行波型球形超声电机定子的优化设计

提出了一种具有同步调心结构的球形超声电机,建立了电机驱动力矩的数学模型,重点对行波型定子进行结构优化设计。利用ANSYS对定子进行模态分析和谐响应分析;通过灵敏度分析确定结构参数优化变量,以最大干扰模态与工作模态频率差和最大定子表面振幅为优化目标,建立设计空间的响应面模型,采用多目标遗传算法(MOGA)进行优化求解得到Pareto前沿,最终确定结构参数并对定子试制件进行定扫频实验。测试结果表明,优化后的定子工作模态频率±2 kHz内无干扰模态产生,且定子两相驻波表面质点具有较大振幅,满足使用要求。     

微小型驻波超声电机定子振动特性的仿真分析

针对直径10 mm的两种驻波型超声电机定子的振动特性进行有限元仿真分析。利用ANSYS有限元软件建立定子的有限元模型,进行了振动模态及谐响应的仿真分析,获得定子的主要振动模态、模态频率及振幅。探讨了2种压电陶瓷及定子长度对其谐振频率和振幅的影响。研究结果表明,驻波型超声电机定子上斜槽或斜齿结构可实现模态转换,是实现电机驱动的关键。在分析的两种驻波型超声电机的8个定子中,采用PZT4压电陶瓷材料、长度16 mm的斜槽式超声电机定子的振幅值最大。     

单相驱动旋转型驻波超声电机的运动机理

尽管单相驱动的旋转型驻波超声电机的原型样机早已研制成功,但对这类电机的运动机理的研究却一直局限在定性研究上。对于单相驱动的旋转型驻波超声电机来说,定子上的齿是运动传递的关键部分。因此对齿的运动特性的研究对进一步研究定、转子的摩擦接触过程有很重要的意义。以单相驱动的旋转型驻波超声电机为研究对象,通过假设定子的振动模态法对单相驱动的旋转型驻波超声电机的定子上的齿的运动特性进行了理论推导,并作了计算机仿真研究,得出了齿的运动轨迹以及速度曲线。     

行波型杆式超声电机定子模态干扰的研究

行波型杆式超声电机定子模态干扰会造成电机工作效率低下,不稳定,难以控制等问题。首先利用有限元法和Hamilton理论,建立行波型杆式超声电机定子的动力学有限元模型;其次进行模态分析,求解各模态频率对定子结构参数的灵敏度,以此为依据进行结构参数调整,实现定子工作模态与干扰模态分离;最后制作了定子样机。其模态试验结果表明达到了模态分离的目的:定子工作模态频率至少在2 kHz范围内不存在其他干扰模态,从而验证了该方法的有效性。     

解决超声电机定子模态混叠的有效方法

针对超声电机定子在设计过程中的模态混叠现象,从定子的灵敏度分析出发,利用有限元法,计算出旋转型行波超声电机定子的模态频率对各结构参数的灵敏度,寻找出分离超声电机定子工作模态与非工作模态的一般方法。文中以南京航空航天大学超声电机研究中心研制的某TRUM-60旋转型行波超声电机为例,对其工作模态与非工作模态进行了分离,计算结果表明,该文提出的方法能很好的把工作模态与非工作模态分开。试验也证明该办法是行之有效的。     

SAMCEF在超声波电机设计中的应用

在微机电领域中,为获得超声波电机的振动模态及谐响应特性,利用SAMCEF有限元分析软件对直径为50 mm的环形行波型超声波电机压电转换器和定子的振动状态进行了分析;在完成超声波电机定子建模的基础上,进行振动模态分析和最优模态选择,并在此基础上进行了谐响应分析。分析结果表明,利用SAMCEF软件对超声波电机进行分析被证明是一种行之有效的方法。     

环形直线行波超声电机定子的模态分析

针对一类环形封闭式的行波型直线超声电机定子的振动模态进行了有限元与实验研究。该类电机的定子由两个半圆环和两段直梁构成。分析了有限元的单元尺度对固有频率及频率差的影响以及压电陶瓷片的粘贴位置对固有频率及弯曲振型的影响。对自行研制的超声电机进行了实验研究。实验结果表明，固有频率差的数值计算值与相应的共振频率之差吻合。     

