Research on Cogging Force Suppression for Toroidal PMLSM Based on Disturbance Observer

For a new type of toroidal permanent magnet linear motor(TPMLSM), this paper analyzes the thrust fluctuation in the constant acceleration operation of the motor from the Angle of the cogging force of the linear motor. For the motor whose structure has been determined and processed, the structural parameters of the motor cannot be changed, and its performance cannot be improved from the perspective of the motor body.Therefore, this paper tries to consider the influence of the cogging force on the normal operation of the motor from the perspective of control. In this paper, starting from the body structure of motor, first on the annular linear motor of the cogging force characteristics were extracted, and its expression is obtained by Fourier decomposition, then investigated considering the cogging force and does not consider the cogging force control of motor model, it can be seen that the control performance deteriorates significantly after considering cogging force of the motor, and the acceleration fluctuation increases significantly during the operation of the motor. On this basis, disturbance observation algorithm is introduced, and feedforward compensation is carried out by extracting the characteristic values of the disturbance model. The results show that the disturbance observer can suppress the thrust fluctuation caused by the motor cogging force to a large extent, and it can reduce the peak-to-peak value of the thrust fluctuation by more than 85% during the motor acceleration operation.

基于PID与cogging力补偿的直线电动机控制

直线电动机cogging力是影响伺服控制定位精度和跟踪精度的重要因素。目前电动机几何结构优化与有效的控制策略是减小直线电动机cogging力的主要措施。在分析已有研究的基础上,提出了一种完全基于试验的cogging力迭代标定方法,并结合PID位置/力控制策略实现了直线电动机cogging力的补偿。所提出的方法已在气浮结构运动平台上进行了验证,给出了cogging力迭代标定的试验结果,对比了cogging力补偿前后的伺服控制跟踪误差。结果表明了提出方法的实用性和有效性。

Reduction of Cogging Torque and Electromagnetic Vibration Based on Different Combination of Pole Arc Coefficient for Interior Permanent Magnet Synchronous Machine

Cogging torque and electromagnetic vibration are two important factors for evaluating permanent magnet synchronous machine(PMSM)and are key issues that must be considered and resolved in the design and manufacture of high-performance PMSM for electric vehicles.A fast and accurate magnetic field calculation model for interior permanent magnet synchronous machine(IPMSM)is proposed in this article.Based on the traditional magnetic potential permeance method,the stator cogging effect and complex boundary conditions of the IPMSM can be fully considered in this model,so as to realize the rapid calculation of equivalent magnetomotive force(MMF),air gap permeance,and other key electromagnetic properties.In this article,a 6-pole 36-slot IPMSM is taken as an example to establish its equivalent solution model,thereby the cogging torque is accurately calculated.And the validity of this model is verified by a variety of different magnetic pole structures,pole slot combinations machines,and prototype experiments.In addition,the improvement measure of the machine with different combination of pole arc coefficient is also studied based on this model.Cogging torque and electromagnetic vibration can be effectively weakened.Combined with the finite element model and multi-physics coupling model,the electromagnetic characteristics and vibration performance of this machine are comprehensively compared and analyzed.The analysis results have well verified its effectiveness.It can be extended to other structures or types of PMSM and has very important practical value and research significance.

Cogging Torque Reduction in Axial Flux PMSM with Different Permanent Magnet Combination

With the increasing requirement for the mechanical vibration and acoustic noise of the permanent magnet synchronous motor(PMSM)drive system,the demand for cogging torque reduction of PMSM has been considerably increased.To solve the problem of oversized cogging torque of axial flux PMSM,a rotor topology with hybrid permanent magnet is proposed to weaken the cogging torque.Firstly,the expression of the cogging torque of the axial flux motor is derived,and the influence of the pole-arc ratio of the permanent magnet on the cogging torque is analyzed.Secondly,the rotor structure with hybrid permanent magnet is adopted to reduce the cogging torque.According to the analytical analysis,the constraints of the size and pole-arc ratio between the hybrid permanent magnets are obtained,and the two permanent magnets related to the minimum cogging torque are determined.And the analysis results are verified by the finite element simulation.Furthermore,the motor performance with and without the hybrid permanent magnet is compared with each other.Finally,the cogging torque is significantly reduced by adopting a rotor structure with hybrid permanent magnets.

