Bogdan Sapiński

Vibration power generator for a linear MR damper

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 Faradays 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 generators 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 generators 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.

Energy-harvesting linear MR damper: prototyping and testing

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.

Vibration isolation using nonlinear damping implemented by a feedback-controlled MR damper

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. (Some figures may appear in colour only in the online journal)

Model of a squeeze mode magnetorheological mount

Recent advances in the research of magnetorheological (MR) fluid based devices have indicated the opportunities for squeeze mode devices using the smart fluids. The mode seems suitable for small amplitude and high force applications. Therefore, it is of a research and engineering interest to explore the model of a controlled squeeze mode MR mount (damper). As such, in the paper the authors highlight the model of a squeeze mode hydraulic mount, then present the simulation results in the form of dynamic stiffness and damping vs. frequency plots, respectively.

MR damper based implementation of nonlinear damping for a pitch plane suspension system

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.

Nondimensional characterization of flow-mode magnetorheological/electrorheological fluid dampers

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.

Modeling of an Adaptive Beam with MR Fluid

This paper is devoted to modeling of a three-layered cantilever beam filled with magnetorheological (MR) fluid. The beam consists of two aluminium outer layers and an MR fluid layer placed between them. The study covers description of MR fluid behavior in the pre-yield regime, analysis of strain and internal forces, formulation of differential equations of motion and finite element model (FEM) and numerical calculations. The aim of the study is to determine maximal amplitudes up to which the MR fluid operates in the pre-yield regime.

Verification of magnetorheological shock absorber models with various piston configurations

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.

Analysis of phase-controlled converters for induction motors

A phase-controlled converter for induction motors is analyzed, using a representation of semiconductor switching devices as two-state resistances. The steady state of symmetrically controlled converters (when the states of the semiconductor switching devices change periodically) is considered, and symmetrical components of the motor phase currents are used. This allows classical equivalent circuits of the induction motor to be used. As a result of the analysis the Fourier spectrum of the motor phase currents and electromagnetic torque is determined. An example that shows the application of the relations presented here is given. >

Investigation of an energy harvesting MR damper in a vibration control system

In this paper the authors investigate the performance of an energy harvesting MR damper (EH-MRD) employed in a semi-active vibration control system (SVCS) and used in a single DOF mechanical structure configuration. Main components of the newly proposed SCVS include the MR damper and an electromagnetic vibration energy harvester based on the Faradays law (EVEH) that converts vibration energy into electrical energy and delivers electrical power supplying the MR damper. The main objective of the study is to indicate that the SVCS, controlled by the specially designed embedded system, is feasible and presents good performance at the present stage of the research. The work describes investigation the unique features of the EH-MRD, i.e. its self-powering and self-sensing capabilities. Two cases were considered and the testing was done accordingly. In the case 1, only the self-powered capability was investigated. It was found out that harvested energy is sufficient to power the EH-MRD damper and to adjust it to structural vibration. The results confirmed the adequacy of the SVCS and demonstrated a significant reduction of the resonance peak. In the case 2, both the self-powering and self-sensing capabilities were investigated. Due to the self-sensing capability, the SCVS does not require any sensor. It appeared that thus harvested energy is sufficient to power the EH-MRD and enables self-sensing action since the signal of voltage induced by EVEH agrees with the relative velocity signal across the device. Similar to case 1, the resonance peak is significantly reduced.