行波型方孔定子超声电机结构设计与性能分析

该文提出了一种新型的方孔定子行波超声电机,并进行了参数设计、仿真分析和实验研究。定子由1个方孔金属体和4块压电陶瓷片组成,通过与直径大于定子内边长的转子配合发生弹性变形,从而对转子产生预压力,便于驱动。利用有限元软件对定子进行模态分析,选择第三阶模态作为工作模态,得到定子最大振幅与激励频率、电压、壁厚、边长及圆角半径的关系,并研究了频率、电压及预压力对转子输出特性的影响。制作了实体样机并测试了其输出特性,测试表明,当电压为100 V、激励频率为31.5 kHz时,其空载转速为215 r/min,堵转力矩达到1.58 mN·m。     

一种不对称激励直线型驻波超声电机的研究

设计研制了一种新型的不对称激励的单足直线型驻波超声波电机,电机定子为一块尺寸为26 mm×13 mm×2 mm (X,Y,Z)矩形铜板和对称粘结其上表面的两块压电陶瓷片组成的复合结构.电机只有一种振动模态且只需单一频率驱动,利用不对称激励使驱动足端产生椭圆运动,不需调整不同模态的频率一致性,结构简单.通过有限元分析确定了电机的结构尺寸,由谐响应分析对电机的激励工作机理进行了分析.最后对制作的样机进行了实验测试,试验结果与理论设计一致.在激励电压为150 V,激励频率为151.9 kHz的激励条件下,测得电机最大输出推力为0.855 N,电机速度为260 mm/s.     

TWUSM振动模态鲁棒滑模观测器研究

考虑到行波型旋转超声电机（TWUSM）控制精度与定子两相振动模态有关,但其不易测量。因此,该文提出了一种具有参数鲁棒性的滑模观测器以实现优化定子振动模态。首先,分析定子两相振动模态及合成行波对TWUSM高精度控制的影响;其次,利用电机可测的电流、电压信号建立振动模态滑模观测器,分析TWUSM参数时变特征,并证明观测器的稳定性与鲁棒性;最后,通过仿真与实验对所提出的振动模态滑模观测器进行验证。结果表明,滑模观测器能准确估计两相振动模态,且具有参数鲁棒性。此外,基于观测结果改善驱动电压,实现定子振动模态优化,从而降低输出转矩脉动,提高电机控制精度。     

Analysis of Radiation from a Traveling-Wave Current and Comparison with the Standing-Wave Sinusoidal Current Filament

The traveling-wave current (TWC) has served as one kind of "canonical" current distribution for simulating the behavior of a wire antenna, as has the standing-wave, sinusoidal current filament (SCF). Besides yielding closed-form solutions for their far-field patterns and radiated powers, the sinusoidal current filament and traveling-wave current can approximate the current on a wire antenna that is appropriately excited. The traveling-wave current's power distributions, as obtained using the induced EMF method and the FARS (far-field analysis of radiation sources) method, together with similar results for the sinusoidal current filament, are discussed in this brief note     

Input impedance of annular ring microstrip antenna using circuit theory approach

Input impedance and bandwidth of an annular ring microstrip antenna have been determined by modeling the antenna as a section of radial line loaded with wall admittances. The effect of mutual coupling between the radiating apertures has been taken into account. The theoretically calculated values of input impedance for TM12-mode are compared with measurements. The agreement is good. Higher order modes have been found to be present in the vicinity of TM12-mode. The reactance due to these modes can be utilized to increase the voltage standing-wave ratio (VSWR) bandwidth of the antenna.     