Analysis and Reduction of Cogging Torque in PM Torque Motors

The investigation involves detailed qualitative analysis and quantitative calculation of cogging torque in PM torque motors. The object of this analysis includes symmetric and non-symmetric motors, and the cause of the presence of Zth and 2Pth cogging torque is revealed.Then the optimum number of teeth per pole for both quasisquare and sinusoidal magnetic fields are presented. Finally, the experimental results are given.

Study on cogging force of permanent magnet linear synchronous motor

Presented the methods to obtain the cogging force of permanent magnet linear synchronous motors(PMLSMs), analyzed the characteristics of the cogging force, and provided a basis for reducing the effect of the cogging force. 2-dimensional finite element method(2D FEM) was used to solve the whole motor when its mover was at dif- ferent position, so that the relation was derived between the cogging force and the mover position. The analysis results show that the cogging force between the two ends of the primary iron-core and the secondary permanent magnets (PMs) is sinusoidal function of the mover position under certain conditions only. Two proposed methods, namely direct and indirect methods, are applied to calculate the cogging force between the primary iron-core teeth and the secondary PMs. The agreement of the two methods is validated.

Influence of Design Parameters on Cogging Torque in Directly Driven Permanent Magnet Synchronous Wind Generators

In order to reduce the cogging torque, this paper investigates the influence of some parameters on the cogging torque developed by directly driven permanent magnet synchronous wind generators. Based on the remanent magnetic flux densities, the cogging torque is computed by using finite element method. It is shown that many parameters have influence on cogging torque and the slot and pole number combination has a significant effect on cogging torque. A simple factor has been introduced to indicate the effect of the slot and pole number combination. Some practical experience to reduce the cogging torque was applied to 2 MW three phase permanent magnet synchronous generator at rated speed of 37.5 rpm for wind energy conversion. The simulation and experiment results verify the effect of the proposed method.

Winding Function Model-based Performance Evaluation of a PM Transverse Flux Generator for Applications in Direct-drive Systems

The magnetic flux in a permanent magnet transverse flux generator(PMTFG) is three-dimensional(3D), therefore, its efficacy is evaluated using 3D magnetic field analysis. Although the 3D finite-element method(FEM) is highly accurate and reliable for machine simulation, it requires a long computation time, which is crucial when it is to be used in an iterative optimization process. Therefore, an alternative to 3DFEM is required as a rapid and accurate analytical technique. This paper presents an analytical model for PMTFG analysis using winding function method. To obtain the air gap MMF distribution, the excitation magneto-motive force(MMF) and the turn function are determined based on certain assumptions. The magnetizing inductance, flux density, and back-electro-magnetomotive force of the winding are then determined. To assess the accuracy of the proposed method, the analytically calculated parameters of the generator are compared to those obtained by a 3D-FEM. The presented method requires significantly shorter computation time than the 3D-FEM with comparable accuracy.

Influence of Magnet Shape on the Cogging Torque of a Surface-mounted Permanent Magnet Motor

The influence of bread-loaf shaped magnet poles under parallel magnetization on the cogging torque of surface-mounted permanent magnet(SPM)motors is studied.For the SPM motors having magnetic poles with eccentricity and sine harmonic compensation,the electromagnetic performances of integer and fractional slot motors are compared.It is found that the cogging torque and torque ripple of the integer and fractional slot motors can be reduced with the same eccentric magnet pole.The cogging torque and torque ripple of a fractional slot motor can be decreased by sine harmonic compensation,however,the same sine harmonic compensation has a small influence in integer slot motors.By varying the magnetic poles,the contribution of the field harmonics(k=(2n+1)p),which are a direct result of magnet magnetization,to the cogging torque also changes.The electromagnetic performance of a 3 kW prototype is tested,and it is found that the experimental results validate the theoretical investigation.

The Characteristics Analysis and Cogging Torque Optimization of a Surface-Interior Permanent Magnet Synchronous Motor

This paper proposes optimal stator skewed slot analytical method for cogging torque reduction in surface-interior permanent magnet synchronous motor(SIPMSM)and analyzes the characteristics of SIPMSM.The series-parallel equivalent magnetic circuit models(EMCMs)of SIPMSM is built based on the characteristics of magnetic circuits,which is used to design the basic electromagnetic parameters of SIPMSM.Analytical expressions of cogging torque are derived from applying analytical techniques.Stator skewed slot for cogging torque minimum is adopted,and the stator skewed slot pitch is confirmed based on the analytical expressions of the resultant cogging torque.The cogging torque,torque ripple,back electromotive force(back-EMF),power-angle characteristics,efficiency and power factor of SIPMSM are analyzed by establishing 3-dimensional finite element model(3-D-FED)of SIPMSM with stator skewed slot and straight slot.It is shown that the comprehensive performance of optimized SIPMSM is improved as confirmed by finite element analysis and analytical calculation results.

