STIFFNESS ANALYSIS OF THE MAIN MODULE FOR PARALLEL MACHINE TOOLS BY FINITE ELEMENT ANALYSIS

With the aid of commercial finite element analysis software package ANSYS,investigations are made on the contributions of main components to stiffness of the main module for parallel machine tools,and it is found that the frame is the main contributor.Then,influences of constraints,strut length and working ways of the main module have also been investigated.It can be concluded that when one of the main planes of the frame without linear drive unit is constrained,the largest whole stiffness can be acquired.And,the stiffness is much better when the main module is used in a vertical machine tool instead of a horizontal one.Finally,the principle of stiffness variation is summarized when the mobile platform reaches various positions within its working space and when various loads are applied.These achievements have provided critical instructions for the design of the main module for parallel machine tools.

Novel Electro-Optical Modulator Utilizing GeO_2-Doped Silica Waveguide

In order to achieve a modulator with broad bandwidth and perfect impedance match,a novel electro-optical modulator based on GeO2-doped silica waveguides on silicon substrate is designed.The finite element model of the whole electro-optical modulator is established by means of ANSYS.With the finite element method analysis,the performance of the novel modulator is predicted.The simulation reveals that the designed modulator operates with a product of 3 dB optical bandwidth and modulating length of 226.59 GHz·cm,and a characteristic impedance of 51.6 Ω at 1 550 nm wavelength.Moreover,the calculated electrical reflected power of coplanar waveguide electrode is below-20 dB in the frequency ranging from 45 MHz to 65 GHz.Therefore,the designed modulator has wide modulation bandwidth and perfect impedance match.

A compact electro-absorption modulator based on graphene photonic crystal fiber

A compact electro-absorption modulator based on graphene photonic crystal fiber is proposed. To enhance the graphene–light interaction efficiency, the innermost six air-holes of photonic crystal fiber are replaced by two large semicircular holes, and monolayer graphene is deposited on the two large semicircular holes. By optimizing the structure parameters, a strong graphene–light interaction is obtained. Moreover, the switch on–off point of the modulator is unchangeable,which is only related to the frequency of the incident light. The influence factors of this composite structure have been analyzed. The proposed modulator is compared with other graphene-based modulators, and the results show that it is filled without dielectric spacer. There are some excellent performances, such as an extinction ratio 7 dB of y-polarization mode,3-dB modulation bandwidth of 70 GHz with small footprint of 205 μm, and a consumption of energy per bit 59 pJ/bit.

Optimal design of modular dual-field modulated permanent magnet linear motors with thrust characteristics

To reduce thrust ripple and cost and improve the average thrust of permanent magnet linear motors,a modular dual-field modulation permanent magnet linear motor was studied,and the parameters were optimized.First,sensitive parameters were selected using the Taguchi method,and then the optimal variables were sampled using the optimal Latin hypercube experimental design method and an ensemble of surrogates model of optimization objectives,and its accuracy was verified.Next,a multi-objective particle swarm optimization algorithm was used to optimize the purpose of“maximum average thrust and minimum thrust ripple”,and the Pareto front of average thrust and thrust ripple was obtained.Finite element analysis showed that the optimized modular dual flux-modulation permanent magnet linear motor(MDFMPMLM)had a 29.5%reduction in thrust ripple and a 5%increase in average thrust compared to the original motor.This study provided an effective method for improving the performance of permanent magnet linear motors.

基于ANSYS ACP的高温复合材料设计分析

由于在航空航天和核工业中存在超高温工况,结构对材料耐高温、耐腐蚀、高强度性能提出了较高要求,此外较低的材料密度也是提升结构轻量化水平的重要性能。碳化硅陶瓷基复合材料因具有低密度、耐高温、高强度等特点,已经在相关领域表现出较大的潜力,并且已有较成熟的工程应用。本文以SiCf/SiC复合材料(碳化硅作为陶瓷基体,SiC纤维作为增强体)为对象,简要论述了国内外相关研究人员对碳化硅陶瓷基复合材料制备加工工艺的研究,根据其各向异性、非均质性以及双模量等特征,结合具体实例进行分析,建立了一种基于ANSYS ACP技术的复合材料设计分析方法,初步形成针对耐高温结构复合材料建模和仿真优化分析的解决方案。

