Dynamic analysis and simulation of four-axis forced synchronizing banana vibrating screen of variable linear trajectory

A new concept of banana vibrating screen which has the same effect as traditional banana vibrating screen in a new way was put forward.The dynamic model of vibrating screen was established and its working principle was analyzed when the action line of the exciting force did not act through the centroid of screen box.Moreover,the dynamic differential equations of centroid and screen surface were obtained.The motions of centroid and screen surface were simulated with actual parameters of the design example in Matlab/Simulink.The results show that not only the amplitude has a significant decrease from 9.38 to 4.10 mm,but also the throwing index and vibrating direction angle have a significant decrease from 10.49 to 4.59,and from 58.10° to 33.29°,respectively,along the screen surface,which indicates that motion characteristics of vibrating screen are consistent with those of traditional banana vibrating screen only by means of a single angle of screen surface.What's more,such banana vibrating screen of variable linear trajectory with greater processing capacity could be obtained by adjusting the relative position of force center and the centroid of screen box properly.

三维振动辅助铣削创成结构型表面的建模与振动参数影响仿真分析

结构型表面因良好的表面特性被广泛应用于光学、生物以及航空航天等重要领域。提出三维振动辅助铣削制备结构型表面的方法,分析施加三维振动激励条件下的铣削加工轨迹。基于正交螺旋理论和空间矩阵变换建立三维振动辅助铣削模型,在正弦函数曲面面型上预测生成的结构型表面微结构形态。探究了振幅以及振动频率对结构型表面微结构形貌的影响规律。

基于轨迹规划法的机械臂抑振研究

为提高机械臂作业时的控制精度,抑制关节处柔性元件引起的弹性振动。以史陶比尔TX40机械臂为研究对象,提出一种考虑机械臂关节柔性的抑振轨迹规划方法。在柔性关节模型的基础上,考虑柔性关节的弹性变形量对轨迹规划的影响,建立系统微分方程,定义抑制关节弹性振动的目标函数,并采用改进的粒子群算法(GAPSO)对目标函数进行优化,得到末端运动轨迹。结果表明,在GAPSO算法的优化下,末端运动轨迹位移波动明显减小,轨迹曲线更加平滑,末端的弹性振动明显减小。与基本粒子群算法相比,GAPSO算法保证了群体多样性,避免了目标函数易陷入局部最优解的问题,且具有更快的收敛速度。

基于ANSYS Workbench的一种几何量轨检仪器检测设备模态分析及随机振动模拟分析

随着轨道检测设备的自动化发展,使检测项目的几何参数计量由静态转变为动态,且提高了对检测仪器的要求。由于动态检测引入了振动源,因此即使有隔振措施,也会导致检测仪器产生微小振动,影响检测结果。本文对一种几何量轨检仪器检测设备进行三维建模,采用ANSYS Workbench软件进行模态分析,并对竖直方向上的微小随机振动功率谱密度对测量精度的影响进行研究。结果表明:当加速度功率谱密度为12350(mm/s^(2))^(2)/Hz时(即振动台隔振效果达93.5%),满足该仪器竖直方向上±1mm检测要求。

Quasi-classical trajectory study of the stereodynamics of a Ne+H_2^+→NeH^++H reaction

We have carried out a quasi-classical trajectory calculation for the reaction ofNe ＋ H2＋ （v = 0, j = 1） → NeH＋ ＋ H on the ground state （12AI） using the LZHH potential energy surface constructed by L/i et al. [Lu S J, Zhang P Y, Han K L and He G Z 2010 J. Chem. Phys. 132 014303]. Differential cross sections at many collision energies indicate that the reaction is dominated by forward-scattering. In addition, the Nell＋ product shows rotationally hot and vibrationally cold distributions. Stereodynamical results indicate that the products are strongly polarized in the direction perpendicular to the scattering plane and that the products rotate mainly in planes parallel to the scattering plane.

Effect of the reagent vibration on stereodynamics of the reaction O（^1D）＋HF→F＋OH

This paper studies the influence of the reagent vibration on the reaction O（1D）＋HF→HO＋F by using a quasiclassical trajectory method on the new ab initio 1A＇ ground singlet potential energy surface （Gomez-Carrasco et al 2007 Chem. Phys. Lett. 435 188 193）. The product angular distributions which reflect the vector correlation are calculated. Four polarization-dependent differential cross sections （PDDCSs） which are sensitive to many photoinitiated bimolecular reaction experiments are presented in the center of the mass frame, respectively. The differential cross section indicates that the OH product mainly tends to the forward scattering, and other PDDCSs are also influenced by the vibration levels of HF.

