Статті в журналах з теми "Magnetic bearings; nonlinear systems mathematical models"
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1
Martynenko, Gennadii. "APPLICATION OF NONLINEAR MODELS FOR A WELL-DEFINED DESCRIPTION OF THE DYNAMICS OF ROTORS IN MAGNETIC BEARINGS." EUREKA: Physics and Engineering 3 (May 31, 2016): 3–12. http://dx.doi.org/10.21303/2461-4262.2016.00074.
Повний текст джерелаАнотація:
A research report has been submitted. It deals with implementing a method for a mathematical description of the nonlinear dynamics of rotors in magnetic bearings of different types (passive and active). The method is based on Lagrange-Maxwell differential equations in a form similar to that of Routh equations in mechanics. The mathematical models account for such nonlinearities as the nonlinear dependencies of magnetic forces on gaps in passive and active magnetic bearings and on currents in the windings of electromagnets; nonlinearities related to the inductances in coils; the geometric link between the electromagnets in one AMB and the link between all AMBs in one rotor, which results in relatedness of processes in orthogonal directions, and other factors. The suggested approach made it possible to detect and investigate different phenomena in nonlinear rotor dynamics. The method adequacy has been confirmed experimentally on a laboratory setup, which is a prototype of a complete combined magnetic-electromagnetic suspension in small-size rotor machinery. Different variants of linearizing the equations of motion have been considered. They provide for both linearization of restoring magnetic or electromagnetic forces in passive and active magnetic bearings, and exclusion of nonlinear motion equation terms. Calculation results for several linearization variants have been obtained. An appraisal of results identified the drawbacks of linearized mathematical models and allowed drawing a conclusion on the necessity of applying nonlinear models for a well-defined description of the dynamics of rotor systems with magnetic bearings.
2
Vardhan, Akash. "Vibrations of a Non Jeffcott Rotor with One Non Linear Bearing." Applied Mechanics and Materials 232 (November 2012): 450–55. http://dx.doi.org/10.4028/www.scientific.net/amm.232.450.
Повний текст джерелаАнотація:
Magnetic bearings support a body by mechanical pulling forces without any mechanical contact. They consist of an electromagnetic actuator, position sensors, power amplifiers and feedback controller. All of these components are characterized by nonlinear behavior and hence the entire system is inherently nonlinear. This paper presents a mathematical model for the vibrations of a non-Jeffcott type rotor supported on a non-linear bearing. The model can be used as a reference for systems supported on nonlinear bearings like magnetic bearings.
3
Kim, Sitae, and Alan Palazzolo. "Shooting/continuation based bifurcation analysis of large order nonlinear rotordynamic systems." MATEC Web of Conferences 211 (2018): 18003. http://dx.doi.org/10.1051/matecconf/201821118003.
Повний текст джерелаАнотація:
This study introduces an improved numerical algorithm that is capable of analyzing nonlinear vibrations and bifurcations of general, finite, large-order rotordynamic systems supported on nonlinear bearings. An industrial rotor generally consists of several sections and stages, but numerical shooting/continuation method has been applied to a simple Jeffcott type rotor instead of complex models due to the computational burden of the numerical procedure; it becomes significant when the rotor combined with nonlinear finite bearing models. Here, some mathematical/computational techniques such as a deflation algorithm and the parallel computing are suggested for acceleration along with the conventional treatment of model reduction scheme. An eight-stage compressor rotor supported by two identical five-pad tilting pad journal bearings (TPJB) is selected as a mechanical model to test the numerical incorporation of the algorithms. The rotor beam is modelled with 35 nodes, 140 DOF based on Euler beam theory, and the fluid reaction forces from the two TPJB are calculated using simplex, triangular type finite meshes on the pads. In the numerical procedure, the shooting/continuation combined with the acceleration schemes identifies the solution curves of periodic responses and determines their stability. The orbital motions of coexistent responses are obtained from the solution manifolds.
4
Dagnaes-Hansen, Nikolaj A., and Ilmar F. Santos. "Permanent magnet thrust bearings for flywheel energy storage systems: Analytical, numerical, and experimental comparisons." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 15 (April 23, 2019): 5280–93. http://dx.doi.org/10.1177/0954406219843952.
Повний текст джерелаАнотація:
A new type of flywheel energy storage system uses a magnetic suspension where the axial load is provided solely by permanent magnets, whereas active magnetic bearings are only used for radial stabilization. This means that the permanent magnet bearing must provide all the axial damping. Furthermore, it must have as low a negative radial stiffness as possible to reduce the workload on the radial active magnetic bearings. Many different mathematical models for determining force, stiffness, and damping of permanent magnet bearings are available in the literature. This work will further develop the most applicable analytical and numerical methods in order to make them directly implementable for designing permanent magnet thrust bearings for flywheel energy storage systems. The outcome is a fast and efficient method for determining force, stiffness, and damping when the bearing setup contains magnetic materials with relative permeability higher than one as well as when it does not. The developed method is validated against numerical and experimental results with good agreement.
5
Vavilov, V. E. "Mathematical model of the hybrid system of magnetic levitation energy production equipment autonomous power 97 supply systems." Transportation systems and technology 2, no. 3 (September 15, 2016): 97–108. http://dx.doi.org/10.17816/transsyst20162397-108.
Повний текст джерелаАнотація:
Introduction. Typically, when developing mathematical models magnetocavitation systems (magnetic bearings, electrostatic bearings, hybrid magnetic bearings (GMP, etc.) is considered just the very bearing as a separate, isolated Electromechanical system. This approach allows us to accurately explore the process magnetocavitation systems, but practically does not allow to evaluate the processes occurring in the system of magnetic bearing-object position. To solve this problem, the author proposes a different approach to the analysis of the processes in magnetocavitation systems in General and GPC in particular considering the magnetic bearing-object position, as a single complex. Goal. The work aimed the creation of a generalized analytical model of high-speed, AMPE with coercivity permanent magnet (VPM) on an elastic bearing supports, taking into account the mutual influence of processes in AMPA and bearing supports. This task is new and relevant and is essential to modern engineering. To solve this problem this paper developed a generalized mathematical model of the rotor system on a hybrid magnetic suspension. Evaluate the impact of hybrid magnetic bearings on the overall behavior of the rotor system. Performed analysis of processes in Electromechanical energy converters and mechanical processes occurring in the rotary system. Method and methodology. The research methodology is based on the joint solution of Maxwell equations and equations describing the mechanical processes of a rotor system with five degrees of freedom. Conclusion. The generalized mathematical model of high-speed, AMPE with VPM on a non-contact bearing supports and conducted her research. Based on research of the developed mathematical model, the authors developed an original control algorithm for the rotor position in a hybrid magnetic bearings, which allows for the design of high-speed, AMPE with VPM to abandon the position sensors of the rotor. In addition, on the basis of the results of calculations, a method was developed for diagnostics of eccentricity of rotor are high-speed, AMPE with VPM, as well as new methods of calculation of high-speed, AMPE with VPM, past experimental verification.
