球基微操作器黏滑摩擦过程建模与分析

球基微操作器通过压电陶瓷管端部与微操作球之间惯性摩擦形成的相对位移实现微操作球三自由度的运动,这种摩擦运动中存在黏滑现象。在简化球面高副连接的条件下,建立了球基微操作器双质量摩擦振子等效工程模型,对球基微操作器黏滑驱动过程进行了阶段细分,基于等效工程模型及动态LuGre摩擦模型建立了黏滑摩擦过程的动力学方程。运用数值仿真方法分析了球基微操作器的参数特性曲线,进行了运动测试实验,进一步验证了分析的正确性。     

压电陶瓷驱动球基微驱动器的动力学研究

研制出了尺寸为30 mm×30 mm×50 mm的压电陶瓷驱动的球基微驱动器样机,并对该微驱动器进行动力学分析以及微型轴孔装配的实验研究。建立了微驱动器金属球空间坐标关系,分析了球基微驱动器的动力学特征,并建立了其动力学模型。采用龙格-库塔法计算出了微驱动器的动力学参数,并利用MATLAB的SIMULINK模块搭建了微驱动器的仿真模型,并对其进行了动力学仿真分析。研制出了球基微驱动器样机,并在此基础上,集成微夹持器形成微操作器,对微驱动器性能进行了实验测试,并开展了Φ180 μm微型轴与Φ200 μm微型孔之间的精密微装配实验研究。最后,分析了微驱动器金属球质量、驱动信号频率、以及金属球与微驱动单元摩擦块接触表面摩擦系数对其性能的影响。实验结果表明:该球基微驱动器的转动分辨率为0.000 1°,转动定位精度为0.000 5°,微驱动器最大工作频率为1 200 Hz。实验结果验证了逆转振动模型的正确性,由该微驱动器所集成的微操作器,完全可以满足对微小元器件的微米级操作与装配等精密作业的要求。     

无线微小型机器人及其驱动控制

研制了一种面向微操作的微小型机器人,并开发了其无缆化控制系统。该机器人机械本体由基于宏／微复合驱动的移动定位平台和3自由度球基微操作器构成。机器人总体尺寸不超过90 mm×70 mm×60 mm。机器人的宏动部分采用轮式驱动,选用轴直径为3 mm的微型电动机,运动速度可达100 mm／s,定位精度0．5 mm,运动分辨率0．1mm。微动部分基于尺蠖蠕动原理通过压电陶瓷和电磁体配合,速度可达200μm／s,定位精度50μm,运动分辨率2 μm。球基微操作器基于黏滑原理利用3根四分压电陶瓷管驱动,可实现旋转和俯仰运动,运动分辨率可达0．001。。所有驱动电路均集成到机器人本体内,采用锂聚合物电池供电,通过蓝牙模块和上位机的图像处理系统通信。嵌入式控制软件将机器人的运动全部分解为简单运动,控制算法采用多线程方式,保证了驱动控制的实时性,并且具有很强的抗干扰能力。     

压电粘滑驱动系统中温度变化的实验研究

压电粘滑驱动系统具有长行程(几十毫米或更多,取决于机械结构)和高精度(几纳米)的特点.摩擦在粘滑驱动器中具有积极的作用.但在驱动器运行中,摩擦也可能造成"明显的"温度变化,在微运动中,该温度变化可能影响驱动器的精度.本次研究的目的是开发一种温度测量系统来测量粘滑驱动器在运行中的温度变化.其关键技术在于如何妥善处理如此小信噪比物理信号.实验表明,通过设计合理的滤波器和选择合适的高分辨率传感器,这里开发的温度测量系统可以很好的测量出温度变化.通过实验发现,压电粘滑驱动器中温度变化既来自于摩擦又来自于压电陶瓷自身发热.由压电陶瓷自身发热导致的温度变化呈非线性,而由摩擦导致的温度变化呈线性.     

压电薄膜型精密运动平台研究

提出了一种利用双压电晶片驱动小型平台的研究方案,该平台可实现水平面内的两自由度精密运动.在对粘滑型运动机构的工作原理进行分析的基础上,建立了压电式粘滑机构的动力学模型并进行了仿真分析,设计研制了试验样机,并从运动性能和承载能力两个方面对样机进行了实验研究.实验结果表明,设计的压电薄膜型精密运动平台结构简单、体积小、质量轻、步距稳定且行程大,电压低于30 V驱动时,步距误差不超过0.5μm,承载能力约为自身质量的7～8倍.     

