Harmonics in the Squirrel Cage Induction Motor Analytic Calculation Part III: Influence on the Torque-speed Characteristic

The harmonics that appear in the squirrel cage asynchronous machine have been discussed in great detail in the literature for a long time. However, the systematization of the phenomenon is still pending, so we made an attempt to fill this gap in the previous parts of our study by elaborating formulas for calculation of parasitic torques. It was a general demand among those who work in this field towards the author to verify his formulas with measurements. In the literature, it seems,only one detailed, purposeful series of measurements has been published so far, the purpose of which was to investigate the effect of the number of rotor slots on the torque-speed characteristic curve of the machine. The main goal of this study is to verify the correctness of the formulas by comparing them with the referred series of measurements. Relying on this, the expected synchronous parasitic torques were developed for the frequently used rotor slot numbers-as a design guide for the engineer.Thus, together with our complete table for radial magnetic pull published in our previous work, the designer has all the principles, data and formulas available for the right number of rotor slots for his given machine and for the drive system. This brings this series of papers to an end.

A Discrete Multi-Objective Squirrel Search Algorithm for Energy-Efficient Distributed Heterogeneous Permutation Flowshop with Variable Processing Speed

In the manufacturing industry,reasonable scheduling can greatly improve production efficiency,while excessive resource consumption highlights the growing significance of energy conservation in production.This paper studies the problem of energy-efficient distributed heterogeneous permutation flowshop problem with variable processing speed(DHPFSP-VPS),considering both the minimum makespan and total energy consumption(TEC)as objectives.A discrete multi-objective squirrel search algorithm(DMSSA)is proposed to solve the DHPFSPVPS.DMSSA makes four improvements based on the squirrel search algorithm.Firstly,in terms of the population initialization strategy,four hybrid initialization methods targeting different objectives are proposed to enhance the quality of initial solutions.Secondly,enhancements are made to the population hierarchy system and position updating methods of the squirrel search algorithm,making it more suitable for discrete scheduling problems.Additionally,regarding the search strategy,six local searches are designed based on problem characteristics to enhance search capability.Moreover,a dynamic predator strategy based on Q-learning is devised to effectively balance DMSSA’s capability for global exploration and local exploitation.Finally,two speed control energy-efficient strategies are designed to reduce TEC.Extensive comparative experiments are conducted in this paper to validate the effectiveness of the proposed strategies.The results of comparing DMSSA with other algorithms demonstrate its superior performance and its potential for efficient solving of the DHPFSP-VPS problem.

Squirrel Search Optimization with Deep Convolutional Neural Network for Human Pose Estimation

Human pose estimation(HPE)is a procedure for determining the structure of the body pose and it is considered a challenging issue in the computer vision(CV)communities.HPE finds its applications in several fields namely activity recognition and human-computer interface.Despite the benefits of HPE,it is still a challenging process due to the variations in visual appearances,lighting,occlusions,dimensionality,etc.To resolve these issues,this paper presents a squirrel search optimization with a deep convolutional neural network for HPE(SSDCNN-HPE)technique.The major intention of the SSDCNN-HPE technique is to identify the human pose accurately and efficiently.Primarily,the video frame conversion process is performed and pre-processing takes place via bilateral filtering-based noise removal process.Then,the EfficientNet model is applied to identify the body points of a person with no problem constraints.Besides,the hyperparameter tuning of the EfficientNet model takes place by the use of the squirrel search algorithm(SSA).In the final stage,the multiclass support vector machine(M-SVM)technique was utilized for the identification and classification of human poses.The design of bilateral filtering followed by SSA based EfficientNetmodel for HPE depicts the novelty of the work.To demonstrate the enhanced outcomes of the SSDCNN-HPE approach,a series of simulations are executed.The experimental results reported the betterment of the SSDCNN-HPE system over the recent existing techniques in terms of different measures.

Harmonics in the Squirrel Cage Induction Motor Analytic Calculation-Part Ⅰ: Differential Leakage, Attenuation, Asynchronous Parasitic Torques

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.

Harmonics in the Squirrel Cage Induction Motor,Analytic Calculation Part Ⅱ:Synchronous Parasitic Torques,Radial Magnetic Forces

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.

