MR Dampers

dampers are devices that can be used for vibration reduction in structures. However, to use these devices in an effective way, a precise modeling is required. In this sense, in this paper we consider a modified parameter identification method of large scale magnetorheological dampers which are represented using the normalized Bouc-Wen model. The main benefit of the proposed identification model is the accuracy of the parameter estimation. The validation of the parameter identification method has been carried out using a black-box model of an MR damper in a smart base-isolated benchmark building. Magnetorheological (MR) dampers are used in this numerical platform both as isolation bearings as well as semiactive control devices.

Magnetorheological (MR) dampers are semi-active controllable devices that utilize magnetorheological fluids (MRF) for generating governable force. The MR fluid contains magnetic micro-sized/nano-sized iron (Fe) particles, non-magnetic-based fluid, and some additives to mitigate sedimentation and agglomeration. The addition of magnetic nano-sized particles exhibits better sedimentation stability relative to common dispersed additives without affecting the MR effect. MR dampers may be treated as fail-safe as they behave as passive dampers in case of a breakdown of the control mechanism. These dampers are simple in construction, own fewer moving parts, make use of less power, are brisk in response, and mitigate the tolerances. MRF have the special potential to vary dynamic yield stress on the application of a magnetic field and damping force is varied by magnetically varying the rheological characteristics of the fluids. This paper investigates the magnetized field produced in the damper using finite element analysis (FEA) and verified using magnetic circuit theory. A 2D axisymmetric MR damper has been firstly modelled using SolidWorks software and then magnetic field density in MRF space on the application of current has been determined using ANSYS Maxwell software v16. For analytical modeling of the MR damper, a program in "C" language for electromagnetic circuit theory has been used to evaluate the shear stress for the MR damper. The "C" program results and FEA results indicated a small variation of 3.63% in magnetic flux density generated for the current flow of 1 A through the coil and this led to the validation of this study.

Streszczenie. Celem artykułu jest przedstawienie moŜliwości wykorzystania symulacji komputerowej do opisu działania układu tłoka gazowego z suwadłem w opracowywanych karabinkach podstawowych Modułowego Systemu Broni Strzeleckiej kalibru 5,56 mm (MSBS-5,56). Zaprezentowano moŜliwości wykorzystania aplikacji CAE -programu MSC.visual Nastran -w procesie rozwiązywania dynamicznych równań ruchu tłoka gazowego i suwadła zgodnie z teorią Newtona-Eulera. Przedstawiono etapy przygotowywania modelu numerycznego wraz z przyjętymi warunkami początkowo-brzegowymi oraz porównano wyniki symulacyjne z doświadczalnymi. Słowa kluczowe: projektowanie broni strzeleckiej, analiza numeryczna, metoda układów wieloczłonowych

His dissertation, Black Writers of the Thirties, was published by Louisiana State University. Dr. Young has taught history and American Studies at several colleges. In addition to writing official histories, he has produced numerous film documentaries and video briefings, several of which have been broadcast on cable television, at the Air Force Museum, and are and are included in university curricula. Dr. Young has written many articles and book reviews and served as a technical advisor for film documentarians, most recently for the Smithsonian's "Frontiers of Flight" and cable television's "X Planes" series. His latest writings include The USAF

This paper deals with the modelling of a magneto-rheological damper as a component of a quarter-car model. The objective is to provide an analysis of the transient and frequency behavior of the suspension system in order to evaluate the inherent linearities of two identified models: a complex one and a control-oriented one. The models have a common structure but the effect of the current and the dynamic behavior has different principle. The results show that the design of experiments is a key issue in the identification process. A quarter of a vehicle which includes a control-oriented damper model is identified as well-suited for the synthesis of controllers that perform well in terms of accurate frequency response when compared with that of a quarter-car with a semi-active suspension simulated with experimental data.

A hybrid type magneto-rheological (MR) fluid damper based on electromagnet and two permanent magnets apart from electromagnet was designed and its characteristics were analyzed numerically. In the proposed MR damper, the magnetic field is generated by the permanent magnet and raised by the additional electromagnet. This combination provides a larger amount of damping force with lower consumption of electric energy. The proposed model has an additional advantage of providing a moderate damping force in case of electromagnet failure. The magnetic circuit of a hybrid MR valve was analyzed by applying Kirchhoff's law and magnetic flux conservation rule. A 2D axisymmetric model of the proposed hybrid MR damper was developed in commercial software where magnetic field properties are analyzed by finite element method. The optimization process was developed to optimize the geometric parameters and generated damping force using design of experiment (DoE) technique. The damping force of the MR damper was selected as an objective function. The optimal solution to the optimization problem of the hybrid MR valve structure was evaluated and compared with the solution obtained from the initial parameters. It is demonstrated that the novel hybrid type provides higher damping force than the previous model.

