Application of linear magnetic gears for pseudo-direct-drive oceanic wave energy harvesting

Session AZ: Magnetic Machine (Poster Session): AZ-07This paper proposes a linear permanent magnet (PM) machine for direct-drive wave energy harvesting by using a linear magnetic gear. The proposed machine consists of a linear magnetic gear cascaded with a linear PM generator in which the high-speed mover of the linear magnetic gear and the translator of the PM generator artfully shares with the same shaft. In short, the slow reciprocating wave motion is directly captured by the low-speed mover of the gear, and then amplified in speed via the gear to actuate the generator, hence producing higher output voltage. By using finite element analysis, the steady and dynamic performances are analyzed, which confirms that the proposed machine can offer higher power density and higher efficiency than its counterpart. © 2011 IEEE.published_or_final_versionThe IEEE International Magnetic Conference (INTERMAG2011), Taipei, Taiwan, 25-29 April 2011. In IEEE Transactions on Magnetics, 2011, v. 47 n. 10, p. 2624-262

A new efficient permanent-magnet vernier machine for wind power generation

This paper proposes a new outer-rotor permanent-magnet (PM) vernier machine for direct-drive wind power generation, which can offer low-speed operation to directly capture wind power, and enable high-speed rotating field design to maximize the power density. Compared with its mechanical gear counterpart, the proposed machine can eliminate the mechanical wear and tear as well as gear transmission loss, thus improving the generation reliability and efficiency. The key is to newly introduce the flux-modulation poles which can effectively modulate the high-speed rotating field of the armature windings and the low-speed rotating field of the PM outer rotor. By using the time-stepping finite-element method, the proposed machine can be accurately analyzed. Hence, its performances are quantitatively compared with other PM vernier machines, thus verifying its validity. © 2006 IEEE.published_or_final_versio

Analysis of doubly salient memory motors using preisach theory

With the introduction of doubly salient memory (DSM) motors, the flux controllability and hence the speed range of permanent magnet (PM) motors have reached a new height. This paper presents a new method to accurately analyze the DSM motor. The key is to incorporate the general expressions of the Preisach hysteresis model (PHM) of the AlNiCo-PM into the time-stepping finite element method (TS-FEM). Based on the proposed PHM-TS-FEM, both static and transient performances of the DSM motor are successfully simulated. Finally, the validity and accuracy of the proposed method are verified by experimental results. © 2009 IEEE.published_or_final_versio

Comparison of coaxial magnetic gears with different topologies

This paper quantitatively compares two coaxial magnetic gears (CMGs) with different topologies, namely, the CMG installed with radially magnetized permanent magnets (CMGRM) and the CMG installed with Halbach magnetized permanent magnets (CMGHM). By using the 3D finite element method, the end-effect and the performances of both CMGs are investigated. Analysis results show that the CMGHM can offer higher pull-out torque, lower torque ripple and lower iron losses than the CMGRM. Experimental results are also given for verification. © 2009 IEEE.published_or_final_versio

Microwave Oscillations of a Nanomagnet Driven by a Spin-Polarized Current

We describe direct electrical measurements of microwave-frequency dynamics in individual nanomagnets that are driven by spin transfer from a DC spin-polarized current. We map out the dynamical stability diagram as a function of current and magnetic field, and we show that spin transfer can produce several different types of magnetic excitations, including small-angle precession, a more complicated large-angle motion, and a high-current state that generates little microwave signal. The large-angle mode can produce a significant emission of microwave energy, as large as 40 times the Johnson-noise background.Comment: 12 pages, 3 figure

Revealing microstructural evolutions, mechanical properties and wear performance of wire arc additive manufacturing homogeneous and heterogeneous NiTi alloy

Heterogeneous microstructure designs have attracted a great deal of attention, not only because they have the potential to achieve an ideal combination of two conflicting properties, but also because the processes involved in their fabrication are cost-effective and can be scaled up for industrial production. The process parameters in the preparation process have an important effect on the microstructure and properties of alloy members prepared by wire arc additive manufacturing (WAAM) technology. It was expected that the spatial heterogeneous microstructure with large microstructural heterogeneities in metals can be formed through changing the process parameters. In this work, homogeneous NiTi thin-walled component and heterogeneous NiTi thin-walled component were fabricated using WAAM technology by adjusting the heat input. The effects of deposition height and heat input on the microstructure, mechanical properties and wear properties of WAAM NiTi alloys were investigated. The results show that grains were gradually refined with the increase of deposition height in the homogeneous WAAM NiTi component. The ultimate tensile strength of homogeneous WAAM NiTi component increased from 606.87 MPa to 654.45 MPa and the elongation increased from 12.72% to 15.38%, as the increase of deposition height. Moreover, the homogeneous WAAM NiTi component exhibited excellent wear resistance, the coefficient of friction decreased from 0.760 to 0.715 with the increase of deposition height. Meanwhile, the grains in the heterogeneous WAAM NiTi component shows the finest grains in the central region. The ultimate tensile strength of the lower region, middle region and upper region of heterogeneous WAAM NiTi components were 556.12 MPa, 599.53 MPa and 739.79 MPa, and the elongations were 12.98%, 16.69%, 21.74%, respectively. The coefficient of friction for the lower region, middle region and upper region of heterogeneous WAAM NiTi components were 0.713, 0.720 and 0.710, respectively. The microhardness and cyclic compression properties of the homogeneous components with higher heat input were better than those of the heterogeneous components for the same deposition height. The tensile yield strength, elongation and wear resistance of the heterogeneous components were superior compared to the homogeneous components. These results can be used to optimize the WAAM process parameters to prepare NiTi components with excellent mechanical properties

Improved blog clustering through automated weighting of text blocks

In this paper, a new clustering algorithm is proposed for blog data clustering. Considering the structure information of text blocks in blog data, we group the features of blog data into three groups and extend the k-means clustering algorithm to automatically calculate a weight for each feature group in the clustering process. We introduce a new objective function with group weight variables and present the Lagrangian method to derive the formula to calculate the group weights. This formula is added as a new step in the standard k-means iterative clustering process to automatically compute the group weights according to the distribution of features. This new process guarantees the convergency of the clustering process to a local optimal solution. The experimental results have shown that this new algorithm performed better than k-means without group feature weighting on different blog data sets.published_or_final_versio