6
Cheng, Baixin, Xin Cheng, Shao Song, Huachun Wu, Yefa Hu, Rougang Zhou, and Shuai Deng. "Active Disturbance Rejection Control in Magnetic Bearing Rotor Systems with Redundant Structures." Sensors 22, no. 8 (April 14, 2022): 3012. http://dx.doi.org/10.3390/s22083012.
Повний текст джерелаАнотація:
At present, magnetic bearings are a better energy-saving choice than mechanical bearings in industrial applications. However, there are strongly coupled characteristics in magnetic bearing–rotor systems with redundant structures, and uncertain disturbances in the electrical system as well as external disturbances, and these unfavorable factors degrade the performance of the system. To improve the anti-interference performance of magnetic bearing systems, this paper proposes the inverse of the current distribution matrix W−1 meaning that the active disturbance rejection control simulation model can be carried out without neglecting the current of each coil. Firstly, based on the working mechanism of magnetic bearings with redundant structures and the nonlinear electromagnetic force model, the current and displacement stiffness models of magnetic bearings are established, and a dynamic model of the rotor is constructed. Then, according to the dynamic model of the rotor and the mapping relationship between the current of each coil and the electromagnetic force of the magnetic bearing, we established the equivalent control loop of the magnetic bearing–rotor system with redundant structures. Finally, on the basis of the active disturbance rejection control (ADRC) strategy, we designed a linear active disturbance rejection controller (LADRC) for magnetic bearings with redundant structures under the condition of no coil failure, and a corresponding simulation was carried out. The results demonstrate that compared to PID+current distribution control strategy, the LADRC+current distribution control strategy proposed in this paper is able to effectively improve the anti-interference performance of the rotors supported by magnetic bearings with redundant structures.
7
Annaswamy, A. M., C. Thanomsat, N. Mehta, and Ai-Poh Loh. "Applications of Adaptive Controllers to Systems With Nonlinear Parametrization." Journal of Dynamic Systems, Measurement, and Control 120, no. 4 (December 1, 1998): 477–87. http://dx.doi.org/10.1115/1.2801489.
Повний текст джерелаАнотація:
Nonlinear parametrizations occur in dynamic models of several complex engineering problems. The theory of adaptive estimation and control has been applicable, by and large, to problems where parameters appear linearly. We have recently developed an adaptive controller that is capable of estimating parameters that appear nonlinearly in dynamic systems in a stable manner. In this paper, we present this algorithm and its applicability to two problems, temperature regulation in chemical reactors and precise positioning using magnetic bearings both of which contain nonlinear parametrizations. It is shown in both problems that the proposed controller leads to a significantly better performance than those based on linear parametrizations or linearized dynamics.
8
Chen, Seng-Chi, Van-Sum Nguyen, Dinh-Kha Le, and Nguyen Thi Hoai Nam. "Nonlinear Control of an Active Magnetic Bearing System Achieved Using a Fuzzy Control with Radial Basis Function Neural Network." Journal of Applied Mathematics 2014 (2014): 1–18. http://dx.doi.org/10.1155/2014/272391.
Повний текст джерелаАнотація:
Studies on active magnetic bearing (AMB) systems are increasing in popularity and practical applications. Magnetic bearings cause less noise, friction, and vibration than the conventional mechanical bearings; however, the control of AMB systems requires further investigation. The magnetic force has a highly nonlinear relation to the control current and the air gap. This paper proposes an intelligent control method for positioning an AMB system that uses a neural fuzzy controller (NFC). The mathematical model of an AMB system comprises identification followed by collection of information from this system. A fuzzy logic controller (FLC), the parameters of which are adjusted using a radial basis function neural network (RBFNN), is applied to the unbalanced vibration in an AMB system. The AMB system exhibited a satisfactory control performance, with low overshoot, and produced improved transient and steady-state responses under various operating conditions. The NFC has been verified on a prototype AMB system. The proposed controller can be feasibly applied to AMB systems exposed to various external disturbances; demonstrating the effectiveness of the NFC with self-learning and self-improving capacities is proven.
9
Youcef-Toumi, K., and S. Reddy. "Dynamic Analysis and Control of High Speed and High Precision Active Magnetic Bearings." Journal of Dynamic Systems, Measurement, and Control 114, no. 4 (December 1, 1992): 623–33. http://dx.doi.org/10.1115/1.2897734.
Повний текст джерелаАнотація:
The successful operation of actively controlled magnetic bearings depends greatly on the electromechanical design and control system design. The function of the controller is to maintain bearing performance in the face of system dynamic variations and unpredictable disturbances. The plant considered here is the rotor and magnetic bearing assembly of a test apparatus. The plant dynamics consisting of actuator dynamics, rigid rotor dynamics and flexibility effects are described. Various components of the system are identified and their corresponding linearized theoretical models are validated experimentally. Tests are also run to identify the coupling effects and flexibility modes. The highly nonlinear behavior of the magnetic bearings in addition to the inherent instability of such a system makes the controller design complex. A digital Time Delay Controller is designed and its effectiveness evaluated using several simulations based on linear and nonlinear models for the bearing including bending mode effects. This controller is implemented as an alternative to an existing linear analog compensator. Several experiments are conducted with each controller for spinning and nonspinning conditions. These include time responses, closed loop frequency responses and disturbance rejection responses. The experimental results and comparisons between those of a digital Time Delay Controller and an analog compensator indicate that the Time Delay Controller has impressive static and dynamic stiffness characteristics for the prototype considered. The Time Delay Controller also maintains almost the same dynamic behavior over a significantly wide range of rotor speeds.
10
Sum, Nguyen Van. "ANFIS CONTROLLER FOR AN ACTIVE MAGNETIC BEARINGS TO SUSPEND A FLYWHEEL ENERGY STORAGE SYSTEM." Hue University Journal of Science: Natural Science 126, no. 1C (October 23, 2017): 57. http://dx.doi.org/10.26459/hueuni-jns.v126i1c.4621.