N-beam nonlinear traveling-wave amplifier analysis

In large-diameter electron stream traveling-wave amplifiers there is a significant variation of the circuit electric field across the stream. Most analyses neglect the effects of these field variations. An approximate method has been used to study the effect of transverse field variations on the gain and effciency of large-signal traveling-wave amplifiers. The annular electron stream is subdivided into a number of annular rings each containing an equal fraction of the total current. It is assumed that the circuit field varies over the stream cross section and that each segment has a different coupling to the circuit. The space-charge field is assumed independent of radius. The effect on gain and efficiency is calculated for a stream diameter of B = 1 and it is found that a subdivision of the stream into two segments with different couplings to the circuit gives a lower saturation efficiency but that further subdivision does not appreciably charge the results.     

Electromagnetic Field-to-Wire Coupling in the SHF Frequency Range And Beyond

Methods have been developed for the treatment of field-to-wire coupling at superhigh frequencies (SHF's) and beyond. In this region, transmission-line lengths and wire separations become very large electrically, and field-to-wire coupling problems become intractable. Several types of transmission lines have been examined in the SHF range, including uniform and nonuniform transmission lines, coaxial transmission lines, and multiconductor transmission lines. Current distributions are found to be predominantly of a standing-wave or traveling-wave form. The higher order modes are not significant for those cases examined. Bounds may be obtained for induced currents in the field-to-wire problem by considering the transmission line as a receiving antenna. The maximum value of induced current under conditions of maximum susceptibility is shown to vary little with frequency.     

A revision of the traveling-wave monopole model

Two time-domain electromagnetic emanation models are introduced into emission security (EMSEC) researches. The standing-wave dipole model can be easily gotten from some other references. But the traveling-wave monopole model addressed by Rothwell cannot be applied directly. A charge release coefficient C/sub q/(t) is introduced into this model, which makes the model more adaptive. Near-zone and far-zone fields are discussed of the revised traveling-wave monopole model through an example.     

Homogeneously broadened CW lasers with uniform distributed loss

The exact equations relating the CW output power to the parameters of a homogeneously broadened laser with distributed loss and its cavity are analytically intractable. In their place, simple approximate expressions are derived which permit convenient evaluation of the laser parameters from output power measurements in cavities with variable coupling, and conversely, of the maximum available oscillator power from small-signal gain and absorption-loss measurements. The approximate solutions have negligible error for lossy standing-wave lasers and are but slightly less accurate for lossy traveling-wave ring lasers.     

Influence of spatial hole burning on the output power of a CW dye ring laser

The output power of a single-mode CW dye ring laser can be enhanced by 50 percent by changing over from standing-wave (SW) operation to traveling-wave (TW) operation. This effect is attributed to smoothing out the SW pattern in the active medium, which gives rise to spatial inhomogeneities of the inversion.     

Rotational level competition in CO2lasers

Competition effects between rotational levels of the rotation-vibration band of CO2at 10.6 μ have been investigated in both traveling-wave and standing-wave CO2lasers operated in a single mode and single frequency. In a ring laser, Doppler shift and gain proportionality as a function of gas flow can be used to generate a gain anisotropy as a function of frequency so that the ring laser operates as a unidirectional oscillator. Over a narrow frequency interval, two rotational levels can be made to oscillate with oppositely directed traveling waves with an intensity crossover between the two Doppler centers. In this way, a discriminant can be derived that allows frequency stabilization to 5 parts in 10¹²in frequency. In standing-wave lasers of high-frequency stability, the rotational level competition can be observed by synchronous detection of a low-frequency variation of the heterodyne beat frequency signal of two lasers. The competition effects are due to intensity-dependent anomalous dispersion arising from saturation.     

Traveling-wave ring circuit for resonant enhancement of electrooptic modulators

Traditional implementations of resonantly enhanced electrooptic modulators are limited in their modulation enhancement and tuning ability. In this letter, a novel electrode structure based on a traveling-wave resonant ring circuit is described for which resonant frequency and resonator quality factor are easily tunable. Experimental results are presented which demonstrate significant improvements over traditional standing-wave designs.     

Large signal bunching of electron beams by standing-wave and traveling-wave systems

Large signal bunching processes in the presence of space charge are studied by extending techniques used to compute multi-cavity klystron bunching. Bunching capability of traveling-wave and standing-wave systems is examined by using an assumed spatial and time distribution of electric field, and interesting high degrees of bunching are predicted.