基于改进松鼠搜索算法优化神经网络的数控机床进给系统热误差预测

为探究数控机床进给系统中各因素对热误差的影响规律,建立精准的热误差预测模型。在进给速度为10 m/min、环境温度20℃的条件下进行进给系统热误差测量实验,获得进给系统关键点的温升及热误差。为提高预测精度,采用Tent混沌改进松鼠搜索算法,并利用改进的算法对神经网络进行优化,建立热误差预测模型。利用热误差测量实验获得的数据进行验证,结果表明改进前的神经网络预测误差为12.23%,改进后的模型预测误差为8.92%,精度有较大提升。利用预测模型针对不同进给速度下相同位置处热误差进行分析,结果表明,进给系统中关键测温点的温度和丝杠各点的热误差随着进给速度的增加而增加。因此提出的预测模型可实现进给系统热误差的准确预测,为误差补偿提供理论依据。

西藏自治区发现不丹大鼯鼠和李氏小飞鼠

2022—2023年,摄影爱好者和中国科学院昆明动物研究所科研人员先后在西藏自治区拍摄和采集到不丹大鼯鼠(Petaurista nobilis)(错那县、亚东县)和李氏小飞鼠(Priapomys leonardi)(巴宜区、墨脱县和错那县)的照片及标本。研究发现不丹大鼯鼠西藏种群形态上与不丹大鼯鼠不丹亚种(Petaurista nobilis singhei Saha,1975)的描述一致;遗传上与米什米大鼯鼠(Petaurista mishmiensis)构成姊妹群,遗传距离较小(Cyt b:1.85%)。考虑到不丹大鼯鼠和米什米大鼯鼠之间的遗传差异过小,分布区连续且栖息地都为中低海拔的常绿阔叶林,故两者应视为同一物种;又因两者之间的毛色差异稳定存在,可作为不同亚种,根据优先律,使用不丹大鼯鼠Petaurista nobilis(Gray,1842)做为种名,米什米大鼯鼠降为不丹大鼯鼠米什米亚种(Petaurista nobilis mishmiensis Choudhury,2009)。李氏小飞鼠西藏种群毛色、头骨和颊齿特征与云南西北部种群一致,但体型较小,且阴茎长度、直径和形状有较大程度的变异;遗传上西藏种群是包含云南西北部种群的并系群,遗传距离较小(12S ribosomal RNA:0.45%~0.91%,16S ribosomal RNA:0.31%~1.05%)。不丹大鼯鼠为中国兽类新纪录,李氏小飞鼠为西藏自治区兽类新纪录。本研究扩展了不丹大鼯鼠和李氏小飞鼠的分布区,提示应进一步加强喜马拉雅地区兽类的调查与监测研究工作,以发现更多的新物种、新纪录。

基于ISSA和IA^(*)的AGV集成作业调度及其路径规划

针对单一算法在求解车间调度和路径问题时最优性和多样性方面的缺陷,提出了优化飞鼠搜索算法ISSA(improved squirrel search algorithm)和优化A^(*)算法并建立集成作业调度和AGV路径规划的双层模型。首先,采用贪婪策略融合飞鼠搜索算法建立考虑能耗的AGV集成作业调度上层模型;其次,将安全距离因子引入A^(*)算法,构建AGV路径规划下层模型,并通过梯度下降法进行路径平滑;进而,运用6个测试函数和kacem实例验证ISSA的寻优能力,结果表明ISSA的其收敛速度较快,运行效率较高,且不容易陷入局部最优;最后,基于栅格法建模进行对比仿真实验,IA^(*)比A^(*)算法拐点数量降低了22%,同时节约了21%的行驶时间,ISSA和IA^(*)均得到了良好的验证。结果表明,ISSA和IA^(*)能够更有效求解AGV集成作业调度及其路径规划问题。