Dostępne na rynku amortyzatory o regulowanej w czasie rzeczywistym charakterystyce tłumienia różnią się zarówno co do istoty funkcjonowania, jak i co do bardziej szczegółowych cech funkcjonalnych. W artykule przedstawiono możliwe do zastosowania typy takich amortyzatorów omawiając budowę i funkcjonowanie zarówno amortyzatorów magnetoreologicznych, jak i amortyzatorów wykorzystujących regulację przy pomocy zaworów proporcjonalnych. Dla wybranych amortyzatorów, omówiono sposób sterowania zaworem oraz przedstawiono metodykę i wyniki badań charakterystyk pracy wybranych konstrukcji. Badania wykonano przy użyciu stanowiska do badań amortyzatorów wymontowanych z pojazdu przy wyposażeniu go w układ sterowania pracą amortyzatora w czasie rzeczywistym oraz system pomiaru parametrów pracy amortyzatora. Do wykonania badań pozwalających określić charakterystyki sterowania amortyzatorów, ich odpowiedzi skokowe, czułość i wpływ prędkości pracy i skoku amortyzatora na jakość sterownia zostały wykorzystane procedury sterujące opracowane w środowisku Matlab/Simulink i zaimplementowane w systemie prototypowania sterowników czasu rzeczywistego. Wykonano również badania wpływu różnych wariantów parametrów sygnałów sterujących na jakość sterowania.Uzyskane wyniki wraz z analizą ich znaczenia dla budowy systemów zawieszeń półaktywnych zostały przedstawione w końcowej części pracy. Omówiono również wnioski dotyczące samej metodyki badawczej.

In this paper detailed description of temperature influence on MR damper working parameters has been described. Prototype of such a device and its mathematical description taking into considerations a thermal balance, have been proposed. Basing on experimental results, a connection between temperature and operating parameters of tested MR damper has been revealed.

In this research work, a self-power shear-mode magneto-rheological (MR) damper that can replace conventional passive damper of a front-loaded washing machine is designed and experimentally evaluated. The self-power damper consists of two main components: the damping component and the self-power one. The damping component is composed of an inner housing with a thin wall, on which the coils are wound directly, and an outer housing to cover the coil and to create a closed magnetic circuit of the damper. The gap between the inner housing and the shaft is filled with MR fluid to create damping force. The self-power component consists of magnetized permanent magnets fastened together on the moving shaft and a slotted stator core covered by an outer housing. The coils are wound directly on the slots of the stator core and connected to the coils of the damping component to generate the required current when the shaft moves reciprocally. After an introduction to suspension system for front-loaded washing machine, the configuration of the self-power MR damper for front-loaded washing machine is proposed. Optimization of the proposed self-power MR damper is then performed considering required damping force, off-state friction force, size, power consumption and low cost of the damper. From the optimal results, simulated performance of the optimized MR damper is obtained and a detailed design of the MR damper is then conducted and presented with discussion.

Multiphysics numerical analysis , which are the magnetic field and time-dependent CFD analysis, validated by experimental results have been performed to obtain the magnetic flux density and relationship of damping force-displacement. The most effective levels of the design parameters  have been determined regarding of the damping force and dynamic range. Also, the expected performances of the optimal MR damper designs and effect each design parameter on performance have been calculated statistically corresponding to different velocity values. Results showed that, from 0.05 m/s to 0.15 m/s of piston velocity, the effect of the gap width was increased by 2.56% while the active length was decreased by 4.12% under constant current.

Witold Wiśniowski BADANIA REZONANSOWE OBIEKTÓW LATAJĄCYCH-METODY I ANALIZA WYNIKÓW Streszczenie Praca jest podsumowaniem kilkunastu lat badań doświadczalnych właściwości dynamicznych konstrukcji lotniczych prowadzonych przez autora i zespół jego współpracowników w Instytucie Lotnictwa w Warszawie. Kilka pierwszych rozdziałów zawiera przegląd i analizę metod badawczych znanych pod ogólną nazwą prób rezonansowych. Oryginalną częścią pracy są nowe metody badań. Można zaliczyć do nich skalowanie rezonansowe tensometrów, rezonansowa wibrodiagnostyka i rezonansowe badanie odporności na drgania, badanie rezonansów o jednakowych częstościach czy też badanie rezonansów z udziałem luzów. Istotną częścią pracy jest opracowanie i zaprezentowanie pewnego rodzaju bazy danych o właściwościach rezonansów konstrukcji lotniczych.

The present paper deals with the transient magnetic model of the magnetorheological (MR) damper and its experimental verification. The response time of MR damper affects the quality of semi-active control of this damper. The lower the response time, the higher the system efficiency. The most important part of the response time of the MR damper is the response time of magnetic field of the MR damper which can be determined by transient magnetic model. The transient magnetic model was created by the software Ansys Electromagnetics 17.1 as 2D axisymmetric and verified by measurement of magnetic field in the gap of MR damper piston. The maximum difference between the model and the experiment was 28 %. The response time depends on the electric current in the coil of MR damper. The transient magnetic model was used for determination of influence of MR fluid type, material of cover and material of magnetic circuit on the response time of magnetic field of MR damper. The type of MR fluid has a significant influence on the response time. The lower the mass concentration of ferromagnetic particles, the lower the response time of magnetic field. A material selection of magnetic circuit is always a trade-off between the response time and the maximum magnetic flux density (dynamic force range) in the gap of the MR damper. According to the verified transient magnetic model, it is possible to find a suitable material of magnetic circuit for specific application (response time).

