Applied Mechanics and Materials Vols. 416-417

Abstract: This paper presents a sinusoidal permanent magnet (PM) shaping technique with third harmonic to improve the electromagnetic thrust force in linear slotless PM machines without sacrificing the thrust force ripple. Slotless PM linear machine possesses relatively low thrust force ripple due to the absence of cogging force, compared with slotted topology. However, thrust force ripple of the machine with rectangular PM shape still exists due to nonsinusoidal airgap flux density distribution produced by PMs. Sinusoidal shaping techniques can be used to reduce the thrust force ripple but the average thrust force is reduced as well. Therefore, a simple PM shaping technique with optimal 3rd harmonic is presented to improve the output thrust force but not to increase the thrust force ripple. The sinusoidal plus 3rd harmonic shaping technique is analytically demonstrated together conventional sinusoidal shaping method and verified with finite element method. The results show that the electromagnetic performance can be significantly improved.

Abstract: When designing a magnetic levitation system it is assumed that the magnets are ideally magnetized. In practice, however, this is not the case and deviations occur in the magnetization. In this paper two types of deviations are considered, namely a constant angular deviation and the magnetization error. Calculations show that a constant error has larger impact on the performance of a gravity compensator than the magnetization error.

Abstract: This paper presents a kind of synthetic boundary conditions for the analytical magnetic field analysis of Halbach magnet array, which are derived from the linear demagnetization characteristic and the equivalent surface current of permanent magnet (PM). With the proposed synthetic boundary conditions, boundaries of Halbach PM array are simplified to only two surfaces. As a result, a relatively simple analytical solutions of Halbach magnetization topology based on the magnetic scalar potential (MSP) are obtained.

Abstract: The operation of linear oscillating system is complicated, involving system nonlinearities of both actuator and load, and variations of driving frequency in order to track the mechanical resonance. In this paper, the state-variable modeling technique is used to analytically investigate the influence of actuator reluctance force on the performance of linear oscillating systems. The analytical derivations will be validated by simulations, and good agreements are achieved.

Abstract: This paper presents a quantitative comparison between the non-rare-earth permanent magnet (PM) and rare-earth PM based linear magnetic gear. By using the finite element analysis, three linear magnetic gears adopting either the non-rare-earth PM or rare-earth PM are analyzed and discussed. Hence, the cost-effectiveness comparison among different types of PMs is conducted. The results indicate that the non-rare-earth PM is preferred to the rare-earth PM for application to linear magnetic gears when cost-effectiveness is emphasized.

Abstract: The detent force of permanent magnet linear synchronous motor (PMLSM) leads to the thrust ripple, vibration and noise inbearing grinding machines, In order to overcome the negative effect, detent force needs to be decreased. Through theanalytical andfinite element methods, two main components of detent force are investigated in this paper. Firstly, finite element analysis (FEA) and fast Fourier transform (FFT) are employed to analyze the end force. Then athree dimensional (3-D) FEA model of a short secondary PMLSM with skewed poles is erected and the cogging force is studied.Compared with the two dimensional (2-D) model of PMLSM without skewed poles, the detent force is remarkably reduced.

Abstract: In order to achieve high thrust density and low thrust ripple simultaneously, a multiobjective optimization design method is applied to ironless permanent magnet linear synchronous motor with non-overlapping windings. On the basis of the magnetic field analysis model, the analytical formulae of key parameters such as No-load back EMF, thrust per copper quality and thrust ripple was deduced. Further, a multiobjective optimization is carried out by genetic algorithm to search for the optimal design variables. The design optimization is verified by 2-D Finite Element analysis and experimental results of the prototype.

Abstract: Based on a simple analytical model, combinations of primary and secondary pole numbers for linear switched-flux permanent magnet (LSFPM) machines with odd pole number of primary are compared, with respect to back electromotive force (EMF) and electromagnetic thrust force. The winding configurations are also determined according to the coil-EMF vector diagram. Based on optimized LSFPM machines, some basic electromagnetic performances are compared in LSFPM machines with 9 primary poles. It is shown that the secondary pole number should be close to the primary pole number and the higher secondary poles can lead to a better performance.

Abstract: For segment-powered linear induction motor (LIM), there is major asymmetry among the mutual inductance of stator windings. Based on magnetic motive force theory, this paper derived the magnetic motive force distribution of single-phase winding of the segment-powered linear induction motor, and confirmed the characteristics of magnetic motive force distribution of the segment-powered linear induction motor. Based on the magnetic motive force distribution of single-phase winding, the analytic expressions of air-gap field distribution of the segment-powered linear motor were derived, and the finite element simulation results verified the analytic results.

Abstract: Dual-redundancy electromechanical servo actuation system used in the more electric aircraft servo actuation system has the advantages of both small size and high power density, and improves aircraft servo control system working reliability. And dual-redundancy permanent magnet brushless machine (DRPMBLM) used to realize electric energy to mechanical energy conversion is the key component, which directly affects the performance of the system. In this paper, The system topology is proposed by the analysis of the kind of redundancy structure of DRPMBLM. The mathmatical models of PWM converter model and state equations for DRPMBLM system were proposed. In these models, the mutual coupling for the mutual inductances between phases in each redundancy is considered. The simulation adapts to time-varying Network model. By using this proposed system model, the dynamic performances and characteristics for the DRPMBLM system are predicted and analyzed. Simulation and experimental results are compared in DRPMBLM system to verify the proposed modeling and characteristics analysis.