Повний текст джерелаАнотація:
<p><span style="font-family: Times New Roman;">A flywheel energy storage system (FESS) is an effective energy-saving device. It works by accelerating a rotor flywheel disc at a very high speed and maintaining the energy in the system as rotational energy. Active magnetic bearings (AMBs) are ideally suited for use at high-speed and are so used in FESSs. This work develops a mathematical model of the electromagnet force and rotor dynamic of a flywheel. The systems for controlling the position and velocity of the flywheel are designed based on the emerging approaches of an adaptive neuro-fuzzy inference system (ANFIS). Fuzzy logic has occurred as a mathematical tool to deal with the uncertainties in human perception. It also provides a framework for applying approximate human reasoning capabilities to knowledge-based systems. Additionally, ANFIS has emerged as an intelligent controller with learning and adaptive capabilities. ANFIS is combined the fuzzy logic controller (FLC) and neural networks (NNs). In the method that is developed herein, the control model uses Takagi-Sugeno fuzzy logic, in which the back-propagation algorithm processes information from neural networks to adjust suitably the parameters of the fuzzy controller, and the output control signal tracks the input signal. This method can be applied to improve the control performance of nonlinear systems. The output signal responses transient performance of systems use an ANFIS that must be trained through a learning process to yield suitable membership functions and weightings. The results of the FESS indicated that the system responds with satisfactory control performance to reduce overshoot, a zero-error steady-state, and short rise time. The proposed controller can be feasibly applied to FESS with various external disturbances, and the effectiveness of the ANFIS with self-learning and self-improving capacities is proven.</span></p>
11
Zhang, Wei Yu, Huang Qiu Zhu, and Ze Bin Yang. "Dynamic Decoupling Control of Electro-Spindle Supported by AC Hybrid Magnetic Bearings Based on Neural Network Inverse Method." Advanced Materials Research 97-101 (March 2010): 2716–19. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.2716.
Повний текст джерелаАнотація:
A dynamic decoupling control method based on neural network inverse system theory is developed for the 5 degrees of freedom (5-DOF) rotor system. The rotor system suspended by AC hybrid magnetic bearings (HMBs) is a multivariable, nonlinear and strong coupled system. Firstly, the configuration of 5-DOF HMBs and the mathematical equations of suspension forces are set up. Secondly, it is demonstrated the system is reversible by analyzing mathematical model. On the basis, the neural network inverse system which is composed of the static neural networks and integrators, and original system are in series to constitute pseudo linear systems. Finally, linear system theory is applied to these linearization subsystems for designing close-loop controllers. The simulation results show that this kind of control strategy can realize dynamic decoupling control, and control system obtains good dynamic and static performances.
12
Yang, Xiongjun, Han Su, Lijun Liu, and Ying Lei. "Identification of the nonlinear characteristics of rubber bearings in model-free base-isolated buildings using partial measurements of seismic responses." Journal of Low Frequency Noise, Vibration and Active Control 39, no. 3 (April 16, 2019): 690–703. http://dx.doi.org/10.1177/1461348419843385.
Повний текст джерелаАнотація:
Rubber-bearing isolation is one of the most successfully and widely used isolation technologies to provide lateral flexibility and energy dissipation capacity for reducing structural vibration and protecting the superstructure from damage. The seismic performance of the base-isolated structures partly depends on the nonlinear characteristics of the base isolation system. However, it is hard to establish proper mathematical models for the nonlinear hysteretic behaviors of base isolation due to the complexities of nonlinearities. Consequently, it is strongly desired to develop model-free methodologies for the nonlinear hysteretic performance identification with no assumption on the nonlinear hysteretic models of base isolation. In this paper, a novel method is proposed for this purpose. Firstly, the base isolation is in the linear state when the structure is under the weak earthquake, the restoring force is only provided by linear stiffness and viscous damping of base isolation, and the structural physical parameters can be estimated based on the extended Kalman filter approach. Then, the base isolation is in the nonlinear state when the structure is under the strong earthquake. The nonlinear hysteretic restoring forces from base isolation are treated as “unknown fictitious inputs” to the corresponding structural systems without base isolation. The generalized Kalman filter with unknown input algorithm is adopted for the simultaneous identification of the corresponding structural systems and the hysteretic restoring force of base isolation using only partial structural responses. No information about the structure is needed, and the responses at the location of the base isolation are not required, the proposed method is capable of identifying nonlinear characteristics of base isolation by the direct use of partial structural dynamic response. To validate the performances of the proposed method, some numerical simulation examples of identifying nonlinear hysteretic restoring forces of base isolation in different models are used.
13
Horyachko, Vsevolod, Orest Hamola, and Taras Ryzhyi. "Analysis of magnetic fields of electrical devices based on their circuit models." Computational Problems of Electrical Engineering 11, no. 1 (April 25, 2021): 7–11. http://dx.doi.org/10.23939/jcpee2021.01.007.
Повний текст джерелаАнотація:
he article deals with an analysis of magnetic fields of electric machines and electromagnetic devices on the basis of their circuit mathematical models. The magnetic systems of electrical devices in these models are presented in the form of planar nonlinear magnetic circuits with lumped elements. The parameters of these elements are determined on the basis of geometric dimensions taking into account the design features of the devices and the physical parameters of the environment.
14
Kosov, Alexander, Edward Semenov, and Alexander Sinitsyn. "First integrals and exact solutions of the generalized models of magnetic insulation." Publications de l'Institut Math?matique (Belgrade) 98, no. 112 (2015): 119–35. http://dx.doi.org/10.2298/pim1512119k.
Повний текст джерелаАнотація:
We suggest generalizations of the mathematical model of magnetic insulation, described by multidimensional quasi potential ODE system or PDE system with two-dimensional Laplace operator. Existence conditions of the first integrals of a certain type for the class of nonlinear quasi potential systems, including the model vacuum diode are obtained. Integrability of the vacuum diode models is justified. We find for PDE system the class of exact radially symmetric solutions given by fractional-rational functions. The class of systems with variable density, reduced to a similar system with the constant current density by special transformations is specified. The class of exact solutions of the non-singular boundary-value problem in annular domain is found.
15
Vikharev, D. Yu, and N. A. Rodin. "Model of implicit pole electric machine based on mathematical formulation of magnetic field in air gap." Vestnik IGEU, no. 6 (December 28, 2021): 27–37. http://dx.doi.org/10.17588/2072-2672.2021.6.027-037.
Повний текст джерелаАнотація:
When modeling transient processes in electric power systems, the issue of designing reliable models of electrical machines is of great interest. The most difficult task is to design the models of synchronous and asynchronous machines. The purpose of the project is to develop mathematical models of synchronous and asynchronous machines based on a generalized model of an implicit-pole machine that considers the change of rotor speed, geometric shapes, and the type of rotor and stator windings. Methods of mathematical modeling of electromagnetic fields in the air gap based on Maxwell equations and methods of the theory of electrical circuits are applied. A system of nonlinear differential equations is considered as a mathematical model of a generalized implicit-pole machine. The key assumption made is the high magnetic permeability of the stator and rotor cores. Technical data of real electric machines have been used for verification. Mathematical models of an implicit pole synchronous machine and an asynchronous machine with a phase rotor have been developed. These models can be used to analyze transient processes in the aggregate without dividing them into electromagnetic and electromechanical ones. The novelty of the models is the fact of non-sinusoidal distribution of the magnetic field in the air gap, various types of multiphase AC windings and rejecting the principle of constant rotation frequency at the time step of the simulation. The proposed mathematical models can be used to solve design problems, to analyze the modes of electric power systems, the operation of relay protection and automation of electric power facilities, and emergency automation. In the future, the equations that consider the influence of the damper circuits and the peculiarities of the windings will be added to the developed mathematical models. The purpose of further research is to develop models of salient-pole synchronous machines and asynchronous machines with a squirrel-cage rotor.
