基于变步长谐振频率跟踪的超声驱动电源

用于超声清洗的超声驱动电源,压电换能器工作在水中的深度不同会导致其固有串联谐振频率产生偏移,进而使得电源输出处于失谐状态,降低了电源的输出效率.针对该问题,采用了一种基于变步长谐振频率跟踪方法,通过测量逆变桥输出电流有效值与直流电源输出电流平均值,并变步长调节电源的输出频率,使得两者的电流比值达到最小,能够使电源输出恢...     

大负载纵弯谐振超声磨削变幅器的设计与试验

基于Mindlin中厚板理论,针对超声磨削系统中的大负载砂轮进行了纵弯谐振变幅器的设计研究。将纵弯谐振变幅器分为变幅杆、基体环盘、磨料层环盘三个部分,分别建立各部分的位移与应力函数,利用边界条件建立纵弯谐振超声磨削变幅器的频率方程。根据频率方程设计了超声磨削变幅器,通过有限元分析和超声谐振试验对所设计的变幅器进行了试验研究。试验结果证明:超声磨削变幅器的谐振频率与设计频率基本一致,实际测得的砂轮振幅曲线与有限元仿真和理论计算取得的曲线的形态基本一致,验证了超声磨削纵弯谐振变幅器设计方法的正确性,为超声磨削系统的设计提供了理论依据。     

平行砂轮超声磨削刀柄设计与加工试验研究

针对目前超声磨削谐振系统中磨具尺寸较小的现状,提出了砂轮变幅器设计原理。设计了平行砂轮的纵弯谐振超声磨削主轴刀柄,由纵向振动变幅杆、横向弯曲振动平行砂轮、换能器、套筒、导电滑环、标准接口刀柄组成。通过阻抗分析、振幅测量实验,研究了超声磨削主轴刀柄的谐振特性。以磨削速度、进给速度和磨削深度为变量,完成了有无超声状态下Si Cp/Al复合材料单因素正交磨削加工试验。结果表明:超声磨削可以显著降低磨削力、降低表面粗糙度、提高零件表面质量。为进一步改善超声磨削刀柄结构、磨削工艺,提高加工效果提供了技术支持。     

表面微坑超声振动加工系统负载调频特性研究

表面微坑超声振动加工技术对于改善缸套—活塞环摩擦副的摩擦润滑状态具有重要意义.针对表面微坑超声振动加工过程中谐振频率随负载漂移的问题,建立微坑加工等效负载与换能器谐振频率和调谐电感的关系模型,通过仿真和试验验证研究了外加负载变化时,谐振频率与调谐电感值的变化规律.结果表明,随着外加工具杆长度增加,换能器谐振频率呈下降趋势;通过在回路中串联一个调谐电感,补偿负载的变化量,可使换能器谐振频率回到设计谐振频率.可见外加调谐电感可有效解决表面超声微坑振动加工过程中谐振频率随负载漂移的问题.     

超声珩齿新型变幅器动力学特性研究

为解决超声珩齿振动系统的设计问题,将齿轮简化为厚环盘,基于变截面变幅杆纵向振动波动方程和中厚圆环板弯曲振动位移方程,根据中间有孔圆锥型变幅杆与中厚圆环组成的新型超声珩齿变幅器的非谐振性和边界条件,推导出了系统谐振频率方程,利用数值计算分析了变幅器的几何参数对系统谐振频率的影响。通过有限元分析得出变幅器的谐振频率与理论计算结果基本一致。在此基础上,对设计的变幅器进行了动力学试验,测得的动力学参数与理论结果一致,其结果不仅证实了非谐振理论的正确性,而且为超声珩齿变幅器的设计和应用提供了理论依据。     

压电超声换能器电负载调频特性研究

压电超声换能器由于具有较高的机械品质因数,因此对谐振频率的变化十分敏感。在负载、温度等工况因素影响下,超声换能器谐振频率会发生偏移,从而造成其出现工作性能下降甚至完全失效。提出一种电负载影响下的超声换能器等效电路,建立谐振频率与电负载的关系模型,并通过仿真以及试验进行验证。结果表明,这种电负载调频的压电超声换能器,可以有效地克服谐振频率偏移带来的性能损失问题,为新型超声加工系统的研制奠定了理论基础。     

基于TMS320F2812DSP的数字式频率跟踪

介绍了数字式频率跟踪的优点,根据实际课题阐述了串联谐振式超音频感应加热电源的主电路工作原理,详细分析了基于TMS320F2812 DSP的频率跟踪的硬件电路工作原理和脉冲捕捉程序,并测得出实际脉冲波形.     

