Small-scale Magnetorheological Damper Research Articles

Comparative study on a single-story RCC frame with large and small-scale magnetorheological damper subjected to seismic excitation

The magnetorheological fluid damper (MRD) is a commonly employed semi-active damping mechanism. The utilisation of this technology has the potential to mitigate the impact of natural hazards on structures, owing to its crucial ability to dissipate energy and its minimal energy consumption. This study aims to compare the performance of a reduced-scale reinforced concrete (RCC) frame with a large MR damper (MRD) attached diagonally, to that of an RCC frame with a smaller-scale MRD attached at different locations. The experimental evaluation of two frames was conducted utilising El-Centro time history data, which was obtained from MTS. The efficacy of the small-scale MRD was also assessed through the El Centro seismic loading before integrating to the RCC frame. Subsequently, it was integrated with the frame and exhibited effective performance in mitigating seismic excitation. The maximum force generated was measured at 2.03kN, accompanied by a notable reduction in displacement of 13.24%. The frame equipped with a diagonal damper directly installed at the beam-column joint exhibits load-carrying capacities that are 12.32% and 19.77% lower than those of the frame equipped with a single and double damper, respectively, positioned at a distance of L/3 from the joint. In comparison to a diagonally placed large damper, the implementation of a small-scale magnetorheological damper (MRD) resulted in a reduction of displacements by 7.99% and 17.59% for single and double MRD configurations installed on the frame, respectively. However, this implementation also led to an increase in forces and alterations in crack patterns. The experimental findings indicate that the inclusion of a substantial quantity of smaller MRD can be a viable approach to mitigating structural responses in regions prone to seismic activity, while still maintaining the aesthetic integrity of the structure.

Experimental realization of rate-independent linear damping using a semiactive damper to enhance the seismic performance of low-frequency structures

Rate-independent linear damping (RILD) has been shown to simultaneously reduce the displacement and acceleration responses of low-frequency structures. However, previous studies on RILD have focused on its theoretical aspects and have almost excluded experimental approaches. Among the existing causal RILD models, the tuned Maxwell–Wiechert model can provide constant loss stiffness in a specified frequency range, thus offering a viable option as a control device intended to be incorporated into a base-isolated structure. A challenge remains regarding its undesired storage stiffness that compromises the flexibility of the base-isolated structure. This study eliminates the undesired storage stiffness via a negative stiffness-tuned Maxwell-Wiechert (NSTMW) model and experimentally investigates its feasibility to enhance the seismic performance of low-frequency structures. However, it is impossible to realize the NSTMW model using mechanical devices owing to the need for the negative damping coefficient of the Maxwell elements in some special cases. Therefore, the NSTMW model's frequency-domain expressions were transformed into time-domain differential equations using a bilinear transformation, and a small-scale magnetorheological damper was designed and fabricated to realize the NSTMW model. A series of real-time hybrid simulations were then conducted to examine the effectiveness of the NSTMW model for the protection of low-frequency structures. The experimental results confirmed that the NSTMW model could effectively control the dynamic response of low-frequency structures, compared with ideal RILD and linear viscous damping.

A hysteretic model considering Stribeck effect for small-scale magnetorheological damper

Magnetorheological (MR) damper is an ideal semi-active control device for vibration suppression. The mechanical properties of this type of devices show strong nonlinear characteristics, especially the performance of the small-scale dampers. Therefore, developing an ideal model that can accurately describe the nonlinearity of such device is crucial to control design. In this paper, the dynamic characteristics of a small-scale MR damper developed by our research group is tested, and the Stribeck effect is observed in the low velocity region. Then, an improved model based on sigmoid model is proposed to describe this Stribeck effect observed in the experiment. After that, the parameters of this model are identified by genetic algorithms, and the mathematical relationship between these parameters and the input current, excitation frequency and amplitude is regressed. Finally, the predicted forces of the proposed model are validated with the experimental data. The results show that this model can well predict the mechanical properties of the small-scale damper, especially the Stribeck effect in the low velocity region.

A Lumped-Parameter Model for Adaptive Dynamic MR Damper Control

The dynamic behavior of a small-scale magnetorheological damper intended for use in a tremor-suppression orthosis is characterized through experimental analysis and mathematical modeling. The combined frequency response of both the electromagnetic coil and the fluid particles is modeled by a third-order transfer function. The output of this function is an effective current that, combined with piston position and velocity, is empirically related to the resistance force of the damper. The derived model demonstrates high-fidelity to experimental testing of the damper under variable piston velocity and applied current within the expected frequency range of pathological tremor. The model is, thus, deemed suitable for use in a control algorithm for the mechanical suppression of tremor via magnetorheological damping.

Magnetorheological fluid composites synthesized for helicopter landing gear applications

Magnetorheological fluid composites were formulated in this study to investigate their performance for potential use in landing gear hydraulic systems, such as shock struts. The magnetorheological fluids synthesized here utilized three hydraulic oils certified for use in landing gear, two average diameters of spherical magnetic particles, and a lecithin surfactant. The magnetorheology of these fluids was characterized, including (a) magnetorheology (yield stress and viscosity) as a function of magnetic field, (b) sedimentation analysis using an inductance-based sensor, (c) cycling of a small-scale magnetorheological damper undergoing sinusoidal excitations at frequencies of 2.5 and 5 Hz, and (d) impact testing of an magnetorheological damper for a range of magnetic field strengths and velocities using a free-flight drop tower facility. The goal of this research is to analyze the performance of these magnetorheological fluid composites, compare their behavior to standard commercial magnetorheological fluid, and determine their feasibility for use in helicopter landing gear.

Design and Characterization of a Small-Scale Magnetorheological Damper for Tremor Suppression

This paper explores the design methodology and effectiveness of small-scale magnetorheological dampers (MRDs) in applications that require variable damping. Previously, applications of MRD have been chiefly limited to vehicle shock absorbers and seismic vibration attenuators. There has been recent biomedical interest in active-damping technology, however, particularly in the field of rehabilitation robotics. The topic at hand is the feasibility of developing MRDs that would be functionally and cosmetically adequate for actuation of an upper limb tremor suppression orthosis. A Bingham plastic model is used to determine MRD's functional characteristics, and experimental data are presented to validate the mathematical model. The feasibility of applying the developed small-scale MRDs to attenuation of tremorous motion is explored.

An Investigation of an Electromagnetic Induction Device for a Small-Scale MR Damper

The study is devoted to the electromagnetic induction device (EID) attached to the magnetorheological (MR) damper. The study covers design considerations, calculations of magnetic field, fabrication and testing of the EID on the dynamic testing machine (DTM).

Modeling and Identification of a Small-scale Magnetorheological Damper

Magnetorheological (MR) dampers are promising devices for vibration mitigation in structures due to their low cost, energy efficiency, and fast response. To use these dampers efficiently it is necessary to have models that describe their behavior with a sufficient precision. However, because a precise modeling of these devices using the laws of physics is an arduous task, semi-physical models are used to describe their behavior instead. Two of these models are explored in this article: a normalized version of the Bouc-Wen model and the Dahl friction model. A methodology for identification is proposed, and the obtained models are tested and validated experimentally.