新型定子永磁游标电机的设计与分析

提出了一种在定子结构上的新型外转子永磁游标电机拓扑结构,在电机定子上引入了有对磁场调制作用的调制齿,通过对调制齿进行设计改动,实现了对磁场的充分利用,使得电机具备较低的齿槽转矩和稳定的电磁转矩。详细阐述了新型定子外转子永磁游标电机的工作原理,提供了具体的二维结构示意图以及设计参数,针对其电磁性能、气隙磁密、空载反电动势和谐波分布进行了分析说明。研究结果说明,这种新型定子外转子永磁游标电机具有有效的谐波调制作用,同时齿槽转矩有明显的降低,并能实现较平稳转矩输出。

Optical modulation of repaired damage site on fused silica produced by CO2 laser rapid ablation mitigation

CO2 laser rapid ablation mitigation(RAM)of fused silica has been used in high-power laser systems owing to its advantages of high efficiency,and ease of implementing batch and automated repairing.In order to study the effect of repaired morphology of RAM on laser modulation and to improve laser damage threshold of optics,an finite element method(FEM)mathematical model of 351 nm laser irradiating fused silica optics is developed based on Maxwell electromagnetic field equations,to explore the 3D near-field light intensity distribution inside optics with repaired site on its surface.The influences of the cone angle and the size of the repaired site on incident laser modulation are studied as well.The results have shown that for the repaired site with a cone angle of 73.3°,the light intensity distribution has obvious three-dimensional characteristics.The relative light intensity on z-section has a circularly distribution,and the radius of the annular intensification zone increases with the decrease of z.While the distribution of maximum relative light intensity on y-section is parabolical with the increase of y.As the cone angle of the repaired site decreases,the effect of the repaired surface on light modulation becomes stronger,leading to a weak resistance to laser damage.Moreover,the large size repaired site would also reduce the laser damage threshold.Therefore,a repaired site with a larger cone angle and smaller size is preferred in practical CO2 laser repairing of surface damage.This work will provide theoretical guidance for the design of repaired surface topography,as well as the improvement of RAM process.

Fast Calculation of Electromagnetic Forces in IPMSMs Under PWM VSI Supply Based on Small-Signal Time-Harmonic Finite Element Method

This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.

《有机化学》课程知识模块重构探究——以金属有机化合物和羰基化合物反应为例

《有机化学》课程知识内容庞杂,章节之间知识点内在关联多,易混淆,本文以金属有机化合物和羰基化合物反应为例介绍“知识模块重构”教学方法。该方法内容上不仅将跨章节具有联系的知识点进行深层次分析总结,重构成新的教学内容,还将实验、科研新成果和思政元素融入重构内容的基础教学中;教学上采用多维度启发、多种教学方法相结合,充分发挥学生的主动性;形成“新思维、多手段、全方位”的教学模式,达到全面提升学生专业素养和综合能力的目的。

齿轮箱内部激励下振动噪声仿真研究

目的研究齿轮箱体在内部激励下的传动稳定性和振动噪声的产生、传播和辐射规律。方法考虑时变刚度、误差激励等因素对齿轮系统的影响,利用集中参数法建立齿轮传动纯扭转动力学模型。结合MATLAB数值计算,从动态啮合力入手,分析振动噪声在内部动态激励作用下的时域和频域特征。建立齿轮箱体有限元模型,进行模态分析和频率响应分析。以动力学分析结果为边界条件,分别利用声学无限元法和无反射边界法进行齿轮箱振动噪声仿真。结果获得了2000Hz内的固有频率、振型和频率响应曲线,结合振动峰值频率,对齿轮箱的振动情况进行了预测。得到了齿轮箱在无界声场中的辐射声功率级曲线、场点声压级曲线、声指向性和声压级云图,并对声学无限元法和无反射边界法的计算结果进行了对比,得到了二者的最佳适用条件。结论齿轮箱内部动态激励具有明显的周期性和冲击性,齿轮传动过程中含有较多的啮合频率和二倍频成分。齿轮箱上下表面为薄壁结构,振动比较明显,是各阶振型发生振动的主要部位。箱体在低阶模态下为单一振型,在高阶模态下出现多种振型耦合的现象。无限元法计算时间较长,但在近场分析时精度较高,适用于近场声学问题分析。无反射边界相比于无限元法耗费更少的计算时间,远场分析的精度更高,适用于高频、远场声学问题分析。

