A new design of magnetic circuits in magnetorheological dampers for simple structure subjected to small stroke and low damping force

2020 ◽  
Vol 30 (1) ◽  
pp. 015036
Author(s):  
Tae-Hoon Lee ◽  
Byung-Hyuk Kang ◽  
Gi-Woo Kim ◽  
Seung-Bok Choi
2019 ◽  
Vol 31 (2) ◽  
pp. 253-262 ◽  
Author(s):  
Jong-Seok Oh ◽  
Key-Sun Kim ◽  
Yang-Sup Lee ◽  
Seung-Bok Choi

This study suggests a relationship between two different types of magnetorheological dampers and the driving performance of the passenger vehicles such as ride quality and stability. One of the magnetorheological dampers has the two different bypass holes in the piston bobbin to achieve a relatively low damping force slope in the low piston velocity region. Without bypass holes, two cylindrical-type magnetorheological dampers have same dimensions (pole lengths, piston radius, and coil size). To enhance the ride quality of the passenger vehicle, the damping force slope of the magnetorheological damper with bypass holes is more gradual than that of the magnetorheological damper without bypass holes. On the basis of the damping force model, three vehicle types with two working modes (soft and hard) are formulated. Driving performance indexes, such as vertical acceleration of the sprung mass and tire deflection, are evaluated in frequency domains under two random road conditions. A comparative study is conducted to prove the effectiveness of the magnetorheological damper with bypass holes through simulation.


Author(s):  
QH Nguyen ◽  
SB Choi ◽  
JK Woo

In this research, a magnetorheological fluid-based damper to attenuate vibration due to unbalanced laundry mass from a front-loaded washing machine is proposed and optimally designed with experimental validation. First, rigid vibration mode of the washing machine due to an unbalanced mass is analyzed, and an optimal positioning of the suppression system for the washing machine is figured out. In order to attenuate vibration from the washing machine, several configurations of magnetorheological damper are proposed considering available space and the required damping force of the system. Based on the Bingham rheological model of magnetorheological fluid, damping force of the proposed magnetorheological dampers is then derived. An optimal design problem for the proposed magnetorheological damper is constructed considering its zero-field friction force and the maximum damping force. The optimization objective is to minimize the zero-field friction force of the magnetorheological damper while the maximum value of damping force is kept being greater than a required value. An optimization procedure based on finite element analysis integrated with an optimization tool is employed to obtain optimal geometric dimensions of the magnetorheological dampers featuring different types of magnetorheological fluid. Optimal solutions of the magnetorheological dampers are then presented and the optimized damper is figured out. In addition, performance characteristics of the optimized magnetorheological damper are presented and discussed.


2012 ◽  
Vol 23 (9) ◽  
pp. 979-987 ◽  
Author(s):  
Holger Böse ◽  
Johannes Ehrlich

Novel concepts for the magnetic circuit in magnetorheological dampers have been proven. In contrast to the established magnetic circuits where the magnetic field for the control of the magnetorheological fluid is generated by the coil of an electromagnet, hybrid magnetic circuits consisting of at least one permanent or hard magnet and an electromagnet are used in the new approaches. Three different technical configurations are distinguished: (1) The electromagnet is combined with two permanent magnets, whose magnetization cannot be modified even by strong magnetic fields of the electromagnet. The main advantage is the improved fail-safe behavior of the damper in case of a power failure. (2) The electromagnet is combined with a hard magnet, whose magnetization can be modified by the electromagnet. This configuration leads to high energy efficiency, because electric power is only required in short pulses for the switching of the hard magnet. (3) All three types of magnetic field sources, permanent, hard, and electromagnet, are combined in the magnetic circuit, which gives the highest flexibility of the magnetic field generation and the damping control at the expense of a relatively large effort. Demonstrators for magnetorheological dampers with all three magnetic circuits were constructed and their performances were tested. The results of the investigations are described in this paper.


2019 ◽  
Vol 31 (2) ◽  
pp. 198-208 ◽  
Author(s):  
Chulhee Han ◽  
Bo-Gyu Kim ◽  
Byung-Hyuk Kang ◽  
Seung-Bok Choi

In this research, a new type of magnetorheological damper for a small-sized aircraft landing gear system is proposed and its performance is evaluated with respect to design parameters of the magnetic core. As a first step, a new configuration of magnetorheological damper for the landing gear system, which consists of orifices, recoil valve, and magnetic circuits, is introduced with working principles. After formulating the governing equations of motion, six different models of magnetorheological damper featuring different number of magnetic core and different pole length are chosen to investigate both the landing stability and the efficiency. Subsequently, the distribution of the magnetic field intensity of each model is analyzed through the finite element method, followed by the calculation of the field-dependent damping force to be used for the landing simulation, which is undertaken by adopting the dynamic model of a half airplane landing gear system. In order to identify the significance of the magnetic core parameters, the landing stability is judged from the sign of the minimum force and the landing efficiency is determined from the energy dissipation during the vertical drop motion.


