电活性聚合物薄膜柔性结构的动态特性分析与实验

针对用电活性聚合物(EAP)薄膜制造柔性智能器件提出的理论模型和性能要求,采用一种铁电高分子聚合物薄膜制作了柔性结构器件,建立了它的动力学方程、振动行为模型及其机电性能描述。研究了预张力-抗弯刚度、驱动电压、器件几何参数对柔性薄膜器件性能的影响。提出了柔性薄膜器件在预张力和抗弯刚度共同作用下的振动行为模型及其特征化描述,用数值模拟和有限元仿真研究了杨氏模量及预张力-刚度比对柔性薄膜结构振动行为的影响,基于有限元模型与激光多普勒技术模拟和实测了EAP薄膜柔性结构的模态振型。此外,基于压电激励-激光拾振方法研究了驱动电压及器件几何尺寸对EAP薄膜柔性结构动态响应特性的影响。实验结果验证了激光多普勒技术用于EAP薄膜智能器件测试的有效性,揭示了EAP薄膜柔性结构器件的工作机理及动态性能,1V驱动电压可产生精密位移21.6nm。本文为研究EAP薄膜器件提供了理论基础和实验依据。     

圆形压电振膜静态位移模型及参数优化分析

结合薄膜变形原理和压电本构方程,在电压激励条件下,对弹性压电薄膜驱动器进行受力分析,建立压电驱动器横向位移计算模型。在文献提供的几何参数和材料物理参数的基础上,对比理论,文献试验以及模拟仿真的结果,偏差不超过10%,验证理论模型可行。并通过试验测试,进一步分析模型计算结果的准确性,结果表明理论计算与试验数据最大误差在7%以内。基于建立的数学模型,分析不同电压、不同半径比以及不同压电厚度和弹性膜厚度对圆形压电驱动器横向位移的影响。结果表明:圆形压电驱动器中心的横向位移随电压线性变化;在压电驱动器厚度和材料物理参数一定时,压电层与弹性层半径比为0.75时,压电驱动器中心横向位移最大;当电压、材料物理参数以及压电驱动器半径比固定的条件下,分析压电厚度和弹性膜厚度对圆形压电驱动器横向位移影响机理,在压电驱动器总厚度一定条件下,得到最优的压电厚度占总厚度的比值。通过分析不同几何参数对压电驱动器横向位移的影响,指导和优化压电驱动器的结构设计。     

一种介电型电活性聚合物材料的非线性超弹性模型

介电型电活性聚合物(Electroactive polymer,EAP)材料的应力应变本构模型是进行EAP驱动器设计和优化的基础。提出一种由非线性弹簧组成的、具有空间网状结构的EAP膜超弹性模型,基于能量法推导出其应力变形关系式,并揭示该模型与Ogden模型之间的关系。采用单轴、等双轴拉伸试验分别对相关模型参数进行拟合,利用该结果对等双轴、单轴拉伸的受力进行预测和对比分析。根据不同条件拟合出的材料参数进行试验预测时,其结果与实际值存在一定差异,提出对单轴、等双轴拉伸试验数据进行综合拟合的方法。采用综合拟合方法后模型分析精度得到很大提高。分析结果表明,3参数的非线性超弹性模型能较准确描述两种试验条件下的EAP膜应力变形关系,模型参数的拟合数据宜选与其工作条件相近的试验方法获取。     

基于绝对节点坐标法的介电弹性体驱动柔性双层板结构动力学模型

基于绝对节点坐标法,引入介电弹性体本构方程,提出了一种以介电弹性体为驱动板、柔性材料为从动板的新型柔性双层板结构动力学模型,利用数值仿真研究了不同材料参数和激励电压对复合结构动力学特性的影响,对软体机器人驱动器选择和设计提供一定参考。仿真结果表明,复合双层板单元结构在一定大小的驱动电压的激励下会产生周期性变形,在各个方向的运动周期与驱动电压无关,保持复合单元的材料参数不变,其末端最大位移与驱动电压呈近似线性正相关;相同电压激励下,弹性模量越高的复合单元末端运动的周期越小,最大位移也越小,其结构的刚度和稳定性越强。当驱动电压过高,从动板单元材料超弹性系数过小时,复合单元柔性过大,末端运动出现将失稳现象。     