Magnetorheological (MR) dampers are devices that can be used for vibration reduction in structures. However, to use these devices in an effective way, a precise modeling is required. In this sense, in this paper we consider a modified parameter identification method of large-scale magnetorheological dampers which are represented using the normalized Bouc-Wen model. The main benefit of the proposed identification algorithm is the accuracy of the parameter estimation. The validation of the parameter identification method has been carried out using a black box model of an MR damper in a smart base-isolated benchmark building. Magnetorheological dampers are used in this numerical platform both as isolation bearings as well as semi-active control devices.

In the paper the System-On-the-Chip (SOC) based on a FPGA circuit is presented to collect input data, perform conditioning and to generate the control signals for the cable system equipped with the MR damper. The FPGA configuration and SOC programming techniques are shown. Experimental results of a semi-active vibration control system controlled by the SOC module are considered. A research is conducted how to mitigate or reduce vibrations by control algorithms.

The paper presents characteristics of the didactic stand for presentation of the vibration propagation in the body of a driver or a passenger of a motor vehicle. The didactic stand was built on the basis of an MTS electrohydraulic pulsator and anthropodynamic dummy in the Laboratory of Automobiles and Tractors of Kielce University of Technology. The structure and characteristics of each element of didactic stand are described. The possibilities of didactic stand were presented.

This paper presents the design of an Magnetorheological (MR) damper that includes an arrangement of a piston and cylinder. This study developed a 3-D model based on the finite element method (FEM) concept on the COMSOL Multiphysics to analyze and investigate the MR damper characteristics. A prototype of the MR damper is being fabricated based on the FEM model and is put through a series of experiments using the Servo-Hydraulic material testing machine (MTS). Maximum and minimum forces, 171.5235N and 249.2749N, were measured at 0.1Hz and 1Hz, respectively, for the FEM model. The fabricated model obtained similar results at 0.1Hz and 1Hz, with maximum and minimum forces of 175.9103N and 252.7765N, respectively. Comparing these two model analyses reveals that the FEMbased model accurately depicts the experimental behaviour of the MR damper in terms of its damping force, although there is minor variation. The findings of this paper will be helpful for designers in creating MR dampers that are more efficient and reliable, as well as in predicting the characteristics of their damping force.

This article presents the results of an experimental investigation on a developed small scale MR damper for seismic response reduction in buildings. The damper is designed for a target capacity of 2kN.The damper was design and fabricated based on the principle of shear mode. Testing was done using MTS servo hydraulic UTM and the results were obtained as Force-velocity and Force displacement plot based on the real time data collected through MTS suite. The force corresponding to all the excitation frequency is obtained and has been plotted as force-velocity so as to compare the percentage increase in damping force. Maximum force was obtained as 252.4N at 1hz and minimum force as 175.9N at 0.1hz with corresponding velocity of 31.2mm/s for 1hz and 3.5mm/s for 0.2hz respectively. The experiment proves that with displacement control and variable excitation frequency, the velocity of the MR damper varies, and as a result, the damping force increases as frequency increases which is the main finding of this paper.

This study concerns the modeling of the hysteretic behavior of magnetorheological (MR) dampers. In general, hysteresis is one of key factors influencing the output of such actuators. So far, more attention has been paid to studying the combined hysteretic behavior of MR actuators by observing the relationships between the output (force/torque) and the inputs (current, velocity, and position). However, these devices feature two distinct hysteretic mechanisms: mechanical/hydraulic and magnetic. The mechanical hysteresis is of different nature than the magnetic hysteresis due to the properties of ferromagnetic materials forming the actuator's electromagnet circuit, and these should be split in the modeling process. In the present study, we separate the magnetic hysteresis from the mechanical/hydraulic one by investigating the magnetic flux vs. exciting current relationship of a commercial flow-mode MR damper subjected to sinusoidal current loading and independently of the mechanical excitations. The resulting behavior of the electromagnetic circuit is then examined using the non-linear inductor approach with hysteresis. Total hysteresis is then modeled using a non-linear inductor model in combination with a phenomenological parametric Maxwell type model of the damper.

The magnetorheological fluid damper (MRD) is a commonly employed semi-active damping mechanism. The utilisation of this technology has the potential to mitigate the impact of natural hazards on structures, owing to its crucial ability to dissipate energy and its minimal energy consumption. This study aims to compare the performance of a reduced-scale reinforced concrete (RCC) frame with a large MR damper (MRD) attached diagonally, to that of an RCC frame with a smaller-scale MRD attached at different locations. The experimental evaluation of two frames was conducted utilising El-Centro time history data, which was obtained from MTS. The efficacy of the small-scale MRD was also assessed through the El Centro seismic loading before integrating to the RCC frame. Subsequently, it was integrated with the frame and exhibited effective performance in mitigating seismic excitation. The maximum force generated was measured at 2.03kN, accompanied by a notable reduction in displacement of 13.24%. The frame equipped with a diagonal damper directly installed at the beam-column joint exhibits load-carrying capacities that are 12.32% and 19.77% lower than those of the frame equipped with a single and double damper, respectively, positioned at a distance of L/3 from the joint. In comparison to a diagonally placed large damper, the implementation of a small-scale magnetorheological damper (MRD) resulted in a reduction of displacements by 7.99% and 17.59% for single and double MRD configurations installed on the frame, respectively. However, this implementation also led to an increase in forces and alterations in crack patterns. The experimental findings indicate that the inclusion of a substantial quantity of smaller MRD can be a viable approach to mitigating structural responses in regions prone to seismic activity, while still maintaining the aesthetic integrity of the structure.