机车牵引电机转子模态试验及仿真优化研究

牵引电机转子作为电机旋转的核心,转子的固有频率应避开实际的工作频率、工作转速。基于软件的有限元分析法是目前在设计阶段应用最广泛的固有频率计算方法,而影响计算结果准确性包括材料参数、各部件间的实际接触状态等。通过LMS公司的采集系统进行实际模态测试,并采用Ansys的有限元分析法,考虑导条和端环、导条和铁心、铁心和转轴实际接触状态计算转子的固有频率。根据实际模态测试结果,以验证Ansys计算结果的实效性,为进一步提高牵引电机转子模态仿真精度提供有益参考,也为进一步改进转子结构,保证转子在实际运行中不会发生共振提供依据。

虚拟同步发电机参数设计及优化研究

虚拟同步发电机的参数众多,参数设计较为复杂,常规方法难以保证设计效果。针对该问题,采用控制变量的方法改变阻尼系数、转动惯量、下垂系数和积分系数值大小,在分析比较不同参数值下虚拟同步发电机的有功、无功动态响应效果的基础上,通过建立以系统动态响应稳定性能为目标的优化函数,提出了一种基于松鼠搜索算法的虚拟同步发电机参数优化设计方法。仿真结果表明,提出的参数优化设计方法能够更准确地选择出合理参数,有效提升了虚拟同步发电机的动态响应性能,具有较好实用性。

鼠笼式电机转子钎焊模卡导条拉脱原因分析及解决措施

某型机车牵引电机鼠笼式转子端环与导条模卡钎焊外观检查合格后进行拉伸试验,部分端环-导条钎焊接头的导条从焊缝位置拉脱,不能满足抗拉强度要求。为解决该问题,通过渗透探伤和宏观检测发现端环内侧与导条的钎缝界面存在微裂纹、钎料填充不致密和分层等缺欠。端环-导条结构设计不合理以及钎焊高温持续时间不足是导致拉脱问题的主要因素。针对这两个因素提出了改进方案:端环槽深由6 mm改为4 mm、增加端环槽内侧45°倒角,冬季钎焊时450℃保温时间延长为90 s。改进后经拉伸试验验证,成功解决了导条拉脱的问题,保障了产品质量。

三相鼠笼异步电动机无传感器转速检测技术及其适应性

针对三相鼠笼异步电机无位置传感器快速傅立叶变换(fast Fourier transformation,FFT)测速方法需要预先知道转子槽数,且测试精度易受噪声干扰和采集时长等因素的影响,提出一种基于奇异值分解-Prony(singular value decomposition-Prony,SVD-Prony)算法的无位置传感器高精度转速测量技术。运用电机学相关理论,研究转子槽谐波测速机理,并给出整数倍率转子槽数的计算方法。在分析并明确定子电流噪声影响和FFT法存在检测精度受采样时长限制等问题的基础上,研究基于奇异值增长率的SVD滤波方法和用于辨识转子槽谐波的Prony算法,并以Y160M-4型电机为研究对象,在不同运行状态下对该技术的适应性进行分析。在此基础上,构建相关物理测试平台,对YE90S-2型电机进行实测。结果表明,在相同采集情况下,所提方法测试绝对误差仅为FFT测速方法的几分之一,检测精度大幅提高。

融合松鼠搜索策略的混沌飞蛾算法

飞蛾算法是一种结构简单、配置参数少且适用范围广的群智能算法,但在收敛精度和收敛速度等方面还有待提高,且存在易收敛到局部最优的问题,为此提出一种融合松鼠搜索策略的混沌飞蛾算法。该策略采用sinusoidal混沌映射获取高质量初始种群;在飞蛾寻优过程中引入松鼠算法中松鼠的寻优途径,设置高质量火焰个体与近距离火焰个体指导飞蛾高质量寻优,通过余弦控制因子触发的捕食者概率促使飞蛾跳出原始火焰对其的吸引,提高飞蛾算法全局搜索能力;改造自适应t分布因子与火焰自适应减少公式,控制适应度较差的种群通过列维飞行进行随机迁移,增加算法的局部搜索能力。通过CEC2017测试集、CEC2022测试集与两个工程应用实例分别与其他15种智能算法进行对比验证,结果表明改进算法在收敛速度、搜索能力和跳出局部最优等方面具有一定优势。

