Search

Spoke-array brushless dual-electrical-port dual-mechanical-port (SA-DEP-DMP) machine is a good candidate for continuously variable transmission device, because of its high compactness, contactless torque transmission, and decoupled rotors. Due to the specific features, including two independent controllable rotors, two set windings, and complex magnetic field coupling, some unique design considerations of SA-DEP-DMP machine are analyzed in this article. First, there is a little accurate analytical model for DEP-DMP machine. An applicable analytical model is proposed to directly describe the characteristic of air-gap magnetic field and calculate the sizing equation. The key innovation is that the inner air-gap permeance with the slot effect is mapped into the magnetic potential by air-gap mapping model, which simplifies the double air-gap structure into a single air-gap structure. Second, the torques of two rotors are always optimized separately at the same time. Using this design method, the optimal torques of two rotors cannot achieve simultaneously for many parameters. In order to solve this problem, a novel constant torque ratio design method is proposed where two windings electric loading distributions are considered. The influences of key parameters, such as combination of slot and pole, stator split ratio, permanent magnet size, etc., on the torque performances are analyzed based on finite-element analysis. Finally, an SA-DEP-DMP prototype is manufactured. [ABSTRACT FROM AUTHOR]

This article investigates the source and reduction methods of cogging torque in dual PM Vernier machines (DPVMs), especially for the ones with unevenly distributed split teeth (UDST). At first, the increase of no-load back electromotive force in DPVMs with UDST is illustrated through the analysis of airgap working flux harmonics. The reason for largely increased cogging torque of DPVMs with UDST is then analyzed, and main flux harmonics that contribute to cogging torque are identified. To reduce cogging torque and torque ripple, several effective methods are introduced in this article, which are mainly based on the reduction or offset of corresponding airgap flux harmonics. The cogging torque reduction effects and torque performances of these methods are compared. Among them, newly proposed N/S-parts offset method is proved to be superior to other methods in DPVMs. A new DPVM prototype with UDST and N/S-parts offset structure is built and tested. Experimental results show that through the N/S-parts offset method, cogging torque of the machine is largely decreased from 9 to 0.3 N·m, which validates the analysis and simulation results. [ABSTRACT FROM AUTHOR]

It is well known that permanent magnet Vernier machine (PMVM) has multiple flux field harmonics, which can produce stable torque. However, some flux field harmonics would create torque that undermines the total torque output. Such as the 6 slots 26 poles split-tooth PMVM here, of which modulated flux field outputs torque while fundamental flux field undermines torque output. In this article, a 26 pole PMVM with coding-shaped tooth is proposed. The coding-shaped tooth can introduce permeance harmonics with specific phase and amplitude, thus modulating flux fields that all output torque. Air-gap permeance harmonics of the proposed and the regular split-tooth PMVM are obtained via FEA. Based on MMF-permeance model, flux fields of two machines and their contributions to average torque are investigated, proving that the proposed machine has multiple flux fields that all output torque. Moreover, by optimizing geometric parameters of coding-shaped tooth, the proposed machine could obtain largest average torque and smallest torque ripple simultaneously. Electromagnetic performances of the optimized machines are studied comparatively in semianalytical way and FEA. It is proved that with same overall size, PM usage, and copper loss, the proposed machine could achieve 30% larger torque density, 86% smaller cogging torque, and 62% lower torque ripple than its counterpart. Finally, a 16-N·m (rated) prototype is built and tested. [ABSTRACT FROM AUTHOR]

Linear permanent magnet Vernier machine (LPMVM) is attracting more and more attentions recently due to its simple structure, high efficiency, and high thrust density at low speed. In this article, a novel fractional pole-pair linear permanent magnet Vernier machine (FP-LPMVM) is proposed, which gives more freedom in the design of the LPMVM to reduce the force ripple of the machine. The operation and force ripple reduction principles of the FP-LPMVM are also given in this article with the help of analytical equations. It is found that some of the proposed FP-LPMVM exhibit inherent good performances such as high EMF symmetry and low thrust ripple due to the combining of the flux modulation effect and the FP-LPMVM. In order to verify the theoretical analysis in this article, two LPMVM prototypes (i.e., 12 slots 20 poles integer pole-pair LPMVM and 18 slots 29 poles fractional pole-pair LPMVM) are manufactured, tested, and compared with each other. The experimental results are consistent with the FEA results, and the validity of the analysis and the superiorities of the proposed FP-LPMVM are verified. [ABSTRACT FROM AUTHOR]

