新型直动式压电伺服阀

提出一种新型压电驱动单级电液伺服阀,其特点是可以提供比传统电磁式电液伺服阀更高的频宽与分辨率,而且结构紧凑、抗污染能力强。该阀采用大行程的压电叠堆(积层式压电驱动器)作为驱动元件直接驱动滑阀,通过基于弹性变形原理的弹性板机构,结合电阻应变式微位移传感器,实现机构及检测一体化。应用有限元法对弹性板机构进行分析优化,试制了直动式压电伺服阀样机并对样机进行了试验研究,得出该阀的频宽约为1 kHz。新型伺服阀可以应用于振动试验台、疲劳试验台及需要快速反应的流体控制系统中,提高系统的响应特性。     

Impact drive rotary precision actuator with piezoelectric bimorphs

An impact drive rotary precision actuator with end-loaded piezoelectric cantilever bimorphs is proposed. According to finite element analysis and experiments of the dynamic characteristics of end-loaded piezoelectric cantilever bimorphs, a specific fixed-frequency and adjustable-amplitude is confirmed to control the actuator. The results show that an actuator excited by fixed-frequency and the adjustable-amplitude ramp voltage waveform works with a large travel range (180°), high resolution (1 μrad), speed (0.2 rad/min) and heavy-load ability (0.02 Nm). With advantages of high-precision positioning ability, simple structure and only one percent the cost of traditional impact drive mechanisms, the actuator is expected to be widely used in precision industries. __________ Translated from Optics and Precision Engineering, 2005, 13(3): 298–304 [译自: 光学精密工程]     

压电型喷嘴挡板阀及其控制方法研究

提出了一种新型压电晶片型喷嘴挡板式电液伺服阀,并对其控制方法进行了研究。采用成本较低的双压电晶片弯曲元件设计了双喷嘴挡板放大器,用其取代原有传统的力矩马达作为双喷嘴电液伺服阀的前置级驱动器。介绍了新型压电晶片型喷嘴挡板式电液伺服阀的工作原理。最后,针对压电元件存在的迟滞、蠕变非线性及系统中存在的时变性因素等问题,采用了具有自学习、自适应和自组织能力的单神经元自适应PSD智能控制算法对系统进行控制。实验结果表明,采用PID控制算法时系统阶跃响应的超调量和稳态时间分别为27.9%和0.13 s,而采用提出的控制算法时系统阶跃响应的超调量和稳态时间只有2.4%和0.07 s,验证了该方法的有效性。新型压电晶片型喷嘴挡板式电液伺服阀结构简单、成本低、精度高,可以满足精密控制系统的要求。     

The Influences of Residual Stress on the Frequency of Ultrasonic Transducers with Composite Membrane Structure

Arrayed ultrasonic sensors based on the piezoelectric thin film (lead-zirconate-titanate : Pb (Zr_o.52Tio.48) O3) having composite membrane structure are fabricated. Different thermal and elastic characteristics of each layer generate the residual stress during the high temperature deposition processes, accomplished diaphragm is consequently bowing. We present the membrane deflection effects originated from the residual stress on the resonant frequencies of the sensor chips. The resonant frequencies(fr) measured of each sensor structures are located in the range of 87.6-111 kHz, these are larger 30–40 kHz than the resultant frequencies of FEM. The primary factors offr deviations from the ideal FEM results are the membrane deflections, and the influence of stiffness variations are not so large on that. Membrane deflections have the effect of total thickness increase which sensitively change thefr to the positive direction. Stress generations of the membrane are also numerically predicted for considering the effect of stiffness variations on thefr.     

应用于压电叠堆泵的微位移放大机构

提出了一种应用于压电叠堆泵的微位移放大机构,该机构以压电叠堆(积层式压电微位移器)为驱动元件,通过基于三角形放大原理的柔性铰链放大机构,放大压电叠堆的输出位移。同时,设计、研制了实验装置,并在试制样机上对其静、动态特性进行了实验。实验测试结果表明:该机构对压电叠堆输出位移的放大倍数达到5倍,并且该机构具有线性良好、高分辨率、高频响应等特点。由有限元分析得到的固有频率达到了1.8 kHz,实际测量的固有频率为1.5 kHz。     

