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Статті в журналах з теми "Magnetic bearings; nonlinear systems mathematical models"
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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: 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>
Дисертації з теми "Magnetic bearings; nonlinear systems mathematical models"
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Ji, Jin-Chen. "Nonlinear dynamics of magnetic bearing systems." Thesis, 2006. http://hdl.handle.net/2440/63568.
Повний текст джерелаАнотація:
The aim of the work outlined in this thesis was to gain a deep insight into the effects of nonlinearities of magnetic bearings and the influence of time delays occurring in the feedback path control on their dynamic behaviour and performance. Emphasis was on stability analysis, bifurcation control, determination of stable operating conditions, prediction of bearing performance, and on aspects of nonlinear dynamic behaviour including bifurcations, coexistance of multiple solutions and complicated motions ... The present thesis comprises 12 papers which were recently published in seven international journals.Thesis (Ph.D.) - University of Adelaide, School of Mechanical Engineering, 2006
Книги з теми "Magnetic bearings; nonlinear systems mathematical models"
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ZnO bao mo zhi bei ji qi guang, dian xing neng yan jiu. Shanghai Shi: Shanghai da xue chu ban she, 2010.
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"Magnetotail particle dynamics and transport": Final report for NAGW-1176. [Washington, DC: National Aeronautics and Space Administration, 1995.
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United States. National Aeronautics and Space Administration., ed. "Magnetotail particle dynamics and transport": Final report for NAGW-1176. [Washington, DC: National Aeronautics and Space Administration, 1995.
Знайти повний текст джерелаТези доповідей конференцій з теми "Magnetic bearings; nonlinear systems mathematical models"
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Virgin, Lawrence N., Thomas F. Walsh, and Josiah D. Knight. "Nonlinear Behavior of a Magnetic Bearing System." In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-341.
Повний текст джерелаАнотація:
This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bearings and subject to rotating unbalance and feedback control. Geometric coupling between the degrees of freedom leads to a pair of nonlinear ordinary differential equations which are then solved using both numerical simulation and approximate analytical techniques. The system exhibits a variety of interesting and somewhat unexpected phenomena including various amplitude driven bifurcational events, sensitivity to initial conditions and the complete loss of stability associated with the escape from the potential well in which the system can be thought to be oscillating. An approximate criterion to avoid this last possibility is developed based on concepts of limiting the response of the system. The present paper may be considered as an extension to an earlier study by the same authors which described the practical context of the work, free vibration, control aspects and derivation of the mathematical model.
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Liu, Mengke, and C. Steve Suh. "Active Magnetic Bearings for High Speed Spindle Design With Nonlinear Time-Frequency Control." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50994.
Повний текст джерелаАнотація:
A novel concept applicable to the control of spindles at high speed is developed by using active magnetic bearings (AMBs) that are non-contact and of low vibration. Though former studies are abundant and demonstrating promising potentials, however, two major issues hamper the broader application of AMBs. The first is the disregard for the gyroscopic effect and geometry coupling that influence the magnitude as well as distribution of the electromagnetic force in AMBs. Not considering the two has a significant implication for the proper control of AMBs. This paper considers the gyroscopic effect and explores the geometry coupling of the electromagnetic actuators to the formulation of a comprehensive nonlinear AMB-rotor model. The model provides the basis for the creation of a novel time-frequency control algorithm whose derivation requires no linearization or mathematical simplification of any kind, thus allowing the model system to retain its true fundamental characteristics. Unlike proportional-integral-derivative (PID) controllers that are dominant in most if not all AMB configurations, the controller developed for the research is inspired by the wavelet-based nonlinear time-frequency control methodology that incorporates the basic notions of online system identification and adaptive control. Due to the fact that dynamic instability is characterized by time-varying frequency and non-stationary spectrum, the control of AMBs needs be executed in the time and frequency-domain concurrently to ensure stability and performance at high speed. Wavelet filter banks and filtered-x least-mean-square (LMS) algorithm are two of the major salient physical features of the controller design, with the former providing concurrent temporal and spectral resolutions needed for identifying the nonlinear state of motion and the latter ensuring the dynamic stability of the AMB-rotor system at extremely high speed. It is shown that the vibration of the rotor is unconditionally controlled by maintaining a mandatory 0.55 mm air gap at 187,500 rpm subject to a tight spatial constraint (tolerance) of the order of 0.1375mm, which is the 25% of the air gap.