Study of highly excited vibrational dynamics of HCP integrable system with dynamic potential methods

Highly excited vibrational dynamics of phosphaethyne(HCP)integrable system are investigated based on its dynamic potentials.Taking into consideration the 2:1 Fermi resonance between H–C–P bending vibrational mode and C–P stretching vibrational mode,it is found that the effects of H–C stretching vibrational mode on vibrational dynamic features of the HCP integrable system are significant and regularly vary with Polyad numbers(P number).The geometrical profiles of the dynamic potentials and the corresponding fixed points are sensitive to the variation of H–C stretching vibrational strength when P numbers are small,but are not sensitive when P numbers become larger and the corresponding threshold values become lower.The phase space trajectories of different energy levels in a designated dynamic potential(P=28)were studied and the results indicated that the dynamic potentials govern the various dynamic environments in which the vibrational states lie.Furthermore,action integrals of the energy levels contained in dynamic potential(P=28)were quantitatively analyzed and elucidated.It was determined that the dynamic environments could be identified by the numerical values of the action integrals of trajectories of phase space,which is equivalent with dynamic potentials.

VIBRATION PROBLEMS OF FLEXIBLE CIRCULAR PLATES WITH INITIAL DEFLECTION

In this paper, the differential equations of flexible circular plates with initial deflection are derived. The stability of motion is investigated in phase plane. The periodical solutions of nonlinear vibration for circular plates with initial deflection are obtained by use of Galerkin method and Lindstedt-Poincare perturbation method. The effect of initial deflection on the dynamic behavior of the flexible plates are also discussed.

Quasi-classical trajectory study of H+LiH（v=0,1,2,j=0）→Li+H2 reaction on a new global potential energy surface

Quasi-classical trajectory(QCT)calculations are reported for the H+LiH(v=0-2,j=0)→Li+H2 reaction on a new ground electronic state global potential energy surface(PES)of the LiH2 system.Reaction probability and integral cross sections(ICSs)are calculated for collision energies in the range of 0 eV-0.5 eV.Reasonable agreement is found in the comparison between present results and previous available theoretical results.We carried out statistical analyses with all the trajectories and found two main distinct reaction mechanisms in the collision process,in which the stripping mechanism(i.e.,without roaming process)is dominated over the collision energy range.The polarization dependent differential cross sections(PDDCSs)indicate that forward scattering dominates the reaction due to the dominated mechanism.Furthermore,the reactant vibration leads to a reduction of the reactivity because of the barrierless and attractive features of PES and mass combination of the system.

Effect of ro-vibrational excitation of NeH^+ on the stereodynamics for the reactions H+NeH^+(v=1-3,j=1,3,5) →H_2^++Ne

The stereodynamics of the abstraction reaction H^＋ NeH^＋（v = 1-3,j = 1,3,5） → H2^＋ ＋ Ne is studied theoretically with a quasi-classical trajectory method on a new ab initio potential energy surface [ S J,Zhang P Y,Han K L and He G Z 2012 J.Chem.Phys.132 014303].The effects of vibrational and rotational excitation of reagent molecules on the polarization of the product are investigated.The reaction cross sections,the distributions of P（θr）,P（φr）,and polarizationdependent differential cross sections（PDDCSs） are calculated.The obtained cross sections indicate that the title reaction is a typical barrierless atom（ion）-ion（molecule） reaction.The initial vibrational excitation and rotational excitation of reagent molecules have distinctly different influences on stereodynamics of the title reaction,and the possible reasons for the differences are presented.

The stereodynamic properties of the F+HO(v,j) → HF+O reaction on^1 A' and ~3A' potential energy surfaces by quasi-classical trajectory calculations:Initial excitation effect(v=1-3, j=0 and v= 0, j=1-3)

The stereodynamic properties of the F ＋ HO （v, j） reaction are explored by quasi-classical trajectory （QCT） calculations performed on the 1At and 3At potential energy surfaces （PESs）. Based on the polarization-dependent differential cross sections （PDDCSs） and the angular distributions of the product angular momentum with the reactant at different values of initial v or j, the results show that the product scattering and product polarization have strong links with initial vibrationalrotational numbers of v and j. The significant manifestation of the normal DCSs is that the forward scattering gradually becomes predominant with the initial vibrational excitation increasing, and the scattering angle of the HF product taking place on the 3At potential energy surface is found to be more sensitive to the initial value of v. The product orientation and alignment are strongly dependent on the initial rovibrational excitation effect. With enhancement in the initial rovibrational excitation effect, there is an overall decrease in the product orientation as well as in the product alignment either perpendicular to the reagent relative velocity vector k or along the direction of the y axis, for which the initial rotational excitation effect is much more noticeable than the vibrational excitation effect. Moreover, the initial rovibrational excitation effect on the product polarization is more pronounced for the 3At potential energy surface than for the 1At potential energy surface.