16
Ma, Zhihao, Gai Liu, Yichen Liu, Zhaocheng Yang, and Huangqiu Zhu. "Research of a Six-Pole Active Magnetic Bearing System Based on a Fuzzy Active Controller." Electronics 11, no. 11 (May 29, 2022): 1723. http://dx.doi.org/10.3390/electronics11111723.
Повний текст джерелаАнотація:
Magnetic bearings have a series of excellent qualities, such as no friction and abrasions, high speed, high accuracy, and so on, which have fundamentally innovated traditional forms of support. In order to solve the problems of the large volume, low power density and high coupling coefficient of three-pole magnetic bearings, a six-pole AC active magnetic bearing is designed. Firstly, the basic structure and working principle of a two-degree-of-freedom (2-DOF) six-pole active magnetic bearing is introduced. Secondly, a suspension force modeling method of a 2-DOF AC active magnetic bearing based on the Maxwell tensor method is proposed, and the mathematical model of active magnetic bearing is established. Considering the fact that AC active magnetic bearing is essentially a nonlinear system, a fuzzy active disturbance rejection control (ADRC) method is designed based on fuzzy control and ADRC theory. Its control algorithm and control block diagram are given, and the fuzzy ADRC method is simulated and verified. Finally, the control block diagram of an experimental system based on the 2-DOF six-pole active magnetic bearing is given, and the experimental platform is constructed. The experimental results show that the mechanical and magnetic circuit structure of the 2-DOF six-pole active magnetic bearing is reasonable, and the fuzzy controllers can realize the stable suspension of the rotor.
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Karimov, Artur, Vyacheslav Rybin, Albert Dautov, Timur Karimov, Yulia Bobrova, and Denis Butusov. "Mechanical Chaotic Duffing System with Magnetic Springs." Inventions 8, no. 1 (January 11, 2023): 19. http://dx.doi.org/10.3390/inventions8010019.
Повний текст джерелаАнотація:
Mechanical systems with inherent chaotic behavior are of notable practical interest due to their applicability in many fields of technology, from industrial mills and concrete mixers to microscopic micromechanical random bit generators. One of the most generic mathematical models for designing chaotic mechanical systems is the Duffing oscillator, which demonstrates chaotic motion under periodic excitation. The mechanical implementation of Duffing oscillator requires nonlinear springs, which can be implemented using different physical principles. In the current study, we propose the mechanical Duffing oscillator with magnetic springs as a low-wear, robust and easy-to-implement solution. We show by simulation and experimentation that the developed mechanical system performs chaotic oscillations in a wide range of parameters. The proposed design can be revised in a problem-specific manner and achieve many practical applications.
18
Yang, Juan, and Jianliang Zhai. "Asymptotics of stochastic 2D hydrodynamical type systems in unbounded domains." Infinite Dimensional Analysis, Quantum Probability and Related Topics 20, no. 03 (September 2017): 1750017. http://dx.doi.org/10.1142/s0219025717500175.
Повний текст джерелаАнотація:
In this paper, we prove a central limit theorem and establish a moderate deviation principle for 2D stochastic hydrodynamical type systems with multiplicative noise in unbounded domains, which covers 2D Navier–Stokes equations, 2D MHD models and the 2D magnetic Bénard problem and also shell models of turbulence. The weak convergence method plays an important role in obtaining the moderate deviation principle.
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Amin, A. K. M. Nurul, Fawaz Mohsen Abdullah, Muammer Din Arif, and Israd H. Jaafar. "Mathematical Model for Chip Serration Frequency in Turning of Stainless Steel with Magnetic Damping from Bottom of Tool Shank." Applied Mechanics and Materials 393 (September 2013): 108–14. http://dx.doi.org/10.4028/www.scientific.net/amm.393.108.
Повний текст джерелаАнотація:
Chatter, a violent and often unpredictable relative oscillatory motion between the tool and work-piece, is a serious concern in turning operations. Its occurrence is usually associated with a loud monotonous sound and usually results in increased surface roughness, reduced material removal rates, shortened tool life, and damaged machine-tool bearings. The established theories for chatter are very limited in scope and are often contradicted by empirical evidences. Therefore, chatter avoidance in the past has relied on inefficient techniques like limiting material removal rates or expensive setups such as actuators and ultrasonic vibration damping systems. However, a deeper investigation into chatter formation reveals that chip morphology and segmentation play a significant role during the incidence of chatter. The novel Resonance theory of chatter combines the concept of mode coupling of the machining setup and serrated chip formation, to explain and predict chatter. To validate the postulates of this theory, models for chip serration frequency are essential. At the same time, a reliable and economical chatter control method is required. With this goal, the current research work has developed an empirical mathematical model of chip serration frequency in turning of stainless steel AISI 304 using Response Surface Methodology (RSM). Also, it investigated the influence of damping provided by magnetic field from a permanent ferrite magnet placed beneath the tool shank. The developed chip serration model is in good accord with the experimental data, demonstrating that the empirical model could be used for further chip morphology and chatter analyses.
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Aoun, Yacine, Dmitry Ioffe, Sébastien Ott, and Yvan Velenik. "Non-analyticity of the Correlation Length in Systems with Exponentially Decaying Interactions." Communications in Mathematical Physics 386, no. 1 (March 14, 2021): 433–67. http://dx.doi.org/10.1007/s00220-021-04038-6.
Повний текст джерелаАнотація:
AbstractWe consider a variety of lattice spin systems (including Ising, Potts and XY models) on $$\mathbb {Z}^d$$ Z d with long-range interactions of the form $$J_x = \psi (x) e^{-|x|}$$ J x = ψ ( x ) e - | x | , where $$\psi (x) = e^{{\mathsf o}(|x|)}$$ ψ ( x ) = e o ( | x | ) and $$|\cdot |$$ | · | is an arbitrary norm. We characterize explicitly the prefactors $$\psi $$ ψ that give rise to a correlation length that is not analytic in the relevant external parameter(s) (inverse temperature $$\beta $$ β , magnetic field $$h$$ h , etc). Our results apply in any dimension. As an interesting particular case, we prove that, in one-dimensional systems, the correlation length is non-analytic whenever $$\psi $$ ψ is summable, in sharp contrast to the well-known analytic behavior of all standard thermodynamic quantities. We also point out that this non-analyticity, when present, also manifests itself in a qualitative change of behavior of the 2-point function. In particular, we relate the lack of analyticity of the correlation length to the failure of the mass gap condition in the Ornstein–Zernike theory of correlations.