二自由度大行程无耦合压电粘滑定位平台

针对微操作与微装配任务对多维大范围精密定位运动的需求,采用粘滑驱动原理并结合压电柔顺机构设计二自由度、大行程、无耦合并联定位平台。利用桥式机构对内置压电驱动器进行位移放大,并与复合解耦结构配合构成二维柔顺驱动机构。交叉滚柱导轨则连接移动台与驱动机构,并通过预紧螺钉调整接触摩擦力,进而获得良好的粘滑运动特性。采用有限元法建立定位平台的静力学模型,并对位移放大倍数、应力和固有频率进行仿真分析。最后,搭建实验测试系统验证定位平台的输出性能。实验结果表明：在扫描驱动模式下,驱动电压为150 V时,平台x和y向的输出位移分别为63.84μm和62.61μm,耦合比为0.52%和0.59%,分辨率为6.5 nm和7.2 nm;在步进驱动模式下,驱动电压为120 V时,平台在x和y向的单步位移分别为47.31μm和47.20μm,耦合比为0.69%和0.73%,x正向、x反向、y正向和y反向的运动分辨率分别为0.49,0.47,0.47和0.42μm,最大垂直负载为50 N,设计的压电粘滑定位平台满足所需性能要求。     

一种无耦合位移和低集中应力的二维微操作器研究

集中应力和耦合位移是影响基于柔性铰链和压电陶瓷驱动器的微操作器性能的关键因素。单平行四杆机构具有低的集中应力，但存在大的耦合位移，双平行四杆机构没有耦合位移但存在较大的集中应力。在分析上述2种经典微操作器机构优缺点的基础上，吸取每一种机构的优点，摈弃各自的缺点，构建了一种复合四杆机构，并对这3种机构进行了对比分析，用有限元仿真的结果证明了理论分析的正确性。本文还设计加工了3种类型的二维微操作器柔性铰链机构与压电陶瓷驱动组成二微维操作器，并进行了对比实验研究，实验结果表明，该复合四杆微操作器性能优于经典的平行四杆微操作器和双平行四杆微操作器。     

压电柔顺微操作器的H∞反馈控制

为保证压电柔顺微操作器的精准性和稳定性,以压电纤维驱动的单自由度柔性微操作器为例,首先,通过在传统Prandtl-Ishlinskii(简称PI)迟滞模型上串联死区算子,建立改进PI迟滞模型并设计相应前馈控制器;其次,将系统模型分解为线性可逆分量和有界分量,并构建权重函数和增广模型设计H_∞反馈控制器,以保证系统的稳定性和精准性;最后,以压电纤维驱动的单自由度柔性微操作器为例,搭建实验测控系统。实验结果表明：在前馈控制下,压电柔顺微操作器的迟滞量从16.5%下降到4.4%,改进PI迟滞模型是可行的。当参考轨迹为阶跃和不同频率的正弦信号、甚至改变微操作器结构参数时,H_∞反馈控制均能有效跟踪给定参考信号且相对控制误差较小,验证了所设计H_∞反馈控制器的有效性。     

含间隙及摩擦的振动系统动力学分析

考虑接触表面工况的差异性,建立一类含两类摩擦及间隙的两自由度碰撞振动系统动力学模型,给出系统在不同运动阶段的判断条件和粘-滑-碰运动行为过渡准则,采用数值仿真方法对系统求解,结合判断条件分析摩擦对系统造成的非光滑运动特性及复杂的动力学行为,同时分析不同摩擦模型对系统动力学特性的影响。结果表明,系统存在瞬时摩擦诱导振动、周期颤振、颤振向粘着过渡及粘-滑-碰之间的转换等摩擦振动现象。     

新型三自由度微操作平台的动力学性能研究

提出了一种新型三自由度柔性并联微操作平台,该平台采用压电陶瓷驱动器为驱动装置,以新型二级杠杆放大机构作为放大器来扩大压电陶瓷驱动器的输出行程,在功能上可以实现X轴、Y轴以及Z轴方向的微米范围内移动。首先通过拉格朗日方程建立了该三自由度柔性并联微操作平台的动力学模型,然后计算了该机构的理论固有频率,最后采用有限元软件对该微操作平台进行了模态分析。结果表明该机构的理论固有频率与有限元仿真分析中的第一阶模态结果相比其误差率仅为2.54%,验证了固有频率理论分析的正确性及可行性。     

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]     

Effect of surface topography on the frictional behavior at the micro/nano-scale

In this paper, the effect of surface topography on the frictional behavior is investigated at micro/nano-scale in order to better understand the influence of asperity contact angle on friction. Experiments were performed to observe the variation in the frictional force as a spherical ball slides across a grooved surface. Specimens with single and multiple grooves of tens of micrometers in width were fabricated on silicon wafers. The frictional behavior between these specimens and steel balls of different diameters were observed with a tribometer built inside a scanning electron microscope (SEM). Normal load in the range of 20 mN and sliding speed of about 1-6 μm/s were applied in the experiments. It was shown that for relative ball/groove dimension that resulted in low contact angle, the overall frictional force was less than that observed for surface without the groove. Also, in situations where there was a great change in the contact angle stick-slip behavior could be observed. This stick-slip behavior is attributed to mechanical interlocking action.In addition to the above experiments, tests were conducted using lateral force microscopy (LFM). Unlike the previous finding that LFM output is dependent on the slope alone, it was found that the signal was more sensitive to the change in slope, especially when the slope was relatively large. Overall, both micro and nano-scale topographic effect on friction was similar. These results will ultimately aid in design of surface topography for micro-systems for best tribological performance.     