Vernier permanent magnet (VPM) machine has become a good candidate to drive the pump and fan loads, since these loads always operate at low speed and require high output torque. In these applications, the machine operates near a fixed speed and requires no speed adjustment capability. Hence, the inverter can be replaced by a line-start unit, and the machine can be connected directly to the grid, which reduces the weight, volume, and cost of the whole system. However, the novel magnetic gearing effect in the VPM machine causes two issues. First, the abundant magnetic field harmonics interact with the line-start unit and produce strong braking torque even at steady-state operation; second, large harmonic leakage inductance reduces the starting capability. Therefore, the traditional method to build a line-start machine is not suitable for the VPM machine. In this article, a line-start VPM (LSVPM) machine topology is proposed. By analyzing two issues above, the structure and pole-pair of both stator armature and rotor wound windings are carefully selected, and finally pole-changing strategy is chosen to start the machine. The performances of the proposed machine are verified by finite element analysis (FEA), which shows it has 49% higher torque density than regular line-start permanent magnet machine, and has the capability to start with the rated pump load. A prototype also has been built and tested to demonstrate the analysis and simulation. [ABSTRACT FROM AUTHOR]

A novel brushless dual-mechanical-port dual-electrical-port (BLDD) machine and its modeling and drive method are introduced in this article. The two-set-of-winding structure of the conventional BLDD machine is replaced by an integrated winding. Thus, the manufacturing of the stator and winding is simplified. Correspondingly, two kinds of current have to be injected into the winding simultaneously. By using the integrated drive method, the copper loss will be reduced by 50% under the ideal condition. In order to achieve the control of two kinds of current in the same winding, the mathematical model of the integrated winding concerning the coupling effect is first developed. Then, the dual-frequency current drive or integrated drive strategy is proposed, in which the transformation matrix of the current and the controller structure are modified to generate the two-frequency current. Furthermore, the harmonics in the currents have been analyzed and its compensation strategy is investigated. Finally, the proposed scheme is implemented on a prototype. The experimental results of the machine have verified the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In recent years, high-precision servo systems have attracted much attention due to the development of aerospace and electronic industries. Given the requirement of the servo systems, the machine torque ripple, including the no-load cogging torque and the load torque ripple, must be limited under a low level to achieve the high precision. The ironless permanent magnet-machine (ironless PMM) is usually adopted in high-precision servo systems due to its characteristics of zero cogging torque and low torque ripple. However, ironless PMM has a lot of drawbacks such as low torque density and large PM consumption, making the system size large and expensive. The permanent-magnet vernier machine (PMVM) is also studied for servo applications for its low torque ripple and large torque density due to the adoption of the so-called magnetic gearing effect. However, its torque ripple is still apparently larger than that of the ironless PMM. In order to achieve low torque ripple and large torque density at the same time, a novel modular stator fractional pole-pair PMVM (MFP-PMVM) is proposed and analyzed in this article. The cogging torque and torque ripple of the proposed MFP-PMVM is 93% and 70% lower than that of the conventional PMVM without an obvious decrease on the rated torque. The proposed MFP-PMVM exhibits a low torque ripple close to the ironless PMM while the torque density and PM utilization of the proposed MFP-PMVM is 163% and 14 times higher than that of the ironless PMM. Based on the finite-element method (FEM) results, the superiorities of the proposed MFP-PMVM are verified. [ABSTRACT FROM AUTHOR]