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CANNAS, SERGIO A., CINTIA M. LAPILLI, and DANIEL A. STARIOLO. "TESTING BOUNDARY CONDITIONS EFFICIENCY IN SIMULATIONS OF LONG-RANGE INTERACTING MAGNETIC MODELS." International Journal of Modern Physics C 15, no. 01 (January 2004): 115–27. http://dx.doi.org/10.1142/s0129183104005553.
Повний текст джерелаАнотація:
Periodic boundary conditions have no unique implementation in magnetic systems where all spins interact with each other through a power law decaying interaction of the form 1/rα, r being the distance between spins. In this work we present a comparative study of the finite size effects oberved in numerical simulations by using first image and infinite image periodic boundary conditions in one- and two-dimensional spin systems with those interactions, including the ferromagnetic, anti-ferromagnetic and competitive interaction cases. Our results show no significative differences between the finite size effects produced by both boundary conditions when the low temperature phase has zero global magnetization, and it depends on the ratio α/d for systems with a low temperature ferromagnetic phase. In the last case the first image convention gives more stronger finite size effects than the other when the system enters into the classical regime α/d≤3/2.
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Kupiec, Emil, and Włodzimierz Przyborowski. "Magnetic equivalent circuit model for unipolar hybrid excitation synchronous machine." Archives of Electrical Engineering 64, no. 1 (March 1, 2015): 107–17. http://dx.doi.org/10.1515/aee-2015-0010.
Повний текст джерелаАнотація:
AbstractLately, there has been increased interest in hybrid excitation electrical machines. Hybrid excitation is a construction that combines permanent magnet excitation with wound field excitation. Within the general classification, these machines can be classified as modified synchronous machines or inductor machines. These machines may be applied as motors and generators. The complexity of electromagnetic phenomena which occur as a result of coupling of magnetic fluxes of separate excitation systems with perpendicular magnetic axis is a motivation to formulate various mathematical models of these machines. The presented paper discusses the construction of a unipolar hybrid excitation synchronous machine. The magnetic equivalent circuit model including nonlinear magnetization curves is presented. Based on this model, it is possible to determine the multi-parameter relationships between the induced voltage and magnetomotive force in the excitation winding. Particular attention has been paid to the analysis of the impact of additional stator and rotor yokes on above relationship. Induced voltage determines the remaining operating parameters of the machine, both in the motor and generator mode of operation. The analysis of chosen correlations results in an identification of the effective control range of electromotive force of the machine.
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Skrypnyk, T. "Anisotropic Zn-graded classical r-matrix, deformed An Toda- and Gaudin-type models, and separation of variables." Journal of Mathematical Physics 63, no. 9 (September 1, 2022): 091702. http://dx.doi.org/10.1063/5.0091807.
Повний текст джерелаАнотація:
We consider a problem of separation of variables for Lax-integrable Hamiltonian systems governed by gl( n) ⨂ gl( n)-valued classical r-matrices r( u, v). We find a new class of classical non-skew-symmetric non-dynamical gl( n) ⨂ gl( n)-valued r-matrices r J( u, v) for which the “magic recipe” of Sklyanin [Prog. Theor. Phys. Suppl. 118, 35 (1995)] in the theory of variable separation is applicable, i.e., for which standard separating functions A( u) and B( u) of Gekhtman [Commun. Math. Phys. 167, 593 (1995)] and Scott [“Classical functional Bethe ansatz for SL( N): Separation of variables for the magnetic chain,” arXiv:hep-th 940303] produce a complete set of canonical coordinates satisfying the equations of separation. We illustrate the corresponding separation of variable theory by the example of the anisotropically deformed A n Toda models proposed in the work of Skrypnyk [J. Phys. A: Math. Theor. 38, 9665–9680 (2005)] and governed by the r-matrices r J( u, v) and by the generalized Gaudin models [T. Skrypnyk, Phys. Lett. A 334(5–6), 390 (2005)] governed by the same classical r-matrices. The n = 2 and n = 3 cases are considered in detail.
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Boboń, A., A. Nocoń, S. Paszek, and P. Pruski. "Determination of synchronous generator nonlinear model parameters based on power rejection tests using a gradient optimization algorithm." Bulletin of the Polish Academy of Sciences Technical Sciences 65, no. 4 (August 1, 2017): 479–88. http://dx.doi.org/10.1515/bpasts-2017-0053.
Повний текст джерелаАнотація:
AbstractThe paper presents a method for determining electromagnetic parameters of different synchronous generator models based on dynamic waveforms measured at power rejection. Such a test can be performed safely under normal operating conditions of a generator working in a power plant. A generator model was investigated, expressed by reactances and time constants of steady, transient, and subtransient state in the d and q axes, as well as the circuit models (type (3,3) and (2,2)) expressed by resistances and inductances of stator, excitation, and equivalent rotor damping circuits windings. All these models approximately take into account the influence of magnetic core saturation. The least squares method was used for parameter estimation. There was minimized the objective function defined as the mean square error between the measured waveforms and the waveforms calculated based on the mathematical models. A method of determining the initial values of those state variables which also depend on the searched parameters is presented. To minimize the objective function, a gradient optimization algorithm finding local minima for a selected starting point was used. To get closer to the global minimum, calculations were repeated many times, taking into account the inequality constraints for the searched parameters. The paper presents the parameter estimation results and a comparison of the waveforms measured and calculated based on the final parameters for 200 MW and 50 MW turbogenerators.
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Malyar, V. S., O. Ye Hamola, V. S. Maday, and I. I. Vasylchyshyn. "Mathematical modelling of starting modes of induction motors with squirrel-cage rotor." Electrical Engineering & Electromechanics, no. 2 (April 10, 2021): 9–15. http://dx.doi.org/10.20998/2074-272x.2021.2.02.