A hybrid type magneto-rheological (MR) fluid damper based on electromagnet and two permanent magnets apart from electromagnet was designed and its characteristics were analyzed numerically. In the proposed MR damper, the magnetic field is generated by the permanent magnet and raised by the additional electromagnet. This combination provides a larger amount of damping force with lower consumption of electric energy. The proposed model has an additional advantage of providing a moderate damping force in case of electromagnet failure. The magnetic circuit of a hybrid MR valve was analyzed by applying Kirchhoff's law and magnetic flux conservation rule. A 2D axisymmetric model of the proposed hybrid MR damper was developed in commercial software where magnetic field properties are analyzed by finite element method. The optimization process was developed to optimize the geometric parameters and generated damping force using design of experiment (DoE) technique. The damping force of the MR damper was selected as an objective function. The optimal solution to the optimization problem of the hybrid MR valve structure was evaluated and compared with the solution obtained from the initial parameters. It is demonstrated that the novel hybrid type provides higher damping force than the previous model.

Magnetorheological (MR) dampers are controlled energy-dissipating devices utilizing smart fluids. They operate in a fast and valveless manner by taking advantage of the rheological properties of MR fluids. The magnitude of the response of MR fluids, when subjected to magnetic fields, is of sufficient magnitude to employ them in various applications, namely, vibration damping, energy absorption, exoskeletons, etc. At the same time, predicting their response to arbitrary mechanical and electrical inputs is still a research challenge. Due to the non-linearities involved in material properties or the design of the solenoid used for activating the fluid modeling the relationships between the control circuit and the material’s response is complex. Modeling studies can be classified into two categories. The parametric approach requires the knowledge of the internal material’s properties and takes advantage of physics formulas to infer the I/O relationships present in the damper. For compar...

Connection of one phase micro-generator to the low voltage network increases voltage asymmetry. The voltage asymmetry is defined as the quotient of negative and positive voltage components. The mathematical background of exact and rough computation of the asymmetry quotient is presented in the paper. Considerations are illustrated by simple examples.

Every country is doing a lot of research and development work on security and defense. A country like India shares their border with different countries from three sides need a lot of protection on border. Countries are making new armors and weapons with latest technologies so that their border can be protected. With the help of stealth technology, we make any object similar to surrounding environment in term of color (vantablack) and shape. If we use this technology in army jeep and tanks, then enemy will not be able to find out the position of our jeep and tanks on border. Stealth vehicle will be very useful from defense point of view on border. To make the vehicle stealth, we will give a new design to the vehicle, do thermal infrared reflective coating on engine and used super alloy to make the body of the vehicle. By applying thermal infrared reflective coating on vehicle, the vehicle will not emit heat and any heat sensor will not be able to detect the position of the vehicle. ...

Presented are issues related to improvement of the vibration isolating properties of semi-active seat suspension. It shows the practical implementation of the force control system for pneumatic spring which was mounted in mass-produced seat suspension. Output control function for pressure valve of pneumatic supply system was proposed. The developed solution allowed to carry out the research of air spring applied to a semi-active suspension system.

Many vehicle systems and industrial equipment face the issue of vibrations. As such, vibration control devices like classical hydraulic dampers are utilized to minimize vibrations. In this context, magenetorheological fluid is introduced as a damper fluid to improve the damper's vibration reduction capability. This damper is known as the MR damper in which the magnetic field required to activate MR fluid is produced by using an electromagnet over the piston inside the damper cylinder. However, some severe problems are observed due to internal electromagnetic piston configuration in the conventional MR damper. Therefore, modification is suggested in the damper in the form of an external permanent magnet assembly's fitment.The proposed model consists of a damper cylinder filled with MR fluid and an external assembly of permanent magnets positioned near the cylinder. The conventional and modified MR dampers have been tested on a test rig by changing the MR fluid configuration, excitation frequency of exciter, and excitation current. The MR effect on velocity and damping force in conventional and modified dampers has been recorded and compared. The results convincingly indicate that the modified MR damper delivers good performance by generating sufficient damping capacity that can be utilized for necessary applications. Importantly, it resolves the problems associated with conventional MR dampers like electric current unavailability at field, clumping, hard cake formation, remanence phenomenon, and excessive heat formation. Index Terms-Magnetorheological Damper (MR damper); Magnetorheological Fluid (MR fluid/MRF), force-velocity characteristics, external permanent magnet, excitation current and frequency I. INTRODUCTION Vibration control technology has remained a challenging area of study for many engineers and researchers. Civil structures, vehicle systems, industrial equipment, etc., have been facing the problem of Manuscript

Many systems in Industrial sector face the problems of vibrations. Vibration control equipment like MR damper is employed to minimize these vibrations. In this context, magenetorheological fluid (MR Fluid) is introduced as a damper fluid to improve the damper’s vibration reduction capacity significantly. This damper is known as Magnetorheological damper (MR damper) in which electromagnetic piston produces attractive impact to enact MR liquid. However, some problems are observed in MR damper due to internal electromagnetic piston configuration. Therefore, modification is proposed in the damper. The proposed design consists of a conventional MR damper filled with MR fluid and an external assembly of permanent magnet fitted around the damper. The modified MR damper has been tested under different parametric conditions with MR fluid AMT-Dampro. The results convincingly indicate that the modified damper delivers excellent performance by generating effective damping capacity that can be u...