基于MongoDB GridFS的遥感影像管理平台设计与开发

针对多源、多时相、多分辨率遥感影像的数据存储形式单一、管理和应用手段比较落后等问题,设计了一套基于MongoDB GridFS的海量遥感影像管理发布服务平台,使用GDAL对遥感影像进行数据处理和自动化混合切片、MongoDB存储影像切片数据和影像元数据、Mongo GridFS存储原始影像、HTTP文件服务器托管COG,构建了以原始影像-元数据-切片-COG为组织结构的遥感影像管理发布服务平台的数据基底,实现了遥感影像在线查询和预览、数据入库和分发等服务,为遥感影像在自然资源监测、生态环境保护、国土空间规划等领域的应用提供了有力支持。

Review of Design and Control Optimization of Axial Flux PMSM in Renewable-energy Applications

Axial flux permanent magnet synchronous motors(AFPMSMs)have been widely used in wind-power generation,electric vehicles,aircraft,and other renewable-energy applications owing to their high power density,operating efficiency,and integrability.To facilitate comprehensive research on AFPMSM,this article reviews the developments in the research on the design and control optimization of AFPMSMs.First,the basic topologies of AFPMSMs are introduced and classified.Second,the key points of the design optimization of core and coreless AFPMSMs are summarized from the aspects of parameter design,structure design,and material optimization.Third,because efficiency improvement is an issue that needs to be addressed when AFPMSMs are applied to electric or other vehicles,the development status of efficiency-optimization control strategies is reviewed.Moreover,control strategies proposed to suppress torque ripple caused by the small inductance of disc coreless permanent magnet synchronous motors(DCPMSMs)are summarized.An overview of the rotor-synchronization control strategies for disc contra-rotating permanent magnet synchronous motors(CRPMSMs)is presented.Finally,the current difficulties and development trends revealed in this review are discussed.

Analysis of an Axial-flux Slotted Limited-angle Torque Motor with Quasi-Halbach Array for Torque Performance Improvement

Better torque performance and higher reliability have long been the focus of research for slotted limited-angle torque motors(LATMs),which are primarily used to position first-stage valves in electrohydraulic servosystems.This paper presents a high reliability axial-flux slotted LATM with quasi-Halbach array for torque performance improvement including constant torque range(CTR)and output torque.Firstly,the structure with two sets of windings and the operation principle of the proposed slotted LATM is analyzed.Secondly,a brief design procedure is presented,the structure selections of open slot and double-stator single-rotor(DSSR)interior rotor with surface mounted quasi-Halbach permanent magnet(PM)array are illustrated,and the geometric parameters are optimized to obtain the optimal design of the proposed slotted LATM.Then,3-D finite-element method(FEM)is employed to compare the proposed slotted LATM with the conventional surface mounted PM slotted LATM in terms of cogging torque,no-load back EMF,and output torque,and the results show that the proposed LATM with quasi-Halbach array has a 10%improvement in output torque and a 25%improvement in CTR.Meanwhile,the flux linkages and torque performance of the two sets of windings under various conditions verify good magnetic isolation.Finally,prototypes of two different rotor types are manufactured and a series of experiments are performed to validate the analysis.

虾源达卡气单胞菌全基因组分析和致病性研究

目的为了解虾源达卡气单胞菌的毒力、耐药基因分布和全基因组信息,并初步评估达卡气单胞菌的致病性。方法对虾源分离株进行分子鉴定和多位点序列分型;利用β-溶血和胞外蛋白酶实验、秀丽隐杆线虫液体毒性实验、细胞毒实验、小鼠实验及毒力基因检测研究其致病性;通过药敏实验及耐药基因检测分析其耐药特征;利用eggnog、Prophage Hunter工具对全基因组序列进行分析。结果菌株18FX22鉴定为达卡气单胞菌。该菌的致病性主要表现:有β-溶血能力和胞外蛋白酶活性;对秀丽隐杆线虫、小鼠成纤维细胞和小鼠均有致病性。经检测,该菌携带7种毒力基因和12种耐药基因,发现其对阿莫西林/克拉维酸、头孢唑林和多粘菌素3种药物有耐药性。全基因组测序结果发现:18FX22的全基因组大小为4811079 bp,GC含量为61.33%。COG注释发现18FX22共有3850个基因,具有20类功能。前噬菌体预测结果发现18FX22的基因组中含有2个前噬菌体序列。全球达卡气单胞菌的聚类结果显示该菌与GCA016729585的进化关系更近。结论本研究从商品虾分离出达卡气单胞菌,发现该菌株的毒性较强,指示应加强海鲜食品安全的管控,并为达卡气单胞菌的防治提供参考。

