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Magnetorheological/electrorheological dampers are complex devices and involve a large set of important material and geometric variable with mutual interactions between them. As such, reliable predictions of the damping force level in these devices are difficult to achieve. However, meaningful results can be obtained with significantly less effort through nondimensional parameters involving all key variables. Therefore, the goal of this study was to propose a robust set of nondimensional parameters for the purpose of modeling of magnetorheological/electrorheological dampers (and other flow-mode devices) as well as the characterization of data from experiments with magnetorheological/electrorheological devices. The proposed scheme employs five parameters characterizing the contribution of flow inertia, viscosity, and yield stress, as well as shear thinning/thickening effects to the damping force output of magnetorheological/electrorheological valves. It is the result of analysis of several constitutive models of non-Newtonian fluid models (Bingham plastic model, biviscous model, biplastic Bingham model, and Herschel–Bulkley model). Specifically, the goal was to derive analytical (exact) formulae for pressure gradient of all examined models excluding the Herschel–Bulkley model. In the Herschel–Bulkley model, the nondimensional relationship between pressure gradient and flow rate is given in a power-law form, and the analytical (exact) solution cannot be obtained. Prior art included analytical (exact) solutions for the Bingham plastic model only. In the most generic form, the expressions can be useful for designing magnetorheological/electrorheological flow-mode devices. Exemplary calculations of the damping force output are presented in this article for a custom single-gap magnetorheological piston. The piston contains a semi-bypass feature in the annulus to allow for low-breakaway forces at near-zero piston velocity inputs. The steady-state calculations are presented for two exemplary damper units, and the model is validated against experimental data. Finally, the expressions allow one to easily characterize flow data into separate regimes of damper operation by means of the proposed scheme.

The present study is concerned with an energy-harvesting linear MR (EH-LMR) damper which is able to recover energy from external excitations using an electromagnetic energy extractor, and to adjust itself to excitations by varying the damping characteristics. The device has three main components: an MR part having a damper piston assembly movable in relation to the damper cylinder under an external excitation, a power generator to produce electrical power according to the relative movement between the damper piston and the cylinder assembly, and a conditioning electronics unit to interface directly with the generator and the MR damper. The EH-LMR damper integrates energy harvesting, dynamic sensor and MR damping technologies in a single device. The objective of the study is to get a better insight into the structure of EH-LMR damper components, to investigate the performance of each component and a device as a whole, and to compare results of experimental study against numerical data obtained in simulations conducted at the design stage. The research work demonstrates that the proposed EH-LMR damper provides a smart and compact solution with the potential of application to vibration isolation. The advantage of the device is its adaptability to external excitations and the fact that it does not need any extra power supply unit or sensor on account of its self-powered and self-sensing capabilities.

The paper describes the structure and the results of numerical calculations and experimental tests of a newly developed vibration power generator for a linear magnetorheological (MR) damper. The generator consists of permanent magnets and coil with foil winding. The device produces electrical energy according to Faraday's law of electromagnetic induction. This energy is applied to vary the damping characteristics of the MR damper attached to the generator by the input current produced by the device.The objective of the numerical calculations was to determine the magnetic field distribution in the generator as well as the electric potential and current density in the generator's coil during the idle run and under the load applied to the MR damper control coil. The results of the calculations were used during the design and manufacturing stages of the device.The objective of the experimental tests carried out on a dynamic testing machine was to evaluate the generator's efficiency and to compare the experimental and predicted data. The experimental results demonstrate that the engineered device enables a change in the kinetic energy of the reciprocal motion of the MR damper which leads to variations in the damping characteristics. That is why the generator may be used to build up MR damper based vibration control systems which require no external power.