基于惯性环节的光伏组件实时热模型

提出一种基于一阶惯性环节的光伏组件温度的实时计算方法,首先,对光伏组件进行传热特性分析,基于一维非稳态导热分析解,推导基于一阶惯性环节的光伏组件温度简化计算模型;然后,使用遗传算法与拟牛顿法串行优化方法,通过数据驱动方式快速确定模型中的参数;最后,使用该文提出的模型,基于BP、LSTM的温度预测模型和传统经验公式对某光伏场站的组件温度进行分析和预测。对比结果表明:该方法表现出良好的预测精度,均方根误差<2℃,且部署模型所需的计算规模更小,运算速度可达神经网络的10倍以上,方便应用于实际控制系统中,且与神经网络方法相比更具可解释性,可作为一种实时计算光伏组件温度的有效方法。

中心距误差对小模数齿轮接触与弯曲强度的影响

为探究小模数齿轮中心距误差对轮齿强度的影响,以及标准GB/T 3480—2021对含中心距误差小模数齿轮强度设计的适用性,推导了含中心距误差的重合度系数、齿廓系数与应力修正系数计算公式,建立了含中心距误差的小模数齿轮有限元接触模型,提出有限元接触模型网格密度的验证方法.对2种计算方法得到的不同中心距误差下接触与弯曲应力进行了对比研究,结果表明,接触区域齿廓有限单元宽度不超过Hertz接触半宽的1/3时,齿轮有限元接触计算精度较高;采用标准GB/T 3480—2021校核含中心距误差的小模数齿轮强度,将产生冗余设计;当中心距误差达到1.33%时,接触应力幅值的最大变化为4.23%,而弯曲应力幅值的最大变化达到了16.25%,中心距误差对小模数齿轮弯曲应力的影响比接触应力更为显著.

计及IGBT模块键合线与芯片焊料层老化的热网络法结温计算

文中提出一种计及IGBT模块键合线与芯片焊料层老化的热网络法结温计算,基于Simulink对短时间尺度下损耗与结温的相互依赖关系进行更新,并分别通过双脉冲测试及有限元仿真修正长时间尺度下键合线与芯片焊料层老化对IGBT结温计算的影响,在此基础上,根据芯片焊料层不同老化状态下键合线的应力特征,实现两种老化模式的相互关联,较为准确地计算IGBT结温。最终利用试验平台与传统结温计算方法进行对比验证了所提结温计算方法的准确性。该结温计算方法有助于在实际运行工况及IGBT模块老化状态下精确计算结温。

基于HOE的全息显示双目视差构建方法

全息光学元件(Holographic Optical Element,HOE)是全息三维显示的重要器件之一。为了解决HOE用于双目全息显示时视差不匹配的问题,本文提出并实现了一种基于HOE的全息显示双目视差构建方法,同时对元件成像时的像差进行了分析校正。通过对HOE的制作原理和成像规律分析,结合光线跟踪技术渲染的虚拟模型和现实场景模型,设计了基于HOE的全息双目显示系统,提出了双目视差构建方法,即在获取人眼坐标位置时为观察者实时提供包含双目视差关系的视点图像。通过进一步分析全息显示系统内部的图像畸变产生原因及过程,提出了去畸变的优化处理算法。实验结果表明,提出的方法不仅能够实现HOE实时显示全息三维图像,而且解决了HOE在全息双目显示中视差不匹配以及成像畸变的问题。

小型线性斯特林制冷机驱动控制方法研究

为了设计一种能使小型线性斯特林制冷机快速启动并获得高效功率输入的控制器,设计了基于STM32F407单片机的驱动控制器。根据控制器的输出电气参数对制冷机中的直线电机部分进行有限元仿真,仿真中未出现磁路饱和现象。基于传统的“低压启动,手动调节至高压运行”的制冷机启动方法,提出了“半压启动,线性升压,高压运行”的制冷机自动启动方法,在避免活塞撞缸的同时加快了制冷机制冷过程。通过脉宽调制技术将制冷机驱动波由正弦波转变为梯形波,以提高逆变电路的直流母线电压利用率。研究结果表明:梯形波驱动方式实现了制冷机输入功率约25 W的提升,制冷量也有相应提高。