Повний текст джерелаАнотація:
Purpose. Development of methods and algorithms for calculation of starting modes of the induction motors with the squirrel-cage rotor. Methodology. Mathematical modelling of starting modes of asynchronous electric drives in various coordinate systems with the use of numerical methods for solving boundary problems for systems of differential equations and nonlinear systems of final equations and calculation with their use of static characteristics. Results. Methods and algorithms for numerical analysis of the starting modes of asynchronous electric drive have been developed, which make it possible to calculate the static characteristics and transients in fixed three-phase and orthogonal two-phase coordinate systems. Academic novelty. Known in the literature methods of calculation of starting modes have in their basis classical equivalent circuits with different approximate methods of calculating the parameters taking into account the saturation of a magnetic core and current displacement in a rotor winding. This approach requires a special solution of the adequacy problem for each problem. The methods described in the article for the saturation accounting use real magnetization characteristics of the main magnetic flux and leakage fluxes separately, and the skin effect phenomenon is taken into account by representing the squirrel-cage rotor winding as multilayer. Such mathematical model of the motor is universal and makes it possible to take into account the saturation and current displacement in any dynamic mode, including the start-up process. Mathematical models developed on the basis of the proposed methods provide the adequacy of results with a minimum amount of calculations and make it possible to perform optimization calculations. Practical value. Created on the basis of developed algorithms calculation programs allow to carry out with high reliability calculation of starting modes both in three-phase and two-phase axes of coordinates that gives the chance to analyze not only symmetric, but also asymmetric modes and to predict special features of functioning of system of the electric drive in the set technological conditions of operation and to form requirements to development and adjustment of starting systems with the purpose of maintenance of power effective and reliable operation of system of asynchronous electric drives.
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Malyar, V. S., O. Ye Hamola, V. S. Maday, and I. I. Vasylchyshyn. "Mathematical modeling of rheostat-reactor start of wound-rotor induction motors." Electrical Engineering & Electromechanics, no. 3 (May 30, 2022): 8–14. http://dx.doi.org/10.20998/2074-272x.2022.3.02.
Повний текст джерелаАнотація:
Introduction. Wound-rotor induction motors are less common compared squirrel-cage induction motors. However, they occupy a significant share among electric drives with difficult starting conditions. Their advantage is obtaining a high starting electromagnetic torque at lower values of starting currents. Problem. Due to the possibility of including different devices in the rotor circuit, it is possible to shape the starting characteristics according to the needs of the technological process. Due to a narrower range of applications of electric drives based on wound-rotor induction motors, they are less investigated. Selection of parameters of starting and regulating devices, included in the rotor circuit, is carried out by simplified methods, which do not satisfy modern requirements to regulated electric drives. Goal. The paper aims to develop mathematical models and methods for calculating the dynamic modes and static characteristics of the wound-rotor induction motor with a reactor in the rotor circuit. Methodology. In the developed algorithms, the mathematical model of the motor is presented by the differential equations made for electric circuits in a system of orthogonal coordinates that allows excluding angular coordinate from equations of electric equilibrium. The elements of the Jacobi matrix of equilibrium equations of motor circuits are eigenvalues, and mutual is the differential inductances of electrical circuits, which are determined based on the magnetization characteristics of the main magnetic flux and leakage fluxes of the rotor and stator circuits. Results. Mathematical models for the study of starting modes of wound rotor induction motor allow to calculate transients and static characteristics and, on their basis, to carry out design synthesis of starting reactors, which provide the law of change of electromagnetic torque during start-up operating conditions. Originality. The mathematical basis of the developed algorithms is the method of solving nonlinear systems of equations by Newton method in combination with the method of continuation by parameter. The developed mathematical models and software made on their basis have high speed that allows to carry out high-reliability calculation of starting modes taking into account saturation of a magnetic circuit of the motor. Practical value. The developed algorithms do not require significant computing resources, have high speed, and can be used both for the design synthesis of start-control devices and control of the electric drive in real time and to predict its course.
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Akbar, Noreen Sher, O. Anwar Beg, and Z. H. Khan. "Magneto-nanofluid flow with heat transfer past a stretching surface for the new heat flux model using numerical approach." International Journal of Numerical Methods for Heat & Fluid Flow 27, no. 6 (June 5, 2017): 1215–30. http://dx.doi.org/10.1108/hff-03-2016-0125.
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Purpose Sheet processing of magnetic nanomaterials is emerging as a new branch of smart materials’ manufacturing. The efficient production of such materials combines many physical phenomena including magnetohydrodynamics (MHD), nanoscale, thermal and mass diffusion effects. To improve the understanding of complex inter-disciplinary transport phenomena in such systems, mathematical models provide a robust approach. Motivated by this, this study aims to develop a mathematical model for steady, laminar, MHD, incompressible nanofluid flow, heat and mass transfer from a stretching sheet. Design/methodology/approach This study developed a mathematical model for steady, laminar, MHD, incompressible nanofluid flow, heat and mass transfer from a stretching sheet. A uniform constant-strength magnetic field is applied transversely to the stretching flow plane. The Buongiorno nanofluid model is used to represent thermophoretic and Brownian motion effects. A non-Fourier (Cattaneo–Christov) model is used to simulate thermal conduction effects, of which the Fourier model is a special case when thermal relaxation effects are neglected. Findings The governing conservation equations are rendered dimensionless with suitable scaling transformations. The emerging nonlinear boundary value problem is solved with a fourth-order Runge–Kutta algorithm and also shooting quadrature. Validation is achieved with earlier non-magnetic and forced convection flow studies. The influence of key thermophysical parameters, e.g. Hartmann magnetic number, thermal Grashof number, thermal relaxation time parameter, Schmidt number, thermophoresis parameter, Prandtl number and Brownian motion number on velocity, skin friction, temperature, Nusselt number, Sherwood number and nanoparticle concentration distributions, is investigated. Originality/value A strong elevation in temperature accompanies an increase in Brownian motion parameter, whereas increasing magnetic parameter is found to reduce heat transfer rate at the wall (Nusselt number). Nanoparticle volume fraction is observed to be strongly suppressed with greater thermal Grashof number, Schmidt number and thermophoresis parameter, whereas it is elevated significantly with greater Brownian motion parameter. Higher temperatures are achieved with greater thermal relaxation time values, i.e. the non-Fourier model predicts greater values for temperature than the classical Fourier model.
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Kudo, Kazutoshi, Makoto Miyazaki, Hirofumi Sekiguchi, Hiroshi Kadota, Shinya Fujii, Akito Miura, Michiko Yoshie, and Hiroki Nakata. "Neurophysiological and Dynamical Control Principles Underlying Variable and Stereotyped Movement Patterns During Motor Skill Acquisition." Journal of Advanced Computational Intelligence and Intelligent Informatics 15, no. 8 (October 20, 2011): 942–53. http://dx.doi.org/10.20965/jaciii.2011.p0942.
