振动式微机械陀螺的带宽特性分析

对振动式微机械陀螺的带宽特性进行了讨论,以设计的一种带解耦结构的振动式微机械陀螺为模型,利用数学工具软件MATLAB对其进行了带宽特性分析.分析结果表明,对于2自由度的陀螺,驱动频率的带宽不仅与驱动模态和检测模态的频率匹配有关,而且与两个模态的阻尼匹配有关.随着驱动模态和检测模态频率匹配的降低,带宽先增加然后基本保持不变.随着驱动和检测模态阻尼匹配的降低,带宽一直减小.通过实现驱动模态与检测模态的频率匹配和阻尼匹配可以获得最大机械灵敏度和最大驱动频率带宽.     

含间隙弹簧振动系统的非线性模态特性

针对含间隙的两自由度弹簧-质量分段振动系统的非线性模态开展了研究.首先,解析确定了分段保守自治系统发生同相和反相模态运动的初始位移,并采用加权平均方法确定了分段振动系统的模态频率,及其在位形空间模态曲线.然后,采用数值方法求解了系统的非线性模态曲线和模态频率,与本文获得的解析模态频率比较,说明本文的结果较等效模态频率有更好的精度.研究结果表明:在一定的参数条件下,系统的非线性模态个数会高于系统的自由度数目,系统可能发生内共振,而产生多余模态.多余模态运动是两振子同向振动中含有异向振动,说明多余模态是在同相模态运动和反相模态运动之间转换的模态.     

基于索-梁结构的斜拉桥非线性振动仿真研究

本文建立了索-梁结构的有限元模型,对斜拉桥线性和非线性振动问题进行研究.首先对结构进行模态分析,发现结构振动表现出全局模态,局部模态以及混合模态,且索梁两者之间固有频率相互影响,对低阶频率影响较大,对高阶频率影响较小.其次,应用有限元软件对索-梁结构的自由振动和强迫振动进行仿真研究.结果表明：整个自由振动过程中频率有先增大后减小的趋势,且最终小于真实频率;在强迫振动中,观察到了丰富的非线性振动现象,包括索的亚谐波共振和内共振,与以往的实验和理论研究结果定性上得到验证;为斜拉桥全桥非线性动力学分析提供参考.     

基于ANSYS的(P/FGM/P)悬臂矩形板的模态分析

基于有限元基本理论,用 ANSYS 软件对( P/FGM/P) 型的带压电层的功能梯度材料悬臂板的结构进行了模态分析,这里选用 SHELL99 单元类型. 给出( P/FGM/P) 型的带压电层 FGM 悬臂矩形板的振动模态图,得到固有频率,并且对前 8 阶模态做模态分析,讨论了其对结构的动力学行为的影响. 通过模态分析可以得知带压电层 FGM 悬臂矩形板的模态振型有横向振动,扭转振动,拉伸振动,横向振动以前两阶模态为主,分析结果对系统的结构设计与优化以及振动特性研究提供了有效的依据.     

基于FEM的叶栅动态特性仿真研究

计算机仿真在航空航天领域得到了广泛的应用.有限单元法是大型复杂结构或多自由度体系分析的有力工具.对大型承载飞机普遍使用的发动机转子叶栅,使用有限单元法(FEM)进行建模,然后对叶栅的结构及旋转状态下的动态特性进行分析.同时在不同转速下计算模态和振动频率,对等效压力分布、等效应力分布和整体形变进行仿真,并绘制了叶栅共振曲线的坎贝尔图,显示了固有振动频率和振动响应条件下共振激励作用.利用有限单元法的建模方法进行仿真,结果表明,使用上述方优化设计,使叶栅转动特性安全有效.     

基于有限元的绕线机主轴箱的结构改进及优化

为提高绕线机主轴箱的振动性能,采用基于有限元方法的COSMOS软件对绕线机的主轴箱进行了模态分析和结构的优化,仿真主轴箱前10阶固有频率和对应的振动模态.结果发现,基频共振频率仅有767 Hz,变形比例达1.31%;第2阶共振频率为801 Hz,变形比例为1.19%,对共振频率极大地限制了绕线机工作转速的提升.通过增设加强筋进行结构的改进,使主轴箱的基频提高了5.4%.第2阶共振频率提高了23.6%.采用结构优化方法使基频得到改善,并在增设加强筋的条件下,优化支撑板间距可使基频共振频率提高28.7%.     

多自由度串联系统传递函数的辨识

本文考虑多自由度串联振动系统传递函数的辨识问题.分析表明,从输入输出结构看这 是一个多级闭环系统,如用模态分析技术建模,需解2n阶状态方程的特征值问题,随着n的增 大,计算量增大,参数估计精度下降.本文从系统辨识角度提出一种二阶振荡系统传递函数辨 识方法,分别处理各个自由度的传递函数辨识,仿真计算结果表明该方法比模态分析法简便有 效.     