Quasiclassical trajectory theoretical study on the chemical stereodynamics of the O(~1D)+H_2→OH+H reaction and its isotopic variants (HD, D_2)

The quasiclassical trajectory （QCT） method is used to study stereodynamic information about the reaction O （1D）＋H2 --4OH＋H on the DK （Dobbyn and Knowles） （llA;） ab initio potential energy surface （PES）. A wide scale of collision energy （Ec） from 0.05 eV to 0.5 eV is considered in the dynamic calculations. To reveal the rovibrational excitation effect, calculations at a collision energy of 0.52 eV are carried out for the v = 0 - 5, j = 0 and v = 0, j -- 0 - 15 initial states. The two popularly used polarization-dependent differential cross sections （PDDCSs）, dtY0o/doh （0, 0） and dtra0/dtot（2, 0）, and two angular distributions, P（φr） and P（φr） are calculated to obtain an insight into the alignment and the orientation of the product molecules. From the calculations, we can obtain that the alignment of the OH product is weaker at high collision energy and becomes stronger with the increase of initial vibrational level, and it is almost insensitive to the initially rotational excitation. Influences of the mass values of isotopes （HD, D2） on the stereodynamics are also shown and discussed. Comparisons between available theoretical results and experimental results are made and discussed.

Enhancing of nominal characteristic trajectory following control for motion systems

The goal of this paper is to enhance a practical nominal characteristic trajectory following(NCTF) controller that is specifically designed for two-mass point-to-point positioning systems. A nominal characteristics trajectory contained in the NCTF controller acts as movement/motion reference and a compensator is utilized to force the object to detect and follow the reference/desired trajectory. The object must follow and track closely and should be as fast as possible. The NCTF controller is designed with two different intelligent based compensator approaches which are fuzzy logic and extended minimal resource allocation network. The proposed controller which is NCTF are compared with the conventional proportional integral compensator. Then the results of simulation are discussed for the positioning performances. The inertia variations due to the effect of the design parameters are also assessed to see the robustness of controllers. The results show that the NCTF control method designed from an intelligent based compensator has a better positioning performance in terms of percentage of overshoot, settling time, and steady state error than the classical based compensator.

Effects of a reagent’s rotational and vibrational excitations on reaction O(~3P) + H_2 (ν=0,3,j = 0,3,5,7,9,12,15) → OH+H

To investigate the effect of a reagent＇s rotational and vibrational excitations on the stereo-dynamics of the reaction product, the title reaction is theoretically simulated using the quasi-classical trajectory （QCT） method on the 3A~ and 3Aq potentiM energy surfaces （PESs）. The reaction cross section is considered as the only scalar property in this work at four different collision energies. Furthermore the vector properties including two polarization-dependent differential cross sections （PDDCSs）, the angular distributions of product＇ rotational momentum are discussed at one fixed collision energy. Effects of reagents＇ rotational excitation on the reaction do exist regularly.

Effect of reagent vibrational excitation and isotope substitution on the stereo-dynamics of the Ba+HF→BaF+H reaction

Based on an extended London-Eyring-Polanyi-Sato （LEPS） potential energy surface （PES）, the Ba q-HF reaction has been studied by the quasi-classical trajectory （QCT） method. The reaction integral cross section as a function of collision energy for the Ba q- HF --＊ BaF q- H reaction is presented and the influence of isotope substitution on the differential cross sections （DCSs） and alignments of the product＇s rotational angular momentum have also been studied. The results suggest that the integral cross sections increase with increasing collision energy, and the vibrational excitation of the reagent has great influence on the DCS. In addition, the product＇s rotational polarization is very strong as a result of heavy-heavy-light （HHL） mass combination, and the distinct effect of isotope substitution on the stereodynamics is also revealed.