Повний текст джерелаАнотація:
While novices who are unfamiliar to a new motor skill typically show variable and unstable movements, highly skilled experts show a stable and accurate performance. These distinct differences in motor control between experts and novices have led researchers to hypothesize that neuromotor noise is reduced in the process of motor skill acquisition. On the other hand, it should be noted that novices’ movements have other characteristics; they are habituated and stereotyped. In this review, we discuss the principles governing spatiotemporal organization of movements in novices and experts while solving specific motor problems under varied conditions, by introducing experimental and theoretical studies that use neurophysiological techniques such as electromyography, functional magnetic resonance imaging, and transcranial magnetic stimulation, and mathematical models such as stochastic and dynamical models. On the basis of the findings from a variety of perceptual-motor skills (e.g., ballthrowing, badminton smash, long-distance running, piano and drum performance, street dance, a popular hand game of rock-paper-scissors, and temporal order judgement task), we argue that the novices’ characteristic movement patterns were organized under specific constraints and typical strategy, without which the variability would increase even more, while experts’ movements were organized with functional and compensatory variability that can drive out erroneous noise variability. We also showed that in a particular type of interlimb coordination, skilled and unskilled movement patterns could be seamlessly described as the time evolution of nonlinear and self-organized dynamical systems, suggesting that the dynamical systems approach is a major candidate for understanding the principle underlying organization of experts’ and novices’ movements.
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Singh, Sundeep, and Roderick Melnik. "Coupled Multiphysics Modelling of Sensors for Chemical, Biomedical, and Environmental Applications with Focus on Smart Materials and Low-Dimensional Nanostructures." Chemosensors 10, no. 5 (April 25, 2022): 157. http://dx.doi.org/10.3390/chemosensors10050157.
Повний текст джерелаАнотація:
Low-dimensional nanostructures have many advantages when used in sensors compared to the traditional bulk materials, in particular in their sensitivity and specificity. In such nanostructures, the motion of carriers can be confined from one, two, or all three spatial dimensions, leading to their unique properties. New advancements in nanosensors, based on low-dimensional nanostructures, permit their functioning at scales comparable with biological processes and natural systems, allowing their efficient functionalization with chemical and biological molecules. In this article, we provide details of such sensors, focusing on their several important classes, as well as the issues of their designs based on mathematical and computational models covering a range of scales. Such multiscale models require state-of-the-art techniques for their solutions, and we provide an overview of the associated numerical methodologies and approaches in this context. We emphasize the importance of accounting for coupling between different physical fields such as thermal, electromechanical, and magnetic, as well as of additional nonlinear and nonlocal effects which can be salient features of new applications and sensor designs. Our special attention is given to nanowires and nanotubes which are well suited for nanosensor designs and applications, being able to carry a double functionality, as transducers and the media to transmit the signal. One of the key properties of these nanostructures is an enhancement in sensitivity resulting from their high surface-to-volume ratio, which leads to their geometry-dependant properties. This dependency requires careful consideration at the modelling stage, and we provide further details on this issue. Another important class of sensors analyzed here is pertinent to sensor and actuator technologies based on smart materials. The modelling of such materials in their dynamics-enabled applications represents a significant challenge as we have to deal with strongly nonlinear coupled problems, accounting for dynamic interactions between different physical fields and microstructure evolution. Among other classes, important in novel sensor applications, we have given our special attention to heterostructures and nucleic acid based nanostructures. In terms of the application areas, we have focused on chemical and biomedical fields, as well as on green energy and environmentally-friendly technologies where the efficient designs and opportune deployments of sensors are both urgent and compelling.
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Singh, Sundeep, and Roderick Melnik. "Coupled Multiphysics Modelling of Sensors for Chemical, Biomedical, and Environmental Applications with Focus on Smart Materials and Low-Dimensional Nanostructures." Chemosensors 10, no. 5 (April 25, 2022): 157. http://dx.doi.org/10.3390/chemosensors10050157.
Повний текст джерелаАнотація:
Low-dimensional nanostructures have many advantages when used in sensors compared to the traditional bulk materials, in particular in their sensitivity and specificity. In such nanostructures, the motion of carriers can be confined from one, two, or all three spatial dimensions, leading to their unique properties. New advancements in nanosensors, based on low-dimensional nanostructures, permit their functioning at scales comparable with biological processes and natural systems, allowing their efficient functionalization with chemical and biological molecules. In this article, we provide details of such sensors, focusing on their several important classes, as well as the issues of their designs based on mathematical and computational models covering a range of scales. Such multiscale models require state-of-the-art techniques for their solutions, and we provide an overview of the associated numerical methodologies and approaches in this context. We emphasize the importance of accounting for coupling between different physical fields such as thermal, electromechanical, and magnetic, as well as of additional nonlinear and nonlocal effects which can be salient features of new applications and sensor designs. Our special attention is given to nanowires and nanotubes which are well suited for nanosensor designs and applications, being able to carry a double functionality, as transducers and the media to transmit the signal. One of the key properties of these nanostructures is an enhancement in sensitivity resulting from their high surface-to-volume ratio, which leads to their geometry-dependant properties. This dependency requires careful consideration at the modelling stage, and we provide further details on this issue. Another important class of sensors analyzed here is pertinent to sensor and actuator technologies based on smart materials. The modelling of such materials in their dynamics-enabled applications represents a significant challenge as we have to deal with strongly nonlinear coupled problems, accounting for dynamic interactions between different physical fields and microstructure evolution. Among other classes, important in novel sensor applications, we have given our special attention to heterostructures and nucleic acid based nanostructures. In terms of the application areas, we have focused on chemical and biomedical fields, as well as on green energy and environmentally-friendly technologies where the efficient designs and opportune deployments of sensors are both urgent and compelling.
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Ma, Shaojuan, Jing Wang, Xinyu Bai, and Qiyi Liu. "Dynamic Behavior of Magnetic Bearing System Under Narrow-Band Excitation." Journal of Nonlinear Mathematical Physics, March 21, 2022. http://dx.doi.org/10.1007/s44198-022-00051-y.
Повний текст джерелаАнотація:
AbstractThe purpose of this paper is to investigate the vibration characteristics and motion of random magnetic bearing systems with narrow band noise. Firstly, the multiple scale method is used to obtain the averaged equations. Secondly, it is found that there exist different motions with the various excitation forces and permeability values by the bifurcation diagram and maximum Lyapunov exponent based on the resulting average equations. Finally, the influence of narrow-band excitation on magnetic bearings is verified, and the conclusion shows that the thickness of the limit cycle increases gradually as the bandwidth of narrow-band excitation changes in a small range.
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Sum, Nguyen Van. "ANFIS CONTROLLER FOR AN ACTIVE MAGNETIC BEARINGS TO SUSPEND A FLYWHEEL ENERGY STORAGE SYSTEM." Hue University Journal of Science: Techniques and Technology 126, no. 2B (October 23, 2017). http://dx.doi.org/10.26459/hueuni-jtt.v126i2b.4277.