界面摩擦过程黏滑行为特征研究

通过建立界面摩擦系统动力学模型,并利用原子力显微镜测试云母、石英以及单晶硅片界面摩擦条件下的黏滑行为特征,探讨摩擦系统内外因素对黏滑频率、幅值的影响。结果表明:同一实验条件下,不同材料的黏滑频率与黏滑波动幅值不同;缓慢滑动时,黏滑的频率主要取决于表面势场的频率,波动幅值取决于表面势场强度,随着滑动速度逐渐增大,黏滑频率同时取决于表面势场频率和探针系统的固有频率,波动幅值取决于表面势场强度和探针系统结构;滑动速度较大时,黏滑频率及波动幅值主要取决于探针系统,且随着滑动速度增大,波动幅值逐渐减小。     

离合器从动盘性能对汽车耸车的影响

为了研究离合器从动盘性能对汽车耸车振动的影响,建立了传动系统-汽车整车的11自由度非线性动力学模型。模型考虑了离合器从动盘的扭转特性、干摩擦阻尼、离合器接合黏滑特性以及变速器轮齿啮合刚度。利用建立的模型计算汽车起步过程系统动力学响应,通过实车测试验证模型的正确性,分析离合器从动盘性能参数对耸车振动的影响。结果表明:汽车的耸车现象发生在离合器完全接合之后;耸车振动频率与传动系第2阶固有频率相近;提高静摩擦因数,降低从动盘转动惯量和2级扭转刚度,可以降低汽车在起步过程中的耸车振动。本研究的建模和分析方法,可以用来计算与分析离合器从动盘结构性能参数对整车耸车振动特性的影响。     

Mathematical model of the stick-slip phenomenon

A mathematical model of the stick-slip phenomenon is presented which is related to the characteristic changes of the friction forces as a function of the slip speed. The model leads to simple differential equations without the necessity of using distribution equations. It can be utilized in a simple way to describe actual friction nodes.     

Numerical analysis of stick-slip instability by a rate-dependent elastoplastic formulation for friction

In various fields of engineering, it is important to clarify friction-induced vibration, such as stick-slip motion, for a wide range of scales from microscopic elements to continental plates. In the present study, we apply a rate- and state-dependent friction model [30] (Hashiguchi and Ozaki, 2008), which can rationally describe the reciprocal transition between the static friction and the kinetic friction by a unified formulation, to the simulation of stick-slip instability for a one-degree-of-freedom spring-mass system under various conditions. It is verified that the various basic experimental findings on stick-slip motion can be pertinently described by the present approach. Moreover, the effect of the dynamic characteristics of the system, such as the mass, stiffness and driving velocity, is discussed, and parameters prescribing the rate of reciprocal transition of static-kinetic frictions and the preliminary microscopic sliding on the instability of the stick-slip motion are also discussed.     

基于非连续能量耗散的界面摩擦黏滑行为动力学研究

建立界面摩擦过程黏滑行为动力学模型,仿真分析摩擦系统内外因素对黏滑行为的影响规律.结果表明:界面摩擦过程中,黏滑行为不仅与材料本身如晶格常数、原子质量、原子间横向刚度系数有关,而且与系统外界参数如滑动速度及滑动部件的质量有关;材料的原子间横向刚度、晶格常数、原子质量、滑动机构质量愈小,黏滑行为愈显著,而相对滑动速度愈大,黏滑行为愈显著.     

Stick-slip algorithm in a tangential contact force model for multi-body system dynamics

Contact force of Multi-body dynamics (MBD) system can be classified two parts. First is a normal force and the other is a tangential force called friction force. And the friction force can be represented by two states such as stick and slip. The stick-slip phenomenon is simply described as a simple contact model which is a rigid body contacted on a sloped surface. If the calculated friction coefficient between the body and sloped surface is less than the static friction coefficient, the body should be stuck. If the calculated friction coefficient is greater than the static friction coefficient, the body will be sliding along the surface. The phenomenon is called as stick and slip state of friction, respectively. Usually many researchers and commercial MBD software used a coulomb friction force model which is defined with an only function of relative velocity. This kind of friction force model will be called a conventional friction force model in this paper. A big problem of the conventional model can not describe a stick state of friction phenomenon. In the case of conventional friction force model, the body will be sliding even though friction state is stick. Because, the relative velocity must have a non-zero value in order to generate the friction force. To solve this kind of problem, we propose a stick-slip friction force model including a spring like force. In the case of stick-slip friction force model, the body can be stuck on the sloped surface because the friction force will be a non-zero value, even though the relative velocity approaches zero. We defined a relative displacement variable called stiction deformation. In this paper, the stick-slip friction model is proposed and applied in the contact algorithm of MBD system. And then two friction models are compared with numerical examples. With the proposed stick-slip friction model, more realistic results are achieved.