石墨烯三相复合材料板的非线性动力学研究

研究带有石墨烯涂层的1-3型压电纤维复合材料(MFC-GP)简支板结构的非线性动力学特性.首先,基于Reddy一阶剪切变形理论、Von Kármán位移应变关系以及Hamilton原理,推导了MFC-GP复合材料板的非线性偏微分方程.根据边界条件选择适当的模态函数,利用Galerkin法将偏微分方程离散成两自由度的常微分方程.采用多尺度方法进行摄动分析,得到结构在1∶1内共振下的频响方程,分析了石墨烯体积分数、电压、温度等对结构非线性频响曲线的影响.通过数值模拟,运用分叉图、相图、波形图研究了外激励对MFC-GP板非线性振动响应的影响.结果表明:不同参数及外激励下,结构出现了复杂的非线性动力学行为,对今后的工程实际应用具有一定的指导意义.     

滚动转子压缩机四倍频异常振动控制

空调压缩机的振动、噪声水平是衡量压缩机质量的重要性能指标之一.本文针对某型号滚动转子压缩机在特定频段4倍频振动幅值大于1倍频振动幅值问题,进行了扫频阶次分析、实验模态分析和振动噪声源识别等测试分析,确定了结构共振是导致4倍频超标的原因,提出了增加储液器质量和加强储液器托架刚度两种方案控制4倍频振动.实验测试表明,两种方案均改变了压缩机的固有振动特征,有效的降低了4倍频振动幅值,加强储液器托架刚度方案具有更小的振动响应.     

基于能量法的超声电机压电振子的耦合动力学模型分析

基于分析动力学的哈密顿原理,采用模态假定将超声电机压电振子复合结构的复杂振动在模态域内等效成单自由度系统的简单振动;考虑压电陶瓷的压电效应,将压电陶瓷诱发应变的激振力的大小用参数力系数描述,建立了超声电机压电振子的机电耦合动力学模型,通过实例计算与实验结果对比,验证该模型是较准确的,可以在超声电机的初步设计阶段替代有限元分析来确定电机的结构及材质参数,并选定合适的工作频率,从而为超声电机进一步的参数化分析和仿真模型的建立,及结构动力特性优化打下理论基础.     

Higher resonant mode effect on the performance of piezo actuated 2-DOF rectangular cantilever shaped resonators (2-DOF RCR) for liquid viscosity and density sensing

According to the demand for a highly sensitive resonant sensor, a 2-DOF RCR (2-degrees of freedom rectangular cantilever shaped resonators) with higher resonant mode of vibration is developed for sensing of liquid viscosity and density. The measurement principle is based on tracking the resonant characteristics of 2-DOF RCR system which depends on the density and viscosity of liquids it operates in. The 2-DOF RCR consists of a driver and absorber mass of identical natural frequency with a disparity in mass and connected by a strong mechanical coupling unit, thus the resonant amplitude and resonant frequency is enhanced at 1st mode compared with 1-DOF (1-degree of freedom) system. For further improving the sensitivity performance, the 3rd resonant mode vibration of 2-DOF RCR system is investigated. The system is evaluated for its performance in liquids of viscosity ranging from 0.23 to 1400 mPas and density ranging from 713 to 1261 kg/m³ at 3rd mode and compared with 1st mode of vibration. Good agreement with the simulated results from theoretical model and experimental results is reported and the enhanced performance of 2-DOF RCR system by using higher mode is also confirmed. Compared to the 1st mode, the sensitivity in terms of resonant frequency against density is improved with 22.75 % and 19 % in aqueous based and oil based liquids respectively and the sensitivity in terms of quality factor against viscosity is improved by 22.4 % and 30 % in aqueous and oil based liquids, at 3rd mode of vibration.

     

Investigation of joint clearance effects on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator

In this study, the effects of joint clearance on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator are investigated. The parallel manipulator is modeled by multi-body system dynamics. The contact effect in revolute joints with clearance is established by using a continuous analysis approach that is combined with a contact force model considering hysteretic damping. The evaluation of the contact force is based on Hertzian contact theory that accounts for the geometrical and material properties of the contacting bodies. Furthermore, the incorporation of the friction effect in clearance joints is performed using a modified Coulomb friction model. By numerical simulation, variations of the clearance joint's eccentric trajectory, the joint reaction force, the input torque, the acceleration, and trajectory of the end-effector are used to illustrate the dynamic behavior of the mechanism when multiple clearance revolute joints are considered. The results indicate that the clearance joints present two obvious separation leaps in a complete pick-and-place working cycle of the parallel manipulator, following a collision. The impact induces system vibration and thus reduces the dynamic stability of the system. The joint clearances affect the amplitudes of the joint reaction force, the input torque, and the end-effector's acceleration, additionally the joint clearances degrade the kinematic and dynamic accuracy of the manipulator's end-effector. Finally, this study proposes related approaches to decrease the effect of joint clearances on the system's dynamic properties for such parallel manipulator and prevent “separation-leap-impact” events in clearance joints.     