基于5R并联机构的二自由度树冠振动装置设计与试验

振动式采收是一种高效的林果机械化采收形式。在现有的激振形式中,非圆周激励可以使果树产生有效的振动,实现整体采收效果。为进一步提高果实的采收效率,针对非圆周激励中不同类型旋轮线轨迹进行深入研究。通过SolidWorks、ANSYS、ADAMS等软件建立果树柔性体模型。将不同轨迹参数的旋轮线位移载荷导入ADAMS,施加于果树模型激振点。比较不同轨迹的旋轮线位移载荷下果树模型的振动响应,确定3支线1号外旋轮线轨迹E为最优激振轨迹。根据最优激振轨迹,设计了由平面5R并联机构驱动的二自由度树冠振动装置。以油茶树为激振对象,确定频率6 Hz、振幅90 mm为激振参数,设计并搭建样机进行试验。试验结果表明,7×7交错分布的激振杆布局方式的激振效果最优,该布局下树冠平均合成加速度响应为22.38 m/s^(2),激振加速度传递效率为77.63%,验证了二维激振轨迹的有效性。

水平井钻柱横向振动分析

随着油气资源需求不断增加,水平井应用越来越广泛,水平井钻柱的横向振动将直接影响钻井效率和钻柱安全。与直井不同,水平井存在造斜段和水平段,钻柱的初始变形和受力条件更加复杂。为了准确分析水平井钻柱的横向振动,文章综合考虑三维井眼轨迹、钻井参数和钻柱与井壁接触等参数,基于Lagrange方程建立了水平井钻柱非线性动力学特性数学模型,采用有限单元法对模型离散并求解,并选取四川某水平井实际参数进行验证,最后讨论了钻压、转速和扶正器对水平井钻柱横向振动的影响。研究结果表明:在钻进过程中,直井段钻柱横向振动较小,造斜段和水平段钻柱横向振动较大,越靠近钻头处,横向振动越大;钻压对水平段和造斜段钻柱横向振动有较大影响,钻压越大,该段钻柱横向振动越大,而直井段钻柱受钻压影响很小;在文章分析条件下(转速为30~120 r/min),全井段钻柱横向振动无明显变化;扶正器可以限制水平段钻柱的横向位移,且扶正器安装位置对其有很大影响。文章所提出的模型也适用于复杂结构井钻柱动力学特性研究,研究成果为水平井钻井提效和钻柱安全提供理论指导。

高空作业车观测器与神经网络滑模控制器设计

针对折叠臂高空作业车的轨迹跟踪控制问题,提出了一种基于扩张状态观测器的神经网络滑模控制器。针对现实情况下臂杆柔性模态变量不可测以及外界扰动的问题,设计扩张状态观测器用于观测系统的模态变量,并将外界扰动作为系统状态变量进行观测。由于滑模控制器的高速切换控制会引起的高频振颤,因此设计了神经网络滑模控制器,使用神经网络的连续控制代替了不连续的切换控制。并采用李雅普诺夫定理证明了整个系统的稳定性。仿真实验结果表明,所设计的基于扩张状态观测器的神经网络滑模控制器在存在建模不确定性以及干扰的情况下能够实现折臂式高空作业车工作平台的轨迹跟踪控制,并且对高空作业车臂架系统存在的振动问题进行了有效抑制。

基于MACSF的移动机械臂振动抑制轨迹规划方法

为满足移动机械臂高精度、低抖动的作业需求,提出一种基于修正非对称组合正弦函数(modified asymmetry combined sine function,简称MACSF)的振动抑制轨迹规划方法。首先,针对传统非对称组合正弦函数(asymmetry combined sine function,简称ACSF)存在加速度突变、启停阶段不稳定等问题,以驱动函数加加速度连续平滑为目标,采用改进型组合正弦函数设计加加速度时间窗口中的加速阶段和减速阶段,以降低移动机械臂的关节力矩波动;其次,通过叠加组合方法求出满足约束条件的通用型驱动函数;最后,基于机器人操作系统(robot operating system,简称ROS)搭建移动机械臂抑振算法验证平台,并使用该平台在样机场景下进行了一系列实验验证。结果表明,MACSF方法能够有效抑制移动机械臂的瞬态振动和残余振动(动态作业过程中振幅优于1 mm),从而验证了该方法的有效性和实用性。

二维超声振动磨削氧化锆陶瓷表面形貌及粗糙度试验研究

对氧化锆陶瓷进行了不同工艺参数下的普通磨削和二维超声振动磨削对比试验,讨论了不同工艺参数下影响工件表面粗糙度的主要因素及其影响规律,研究了二维超声振动磨削对工件表面形貌的影响。实验结果表明:在一定范围内,二维超声振动磨削的表面粗糙度均低于普通磨削,但当砂轮线速度过大时,二维超声振动作用将逐渐减弱;相比于普通磨削,二维超声振动磨削所得表面轮廓较平整,表面峰谷较均匀,二维超声振动磨削能够增加塑性去除的比例,获得更优的表面质量。