Many vehicle systems and industrial equipment face the issue of vibrations. As such, vibration control devices like classical hydraulic dampers are utilized to minimize vibrations. In this context, magenetorheological fluid is introduced as a damper fluid to improve the damper's vibration reduction capability. This damper is known as the MR damper in which the magnetic field required to activate MR fluid is produced by using an electromagnet over the piston inside the damper cylinder. However, some severe problems are observed due to internal electromagnetic piston configuration in the conventional MR damper. Therefore, modification is suggested in the damper in the form of an external permanent magnet assembly's fitment.The proposed model consists of a damper cylinder filled with MR fluid and an external assembly of permanent magnets positioned near the cylinder. The conventional and modified MR dampers have been tested on a test rig by changing the MR fluid configuration, excitation frequency of exciter, and excitation current. The MR effect on velocity and damping force in conventional and modified dampers has been recorded and compared. The results convincingly indicate that the modified MR damper delivers good performance by generating sufficient damping capacity that can be utilized for necessary applications. Importantly, it resolves the problems associated with conventional MR dampers like electric current unavailability at field, clumping, hard cake formation, remanence phenomenon, and excessive heat formation.

Many systems in Industrial sector face the problems of vibrations. Vibration control equipment like MR damper is employed to minimize these vibrations. In this context, magenetorheological fluid (MR Fluid) is introduced as a damper fluid to improve the damper's vibration reduction capacity significantly. This damper is known as Magnetorheological damper (MR damper) in which electromagnetic piston produces attractive impact to enact MR liquid. However, some problems are observed in MR damper due to internal electromagnetic piston configuration. Therefore, modification is proposed in the damper. The proposed design consists of a conventional MR damper filled with MR fluid and an external assembly of permanent magnet fitted around the damper. The modified MR damper has been tested under different parametric conditions with MR fluid AMT-Dampro. The results convincingly indicate that the modified damper delivers excellent performance by generating effective damping capacity that can be utilized for necessary applications.

A scientific literature review has been conducted on Magnetorheological Fluid Damper technology and its applications, in order to understand the requirement, the working style and the opportunities for damper development. In the last years, Magnetorheological fluid (MRF) Damper technology has attracted great attention in the field of vibration reduction. Magnetorheological fluid is a smart material used for vibration control. Its shear yield stress can be changed in few milliseconds under the active magnetic field. Essential properties of MR fluid are its rheological ones, its redispersibility and its anti-settlement stability. Magnetorheological Damper is an active flexible device used for vibration reduction due to its efficient control ability in the on-off state. MR Damper produces large damping force by using low energy. The existing MR damper includes internal electromagnet in order to generate magnetic effect required for activation of MR fluid. This paper contains a review about Magnetorheological Fluid technology (i.e. preparation, properties, comparison with ER fluid), its use in a semi-active device like MR damper, its use limitations, various design approaches of MR damper and MR suspension application.

Aby zrealizować ideę komunikacji kolejowo-tramwajowej, niezbędne jest posiadanie pojazdu trakcyjnego, który będzie mógł być zasilany z sieci kolejowej 3300Vdc i typowej sieci tramwajowej 600Vdc. Jednym z rozwiązań jest zbudowanie przekształtnika obniżającego wysokie napięcie. W artykule przedstawiono projekt i wyniki badań laboratoryjnych przekształtnika rezonansowego z transformatorem toroidalnym. Ze względu na zakres napięcia wejściowego 3300Vdc zastosowano konfigurację układu półmostka z szeregowym obwodem rezonansowym po stronie pierwotnej transformatora. Praca w trybie rezonansowym umożliwia zwiększenie częstotliwości pracy układu, dzięki temu mogą być mniejsze wymiary i masa transformatora. Głównym zastosowaniem przekształtnika ma być zasilanie układu napędowego (falownikowego) w dwusystemowym pojeździe tramwajowokolejowym 3000Vdc/600Vdc. Do tego celu został specjalnie zaprojektowany i wykonany transformator z nanokrystalicznym rdzeniem toroidalnym o mocy czynnej 120kW. Artyku...

This paper presents the materials analysis for a new mixed mode Magnetorheological (MR) damper. The selection of materials was considered in order to obtain the best design of MR damper with the optimum magnetic field strength at the effective areas. Electromagnetic circuit design is one of the important criteria in designing MR dampers besides the working mechanism and the types of MR damper. The increase in the magnetic field strength is an indication of the improvement in the damping performance of the MR damper. Eventually, the experimental test was performed under quasi-static loading to observe the performances of MR damper in shear mode, squeeze mode and mixed mode. The results showed that the increment of forces was obtained with the increased current due to higher magnetic flux density generated by electromagnetic coils. In general, it can be summarized that mixed mode generates higher forces than single mode for the same experimental parameters throughout the study.

