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An exact analytical model of a surface-mounted bearingless permanent-magnet synchronous motor (BPMSM) with rotor eccentricity by a perturbation method is proposed in this paper and its computational accuracy is verified by the finite-element method. Considering the rotor eccentricity, a compensation control system is implemented based on the mathematical model of levitation force by applying a coefficient of the rotor eccentricity calculated by the exact analytical method (EAM). The experimental results suggest the improvements of the dynamic and the static performances of the stable suspension state for the surface-mounted BPMSM and the feasibility and effectiveness of the EAM. [ABSTRACT FROM AUTHOR]

This paper studies an auxiliary poles technique that is used to reduce the end effect detent force for permanent magnet linear synchronous motor (PMLSM). Based on the lateral force method, the analytical model of the end effect detent force is built. The expressions of the optimal position and the optimal width for the auxiliary poles are derived. Through the use of finite-element calculations, the influence of the position, width, and height of the auxiliary poles on the end effect detent force is obtained. In addition, the detent force characteristics for five PMLSMs with typical slot–pole combinations after adopting the auxiliary poles are analyzed. The inhibitory effect of the auxiliary poles on the end effect detent force is separated from the slot effect detent force using harmonic analysis. The simulation results of the optimal auxiliary poles positions match the analytical expressions well, which proves the correctness of the analytical model. Finally, a prototype of the PMLSM with auxiliary poles, which has a better structure strength and eliminates the installation error, is manufactured and tested. [ABSTRACT FROM AUTHOR]

This paper develops a novel magnetomotive forces (mmfs) distribution model along the transverse direction for the 3-D analysis of linear induction motor, and it investigates the influence of a laterally asymmetric cap-secondary on the thrust, vertical force, lateral force, and efficiency in a prototype single-sided linear induction motor for linear metro. First, the mmf distribution model and its working conditions are defined, and the model is transferred into a mathematical model. Second, the air-gap flux and secondary eddy current in a prototype linear motor with a cap-secondary are obtained by a 3-D space harmonic analytical method. Third, the thrust, vertical force, lateral force, and efficiency of the test motor are analyzed with various lateral deflection, and the power factor in secondary is also presented. Finally, these results are experimentally verified by measurements on the test rig of the linear motor, and the comprehensive effect on the operating performance can be accurately calculated by the mmf model. [ABSTRACT FROM PUBLISHER]

In the nanopositioning system, a damping force is generated by eddy current in the cooling plate and it is a disturbing force for this system. In this paper, a new method is introduced to suppress eddy current by offsetting back EMF. In order to offset back EMF, several slits have been incorporated in the cooling plate, which can help with regulating the series order in every region. Based on the electromagnetic theory, the analytical model of new cooling plate is established. The analytical model and eddy current suppression effect of the new cooling plate are proven by experiment: 17% reduction in the damping force significantly help with reducing the thrust fluctuation, with less than 4% analytical error. [ABSTRACT FROM AUTHOR]

This paper deals with the dynamic characteristics of a linear induction motor (LIM) in terms of acceleration times and jerk conditions. We employed Matlab Simulink for conducting simulations of the dynamic modeling of LIM operated by a space vector pulse width modulation inverter. From the simulation results, the maximum load conditions and minimum acceleration times to guarantee passengers' safety were determined. Further, the electromagnetic field theory was employed to derive equivalent circuit parameters, and the results were validated by the finite element method. The analysis model was applied to a magnetic levitation vehicle for providing electromagnetic propulsion force, and its dynamic characteristics were analyzed to predict its operating performance; moreover, experimental results were employed to demonstrate the validity. We believe that the proposed prediction technique for the operating characteristics of LIMs can contribute to improving passengers' safety and riding quality. [ABSTRACT FROM AUTHOR]

The stationary discontinuous armatures that are used in permanent magnet linear synchronous motors (PM-LSMs) have been proposed as a driving source for transportation systems. However, the stationary discontinuous armature PM-LSM contains the outlet edges which always exist as a result of the discontinuous arrangement of the armature. For this reason, the high alteration of the outlet edge cogging force produced between the armature's core and the mover's permanent magnet when a mover passes the boundary between the armature's installation part and non-installation part has been indicated as a problem. Therefore, we have examined the outlet edge cogging force by installing the stair-shaped auxiliary teeth at the armature's outlet edge in order to minimize the outlet edge cogging force generated when the armature is arranged discontinuously. This paper presents the results of 2-D numerical analysis by FEM of the cogging force exerted by the outlet edge. [ABSTRACT FROM AUTHOR]

An objective in the design of high performance machinery is to minimize weight so magnetic bearings are often designed to operate slightly lower than their magnetic material saturation. Further weight reduction in the bearings requires operation in the nonlinear portion of the B\-H curve. This necessitates a more sophisticated analysis at the bearing and rotordynamic system levels during the design stage. This paper addresses this problem in a unique manner by developing a fully nonlinear homopolar magnetic bearing model. The nonlinear dynamics of a permanent magnet-biased homopolar magnetic bearing (PMB HoMB) system with a flexible rotor is analyzed. Nonlinear effects due to power amplifier voltage and current saturation and position dependent reluctances are also included in the model. A new curve fit model of the B\-H curve is shown to have significantly better agreement with the measured counterpart than conventional piecewise linear. The modified Langmuir method, with a novel correction terms for the weak flux region, is used to form an analytical model of the experimental magnetization curve of Hiperco 50. High static and dynamic loads applied to the rotor force the magnetic bearing to operate in a flux saturated state. The response of the heavily loaded 4-DOF rotor-bearing system shows that limit cycle stability can be achieved due to the magnetic flux saturation or current saturation in the amplifier. The stable limit cycle prevents the linear model instability, creating what is experimentally observed as a “virtual catcher bearing.” To the authors' knowledge this is the first explanation of this commonly observed phenomenon. [ABSTRACT FROM PUBLISHER]

This paper considers analytical and numerical techniques to model the magnetic field distribution in a tubular actuator with skewed permanent magnets (PMs). A fast 3-D analytical model based on Fourier analysis is developed for calculation of the various field components resulting from the skewed PMs for various skewing topologies. This techniques provides means for validating the assumptions of 2.5-D multilayer methods. Furthermore, a 2.5-D analytical multilayer model is derived for calculation of the cogging force due to the slot openings including skewed PMs. The analytical methods are validated by means of 3-D finite element analysis. [ABSTRACT FROM PUBLISHER]

The touch-down test is widely used to calibrate the flying-height (FH) of sliders by gently contacting the disk with the thermal protrusion of thermal FH control (TFC) sliders. However, the dynamic instability of TFC slider during the touch-down process may significantly affect the contact detection and the FH calibration, and therefore, hinders further reduction of the FH of TFC sliders. This paper highlights the nonlinear dynamics perspectives on the instability of TFC sliders during the touch-down process. A single-DOF (degree-of-freedom) and a 2-DOF nonlinear dynamics models were developed respectively to quantitatively study instability of TFC sliders at the near contact regime and to explain the nonlinear dynamic behaviors of TFC sliders at touch-down. The simulation results from the nonlinear analytical models reveal that the existence of multiple equilibriums and the self-excited vibrations of the slider-air bearing system are the main reasons for the instability and bouncing of TFC sliders during touch-down process. [ABSTRACT FROM AUTHOR]