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Yoo, Seong-yeol, and Myounggyu Noh. "A Comparison Study of Power Minimizing Controllers for Active Magnetic Bearings." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63554.
Повний текст джерелаАнотація:
This paper describes a comparison study of power consumption of power minimizing controllers for active magnetic bearing (AMB) system. AMB system usually used bias currents in order to linearize force-current nonlinear relation. Using linearization with bias currents, AMB system achieves better dynamic performance and system linearity while bias currents always have to be consumed. The ohmic loss caused by them is one of the major energy losses of magnetic bearing systems. There are several researches to reduce constant power consumption by bias current. However, they all claim to reduce the power consumption of AMBs compared to the conventional PD-type controller, no study has been to compare these techniques. In this paper, we studied and implement previous researches with identical system frame for reasonable comparison. For comparison study, we derived simulation models using identical frame work and also built 2 degree-of-freedom (DOF) test bed.
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Chooi, Weng W., and S. Olutunde Oyadiji. "Mathematical Modelling and Design and of MR Dampers." In ASME 7th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2004. http://dx.doi.org/10.1115/esda2004-58447.
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Most magnetorheological (MR) fluid devices are fixed-pole valve mode devices where the fluid flows through a magnetically active valve. Controlling the strength of the magnetic field inside the valve allows the rheological properties of the MR fluid to be varied. Upon the application of a magnetic field, MR fluids develop a yield stress, which must be overcome before any flow is possible. This behavior can be represented mathematically by models of fluid with a yield stress like the Bingham plastic model. MR dampers have utilized this property of the MR fluids to provide controllable, semi-active vibration control. The most effective and widely used configuration of MR dampers incorporates an annular gap through which the MR fluid is force to flow. This paper presents a solution for annulus flows, derived from fundamental equations of fluid mechanics, of any general model of fluid with a yield stress. An example of the application of the general analytical expressions using the Herschel-Buckley model is given, and the limitations of the parallel plate approximation is illustrated for configurations whereby the size of the annular gap relative to the mean radius is large. Finally, the flow solution is incorporated into the mathematical model of an MR damper designed at the University of Manchester, and simulation results incorporating the effects of compressibility in the modeling procedure are presented. It was shown that this model can describe the major characteristics of such a device — nonlinear, asymmetric and hysteretic behaviors — successfully.
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Hawkins, Lawrence A. "Shock Analysis for a Homopolar, Permanent Magnet Bias Magnetic Bearing System." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-230.
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A transient, nonlinear analysis was developed and used to study the effect of shock machine testing on a gas turbine simulator supported by homopolar, permanent magnet bias magnetic bearings. The magnetic bearing nonlinearities modeled included saturation effects, clearance effects, and integrator and current limits. Free vertical travel of the shock machine anvil table supporting the simulator was also modeled. The magnetic bearing model was coupled to characteristic matrix based models of the rotor and support system and integrated to produce a time simulation of system performance. The results indicate saturation of the magnetic bearing for brief periods following impacts significant enough to exceed design load capacity, followed by recovery to stable operation in less than a second. The analysis was used to evaluate sizing for the magnetic bearing and backup bearing systems and to evaluate the control system strategy.
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Gudmundsson, Ketill H., Fjola Jonsdottir, and Freygardur Thorsteinsson. "A Multi-Objective Design Optimization of a Smart Magneto-Rheological Prosthetic Knee." In ASME 2009 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2009. http://dx.doi.org/10.1115/smasis2009-1237.