傅里叶变换的行波型中空超声电机的系统效率

由于行波型中空超声电机的驱动信号为高压、高频信号,因此,由行波型中空超声电机及其驱动器组成的系统的各级功率与效率不容易获取,这些因素均影响到后续对行波型中空超声电机性能的研究。针对此问题,首先,通过傅里叶变换的方法对超声电机驱动信号进行处理,构建了电机及其驱动系统各级效率的计算方法;然后,通过实验获取了行波型中空超声电机及其驱动器组成的系统的效率,并进一步研究了驱动频率、驱动电压及谐振匹配点对系统效率的影响。实验表明:驱动频率越靠近谐振频率,系统总效率越高;驱动电压越大,系统总效率越高;驱动电路匹配的谐振点远远高于电机机械谐振频率,使得驱动信号频率介于电路谐振频率和机械谐振频率之间时系统的效率最高。     

基于声波分析的臭氧发生器电源谐振频率测量仪

由于当前臭氧发生器高频电源谐振频率检测方法具有昂贵、危险等缺点,设计一种基于声波频谱分析的高频电源谐振频率检测仪器。通过分析臭氧发生器工作环境下的声波数据与高频电源谐振状态的关系,找到测量谐振频率的方法。该仪器使用STM32单片机作为核心控制及计算单元,通过声波采集电路将声波数据传送给单片机,单片机基于声波数据使用频谱分析程序测量出谐振频率。实践分析结果表明,基于声波分析的臭氧发生器电源谐振频率测量仪具有高效、安全、经济等优点。     

基于Workbench的夹心式压电超声换能器的尺寸优化

为了使设计和制作的夹心式压电超声换能器的谐振频率和工作频率趋于一致,运用Solid Works与Workbench软件实现换能器建模与仿真的同步协同,对不同后端盖尺寸的换能器进行模态分析。结果表明,随着后端盖尺寸的变化,换能器的谐振频率随之变化。在设计和制作的换能器的谐振频率与工作频率不一致时,可以通过改变后端盖的尺寸使换能器的谐振频率和工作频率趋于一致。     

Design of ultrasonic elliptical vibration cutting system for tungsten heavy alloy

Nanoscale surface roughness of tungsten heavy alloy components is required in the nuclear industry and precision instruments. In this study, a high-performance ultrasonic elliptical vibration cutting (UEVC) system is developed to solve the precision machining problem of tungsten heavy alloy. A new design method of stepped bending vibration horn based on Timoshenko’s theory is first proposed, and its design process is greatly simplified. The arrangement and working principle of piezoelectric transducers on the ultrasonic vibrator using the fifth resonant mode of bending are analyzed to realize the dual-bending vibration modes. A cutting tool is installed at the end of the ultrasonic vibration unit to output the ultrasonic elliptical vibration locus, which is verified by finite element method. The vibration unit can display different three-degree-of-freedom (3-DOF) UEVC characteristics by adjusting the corresponding position of the unit and workpiece. A dual-channel ultrasonic power supply is developed to excite the ultrasonic vibration unit, which makes the UEVC system present the resonant frequency of 41 kHz and the maximum amplitude of 14.2 μm. Different microtopography and surface roughness are obtained by the cutting experiments of tungsten heavy alloy hemispherical workpiece with the UEVC system, which validates the proposed design’s technical capability and provides optimization basis for further improving the machining quality of the curved surface components of tungsten heavy alloy.     

