables us to control the MR-STMD natural frequency. Both the damping and natural frequency are tuned according to Den Hartog’s formulae to the actual dominant frequency of the main structure irrespective of whether it is a resonance or a forced frequency. The MR-STMD is experimentally validated on the Empa bridge with a 15.6 m main span for different added masses to shift its resonance frequency 12.2% andC10.4% away from its nominal value. The experimental results are compared to those obtained when the MR-STMD is operated as a passive TMD that is precisely tuned to the nominal bridge. The comparison shows that the MR-STMD outperforms the TMD both in the tuned and all de-tuned cases by up to 63%. Simulations of the MR-STMD concept point out that the proposed semi-active control algorithm is most suitable for MR-STMDs due to the small amount of clipped active forces. A sensitivity analysis demonstrates that the real MR-STMD could be even more powerful if the force tracking errors in the MR damper force due to the current driver and MR fluid dynamics and remanent magnetization effects could be further reduced. The MR-STMD under consideration represents the prototype of the 12 MR-STMDs that have been running on the Volgograd Bridge since late fall 2011. (Some figures may appear in colour only in the online journal)

Method and apparatus for varying the stiffness of a suspension bushing

Abstract: A variable stiffness suspension bushing (18) for use in a suspension of a motor vehicle comprises a shaft or rod (40) connected to a suspension member (12), an inner cylinder (42) fixedly connected to the shaft or rod (40), and an outer cylinder (44) fixedly connected to a chassis member (16). A magnetorheological (MR) elastomer (48), having iron particles embedded therein, is interposed between the inner (42) and outer (44) cylinders, and a coil (54) is disposed about the inner cylinder (42). When the coil (54) is energized by electrical current provided from a suspension control module (20), a variable magnetic field is generated so as to influence the magnetorheological (MR) elastomer (48) whereby variable stiffness values of the elastomer (48) are obtained to provide the bushing (18) with variable stiffness characteristics in order to eliminate compromises heretofore necessary when using single, fixed rate bushings.

Semi-Active Suspension Systems for Railway Vehicles Using Magnetorheological Dampers. Part I: System Integration and Modelling

Abstract: In this paper, it is aimed to investigate semi-active suspension systems using magnetorheological (MR) fluid dampers for improving the ride quality of railway vehicles. A 17-degree-of-freedom (DOF) model of a full-scale railway vehicle integrated with the semi-active controlled MR fluid dampers in its secondary suspension system is proposed to cope with the lateral, yaw, and roll motions of the car body, trucks, and wheelsets. The governing equations combining the dynamics of the railway vehicle integrated with MR dampers in the suspension system and the dynamics of the rail track irregularities are developed and a linear quadratic Gaussian (LQG) control law using the acceleration feedback is adopted, in which the state variables are estimated from the measurable accelerations with a Kalman estimator. In order to evaluate the performances of the semi-active suspension systems based on MR dampers for railway vehicles, the random and periodical track irregularities are modelled with a uniform state-space formulation according to the testing data and incorporated into the governing equation of the railway vehicle integrated with the semi-active suspension system. Utilising the governing equations and the semi-active controller developed in this paper, the simulation and analysis are presented in Part II of this paper.

Adjustable valve and vibration dampers utilizing same

Abstract: An adjustable valve including a passageway, a field responsive fluid within the passageway, and fluid flow adjustment through the passageway. The valve is preferably used in a vibration damper. One damper includes a body, a piston, first and second chambers, a damping valve, a piston rod, an auxiliary chamber, a passageway interconnecting to the auxiliary chamber, a field responsive fluid, a field responsive fluid valve for controlling flow to the auxiliary chamber, and pressurization means. Preferably included is a cavity partition having field responsive fluid disposed on one side and non-field responsive fluid disposed on the other. This allows a reduction of MR fluid allowing use of lighter-weight, less-expensive, hydraulic fluids for flow through the piston's damping valve. In another aspect, the damper includes mechanical adjustment means for manually adjusting the damping level. Adjustment is accomplished by a moveable permanent magnet, moveable pole piece, moveable pole-and-magnet assembly, or magnetic shunt. Manual adjustment may include a knob, lever, or cable actuation. Alternately, magnetic flux is provided by an electromagnet. The valve and damper finds utility in any suspension system where a damper body is attached to a frame component, such as a bicycle frame, and the piston rod is attached to a suspension component, such as a bicycle's swingarm.