鼠笼转子端部扭振特性研究及其对结构可靠性影响

针对变频器驱动下牵引电机受到谐波转矩的影响,分析了谐波转矩对铜条式鼠笼转子结构的作用机理。采用试验与仿真相结合的方法识别鼠笼转子端部特性。首先,通过模态分析,获取了鼠笼转子的模态参数;然后,建立了基于模态试验的转子等效有限元模型,分析了其在12倍频特征电磁激励下的静强度及谐响应。最后,基于导条振动测试平台,研究了鼠笼转子端部扭振特性,并对载荷放大效应进行了验证,为提升铜条式鼠笼转子端部结构的可靠性提供了一定的理论支撑。

一种用于DBMS模糊测试的自适应变异策略

数据库管理系统(DBMS)被广泛应用于各个领域,并在其中发挥着不可替代的作用.因此发现DBMS中的bug,防止其被攻击者利用至关重要.为了检测DBMS中潜藏的bug,研究者提出了DBMS模糊测试技术.使用这项技术,研究者成功在DBMS中发现了大量bug.然而现有的DBMS模糊测试技术依然存在一定的局限性.现有的技术在对SQL语句的抽象语法树(AST)进行变异时,没有根据不同节点和变异结果的重要性分配计算资源,而是采取了一种平均分配的策略,这降低了测试的效率.为了解决这个问题,本文提出了一种使用基于语法信息的变异方法的自适应变异策略.这种变异策略能够自动计算不同节点和变异结果的重要性,并根据重要性为更重要的操作分配更多的计算资源.基于语法信息的变异方法可以将变异操作与变异结果直接关联,消除了变异操作和变异结果之间的偏差.我们在一种新的DBMS模糊测试工具Pinecone中实现了这种变异策略,并使用Pinecone对两款广泛使用的DBMS进行测试.实验证明,与Squirrel相比,Pinecone在MariaDB和MySQL中发现的路径数分别提升了4.52%和19.4%,位图覆盖率分别提升了15%和13.8%,发现的Bug数量提升了26.7%和75%,这证明了本文提出的方法可以有效提升模糊测试的效率.

改进松鼠搜索算法求解分布式节能柔性调度

为了优化同时考虑最大完工时间和机器能耗的双目标分布式柔性作业车间调度问题,提出了一种改进的多目标松鼠搜索算法。引入了基于升序排列规则的转换机制,实现了松鼠位置向量与调度解之间的转换,并针对机器空闲时间设计了从半主动到主动的解码策略。针对不同优化目标设计了三种种群初始化策略。同时提出了动态捕食者策略来更好地协调算法的全局探索和局部开发能力。设计了四种领域搜索策略用于增加种群多样。20个实例上的实验结果验证了改进后的算法求得解的质量和多样性更好,从而证明了其可有效求解分布式节能柔性调度问题。

达乌尔黄鼠季节性肥胖与胰腺功能稳态

储脂类冬眠动物在入眠前的育肥阶段大量积累体脂作为越冬的重要能源物质。达乌尔黄鼠(Spermophilus dauricus)在短短2~3个月的育肥期间体质量增加近1倍,然而该物种快速育肥过程是否引起糖脂代谢的紊乱以及类似于人类肥胖相关的代谢异常尚不清楚。在本研究中,我们检测了育肥不同阶段黄鼠血糖含量、糖耐受情况、血清和非脂肪类器官中甘油三酯和游离脂肪酸含量以及血清中胰岛素和胰高血糖素含量。结果显示,达乌尔黄鼠在育肥期间血糖保持稳定,心脏、肝脏及肾脏等非脂肪类器官中甘油三酯和游离脂肪酸含量无显著性变化。血清中甘油三酯及胰岛素含量无显著性差异,但游离脂肪酸含量显著升高,胰高血糖素含量显著下降。这些结果说明,达乌尔黄鼠在育肥期间并没有产生高血糖、高血脂、脂质异位堆积和胰岛素抵抗等症状。育肥期间胰高血糖素的降低或许是维持其血糖稳定的机制之一。此外,在冬眠之前,黄鼠胰岛面积以及胰岛细胞数目呈现增加趋势,提示育肥期间可能存在胰岛细胞新生,这可能与育肥期间胰岛功能维持有关。达乌尔黄鼠作为储脂类的冬眠动物,具有独特的体脂积累机制,或将为肥胖引起的代谢综合征的治疗提供借鉴。