一种轻小型四极杆质谱仪射频电源的研制

四极杆结构是四极杆质谱仪的核心结构，由射频电源分别施加两组高压高频信号进行驱动，利用电场的变化和输入离子的质荷比差异对离子进行筛选。针对四极杆质谱仪小型化的研制需求，以信号调制模块、放大模块、反馈电路和直流模块为基本构型，设计了一种应用于轻小型四极杆质谱仪的射频驱动电源。经实际测试，该电源可以在谐振频率1.33 MHz、扫描频率10 Hz的输入条件下，输出峰 峰值电压最高可达3.33 kV的调幅射频高压信号并驱动四极杆结构，扫描切换时间不高于1 ms。射频电源输出信号稳定、波动小、交直比的波动为0.1%。该射频电源相较于常规的四极杆射频电源具有更高的扫描范围，体积小巧，功耗仅30 W，接口简单，有较高的实用价值。     

Dynamic model of shock-vibrating machining of welded joints by ultrasonic tools with an intermediate striker

Using the methods of the theory of shock-vibrating machining systems, machining by ultrasonic tools with a loose striker is considered in the form of forced oscillations of a two-weight system with two impact joints. The amplitude-frequency and phase-frequency characteristics of an ultrasonic shock-vibrating system under machining load are computed. The stability of shock-vibrating oscillations as a function of the tool design parameters and machining conditions is investigated. The independence of the ultrasonic converter resonant frequency from the clamping pressure up to the stability threshold is established. The parameters (clamping, excitation frequency) of the most effective mode of shock-vibrating machining, in which a maximum transfer of acoustic energy to the medium being machined is achieved, are determined. It is shown that the resonant frequency of the converter under load does not coincide with the maximum of the amplitude-frequency characteristic of the striker; therefore, the traditional automatic frequency control system adjustment to the converter resonance is not capable of ensuring oscillation excitation of the shock-vibrating system at the frequency of the most productive mode of machining.     

STUDY ON MECHANISM OF ARC-EXCITED ULTRASONIC

A mechanism of excited arc to be an controlled "ultrasonic emission source" is described. An developed electrical source with an certain frequency bandwidth for the purpose of the arc-excited is connected with an conventional welding power supply through coupling the cables for the experiment. Some resonant frequency bands for the arc-excited ultrasonic are discovered in the welding process, and its frequency, amplitude and phase'shift are recorded. This principle demonstrates that arc can be used not only for a thermal source, but also for an ultrasonic emission source, which may be extent to the industrial application in some new ways, such as for automatic welding process control and quality inspection.     

Design and dynamic modeling of a 2-DOF decoupled flexure-based mechanism

Flexure mechanisms with decoupled characteristics have been widely utilized in precision positioning applications.However,these mechanisms suffer from either slow response or low load capability.Furthermore,asymmetric design always leads to thermal error.In order to solve these issues,a novel 2-DOF decoupled mechanism is developed by monolithically manufacturing sets of statically indeterminate symmetric(SIS) flexure structures in parallel.Symmetric design helps to eliminate the thermal error and Finite Element Analysis(FEA) results show that the maximum coupling ratio between X and Y axes is below 0.25% when a maximum pretension force of 200 N is applied.By ignoring the mass effect,all the SIS flexure structures are simplified to "spring-damper" components,from which the static and dynamics model are derived.The relation between the first resonant frequency of the mechanism and the load is investigated by incorporating the load mass into the proposed dynamics model.Analytical results show that even with a load of 0.5 kg,the first resonant frequency is still higher than 300 Hz,indicating a high load capability.The mechanism’s static and dynamic performances are experimentally examined.The linear stiffnesses of the mechanism at the working platform and at the driving point are measured to be 3.563 0 N·μm-1 and 3.362 1 N·μm-1,respectively.The corresponding estimation values from analytical models are 3.405 7 N·μm-1 and 3.381 7 N·μm-1,which correspond to estimation errors of-4.41% and 0.6%,respectively.With an additional load of 0.16 kg,the measured and estimated first resonant frequencies are 362 Hz and 365 Hz,respectively.The estimation error is only 0.55%.The analytical and experimental results show that the developed mechanism has good performances in both decoupling ability and load capability;its static and dynamic performance can be precisely estimated from corresponding analytical models.The proposed mechanism has wide potentials in precision positioning applications.     