基于仿真离散数据的偏转板射流式伺服阀液动力计算方法研究

基于偏转射流式伺服阀工作机理,提出关于其动态特性分析及前置级液动力计算检测的问题。建立关于力矩马达、射流盘前置级以及功率滑阀三部分的完整伺服阀动态模型,确定前置级液动力的近似公式,并对整阀特性进行频率分析,验证了数学模型的正确性;建立伺服阀前置级内部的二维流场模型,并基于流场仿真所获得的离散数据,给出两种可用于计算稳态液动力的方法,即动量定理法和压差法,通过计算某型伺服阀的液动力,验证上述两种方法能够相互印证;设计并实现了一种双自由度的液动力测试平台,实现了对液动力的间接测试。结果表明,采用动量定理法和压差法计算得到的液动力值,与其近似计算公式以及试验结果一致,证明了提出的液动力计算方法与测试系统均具有可行性,为此类伺服阀的改进与优化提供了技术支撑。     

Variable identification and automatic tuning of the main module of a servo system of parallel mechanism

The variables of the main module of a servo system for miniature reconfigurable parallel mechanism were identified and automatically tuned. With the reverse solution module of the translation, the module with the exerted translation joint was obtained, which included the location, velocity and acceleration of the parallelogram carriage-branch. The rigid dynamic reverse model was set as the virtual work principle. To identify the variables of the servo system, the triangle-shaped input signal with variable frequency was adopted to overcome the disadvantages of the pseudo-random number sequence, i.e., making the change of the vibration amplitude of the motor dramatically, easily impact the servo motor and make the velocity loop open and so on. Moreover, all the variables including the rotary inertia of the servo system were identified by the additive mass. The overshoot and rise time were the optimum goals, the limited changing load with the attitude was considered, and the range of the controller variables in the servo system was identified. The results of the experiments prove that the method is accurate. __________ Translated from Chinese Journal of Mechanical Engineering, 2006, 42(4): 1–7 [译自: 机械工程学报]     

Design of a piezoelectric transducer cylindrical phase modulator for simulating acoustic emission signals

To conveniently carry out the pipeline leak experiment in a laboratory, leak acoustic signals are simulated by using the converse piezoelectric effect of a piezoelectric transducer (PZT) cylindrical phase modulator. On the basis of the piezoelectric equations and electromechanical equivalence principle, the transfer function of a PZT cylindrical phase modulator is delivered. A PZT cylindrical phase modulator is designed, and the numerical simulation is conducted. Results prove that the PZT cylindrical phase modulator can effectively simulate leak acoustic emission signals when the frequency is lower than 25 KHz. __________ Translated from Journal of Beijing University of Technology, 2006, 32(8): 683–687 [译自: 北京工业大学学报]     

双喷嘴挡板电液伺服阀前置级流固耦合分析

分析双喷嘴挡板电液伺服阀前置级的动态流场,研究衔铁挡板组件受力发生偏转导致前置级流场发生变化,分析固定节流口、喷嘴、回油口处的流速、压力变化和功率损失,以及衔铁挡板组件、滑阀阀芯的位移及受力情况。该研究利用ANSYS软件,采用流固耦合分析方法对双喷嘴挡板电液伺服阀衔铁挡板组件及前置级流场进行分析,为双喷嘴挡板电液伺服阀的流场分析提供了一种更接近实际的分析方法,得到更为精确的分析结果,为模型结构参数及固体材料的选择提供一定的指导。     

Fluid-dynamic analysis and multi-objective design optimization of piezoelectric servo valves

This paper proposes an effective methodology for the fluid-dynamic design optimization of the main spool of a piezoelectric servo valve. The aim is to improve global performances of the piezoelectric servo valve by reducing the flow force acting on the main spool and the mass of the main spool. The main disturbance forces acting the main spool were analyzed. The steady-state flow force acting on the main spool was derived and the relationship between the flow force and the design parameters of the main spool was established. The design problem of the main spool was formulated mathematically as a multi-objective optimization problem. The minimum steady-state flow force and the minimum mass of main spool were considered as optimization objectives. The elitist non-dominated sorting genetic algorithm (NSGA-II) was applied and a set of Pareto-optimal solutions was calculated. The optimized results were analyzed and the final design parameters of the main spool were selected for the simulation analysis and experimental research. The computational fluid dynamics (CFD) simulation was employed to calculate the forces acting on the main spool. Simulation results show the flow force acting on the optimized main spool is significantly reduced. The unoptimized and optimized main spools were machined and experimental study was performed. Results show that the piezoelectric servo valve equipped with the optimized main spool has better response performance and dynamic bandwidth. The dynamic bandwidth is measured to 172 Hz under the amplitude attenuation of −3 dB. Compared with the piezoelectric servo valve with unoptimized main spool, the dynamic bandwidth of the piezoelectric servo valve with optimized main spool is increased by 26%.     