With complicated structures and complex physicochemical reactions, most industrial processes are intrinsically characterized by high dimensionality, nonlinearity, non-Gaussianity, and self-correlation. In this article, a novel probabilistic generative model, called weighted copula regression (WCR), is developed for complex processes. This method employs a probabilistic graphical tool (vine copula) to flexibly handle the underlying patterns via the factorization of complex dependence structures into multiple bivariate copulas. Monte Carlo estimation is incorporated for establishing a fast and reliable computing framework. To avoid overinterpretation of the industrial data, an adaptive sample selection strategy is proposed to explore the underlying distribution of the sample space and to select the most “informative” samples. By considering the copula weights that carry crucial information on the local data, the probabilistic WCR method can provide fast point estimate with prediction uncertainty for every predicted sample. The proposed WCR method is compared with six state-of-the-art methods, and the efficiency is validated using a numerical example and the ethylene cracking furnace process. [ABSTRACT FROM AUTHOR]

Permanent magnet magnetic geared machine (PM-MGM) is widely researched as a potential core component of electrical continuously variable transmission system. Due to the dual mechanical port structure, back electromotive force (EMF) characteristics of PM-MGMs are quite different from that of conventional permanent magnet (PM) machines. In this article, back EMF harmonic features of PM-MGMs are thoroughly analyzed. The back EMF harmonic amplitude and order are analytically deduced, it can be found that both of them are variable and related with normalized speed ratio. A simulation/experiment method is proposed to separate and calculate different flux linkage components. A novel distortion factor criterion for PM-MGMs is defined to evaluate the variable back EMF distortion value. Different from existing criteria, the proposed criterion is a function of normalized speed ratio, hence it is more comprehensive for PM-MGM back EMF comparison and machine design. The torque ripple caused by back EMF harmonics is also analyzed. A PM-MGM prototype has been manufactured, and back EMF features as well as validity of the proposed distortion factor are verified by experiment. [ABSTRACT FROM AUTHOR]

Permanent magnet vernier (PMV) machines have attracted more and more attentions due to their desirable features of high torque density. However, nearly all the proposed PMV machines are driven by converters. In this article, two methods including stator winding pole-changing and cascading method to acquire self-starting capability for PMV machine are analyzed and compared. The inverters can be omitted due to the self-starting capability of the novel topologies. First, the structure and circuit of pole-changing line-start permanent magnet vernier (PCLSPMV) machine are given and analyzed. Then, a dual-stator LSPMV machine, which cascades an induction machine and a PMV machine is also analyzed. Additionally, the starting and steady-state performance between pole-changing and cascading LSPMV machine. Finally, a prototype of a PCLSPMV machine has been built and tested to demonstrate the analysis and simulation. [ABSTRACT FROM AUTHOR]

Line-start permanent magnet (LSPM) machines have significant advantages in efficiency and power factor compared with regular induction motors; however, the poor starting torque and synchronization capability prevent the widespread of LSPM machines. In this article, winding reconfiguration methods are proposed to improve the starting performance and steady-state performance of LSPM machines. The turns-changing method is to increase asynchronous torque by reducing coil turns in starting, and the pole-changing method is to reduce and even eliminate the permanent magnet (PM) braking torque by changing the pole pair number of stator windings in the early starting period. Both of them can be adopted for an LSPM machine simultaneously to improve average torque in the starting stage. The starting performance is also compared between the turns-pole-changing LSPM machine and pole-increasing LSPM machine. Finite-element analysis is carried out to show the performance differences of LSPM machines using different starting strategies. A turns-changing LSPM machine is also manufactured and tested to validate the starting improvement. [ABSTRACT FROM AUTHOR]

Brushless dual-electrical-port dual-mecha-nical-port (BLDD) machine has become a good candidate to replace the traditional mechanical continuously variable transmission owing to its high compactness, reliability, and torque transmission capability. However, the mutual coupling between two sets of windings fed by different frequency currents leads to strong interference during both health and fault conditions, whereas the coupling effect is difficult to be reduced in the regular BLDD machine due to its operation principle. This paper presents a systematic analysis on a novel spoke-type BLDD (STBLDD) machine, aiming to eliminate coupling of windings. Using the winding function theory, the decoupling principle is analyzed in detail, and corresponding slot/pole combinations are derived. Through finite-element analysis, parameter influences on the performance of this STBLDD machine are then studied. A prototype and test bed have been designed and manufactured, and the experimental results verify the analysis results. [ABSTRACT FROM AUTHOR]