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<p><span style="font-family: Times New Roman;">A flywheel energy storage system (FESS) is an effective energy-saving device. It works by accelerating a rotor flywheel disc at a very high speed and maintaining the energy in the system as rotational energy. Active magnetic bearings (AMBs) are ideally suited for use at high-speed and are so used in FESSs. This work develops a mathematical model of the electromagnet force and rotor dynamic of a flywheel. The systems for controlling the position and velocity of the flywheel are designed based on the emerging approaches of an adaptive neuro-fuzzy inference system (ANFIS). Fuzzy logic has occurred as a mathematical tool to deal with the uncertainties in human perception. It also provides a framework for applying approximate human reasoning capabilities to knowledge-based systems. Additionally, ANFIS has emerged as an intelligent controller with learning and adaptive capabilities. ANFIS is combined the fuzzy logic controller (FLC) and neural networks (NNs). In the method that is developed herein, the control model uses Takagi-Sugeno fuzzy logic, in which the back-propagation algorithm processes information from neural networks to adjust suitably the parameters of the fuzzy controller, and the output control signal tracks the input signal. This method can be applied to improve the control performance of nonlinear systems. The output signal responses transient performance of systems use an ANFIS that must be trained through a learning process to yield suitable membership functions and weightings. The results of the FESS indicated that the system responds with satisfactory control performance to reduce overshoot, a zero-error steady-state, and short rise time. The proposed controller can be feasibly applied to FESS with various external disturbances, and the effectiveness of the ANFIS with self-learning and self-improving capacities is proven.</span></p>
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Majumder, Gargi, and Rajiv Tiwari. "Transverse Vibration of Geared-Rotor Integrated With Active Magnetic Bearings in Identification of Multiple Faults." Journal of Dynamic Systems, Measurement, and Control 143, no. 9 (April 15, 2021). http://dx.doi.org/10.1115/1.4050506.
Повний текст джерелаАнотація:
Abstract This paper presents a novel concept of the modeling, active control of transverse vibration responses, and identification of fault parameters in a geared-rotor system integrated with active magnetic bearings (AMBs). The sources of error in gears while in the operation are the gear mesh deformation, transmission error, and runout, resulting in dynamic forces, excessive vibration, and noise. To avoid any undesirable effect on the gear-pair and other supporting structures, it is essential to investigate these forced vibrations in time and frequency domain. Hence, an approach to monitor and control the transverse vibration of mating gears is presented with the help of AMBs. The AMBs are capable of suppressing the vibration of the system (transients as well as steady-state) by controlled electromagnetic forces considering the rotor vibrational displacement with a closed-loop feedback system. A mathematical model has been developed with geared rotor faults, like the mesh deformation, gear run-out, and asymmetric transmission error. The transmission error has been modeled as the sum of mean and varying components of error in two orthogonal transverse directions. Based on the mathematical model, an identification algorithm has been developed. Considering full spectrum analysis of the rotor vibration and AMB current information, estimation of system parameters, i.e., the equivalent mesh stiffness, mesh damping, gear runouts, the mean and varying transmission error magnitude and phase angles, and the current and displacement constants of AMBs has been performed. Gaussian noise in responses and modeling errors in mathematical models have been added to test the robustness of the proposed algorithm to comply with the experimental settings.
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Abubakar, J. U., Q. A. Omolesho, K. A. Bello, and A. M. Basambo. "Casson rheological flow model in an inclined stenosed artery with non-Darcian porous medium and quadratic thermal convection." Journal of the Egyptian Mathematical Society 30, no. 1 (December 23, 2022). http://dx.doi.org/10.1186/s42787-022-00157-8.
Повний текст джерелаАнотація:
AbstractThe current study investigates the combined response of the Darcy–Brinkman–Forchheimer and nonlinear thermal convection influence among other fluid parameters on Casson rheology (blood) flow through an inclined tapered stenosed artery with magnetic effect. Considering the remarkable importance of mathematical models to the physical behavior of fluid flow in human systems for scientific, biological, and industrial use, the present model predicts the motion and heat transfer of blood flow through tapered stenosed arteries under some underline conditions. The momentum and energy equations for the model were obtained and solved using the collocation method with the Legendre polynomial basis function. The expressions obtained for the velocity and temperature were graphed to show the effects of the Darcy–Brinkman–Forchheimer term, Casson parameters, and nonlinear thermal convection term among others. The results identified that a higher Darcy–Brinkman number slows down the blood temperature, while continuous injection of the Casson number decreases both velocity and temperature distribution.
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Zaidi, Abdelaziz, Asma Charaabi, Oscar Barambones, and Nadia Zanzouri. "Robust Passivity-Based Control Scheme for 1.26 KW Proton Exchange Membrane Fuel Cell Under Temperature and Load Variations." Journal of Electrochemical Energy Conversion and Storage 18, no. 4 (June 15, 2021). http://dx.doi.org/10.1115/1.4051331.
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Abstract The model-based system engineering (MBSE) is based on simplified mathematical models that reflect the dynamic behavior of the systems. These are most of the time nonlinear and need control schemes taking in consideration of exogenous perturbations. The main contribution of this article is the design of a robust passivity-based sliding mode control scheme for a 1.26 KW proton exchange membrane fuel cell (PEMFC). The uncertainties considered in this article are temperature and load variation. The fuel cell (FC) reference current is adapted in a linear transformation by introducing a temperature sensor. This information is present in most of commercial PEMFC and not used in the closed-loop system. Moreover, the proposed approach cancels the errors caused by the average approach modeling and the observer (the part, which replaces current sensor). Robustness against load variation is assured via a proportional integral compensation of the incremental value of load resistance. The performance of the controller and the effectiveness of our approach is shown through the simulation with matlab-simulink software.
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da Silva, Roberto. "Random matrices theory elucidates the nonequilibrium critical phenomena." International Journal of Modern Physics C, November 9, 2022. http://dx.doi.org/10.1142/s0129183123500614.
Повний текст джерелаАнотація:
The earlier times of the evolution of a magnetic system contain more information than we can imagine. Capturing correlation matrices built from different time evolutions of a simple testbed spin system, as the spin-1/2 and spin-1 Ising models, we analyzed the density of eigenvalues for different temperatures of the so called Wishart matrices. We observe a transition in the shape of the distribution that presents a gap of eigenvalues for temperatures lower than the critical temperature, or in its roundness, with a continuous migration to the Marchenko–Pastur law in the paramagnetic phase. We consider the analysis a promising method to be applied in other spin systems, with or without defined Hamiltonian, to characterize phase transitions. Our approach differs from the alternatives in literature since it uses the concept of magnetization matrix, not the spatial matrix of single spins.