Research on acoustic-structure sensitivity using FEM and BEM

Acoustic-structure sensitivity is used to predict the change of acoustic pressure when a structure design variable is changed. The sensitivity is significant for reducing noise of structure. Using FEM (finite element method) and BEM (boundary element method) acoustic-structure sensitivity was formulated and presented. The dynamic response and response velocity sensitivity with respect to structure design variable were carried out by using structural FEM, the acoustic response and acoustic pressure sensitivity with respect to structure velocity were carried out by using acoustic BEM. Then, acoustic-structure sensitivity was computed by linking velocity sensitivity in FEM and acoustic sensitivity in BEM. This method was applied to an empty box as an example. Acoustic pressure sensitivity with respect to structure thickness achieved in frequency ranges 1–100 Hz, and its change rule along with stimulating frequency and design variable were analyzed. Results show that acoustic-structure sensitivity method linked with FEM and BEM is effective and correct. __________ Translated from Journal of Vibration Engineering, 2005, 18(3): 366–370 [译自: 振动工程学报]     

Analysis of the Internal Characteristics of a De ector Jet Servo Valve

In current research on deflector jet servo valves, the receiver pressure estimated using traditional two-dimensional simulation and theoretical calculation is always lower than the experimental data; therefore, credible information about the flow field in the prestage part of the valve can hardly be obtained. To investigate this issue and understand the internal characteristics of the deflector jet valve, a realistic numerical model is constructed and a three-dimensional simulation carried out that displays a complex flow pattern in the deflector jet structure. Then six phases of the flow pattern are presented, and the defects of the two-dimensional simulation are revealed. Based on the simulation results, it is found that the jet in the deflector has a longer core area and the fluid near the shunt wedge cannot resist the impact of the high-speed fluid. Therefore, two assumptions about the flow distribution are presented by which to construct a more complete theoretical model. The receiver pressure and prestage pressure gain are significantly enhanced in the calculations. Finally, special experiments on the prestage of the servo valve are performed, and the pressure performance of the numerical simulation and the theoretical calculation agree well with the experimental data. Finally, the internal mechanism described by the theoretical and numerical models is verified. From this research,more accurate numerical and theoretical models are proposed by which to figure out the internal characteristics of the deflector jet valve.     

Acoustic analysis of lightweight auto-body based on finite element method and boundary element method

A lightweight automotive prototype using alternative materials and gauge thickness is studied by a numerical method. The noise, vibration, and harshness (NVH) performance is the main target of this study. In the range of 1–150 Hz, the frequency response function (FRF) of the body structure is calculated by a finite element method (FEM) to get the dynamic behavior of the auto-body structure. The pressure response of the interior acoustic domain is solved by a boundary element method (BEM). To find the most contributing panel to the inner sound pressure, the panel acoustic contribution analysis (PACA) is performed. Finally, the most contributing panel is located and the resulting structural optimization is found to be more efficient. __________ Translated from Journal of Shanghai Jiaotong University, 2006, 40(1): 177–180 [译自: 上海交通大学学报]     

射流管伺服阀前置级的动态流场分析

射流管电液伺服阀的喷嘴到接收孔间的流场较为复杂,尤其在射流管偏转及阀芯运动的动态情况下,会存在回流、漩涡等现象。以某型射流管电液伺服阀结构为模型,结合射流管偏转时的阀芯力平衡关系,得到阀芯的运动方程,应用雷诺平均方程和标准两方程模式的封闭方程,通过流体动力学软件FLUENT建立射流管伺服阀喷嘴到阀芯两腔的三维可视化模型,仿真分析了喷嘴到接收孔的前置级瞬态流场及阶跃响应。仿真结果表明:接收孔中的涡量强度会影响射流管电液伺服阀的阶跃响应,涡量强度越大、振荡越大、阶跃响应越慢,并通过试验测试阀芯位移验证了数值计算的正确性,同时对比了不同接收孔间夹角的同时刻涡量及阶跃响应,得到接收孔间夹角为45°的最优设计。研究方法和结果对于提高射流管电液伺服阀的动态响应有重要参考价值。     

