MR Dampers

Aim of this study is to propose a control strategy based on Simulated Annealing (SA) as a metaheuristic algorithm and Fuzzy Logic Controller (FLC) for semi-active nonlinear control of structures equipped with Magnetorheological (MR) dampers to prevent damage from severe dynamic loads such as earthquakes. MR dampers as promising semi-active control mechanisms are focus of attention for reducing seismic response of structures in the world of structural engineering. A fuzzy controller is applied to establish interactive relationships between structural responses and input voltages to the MR damper. A modified simulated annealing algorithm is employed as an evolutionary algorithm to design the fuzzy controller, which is herein described as a Modified Simulated Annealing-Fuzzy Logic Controller (MSA-FLC). Results of numerical simulations demonstrated the efficiency of the proposed smart strategy compared to similar methodologies recommended by other researchers.

Streszczenie

Rozprawa doktorska dotyczy układów redukcji drgań mechanicznych zawierających w swojej strukturze tłumik MR oraz elektromechaniczny przetwornik energii działający zgodnie z prawem Faradaya. Celem rozprawy jest modelowanie, implementacja i przeprowadzenie badań układu redukcji drgań z tłumikiem MR zasilanego energią drgań. Działanie takiego układu sprawdzono w dwóch aplikacjach mechanicznych o jednym i dwóch stopniach swobody. Będące przedmiotem badań układy należą do grupy semiaktywnych układów redukcji drgań, w których realizowany jest odzysk energii kinetycznej drgającego obiektu. Energia kinetyczna jest przetwarzana przez przetwornik na energię elektryczną wykorzystywaną do zasilania cewki sterującej tłumika MR i w konsekwencji do zmiany siły tłumienia w układzie. Tego rodzaju układy redukcji drgań posiadają wewnętrzne fizyczne sprzężenie zwrotne od prędkości drgań. Zaproponowane rozwiązanie prowadzi do uproszczenia budowy semiaktywnego układu redukcji drgań, gdyż elektromechaniczny przetwornik energii zastępuje zewnętrzne źródła zasilania (niezbędne do sterowania tłumikiem MR). W rozprawie zbadano także znajdujące się pomiędzy cewką przetwornika i cewką sterującą tłumika MR układy kondycjonująco-przetwarzające napięcie wytwarzane przez przetwornik.

Summary

The doctoral dissertation concerns mechanical vibration reduction systems containing in their structure an MR damper and an electromechanical energy transducer operating in accordance with Faraday's law. The purpose of the doctoral thesis is modeling, implementation and testing of the vibration reduction system with an MR damper supplied by the energy of vibration. Operating of such a system was tested in two mechanical applications, having one or two degrees of freedom. The systems being subject of the research belong to the group of semiactive vibration reduction systems, which carry out recovery of kinetic energy of the oscillating object. The kinetic energy is converted by the transducer into electrical energy, used to power the MR damper coil and, consequently, to change the damping force in the system. This type of vibration reduction systems has an internal physical feedback from vibration velocity. The proposed solution allows to simplify the construction of the semiactive vibration reduction system, because the electromechanical energy transducer replaces external power supplies (needed to control the MR damper). Conditioning systems located between the transducer coil and the MR damper coil,  which transform the voltage produced by the transducer, were investigated, as well.

The magnetorheological (MR) damper is one of the utmost progressive applications of asemi-active damper. Uninterrupted controllability in both on and off state is an important factor of its plenitude application. Current research is attempting to make the damper more effective and efficient by minimizing the existing limitations such as MR fluid’s sedimentation, power consumption and temperature rising, and design optimization. We have broadly analyzed the optimization of MR dampers design with finite element simulation where various parameters of the MR damper have been considered for more accurate results. A prototype MR fluid has been prepared by coating the carbonyl iron particles with xanthan gum to reduce sedimentation. The SEM and Turbiscan results noticeably verify the improved sedimentation stability. In addition, a power-saving MR damper model has been developed by finite element analysis using ANSYS software. Prolonged operation raises the damper’s body temperature and degrades the performance. However, in this energy-saving MR damper model the temperature is not rising to a higher value compared to the conventional dampers, and consequently promotes damper efficiency.

Control of civil engineering structures for earthquake hazard mitigation represents a relatively new area of research that is growing rapidly. Passive and active control systems represent the two ends of the spectrum in the use of supplemental damping strategies for response reduction in civil engineering structures subjected to strong earthquakes. On the other hand, semi-active control systems combine the best features of approaches, offering the reliability of passive devices, yet maintaining the versatility and adaptability of fully active systems. Magnetorheological (MR) damper is the major part of this system which produces the control force by virtue of fluid rheology. The influence of position and number of these devices in attenuating the seismic response of an eight storey symmetrical shear building is studied. The optimal configuration for which the response reduction is more is identified. Also the effect of various control algorithms on the behavior of MR damper is studied.

This research is concerned with an optimization study of magneto-rheological damper to achieve a satisfying degree of comfort to the passengers without loss of the vehicle stability. This study explains the effect of using magneto-rheological damper in the construction of vehicles seats by using MATLAB-Simulink software to compare between the passive and active damping systems for various excitations with different frequencies. Moreover, the effect of an active system on the vehicles construction is considered.

This study investigates the automotive magnetorheological (MR) shock absorber behaviour in conditions of changing temperature. Its temperature-dependent behaviour was quantified between ambient and maximal operating temperatures of the device. Aspects addressed include the temperature dependence of the control coil resistance in the absorber, the influence of operating current level on control coil temperature and the temperature dependence of the absorber force response and energy dissipation in the system. The results of experiments enabled us to evaluate the mechanical performance of the absorber at varied temperatures.

The newly developed ideal rectifier bridge equipped with four N-type MOSFETs and two rail-to-rail operational amplifiers is a part of a typical energy harvesting conditioning circuit responsible for the rectification stage in the system of converting the energy harvested from vibrations into electrical energy to power the MR damper. The only energy loss in the bridge is caused by the voltage loss in transistors’ channels. The first sections of the work summarises the structural design of the bridge, the simulation procedure under the RL load and by sine voltage inputs with predetermined frequency and amplitude range, and benchmarks the results against those obtained for the conventional bridge based on Schottky diodes. In the second section, the PCB prototype of the bridge is analysed, and measurement data are compiled. The third section reports on the laboratory testing of the developed bridge converting the harvested energy in an MR damper-based vibration reduction system.

Magnetorheological (MR) damper is one of the most advanced application of semi active devices. Its use is increasing day by day due to its huge advantages and wide range of application. The force delivered by MR damper can be varied by changing the viscosity of its internal MR fluids. Till now no details experimental analysis has been accomplished by considering various parameters. In this paper a brief experimental analysis has been investigated with the help of Universal Testing Machine to characterize MR damper. To characterize accurately MR damper has been analyzed experimentally for different stroke length, stroke rate, stroke mode. From the experimental results it is seen that the force delivered by MR damper has a proportional relation with input excitation current, stroke length and stroke rate.