COG1410对视网膜缺血-再灌注损伤小鼠视网膜神经节细胞的保护作用及其机制

目的探索载脂蛋白E模拟肽COG1410对小鼠视网膜缺血-再灌注(IR)损伤后M1/M2小胶质细胞极化及视网膜神经节细胞(RGCs)存活的影响及其可能的机制。方法将18只8周龄C57BL/6J雄性小鼠按照随机数字表法分为正常对照组6只、IR 3 d组6只、IR 7 d组3只和IR 14 d组3只,其中IR组小鼠使用生理盐水进行前房灌注,将眼压提高至100 mmHg(1 mmHg=0.133 kPa)并维持1 h,以建立视网膜IR损伤模型。取正常对照组和IR 3 d组各3只,采用视网膜冰冻切片免疫荧光染色法观察视网膜小胶质细胞的分布情况。取正常对照组、IR 3 d组、IR 7 d组和IR 14 d组各3只,通过视网膜铺片免疫荧光染色法观察视网膜M1型、M2型小胶质细胞随IR损伤后时间的变化。另取91只C57BL/6J小鼠按照随机数字表法随机分为正常对照组19只、IR组24只、生理盐水组24只、COG1410组24只,其中正常对照组小鼠维持正常眼压,其余3个组均建立IR损伤模型,且COG1410组和生理盐水组在造模后分别尾静脉注射1 mg/kg COG1410和等体积生理盐水。采用视网膜铺片免疫荧光染色法观察各组小胶质细胞表型及RGCs存活率;采用实时荧光定量PCR法检测各组视网膜肿瘤坏死因子α(TNF-α)、白细胞介素-1β(IL-1β)mRNA的相对表达量;采用TUNEL法观察视网膜神经细胞的凋亡情况;采用Western blot法检测各组视网膜核因子κB(NF-κB)、B淋巴细胞瘤2(Bcl-2)、Bcl-2关联X蛋白(Bax)蛋白的表达水平。结果正常对照组与IR 3 d组视网膜小胶质细胞主要分布在神经节细胞层、内丛状层和外丛状层。正常对照组、IR 3 d组、IR 7 d组和IR 14 d组M1型、M2型小胶质细胞数目总体比较差异均有统计学意义(F=29.83、57.62;均P<0.001);与正常对照组相比,IR 3 d组M1型小胶质细胞数量增多,IR 7 d组M2型小胶质细胞数量增多,差异均有统计学意义(均P<0.05)。正常对照组、IR组、生理盐水组、COG1410组M1型小胶质细胞比例分别为(4.25±0.57)%、(65.26±10.43)%、(63.01±4.93)%和(33.13±4.46)%,M2型小胶质细胞的数目分别为(4.50±0.20)%、(11.47±0.24)%、(11.75±0.17)%和(38.93±4.26)%,总体比较差异均有统计学意义(F=23.33、50.82;均P<0.05);与IR组比较,COG1410组M1型小胶质细胞数目减少而M2型小胶质细胞数目增多,差异均有统计学意义(均P<0.05);各组RGCs存活率及视网膜TNF-αmRNA、IL-1βmRNA相对表达量、凋亡细胞数目、NF-κB和Bax蛋白表达水平、Bax/Bcl-2值总体比较差异均有统计学意义(F=30.77、12.52、6.74、28.72、13.02、7.94、7.58,均P<0.05);与正常对照组比较,IR组RGCs存活率明显降低,视网膜凋亡细胞数增多,TNF-α和IL-1βmRNA表达量升高,视网膜NF-κB和Bax蛋白表达水平升高,Bax/Bcl-2比值升高,差异均有统计学意义(均P<0.05);与IR组比较,COG1410组视网膜RGCs存活率升高,TNF-α和IL-1βmRNA表达量降低,TUNEL阳性细胞减少,NF-κB和Bax蛋白表达水平降低、Bax/Bcl-2比值降低,差异均有统计学意义(均P<0.05)。结论视网膜IR后3 d,COG1410促进M1型小胶质细胞向M2型极化,抑制视网膜NF-κB及下游炎症因子表达,减轻视网膜炎症反应,同时抑制凋亡相关蛋白的表达,从而促进RGCs存活。