2012 ◽  
Vol 77 ◽  
pp. 86-95
Author(s):  
Holger Böse ◽  
Johannes Ehrlich

Adaptive damping systems based on magnetorheological (MR) fluids allow the continuous control of vibration damping forces depending on the current conditions. In magnetorheological dampers known so far, the magnetic field for the control of the MR fluid is generated by the coil of an electromagnet. Two novel concepts for the magnetic circuit in magnetorheological dampers have been proven where hybrid magnetic circuits consisting of at least one permanent or hard magnet and an electromagnet are used. In the first concept, the electromagnet is combined with two permanent magnets, whose magnetization cannot be modified even by strong magnetic fields of the electromagnet. The main advantage of this configuration is the improved fail-safe behaviour of the damper in case of a power failure. In the second approach, the electromagnet is combined with a hard magnet, whose magnetization can be modified by the electromagnet. This configuration leads to high energy efficiency, because electric power is only required in short pulses for the switching of the hard magnet. Magnetic circuits with the combination of different magnetic field sources were designed supported by simulations of the magnetic flux distribution. Demonstration models for magnetorheological dampers with the distinguished magnetic circuits were constructed and their performances were tested. The results of the investigations are described in this contribution.


Methodology ◽  
2019 ◽  
Vol 15 (Supplement 1) ◽  
pp. 43-60 ◽  
Author(s):  
Florian Scharf ◽  
Steffen Nestler

Abstract. It is challenging to apply exploratory factor analysis (EFA) to event-related potential (ERP) data because such data are characterized by substantial temporal overlap (i.e., large cross-loadings) between the factors, and, because researchers are typically interested in the results of subsequent analyses (e.g., experimental condition effects on the level of the factor scores). In this context, relatively small deviations in the estimated factor solution from the unknown ground truth may result in substantially biased estimates of condition effects (rotation bias). Thus, in order to apply EFA to ERP data researchers need rotation methods that are able to both recover perfect simple structure where it exists and to tolerate substantial cross-loadings between the factors where appropriate. We had two aims in the present paper. First, to extend previous research, we wanted to better understand the behavior of the rotation bias for typical ERP data. To this end, we compared the performance of a variety of factor rotation methods under conditions of varying amounts of temporal overlap between the factors. Second, we wanted to investigate whether the recently proposed component loss rotation is better able to decrease the bias than traditional simple structure rotation. The results showed that no single rotation method was generally superior across all conditions. Component loss rotation showed the best all-round performance across the investigated conditions. We conclude that Component loss rotation is a suitable alternative to simple structure rotation. We discuss this result in the light of recently proposed sparse factor analysis approaches.


2021 ◽  
Vol 26 (2) ◽  
pp. 04020119
Author(s):  
Peng Zhou ◽  
Min Liu ◽  
Weiming Kong ◽  
Yingmei Xu ◽  
Hui Li

2020 ◽  
pp. 54-58
Author(s):  
S. M. Plotnikov

The division of the total core losses in the electrical steel of the magnetic circuit into two components – losses dueto hysteresis and eddy currents – is a serious technical problem, the solution of which will effectively design and construct electrical machines with magnetic circuits having low magnetic losses. In this regard, an important parameter is the exponent α, with which the frequency of magnetization reversal is included in the total losses in steel. Theoretically, this indicator can take values from 1 to 2. Most authors take α equal to 1.3, which corresponds to the special case when the eddy current losses are three times higher than the hysteresis losses. In fact, for modern electrical steels, the opposite is true. To refine the index α, an attempt was made to separate the total core losses on the basis that the hysteresis component is proportional to the first degree of the magnetization reversal frequency, and the eddy current component is proportional to the second degree. In the article, the calculation formulas of these components are obtained, containing the values of the total losses measured in idling experiments at two different frequencies, and the ratio of these frequencies. It is shown that the rational frequency ratio is within 1.2. Presented the graphs and expressions to determine the exponent α depending on the measured no-load losses and the frequency of magnetization reversal.


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