益口槟葛对金黄地鼠健康的影响研究

目的:研究连续嚼食基于葛根制备的槟榔风味咀嚼块益口槟葛4周对金黄地鼠的健康影响,评估益口槟葛的嚼食安全性。方法:将40只金黄地鼠随机分为4组,分别为空白对照组、葛根组、益口槟葛组和槟榔组,每组10只。空白组金黄地鼠用10%水合氯醛以3mL/kg剂量进行麻醉,以保证各组处理条件一致,其他实验组金黄地鼠在麻醉后将葛根、槟葛或槟榔(均切碎呈小颗粒状)塞至两颊,每2天1次,共持续给药4周。每两周用游标卡尺测金黄地鼠口腔开合度;第4周对各组金黄地鼠进行高架十字迷宫实验,评估葛根、益口槟葛和槟榔对金黄地鼠行为能力的影响;饲喂嚼食4周后,处死各组金黄地鼠,检测各主要脏器指数、肝转氨酶活性,评估其生理健康状况;取颊囊组织进行染色,并提取RNA,检测与口腔黏膜下纤维化有关的关键基因表达情况。结果:饲喂4周后,各实验组地鼠摄食量及体质量出现明显下降。槟榔组转氨酶显著升高,肾指数各组间无明显差异。各组地鼠颊囊无明显外观改变,开口度无明显差异,组织染色结果显示各咀嚼组出现一定的黏膜组织改变,槟榔组出现更明显的炎性细胞浸润。mRNA水平上的纤维化相关基因差异表达提示,槟榔咀嚼组出现一定的口腔黏膜下纤维化征兆,益口槟葛组尚不明显。此外,高台十字迷宫实验结果表明,嚼食益口槟葛后,金黄地鼠活动兴奋性显著提高,表现出强烈的探索意识。结论:持续4周嚼食益口槟葛对金黄地鼠的健康无明显影响,未见对口腔的损伤,同时具有较好的神经兴奋作用。

基于高通量测序的贵州北部地区红腿长吻松鼠秋季食性分析

红腿长吻松鼠(Dremomys pyrrhomerus)是一种主要分布于我国的长吻松鼠,但对其生物学和生态学特征鲜有研究报道。为揭示红腿长吻松鼠的食物种类组成及其取食偏好,运用高通量测序技术对贵州北部地区采集的红腿长吻松鼠进行食性分析。结果表明:红腿长吻松鼠所食植物包含4门85科180属,动物包含3门59科71属,其中,胡桃科(Juglandaceae)、禾本科(Poaceae)、壳斗科(Fagaceae)、蔷薇科(Rosaceae)、鼠李科(Rhamnaceae)和樟科(Lauraceae)等是红腿长吻松鼠主要的植物性食物,而田螺科(Viviparidae)、蚌科(Unionidae)、剑水蚤科(Cyclopidae)、沼大蚊科(Limoniidae)、管蓟马科(Phlaeothripidae)和螽斯科(Tettigoniidae)等是其主要的动物性食物。此外,不同性别红腿长吻松鼠的食性具有一定的差异性,雌性红腿长吻松鼠的食物多样性均高于雄性,雌性和雄性的植物性食物重叠度较高,而动物性食物重叠度较低。研究结果丰富了黔北喀斯特台原地区小型哺乳动物的摄食生态学。

异步电动机的转子断条问题研究

讨论了异步电动机转子断条故障的特征机理,介绍了通过定子电流监测进行故障诊断的方法。概述了鼠笼式异步电动机转子断条故障可能由机械应力、过载电流和设计缺陷等因素引起,并强调了这种故障对电机性能的负面影响,包括转速异常、噪声增大和潜在的安全风险。提出了通过监测气隙磁场变化和定子电流频谱分析来诊断故障的方法。在正常情况下,电机磁动势平衡对称,而转子断条破坏了这种对称性,导致转矩波动和平均转矩下降。通过对定子电流进行频谱分析,检测到特定的谐波分量。提出结论,尽管传统理论侧重于基波的影响,实际上其他定子电流成分也参与了谐波的生成,并且可以通过监测特定频率的谐波分量来判断转子是否存在断条故障。