大垫尖翅蝗转录组分析

【目的】大垫尖翅蝗Epacromius coerulipes(Ivanov)是广泛分布的草原蝗虫之一,但其基因资源缺乏。为了获得大垫尖翅蝗的基因数据,对其进行了转录组测序和分析。【方法】利用Illumina公司paired-end转录组的测序技术进行从头组装。【结果】总计获得了63 033条unigenes,平均长度为772 bp,N50为1 589 bp。通过BLAST搜索,确定有25 132条(39.87%)unigenes与NCBI数据库已知的蛋白质相匹配,其中有24 841,16 490,11 558和8 013条unigenes成功注释到Nr,Swiss-Prot,GO和COG数据库中。KEGG数据库中,7 218条unigenes形成218条代谢或信息通路。其中,189条unigenes参与外源性物质或药物的代谢通路。进一步分析显示,213条unigenes被确认为可能参与外源性物质的解毒作用,29条unigenes被确定为编码杀虫剂的目标蛋白。此外,检测到5 696条简单重复序列。【结论】该转录组测序分析将为进一步研究大垫尖翅蝗的基因功能分析及杀虫剂的抗药性机制分析奠定分子基础。

擎天凤梨花器官全长cDNA文库的构建及EST分析

为了通过基因工程手段来培育花色丰富、花型奇特的擎天凤梨新品种,从擎天凤梨中筛选出花色、花型相关调控基因则是十分必要的。本研究以擎天凤梨属品种Ostara为材料,采用SMART技术成功构建了擎天凤梨花器官的质粒型全长cDNA文库,初始文库滴度为3×106,插入片段平均长度大于1kb;随机挑取2004个阳性克隆进行5'EST测序,获得高质量序列1758条,经拼接获得1365条单基因簇(unigene),其中跨叠群(contig)175个和单条序列(singlet)1195个;经ORF寻找共获得有效ORF1283条;经COG分析EST序列编码的蛋白质被分为22类;经Blast分析后,获得一批花色、花器官发育、花期调控以及其它育种价值基因(包括cDNA全长或片段)。该研究结果为擎天凤梨的花色、花型转基因等育种奠定了基础。

茶树品种福鼎大白茶和小雪芽叶片基因转录组研究

以茶树品种福鼎大白茶和低温诱导型新梢白化茶树品种小雪芽叶片为材料,构建基因转录本;组装得到79 797条茶树参考基因库(Unigene),其中,基因序列长度在1 000 bp以上的有11 371条,占Unigene库总数的14.25%。SSR分析显示,共有6 439条SSR,其中1～3个碱基的完美重复SSR占84.32%。基因表达丰度RPKM值显示,小雪芽表达上调的基因数为1 821个,表达下调基因数为1 779个。差异表达基因GO和COG分析显示,引起低温诱导型茶树新梢白化的可能遗传机理存在于蛋白质翻译后的修饰过程,而且这些变异主要发生在细胞内。

脑卒中患者下肢外骨骼康复机器人步态规划与运动学仿真

为满足越来越多的脑卒中患者辅助行走和康复训练的需要,设计了一款下肢外骨骼机器人模型,采用D-H参数法建立踝关节、膝关节、髋关节坐标系,推演出步态周期内的坐标方程。为了安全起见,要求脑卒中患者步行速度慢且步长短,利用CoG(Center of Gravity,重心地面投影点)作为步态规划中的稳定性判断依据,并用Robotics Toolbox for Matlab仿真,结果表明:下肢外骨骼康复机器人在康复训练过程中各关节具有连续且稳定的步态轨迹,为后续脑卒中患者使用的下肢外骨骼康复机器人样机研制提供了必要的理论依据。

基于Cog Tool的数字界面交互行为认知模型仿真研究

目的确定人在视觉信息搜索中的通用认知模式,归纳符合用户认知模式的基本设计准则。方法在用户需求一致性的前提下,通过Cog Tool可视化仿真模型将用户交互过程中的每一步骤进行拆解分析,找出用户在面对不同界面引导作用下的内在认知规律,并探讨界面布局的不同对用户搜索用时的影响,同时结合眼动实验,对比用户在实际操作过程中与模拟操作情况下的认知差异。结果通过Cog Tool的仿真分析与眼动实验相结合的实验数值对比,将用户在交互过程中的内在认知规律提取出来。结论本研究提出的面向界面布局的设计准则,可帮助设计师提高信息认知效率。