The paper deals with a semi-active vibration control system based on a magnetorheological (MR) damper. The study outlines the model and the structure of the system, and describes its experimental investigation. The conceptual design of this system involves harvesting energy from structural vibrations using an energy extractor based on an electromagnetic transduction mechanism (Faraday's law). The system consists of an electromagnetic induction device (EMI) prototype and an MR damper of RD-1005 series manufactured by Lord Corporation. The energy extracted is applied to control the damping characteristics of the MR damper.The model of the system was used to prove that the proposed vibration control system is feasible. The system was realized in the semi-active control strategy with energy recovery and examined through experiments in the cases where the control coil of the MR damper was voltage-supplied directly from the EMI or voltage-supplied via the rectifier, or supplied with a current control system with two feedback loops. The external loop used the sky-hook algorithm whilst the internal loop used the algorithm switching the photorelay, at the output from the rectifier. Experimental results of the proposed vibration control system were compared with those obtained for the passive system (MR damper is off-state) and for the system with an external power source (conventional system) when the control coil of the MR damper was supplied by a DC power supply and analogue voltage amplifier or a DC power supply and a photorelay.It was demonstrated that the system is able to power-supply the MR damper and can adjust itself to structural vibrations. It was also found that, since the signal of induced voltage from the EMI agrees well with that of the relative velocity signal across the damper, the device can act as a 'velocity-sign' sensor.

The main problem of using a conventional linear damper on a vibration isolation system is that the reduction of the resonant peak in many cases inevitably results in the degradation of the high-frequency transmissibility. Instead of using active control methods which normally depend on the model of the controlled plant and where unmodelled dynamics may induce stability concerns, recent studies have revealed that optimal vibration isolation over a wide frequency range can be achieved by using nonlinear damping. The present study is concerned with the realization of the ideal nonlinear damping characteristic using a feedback-controlled MR damper. Both simulation and experimental studies are conducted to demonstrate the advantages of the simple but effective vibration control strategy. This research work has significant implications for the effective use of MR dampers in the vibration control of a wide range of engineering systems.

Suppression of vibration transmission from working machineries and other sources is important for the normal operation of a wide range of engineering systems. Traditionally, viscous dampers with approximately linear characteristics are often used to address the issue. However, this solution can have the problem of not being able to reduce the vibration transmission over the whole range of frequencies. In recent studies, the authors have revealed, by both theoretical analysis and experimental test, that nonlinear damping can be applied to resolve the problem. The present study is concerned with the exploitation of this beneficial effect of nonlinear damping to the vibration control of a pitch plane suspension system. A magneto-rheological (MR) damper based implementation of nonlinear damping is applied to provide a novel solution to the pitch plane system vibration control problem. Simulation studies are conducted to demonstrate the effectiveness of the MR damper implementation, and the beneficial effect of nonlinear damping on the pitch plane suspension system vibration control.

In this study, a mathematical model of a monotube magnetorheological (MR) shock absorber is presented and verified with an emphasis on leakage flow mechanisms and their impact on the damping force output. The model can be used in shock absorber design studies as well as vehicle simulations. To copy the force increase with yield stress, the authors employed the generic biplastic Bingham model for capturing the hydraulic resistance of the annular flow path in the piston. Moreover, the authors considered the impact of high-speed losses, fluid chamber compressibility, cavitation, elastic deformation of cylinder, fluid inertia, floating piston inertia, gas chamber pressure and Coulomb friction between damper components and the cylinder. The presented MR shock absorber model of is verified against experimental data involving three prototype shock absorber units. One shock absorber unit was a conventional unit with only one annular flow path, the second one employed the thru-core flow bypass for force roll-off at low piston velocities. The third unit utilized a so-called flux bypass to lower the magnetic field strength in the annulus to initiate the flow of MR fluids at lower yielding pressures across the piston. The flux bypass was located in the annulus. Except for the bypass features, all units were identical. All secondary flow features affect on the damping force at low piston velocities in particular. The experiment covered all key flow regimes of MR shock absorber operation from low speed to high speed. The results show that the proposed approach is capable of capturing key characteristics across the examined range of piston velocities and coil current levels.