Dynamical research on spherical micro actuator with piezoelectric ceramic stacks drivers

This paper develops a 30 mm × 30 mm × 50 mm spherical micro actuator driven by piezoelectric ceramic stacks (PZT), and analyzes its dynamic performances. First, the space coordinate relationship of the spherical micro actuator and a dynamic model are set up. Second, The Runge-Kutta arithmetic is used to calculate the dynamical parameters of the micro actuator; the SIMULINK module of MATLAB is used to build the dynamical simulating model and then simulate it. Third, an experimental sample of the spherical micro actuator is developed, a micromanipulator is integrated with a micro-gripper based on the sample spherical micro actuator, and the experimental research on the micro assembly is conducted between a micro shaft of Φ180 μm and a micro spindle sleeve of Φ200 μm. Finally, the characteristics of the spherical micro actuator influenced by the mass of the metal sphere of the micro actuator, driving signal frequency, friction coefficient of the contact surface between the metal sphere and the friction block of the micro driving unit are analyzed. The experimental results indicate that the rotation resolution of the micro actuator reaches 0.000 1°, the rotation positioning precision reaches 0.000 5°, and the maximum working frequency is about 1200 Hz. The experimental results validate the back rotation vibration model of the spherical micro actuator. The micromanipulator integrated by the spherical micro actuator can meet the requirements of precise micro operation and assembly for micro electro mechanical systems (MEMS) or other microelements in micro degree fields. __________ Translated from Optics and Precision Engineering, 2007, 15(2): 248–253 [译自: 光学精密工程]     

大流量数字阀伺服螺旋机构的仿真研究

大流量数字阀的前置级采用伺服螺旋机构,它将阀芯的旋转运动转换为轴向运动,实现伺服阀液压功率放大.通过建立伺服螺旋机构 数学模型,着重研究不同结构参数下其对伺服阀动态性能的影响,以指导实际产品的设计工作.     

A nanosecond optical parametric oscillator in the mid-IR region with double-pass pump

An optical parametric oscillator (OPO) with double-pass pump based on MgO:PPLN and PPLN periodic structures is described. A compact nanosecond Nd:YLF laser has been used as a pump source at 1.053 μm (the pumping pulse duration is 5–7 ns at a maximum pulse energy of 300 μJ at frequencies of 1–7 kHz). The oscillation threshold of the OPO based on MgO:PPLN was varied in a range of 11–28 μJ at wavelength of 2.1–4.3 μm. The conversion efficiency from the pump wave to an idler wave decreased from 8.6 to 2.5% in the range of 2.0–4.3 μm. For PPLN-OPO the measured threshold was 36 μJ at 4.2 μm and 49 μJ at 4.7 μm. The conversion efficiency of the pump energy into the energy of an idler wave was 3.3μ-0.4% at wavelengths of 4.2–4.7 μm.     

积层式压电驱动器的有限元建模分析

该文利用有限元分析法对直动式压电伺服阀驱动元件-积层式压电驱动器的静、动态特性进行了深入的分析,建立了积层式压电驱动器多层压电结构的有限元模型,得到静态与动态工作的分析结果。理论分析的结果表明,积层式压电驱动器具有较大的输出位移与输出力,以及具有良好的动态响应特性,由其构造压电伺服阀,不会限制系统的频宽,结合合理的放大机构与阀体结构,有望达到高速、精密的伺服控制。     

Modal disturbance investigation of rod-shaped ultrasonic motor using bending vibrations

Modal disturbance of a rod-shaped ultrasonic motor using bending vibrations can cause problems such as low motor efficiency, instability, and poor control. In this paper, a dynamic analysis model of a stator is created on the basis of the finite element method (FEM) and Hamilton principle. The modal frequency sensitivities of the stator to the structure parameters are investigated by modal analysis. Accordingly, the structure parameters of the stator are modified to separate working modes from disturbance modes. A rod-shaped ultrasonic motor stator is fabricated, and the experimental results of its amplitude frequency response characteristics show that the purpose of modal separation is achieved. The frequency separation between working modes and disturbance modes is more than 2 kHz. The validity of the method is verified. __________ Translated from Piezoelectrics & Acoustooptics, 2008, 30(6) [译自: 压电与声光]