Winding Method to Reduce Vibration and Loss Caused by Fractional Slot of Synchronous Machine

Fractional‐slot windings are widely used in rotating machines in order to improve the output voltage waveform, increase the design flexibility, and gain many other advantages. However, fractional‐slot windings are known to produce different harmonic components such as an even order and/or fractional number of space flux harmonics compared to integral‐slot windings. These harmonics may increase stray losses and cause stator core vibration. This paper describes an analysis of space flux harmonics and proposes new winding methods such as “novel interspersed windings” to reduce these harmonic components. The proposed winding methods were verified by numerical analysis and model tests.     

PLA/HA复合材料的蠕变行为的研究

研究在温度为36℃,应力为15~25 MPa范围内,羟基磷灰石( HA)质量分数分别为0%、3%、5%、15%的聚乳酸/羟基磷灰石( PLA/HA)复合材料的蠕变性能。研究表明：在蠕变过程中,相同应力时随着HA质量分数的增加蠕变寿命和蠕变应变逐渐变短;在相同的HA质量分数时,随着应力的增大,蠕变寿命逐渐变短,最小蠕变速率逐渐增大;随着HA质量分数的增加,复合材料最小蠕变速率的增长程度逐渐降低,并在HA含量为5%时达到最佳。     

PLA/HA复合材料蠕变行为研究

研究在温度为36℃、应力为15~25 MPa范围内,羟基磷灰石(HA)质量分数分别为0%、3%、5%、15%的聚乳酸/羟基磷灰石(PLA/HA)复合材料的蠕变性能。研究表明:在蠕变过程中,相同应力时,随着HA质量分数的增加,蠕变寿命和蠕变应变逐渐变短;在相同的HA质量分数时,随着应力的增大,蠕变寿命逐渐变短,最小蠕变速率逐渐增大;随着HA质量分数的增加,复合材料最小蠕变速率的增长程度逐渐降低,并在HA含量为5%时达到最佳。     

Order selection of a multivariate autoregressive model by a modification of the FPE criterion

The FPE criterion defined by Akaike for univariate autoregressive model fitting is extended to multivariate cases in order to minimize the estimate of the mean quadratic loss of the one-step-ahead prediction error. Asymptotic properties of the procedure are given, and some versions of multivariate FPE criteria suggested by Akaike are shown to be equivalent to certain cases of this method. Some computer simulations are carried out to illustrate the behaviour of the proposed method.     

SEGMENTATION OF NATURAL IMAGES USING ANISOTROPIC DIFFUSION AND LINKING OF BOUNDARY EDGES

We present a segmentation method of natural images that uses an anisotropic diffusion algorithm and a region growing algorithm. We propose a modified version of the anisotropic diffusion algorithm as a precise edge-preserving smoothing technique modified by using boundary edges. We incorporate a linking algorithm for boundary edges based on a directional potential function into the anisotropic diffusion algorithm to improve the ability of edge-preserving smoothing. As a result, unnecessary details of images are effectively smoothed before performing a region growing algorithm. Therefore, the proposed method is suitable for an accurate segmentation of natural images. Several simulated examples are presented that demonstrate the effectiveness of the proposed technique.     

Data‐Driven Controller Tuning for Nonminimum Phase Plants with Stability Constraints

This paper addresses the model reference control problem, which is a typical control problem found in data‐driven controller tuning methods. For nonminimum phase plants, the unstable zeros of the plant should be included in the reference to avoid destabilization of the resulting closed‐loop system and improve tracking performance. First, we propose a data‐driven controller tuning method with closed‐loop stability taken into consideration and with the tuned controller parameters in the time domain. If the plant has unstable zero(s), the proposed method would not lead to destabilizing controller in the worst case. Closed‐loop stability is checked using linear inequalities described with input/output data. This contributes to reducing computation in the proposed method. Moreover, this paper proposes a data‐driven controller tuning method for nonminimum phase plants estimating the unstable zero(s) using a flexible reference model at each parameter update and reflecting them into the resulting reference model. The effectiveness of the proposed method is confirmed through numerical experiments.