基于ADAMS-MATLAB的磁悬浮轴承转子系统联合仿真

建立了磁悬浮轴承转子系统的单自由度和五自由度仿真模型。采用ADAMS和MATLAB2种软件以及传统PID（比例积分微分）、不完全微分PID和模糊自调整PID3种控制方法分别对系统的轴向自由度和五自由度进行了联合仿真,分析了磁悬浮转子系统在限制控制电流和不限控制电流2种情况下转子承受冲击载荷的能力以及在外力作用下的振动情况。根据仿真结果,对传统PID控制、不完全微分PID控制以及模糊自调整PID控制的控制参数进行了优化,并在此基础上对上述3种控制方法的优劣给予了评判,为系统控制策略的选择和优化提供了1种有效的方法。     

带控制截面机翼结构基于非线性能量阱的颤振抑制

二元刚性机翼结构简化为三自由度结构,在浮沉位移和俯仰位移方向的非线性刚度简化为立方非线性,对于控制截面存在间隙采用双线性刚度代替.基于靶能量转移的原理在机翼结构耦合非线性能量阱,实现对机翼颤振的抑制.考虑准定常气流,建立机翼减振前后的运动方程,通过数值模拟构造减振前后峰值-峰值图,初步反应其整体的减振效果.通过弧长数值连续法和结合Floquet算子构造减振前后的分岔图,并研究其稳定性.通过分岔图结合数值模拟的峰值图,讨论在不同风速下的减振效果,结果表明机翼结构颤振可以部分甚至全部抑制.     

Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631–1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s² and 0.14 rad/s². The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631–1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable.

Statement of Relevance: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.     

Vibration analysis of cable-driven parallel manipulators

A cable-driven parallel manipulator is a manipulator whose end-effector is driven by a number of parallel cables instead of rigid links. Since cables always have more flexibility than rigid links, a cable manipulator bears a concern of possible vibration. Thus, investigation of vibration of cable manipulators caused by cable flexibility is important for applications requiring high system stiffness or bandwidth. This paper provides a vibration analysis of general 6-DOF cable-driven parallel manipulators. Based on the analysis of the natural frequencies of the multibody system, the study demonstrates that a cable manipulator can be designed stiff enough for special applications like the cable-manipulator based hardware-in-the-loop simulation of contact dynamics. Moreover, under an excitation, a cable may vibrate not only in its axial direction, but also in its transversal direction. The paper also analyzes the vibration of cable manipulators caused by cable flexibilities in both axial and transversal directions. It is shown that the vibration of a cable manipulator due to the transversal vibration of cables can be ignored comparing to that due to the axial flexibility of cables.     

固定翼无人机自动着陆的一体化制导控制

本文基于制导控制一体化方法的思想,将滑模变结构控制和自抗扰控制技术结合于动态面控制结构中,提出一种固定翼无人机自动着陆方法.在建立六自由度无人机模型、无人机和目标点间的相对视线角度模型的基础上,在动态面控制框架下加入滑模变结构控制来设计制导控制一体化方法.在此过程中加入自抗扰控制技术,提高了系统对未建模部分、参数的不确定性和外界干扰的鲁棒性,并抑制了滑模变结构控制的抖振.该方法使得无人机在平稳地飞向目标点的同时能够满足着陆视线角度的约束.文中详细论述设计思想和设计方法,最后通过仿真验证说明本文方法的有效性.     

Design and implementation of a 6-DOF robot flexible bending system

This study proposed a new design, analytical algorithms, and control of a novel 6-DOF robot flexible bending (RFB) system to manufacture bending components with complex spatial structures. First, a novel 6-DOF RFB system was designed based on the principles of RFB technology. Then, novel analytical algorithms named the incremental analysis algorithm (IAA), and space attitude analysis algorithm (SAAA)) were proposed for the 6-DOF RFB system to analyse the forming procedures of 3D complex-shaped hollow components. According to the IAA, a novel physical prototype and a control program of the 6-DOF RFB were built. The feasibility of the 6-DOF RFB system and the reliability of the IAA were verified by the bending experimentation on the AA6061-T6 spatial spiral tube. The dimensions of the test sample were measured using a 3D optical scanner system to evaluate the forming precision of the established 6-DOF RFB system. The results showed that the 6-DOF RFB system could effectively form complex-shaped hollow components. However, there are still large deviations in the test sample, with an average error of 0.68% in the actual bending angle and an average deviation of 6.93 mm in the spatial axis.     

7自由度机器人的图谱问题

本文在分析、归纳、综合的基础上作出了7自由度机械臂的图谱.包括位置空间、奇异空间、回避障碍和回避奇异等问题.给出了一种普遍适用的方法.并介绍了该方法的使用,对7自由度机器人的结构设计和选型有一定的参考价值.     

主被动一体悬架构型的多目标粒子群最优控制

为了解决轮毂电机电动汽车中轮毂电机导致的振动负效应问题,提出了将动态减振与主动悬架结合的悬架新构型方案.针对新构型中结构及控制参数复杂的特点,建立了能够表征平顺性、操稳性以及悬架作动效率的11自由度整车动力学模型.设计基于新构型的多目标粒子群线性二次最优(MOPSO–LQR)控制器.对模型进行仿真分析,仿真结果表明,新构型方案能够实现车辆平顺性、操稳性以及悬架效率的全局最优,对比传统轮毂电机悬架构型方案,在解决轮毂电机振动负效应问题上有良好的效果.