No abstract

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.