Przetwornik pr dowo-napi ciowy ze zmodyfikowanym rdzeniem amorficznym do pomiarów pr dowych przebiegów odkszta conych W artykule zaprezentowano i omówiono wyniki bada w a ciwo ci metrologicznych przetwornika pr dowo-napi ciowego z zastosowanym zmodyfikowanym rdzeniem amorficznym przydatnym do pomiarów pr dowych, zw aszcza przebiegów odksztaconych w uk adach nap dowych. Wyznaczono warto ci b dów pr dowych i k towych przetwornika w szerokim zakresie zmian warto ci skutecznych i cz stotliwo ci mierzonych pr dów.

przedstawia stanowisko badawczo-dydaktyczne pozwalające poznać wpływ wprowadzenia do układu broń ramienna-strzelec systemu programowania przebiegu zjawiska odrzutu przez zastosowanie zsynchronizowanego układu sterowanych tłumików magnetoreologicznych (MR). Badanie ma na celu oszacowanie wpływu tłumienia wysokoenergetycznego impulsu pochodzącego od broni małokalibrowej ramiennej na siłę pchnięcia. Dla dostępnego zestawu tłumików MR dobierany jest doświadczalnie zakres prądów sterowania cewką urządzeni MR. Opracowanie wyników w szczególny sposób dotyczy związku układu MR z przebiegiem i wielkością siły pchnięcia, mającej bezpośredni wpływ na celność broni. Otrzymane wyniki badań dowodzą, że zaproponowany układ: obiekt specjalny-tłumik MR-strzelec wpływa korzystnie między innymi na jego stabilność (odrzut oraz podrzut). W artykule przedstawiono schematyczną budowę stanowiska, podstawowe parametry badanego układu oraz wybrane wyniki badań.

Streszczenie. Artykul przedstawia stanowisko badawczo-dydaktyczne pozwalające poznac wplyw wprowadzenia do ukladu bron ramienna–strzelec systemu programowania przebiegu zjawiska odrzutu przez zastosowanie zsynchronizowanego ukladu sterowanych tlumikow magnetoreologicznych (MR). Badanie ma na celu oszacowanie wplywu tlumienia wysokoenergetycznego impulsu pochodzącego od broni malokalibrowej ramiennej na sile pchniecia. Dla dostepnego zestawu tlumikow MR dobierany jest doświadczalnie zakres prądow sterowania cewką urządzeni MR. Opracowanie wynikow w szczegolny sposob dotyczy związku ukladu MR z przebiegiem i wielkością sily pchniecia, mającej bezpośredni wplyw na celnośc broni. Otrzymane wyniki badan dowodzą, ze zaproponowany uklad: obiekt specjalny–tlumik MR–strzelec wplywa korzystnie miedzy innymi na jego stabilnośc (odrzut oraz podrzut). W artykule przedstawiono schematyczną budowe stanowiska, podstawowe parametry badanego ukladu oraz wybrane wyniki badan. Slowa kluczowe: odrzut, p...

przedstawia stanowisko badawczo-dydaktyczne pozwalające poznać wpływ wprowadzenia do układu broń ramienna-strzelec systemu programowania przebiegu zjawiska odrzutu przez zastosowanie zsynchronizowanego układu sterowanych tłumików magnetoreologicznych (MR). Badanie ma na celu oszacowanie wpływu tłumienia wysokoenergetycznego impulsu pochodzącego od broni małokalibrowej ramiennej na siłę pchnięcia. Dla dostępnego zestawu tłumików MR dobierany jest doświadczalnie zakres prądów sterowania cewką urządzeni MR. Opracowanie wyników w szczególny sposób dotyczy związku układu MR z przebiegiem i wielkością siły pchnięcia, mającej bezpośredni wpływ na celność broni. Otrzymane wyniki badań dowodzą, że zaproponowany układ: obiekt specjalny-tłumik MR-strzelec wpływa korzystnie między innymi na jego stabilność (odrzut oraz podrzut). W artykule przedstawiono schematyczną budowę stanowiska, podstawowe parametry badanego układu oraz wybrane wyniki badań.

In this paper detailed description of temperature influence on MR damper working parameters has been described. Prototype of such a device and its mathematical description taking into considerations a thermal balance, have been proposed. Basing on experimental results, a connection between temperature and operating parameters of tested MR damper has been revealed.

Badania właściwości drganiowych mogą być przeprowadzone różnymi metodami, w zależności od sposobu wzbudzania oraz analizy odpowiedzi obiektu. Od wielu lat skuteczną i dokładną, choć nie najszybszą metodą identyfikacji dynamicznej płatowców pozostają badania rezonansowe. W Instytucie Lotnictwa przeprowadzono badania rezonansowe wielu samolotów, szybowców i śmigłowców a także innych, nielotniczych konstrukcji. Przedstawione poniżej wnioski z analizy wyników pomiarów tłumienia z wykonanych badań rezonansowych powinny być przydatne przy obliczeniach flatterowych jak i przy badaniach flatterowych w locie.