Повний текст джерелаАнотація:
Magneto-rheological (MR) fluids have been successfully introduced to prosthetic devices. One such a device is a biomechanical prosthetic knee joint that uses a MR fluid to actively control its rotary stiffness while an amputee walks. The knee is a synergy of artificial intelligence, advanced sensors and MR actuator technology. The MR fluid has response time in the order of milliseconds, making it possible to vary the knee’s stiffness in real-time, depending on sensors data. The focus of this paper is on the design of the magnetic circuit of the actuator and on the geometry of the fluid chamber. The paper describes the function of the MR rotary actuator and shows how design optimization techniques can aid in the development of the actuator. The design is optimized, with respect to three important design objectives. These objectives are: the maximum obtainable field-induced braking torque, the minimum obtainable rotary damping in the absence of a magnetic field, and the weight of the actuator. Multi-objective design optimization techniques are presented and applied to the prosthetic knee actuator design problem. Trade-offs between design objectives are investigated giving valuable information on the development of the actuator. Maximizing the field-induced braking torque is important for the knee to be capable of supporting heavy amputees. Minimizing the off-state stiffness is important for fast movements of the knee, in load-free movements. Furthermore, minimizing the weight of the actuator is important for allowing heavy components like batteries to be installed. It is realized that these design objectives can not be addressed separately and to some extend, the design goals are contradictory. Mathematical models are presented that describe the design objectives as a function of selected design parameters. Determining the field-induced braking torque requires a magnetic finite element analysis, to evaluate the magnetic flux density in the MR fluid, and the shear-yield stress curve of the MR fluid. Evaluating the off-state stiffness requires the off-state viscosity of the MR fluid, along with friction in bearings and oil seals. The models are based on rheological measurements of the MR fluid employed in the knee. Evaluating the weight of the actuator requires the geometry of the actuator and the density of its materials. The optimization is restricted by practical manufacturing design constraints. Mapping the dependency between the maximum torque, the minimum damping, and the weight of the MR actuator gives valuable insight into the design of the prosthetic knee actuator.
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Cao, Jianming, Paul Allaire, Timothy Dimond, and Saeid Dousti. "Auxiliary Bearing System Optimization for AMB Supported Rotors Based on Rotor Drop Analysis: Part I — Rotor Drop Analysis Method." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56323.
Повний текст джерелаАнотація:
For rotors supported with active magnetic bearings (AMBs), the auxiliary bearing system or backup bearing system is needed to avoid serious potential internal damaging in the event of AMB loss of power or overload. The evolution of auxiliary systems has been made a priority by the American Petroleum Institute using analytical or experimental methods. In part I of this paper, a detailed rotor drop nonlinear transient analysis method including flexible shaft, rolling element bearing components including inner/outer races and balls, as well as flexible/damped supporting structures is given. A finite element based 6-DOF flexible rotor model is used to indicate shaft motion before the drop (operating conditions) and during the rotor drop event. Un-lubricated Hertzian contact models are used between the shaft and inner/outer races, between balls and races. To avoid heavy calculating time, two different methods to calculate ball bearing contact loads are discussed and the simulation results are compared. These models are applied to predict shaft-race-ball displacements and angular speeds, contact loads and ball bearing stresses during the drop for angular contact auxiliary bearings. This method also can be used to design and optimize the auxiliary bearing system as presented in the 2nd part of this paper.
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Panyam, Meghashyam, and Mohammed F. Daqaq. "Response of an Axially-Loaded Terfenol-D Rod to a Harmonic Base Excitation." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3313.
Повний текст джерелаАнотація:
Performance characteristics of the giant magnetostrictive alloy, Terfenol-D, have been studied by many researchers for actuation, sensing and energy harvesting applications. Mathematical models characterizing the magneto-elastic behavior and describing the effects of bias conditions — compressive prestress and magnetic bias — on the material performance, have been developed. For the most part, the models used to describe the material are linear models that can hide essential features of the dynamic performance. While nonlinear constitutive models of Terfenol-D exist, such models have not been utilized to study the dynamic frequency response characteristics that are essential towards a comprehensive understanding of its performance in actuation, sensing or energy harvesting. To address this problem, this effort investigates the role of empirically determined material nonlinearities in the dynamic performance of Terfenol-D. Towards that objective, a polynomial type stress-strain relation is used to construct a nonlinear distributed-parameters model for a Terfenol-D rod fixed at one end and mass loaded at the other while being subjected to a sinusoidal base excitation. Additionally, the model accounts for the rod being subjected to an axial prestress prior to excitation. Using the method of multiple scales, the nonlinear frequency response of the rod is investigated by obtaining analytical expressions for the steady-state response amplitude. It is demonstrated that the axial prestress results in a shift in the fundamental vibration frequencies of the rod and a change in the effective nonlinearity of the system. A qualitative analysis of the solution reveals that, the magnitude of axial load can be used to maximize the response amplitude over a larger bandwidth of frequencies.