一种改进的基于响应耦合子结构法的刀尖点频响函数预测方法

针对现有的基于响应耦合子结构法(RCSA)的刀尖点频响函数预测方法需要辨识主轴-刀柄、刀柄-刀具结合面参数以及需要自制刀柄模型等引起的预测误差和预测过程复杂等问题,提出一种改进的基于RCSA的铣刀刀尖点频响函数预测方法。该方法首先改进已有的子结构划分方法,将机床-主轴-刀柄-刀具系统划分为机床-主轴-刀柄-部分刀杆、剩余刀杆和刀齿三个子结构;然后改进主轴-刀柄处转动频响函数的计算方法,通过铣刀的模态锤击实验采用反向RCSA和有限差分法计算机床-主轴-刀柄-部分刀杆结构的转动频响函数,并基于Euler梁模型计算出剩余刀杆、刀齿子结构的频响函数;最后将三个子结构的频响函数耦合确定刀尖点的预测频响函数。以一立式加工中心为研究对象,应用所提出的方法对铣刀刀尖点的频响函数进行了预测,并与其实测频响函数进行对比。对比结果表明：刀尖点的预测频响函数与实测频响函数符合程度较高,其预测、实测前三阶固有频率之间的误差在6.9%以内,所提出的方法可行有效、简单方便,且可直接基于铣刀的模态实验计算主轴-刀柄的频响函数,避免了相关结合面参数的辨识和刀柄模型的制作。     

Rotary ultrasonic machining: effects of tool natural frequency on ultrasonic vibration amplitude

Rotary ultrasonic machining (RUM) is a hybrid machining process that combines the material removal mechanisms of grinding and ultrasonic machining. RUM has been applied to hole-making for a wide range of materials. It is known that ultrasonic vibration amplitude has significant effects on cutting force, torque, and surface finish in RUM. One experimental observation that has been reported in the literature multiple times states that different tools show different vibration amplitudes on the same ultrasonic power level. However, no analyses can be found in the literature to explain this observation. The existence of this knowledge gap makes it difficult to explain some experimentally obtained trends or to conduct more realistic physics-based modeling work. The objectives of this research are to understand the effects of tool natural frequency on ultrasonic vibration amplitude in RUM, to provide an explanation to the observation and verification of measurement methods, and also to guide tool design and selection in RUM. Ultrasonic vibration amplitudes of tools are measured by three methods and compared. It is found that tool natural frequency significantly affects ultrasonic vibration amplitude. The tool with its natural frequency closest to that of the ultrasonic power supply (20?kHz) generates the highest ultrasonic vibration amplitude on every ultrasonic power level tested.     

An identification method for spindle rotation error of a diamond turning machine based on the wavelet transform

This paper presents an identification method for the spindle rotation error from the flatness error in the workpiece surface. The spindle rotation error is identified by the wavelet transform, Weierstrass function, and power spectral density (PSD). The flatness error comprises various errors of the machine tool, such as spindle rotation error, guideway error, motor error, and ball screw error, therefore, wavelet transform is used to process the measured result of the workpiece and the signal is decomposed into high-frequency and low-frequency signal. Weierstrass function is used to fit the spindle rotation error. According to the PSD analysis of the processed signal in the frequency domain, the spindle rotation error is identified from the measured flatness error, this method provides a basis for the identification of machine tool errors.     

基于谐振式MEMS传感器的仪表开发关键技术

针对基于谐振式MEMS传感器开发数字智能仪器仪表的高精度、快响应频率测量技术展开研究。以一谐振式MEMS气压传感器为开发样件,其差分输出是两路40～70 kHz之间的正弦频率信号。对传统的频率测量方法进行阐述分析,提出一种新的结合传统测频方法各自优点的频率检测方法。设计实现相关软、硬件,搭建测试系统,实验结果表明该测频方案针对40～70 kHz的频率信号误差小于±0.02 Hz,响应时间为1 s以内。     

Design and fabrication of a novel vibrational system for ultrasonic assisted oblique turning process

We designed and fabricated suitable vibrational equipment for ultrasonic assisted oblique turning process to enable researchers to perform experimental tests with the operating conditions closest to common assumptions of cutting mechanics theories. Applying ultrasonic vibrations to the tool cutting edge along tangential direction and in the presence of inclination and tool cutting edge angles necessitates a novel design and fabrication of vibrational horn with special oblique geometry. In this vibrational horn, the natural frequency of longitudinal vibration mode is forced to be in a certain frequency range of the ultrasonic power supply. The novel tool-workpiece assembly was designed using modal analysis to provide the most conformity of cutting geometry and process parameters between theory and practice. Three-dimensional cutting forces were measured experimentally in vibrational oblique turning process carried out by the mentioned horn. The most suitable conditions to profit from ultrasonic vibrations in oblique turning process were determined, and these experimental results were in agreement with modal analysis results.