Stealth or low observability, high speed and maneuv erability are very important characteristics for modern military aircraft. Planf orm shaping is fundamental to achieve stealthy aircraft. As well as Radar Cross Section (RCS), the supersoni c aerodynamics characteristics are crucial to achieve th optimum. In order to follow the current trend of the military field in stealth desi gn ng and application, this study on supersonic aircraft geometries is investigated in b oth aspects. Using Soliworks® software, 3D CAD models were developed and designed . Using the tool SOM, it was possible to choose the aircraft model with lowest w ave drag coefficient ( CDwavedrag). The RCS part of this model was simulated using POFACETS software. This program was developed by Naval Postgraduate School (NPS) under the MATLAB® platform. It is based on physical optics (PO) method to predict the RCS targets (3D CAD models) using triangular facets. The radar signature analys is are done to : a) investigate ...

This paper presents the design of an Magnetorheological (MR) damper that includes an arrangement of a piston and cylinder. This study developed a 3-D model based on the finite element method (FEM) concept on the COMSOL Multiphysics to analyze and investigate the MR damper characteristics. A prototype of the MR damper is being fabricated based on the FEM model and is put through a series of experiments using the Servo-Hydraulic material testing machine (MTS). Maximum and minimum forces, 171.5235N and 249.2749N, were measured at 0.1Hz and 1Hz, respectively, for the FEM model. The fabricated model obtained similar results at 0.1Hz and 1Hz, with maximum and minimum forces of 175.9103N and 252.7765N, respectively. Comparing these two model analyses reveals that the FEMbased model accurately depicts the experimental behaviour of the MR damper in terms of its damping force, although there is minor variation. The findings of this paper will be helpful for designers in creating MR dampers that are more efficient and reliable, as well as in predicting the characteristics of their damping force.

This article presents the results of an experimental investigation on a developed small scale MR damper for seismic response reduction in buildings. The damper is designed for a target capacity of 2kN.The damper was design and fabricated based on the principle of shear mode. Testing was done using MTS servo hydraulic UTM and the results were obtained as Force-velocity and Force displacement plot based on the real time data collected through MTS suite. The force corresponding to all the excitation frequency is obtained and has been plotted as force-velocity so as to compare the percentage increase in damping force. Maximum force was obtained as 252.4N at 1hz and minimum force as 175.9N at 0.1hz with corresponding velocity of 31.2mm/s for 1hz and 3.5mm/s for 0.2hz respectively. The experiment proves that with displacement control and variable excitation frequency, the velocity of the MR damper varies, and as a result, the damping force increases as frequency increases which is the mai...

This paper presents a new algorithm which is applicable in designing a smart damping system for vibration mitigation. The algorithm, which is extended into a unified system from Lyapunov stability theory, enables us to decrease the errors by its increased stability. The validity of this design method was proved in the experiment on a control model of three-storied building structure. Smart damper was used for MR (Magneto-Rheological fluid) damper in the experiment, and its control effectiveness was evaluated. In order to make a more accurate control model mathematically, we updated the model on the basis of the analysis of dynamic characteristics of structure and of the mathematical analysis of a lumped mass model, and then employed a state space model redefined by structural property matrix. Using this improved control model, control effect on structures that were under the influence of each different earthquake magnitude was analyzed with various performance indexes, and thus the algorithm presented here is proved to be valid.

This paper provides information on the latest R&D within COVICOCEPAD project approved in the framework of Eurocores program. It addresses the use of TLD, base isolation devices, MR dampers and a hybrid technique using both devices together. Some results are provided associated with calibration of a MR damper at FEUP, as well as its inclusion in a small scale laboratory setup with proper equations of motion of the controlled smart structure. An application of semi-active control technique to a bridge is outlined. Further remarks and details on future tests to be performed in LNEC shaking table, within COVICOCEPAD project, are provided.

The current research work is directed to study and improve vehicle behavior during crashes. Hence, a crash-pitch controller integrated with Magnetorheological (MR) dampers implemented in both vehicle suspension systems and front-end structures is designed and studied. The methodology of the work is based on modeling the vehicle's dynamical attitude as a half-car mathematical model that is developed with 3 degrees of freedom (DOF). The model is constructed to study the vehicle’s dynamic response in a full-frontal collision against a fixed barrier. Additionally, a fuzzy logic controller is developed to integrate the suspension MR dampers with another set of MR dampers implemented within the vehicle’s front-end structure. Four different vehicle cases were discussed and compared within the simulation results of the developed model. Moreover, the four cases can be clarified as the first is free-rolling, In which a conventional suspension and conventional front-end structure systems are considered. Then, the second is by replacing the vehicle’s conventional dampers with MR dampers, the third by implementing MR dampers within the vehicle’s front-end structure, and finally the fourth case through the integration of MR dampers implemented within both front-end structure and suspension system. Hence, the 4th case was implemented through the augmentation of simultaneous crash-pitch controllers. The simulation results showed a noticeable improvement in the front-end structure deformation as it’s reduced. Moreover, the vehicle’s body attitudes are improved, where the pitch angle is reduced as well as its settling time. Also, pitch acceleration is reduced as well, which benefits human body exposure