薄壁舱体构件电子束焊接变形模拟分析与优化

大型、多焊缝的薄壁类航天舱体构件在电子束焊接后,存在焊后变形校正难的问题,模拟计算可以预测变形趋势并优化焊接工艺以获得最小变形量。该文对铝合金航天用舱体结构进行了焊接过程的数值模拟,采用平板结构进行了有限元模型的建立与校核,对舱体结构进行了建模,研究了焊接顺序、焊接工艺参数对焊后最大变形量的影响及构件焊后变形趋势。结果表明,构件整体弯曲变形,优先焊接2条纵缝会导致较大的变形量,热输入越大,构件焊后变形量越大。在达到6 mm熔深时,采用高焊接速度35 mm/s及较小的功率5.4 kW可以获得最小的焊接变形,为0.35 mm。该文为薄壁大型舱体结构焊接工艺参数优化提供了依据。

45°双驱动弹光调制高速椭偏测量方法

为解决传统机械旋转补偿器型椭偏仪测量速度较慢问题,提出一种电驱动的双弹光调制的高速椭偏测量方法。通过理论分析并仿真研究45°双驱动弹光调制器工作在纯行波模式下的调制方式。结果发现,当双驱动弹光调制器工作在纯行波模式可实现快轴方向的高速周期性旋转,且相位延迟量为常量。结合椭偏原理,详细研究一种基于双驱动弹光调制的高速椭偏测量理论模型,结果表明,该模型光学周期<10μs,用于实际可真正实现超高速偏光调制。通过研究,有望解决半导体集成电路,微电子和光伏电池等生产过程中薄膜超高速检测难题,对薄膜在线检测、瞬态变化测量具有重要意义和学术价值。

扦样机混样模块的有限元分析

中国作为粮食大国,历来重视粮食储存安全问题。目前,国内粮库一般使用扦样机对仓内粮食进行抽样检测,但是准确率较低。因此,高质量的扦样设备更能保证粮食检测结果的准确性。以电机驱动的扦样机的混样模块为研究课题,主要研究任务是对该混样模块进行有限元分析,主要研究任务有以下几个部分:使用EDEM离散元软件,确定工作过程中各部件的受力大小;将混样模块的模型导入进有限元分析软件中,对其进行前处理;分析该模块的受力情况,并提取其中最容易断裂的搅拌叶片进行更精细的有限元分析。

颗粒物沉降对光伏资源影响的模型研究进展

归纳并比较了与积尘密度、积尘组分、积尘颗粒形态及积尘消光参数等积尘性质以及相对湿度、降水量和降水强度、风速与风向等气象要素相关的积尘对光伏发电影响的模型,梳理了各因素之间的相互关系,发现积尘密度是最主要的因素。然后提出了新的光伏资源分布评估流程,最后进行了展望:1)积尘密度不等价于颗粒物干沉降累积通量,可根据颗粒物受力机制与湿沉降过程作修正。2)需开发验证方法比较各模型评估结果的差异,并评价不同来源的数据对模型评估结果的影响。3)微观影响机制的量化建模方法有待进一步发展。4)模型可与清洗规划模型耦合,得到颗粒物沉降对光伏电站运行成本影响的空间分布,或将颗粒物沉降对光伏组件发电量的影响转化为碳排放量,评价不同减排策略对实现“双碳”目标的影响。

分裂齿集中绕组永磁游标电机电磁转矩特性分析

为了研究分裂齿集中绕组永磁游标电机(PMVM)的电磁转矩特性,基于磁场调制原理建立PMVM的磁动势磁导模型,给出永磁体和电枢绕组单独作用下气隙磁密谐波的次数和转速表达式,分析产生平均转矩和转矩脉动的谐波次数。采用麦克斯韦应力张量法计算各主次谐波产生转矩的大小,确定各主次谐波对电磁转矩的影响。通过有限元分析对结果进行了验证。结果表明:PMVM的电磁平均转矩绝大部分由16次谐波产生,占比98.83%,转矩脉动主要由16、34、48次谐波产生,占比52.29%。PMVM电磁平均转矩的来源主要为永磁体产生的气隙磁密基波,因此可改变永磁体的用量和形状增大其产生的气隙磁密基波以提升PMVM电磁转矩性能。