A new magnetorheological (MR) damper has been designed, manufactured, modelled and tested under cyclic loads. A faulty behaviour of the damper was accidentally detected during the experiments. It was deduced that the presence of air bubbles within the MR fluid is the main reason for that failure mode of the damper. The AMT-Smartec+ MR fluid used in the current study, a new MR fluid whose characteristics are not available in the literature, exhibits good magnetic properties. However, the fluid has a very high viscosity in the absence of magnetic field. It is assumed that this high viscosity enables the retention of air bubbles in the damper and causes the faulty behaviour. To prove this assumption, a coupled numerical approach has been developed. The approach incorporates a Finite Element Analysis (FEA) of the magnetic circuit and a Computational Fluid Dynamics (CFD) analysis of the fluid flow. A similar approach was presented in a previous publication in which an ideal behaviour of ...

This paper provides information on the latest R&D within COVICOCEPAD project approved in the framework of Eurocores program. It addresses the use of TLD, base isolation devices, MR dampers and a hybrid technique using both devices together. Some results are provided associated with calibration of a MR damper at FEUP, as well as its inclusion in a small scale laboratory setup with proper equations of motion of the controlled smart structure. An application of semi-active control technique to a bridge is outlined. Further remarks and details on future tests to be performed in LNEC shaking table, within COVICOCEPAD project, are provided.

This paper presents an analysis of the application of a multi-phase matrix converter (PM) based device as a phase shifter (PS). The analysis was conducted using simulation techniques and measurements performed on a six-phase converter model built in a laboratory. Three basic control schemes and their relation to PM properties are presented. In addition to the phase shifter's ability to change active power transfer, the device's impact on reactive power transmission was also shown in the paper. Newly assessed PM properties permit the construction of a PS with higher power system control capacity than with currently available devices. Capabilities of various variants of PM control and fast rate of response of the PS based on it, will undoubtedly be useful in the control of dynamic states of the power system operation (postdisturbance states), e.g. for rapid elimination of generator oscillations or power flow adjustment. This study is an extension of the phase shifter concept presented in previous years, and the continuation assumes the construction of a shifter model for use in an already developed at Cracow University of Technology power system model.

A fuzzy logic control algorithm, which includes the MR damper dynamics, has been developed by fuzzification of force-velocity curve of the MR damper. The method does not require any analytical model of MR damper characteristics, such as Bouc-Wen model, to be incorporated in the control algorithm. The control algorithm has the feedback structure and is implemented by using the Fuzzy Logic and Simulink toolboxes of MATLAB. In order to study the performance of the algorithm, the control scheme is used to control the responses of an example three storey model building frame taken from the literature. The results indicate that the proposed scheme provides nearly the same percentage reduction of responses as that obtained by clipped optimal control with much less control force and much less command voltage. Position of the damper is found to significantly affect the controlled responses of the structure. It is observed that there is a saturation level of the capacity of the damper for opt...

Magnetorheological (MR) fluids belong to a class of controllable fluids, and the composition and concentration of its components govern its magnetorheological properties. In this study, an optimum particle loading (or mass fraction) and size of iron particles in MR fluid for use in a shear mode monotube MR damper were determined based on the damping force and off-state viscosity of synthesized MR fluid samples. Initially, the morphological and magnetic properties of carbonyl iron particles were characterized. Six MR fluid samples were prepared composed of combination of three different particle loadings and two sizes of iron particles. Magnetorheological tests were conducted on these samples to determine the flow curves at off-state and on-state magnetic field conditions. Herschel-Bulkley model was used for mathematical representation of flow curves at different magnetic fields and to determine their dynamic yield stress. Further, a shear mode monotube MR damper with accumulator was designed by using optimization technique for desired dynamic range and damping force. Magnetostatic analysis was performed to determine the magnetic field strength generated in the shear gap at different currents. The damping force was calculated for synthesized MR fluids based on their dynamic yield stress corresponding to the magnetic field strength in the shear gap. Analysis of variance was performed to analyse the significance of independent factors on the damping force and off-state viscosity of MRF. The optimal particle loading and size which yielded maximum damping force with minimum off-state viscosity were determined using a multi-objective genetic algorithm.

A new magnetorheological (MR) damper has been designed, manufactured, modelled and tested under cyclic loads. A faulty behaviour of the damper was accidentally detected during the experiments. It was deduced that the presence of air bubbles within the MR fluid is the main reason for that failure mode of the damper. The AMT-Smartec+ MR fluid used in the current study, a new MR fluid whose characteristics are not available in the literature, exhibits good magnetic properties. However, the fluid has a very high viscosity in the absence of magnetic field. It is assumed that this high viscosity enables the retention of air bubbles in the damper and causes the faulty behaviour. To prove this assumption, a coupled numerical approach has been developed. The approach incorporates a Finite Element Analysis (FEA) of the magnetic circuit and a Computational Fluid Dynamics (CFD) analysis of the fluid flow. A similar approach was presented in a previous publication in which an ideal behaviour of ...