介电弹性体线性驱动器研究

为满足未来机电系统对新型驱动器的需求,研究菱形介电弹性体线性驱动器。在分析驱动器工作原理的基础上,通过驱动器力—位移曲线和预载荷关系的分析,确定弹性预载荷元件。驱动器通电后能迅速响应,线性位移达到21 mm,弹性体面积变化率达到98%;驱动器失电后能迅速退回,最终退回到初始位置。通过试验分析电压和负载对驱动器的影响,试验表明：驱动器输出位移取决于电压;负载在驱动器输出力范围内对输出位移影响不大,但会影响其运动速度。并根据驱动器的特点,指出驱动器的应用范围。     

介电型EAP柔性摆动驱动器研究

为研究介电型EAP摆动驱动器的性能,设计制作了柔杆式介电型EAP摆动驱动器。对驱动器的摆动性能进行了测试,获得了不同施加电压下驱动器的摆动角度与阻转力。结果表明,随着施加电压的增加,驱动器的摆动角度、阻转力也在增加,且在电压较大时增加更快。此外,EAP的拉伸率对驱动器性能也有一定的影响,并指出了该驱动器在结构与性能优化的基础上,可潜在用于仿生机器人的摆动驱动。     

介电型EAP柔性摆动驱动器研究

为研究介电型EAP摆动驱动器的性能,设计制作了柔杆式介电型EAP摆动驱动器。对驱动器的摆动性能进行了测试,获得了不同施加电压下驱动器的摆动角度与阻转力。结果表明,随着施加电压的增加,驱动器的摆动角度、阻转力也在增加,且在电压较大时增加更快。此外,EAP的拉伸率对驱动器性能也有一定的影响,并指出了该驱动器在结构与性能优化的基础上,可潜在用于仿生机器人的摆动驱动。     

电活性聚合物材料及其在驱动器中的应用研究

介绍电活性聚合物(Electro-active polymer,EAP)材料的基本概念与分类,并以离子聚合物-金属复合材料(Ionicpolymer-metal composites,IPMC)和介电弹性材料(Dielectric elastomers,DE)分别作为离子型和电子型EAP材料的典型代表,详细介绍其国内外研究现状。重点介绍本课题组对上述两种材料的制备工艺、基础理论等方面的研究进展及成果。针对IPMC材料,研究了制备工艺对电极沉积的影响及工艺优化、IPMC界面物理模型、铸膜及封装技术、IPMC材料大变形机理及建模;针对DE材料,研究其电致驱动的机电耦合特性及预拉伸、温度及黏弹性对其机电耦合稳定性的影响。简要介绍本课题组在基于EAP材料的微泵、微镜头驱动器以及面向微创手术的多自由度机械臂等方面的应用研究成果。     

导电聚合物驱动器电化学机械特性的研究

采用自行搭建的导电聚合物驱动器弯曲特性测试实验系统,研究其电化学机械特性。对不同长度的驱动器施加0~1V低电压,测量其顶端弯曲变形量;通过分析驱动器弯曲位移与电压的关系及位移与频率的关系,建立电机械转换模型。实验测试结果表明,电压与驱动器顶端力成线性关系;当电压为0.8V、采样周期为0.02s时,随着频率的增大,驱动器的弯曲位移逐渐减小。最后通过不同尺寸驱动器举起重物,验证了驱动器宽度越大,顶端弯曲力越大;驱动器长度越长,顶端弯曲力越小。     

高频周期位移激励下的叶片辊轧机振动特性研究

根据齿轮齿条啮合特性,建立了含有高频周期位移激励的叶片辊轧机非线性垂直振动模型。采用多尺度法求解了系统非线性振动的近似解,研究了高频周期位移激励的振幅、频率对叶片辊轧机非线性垂直振动的影响。研究结果表明:随着高频周期位移激励振幅的增加,系统振幅增加,且振动系统出现了高次谐波振动;高频周期位移频率的增加使振动系统振幅、频率减小,且高次谐波振动减弱。研究结果为叶片辊轧机系统动态特性优化提供理论依据。     

基于扫频响应反推黏弹性材料分数阶导数模型

提出了基于测试获得的扫频响应反推黏弹性材料分数阶导数模型参数的方法。在同时考虑黏弹性材料阻尼和剩余等效黏性阻尼的基础上,建立了基础激励作用下黏弹性复合板动力学方程,给出了求解振动响应的方法。提出利用基于灵敏度的匹配计算实现分数阶导数模型参数辨识的方法。以贴敷ZN-1型黏弹性材料的悬臂钛板为例,辨识得到了该黏弹性材料的分数阶导数模型。将结果代入到黏弹性阻尼板振动响应分析模型中,通过理论与实验的对比,证明了辨识参数的合理性。     

Optimal Design of Novel Electromagnetic-Ring Active Balancing Actuator with Radial Excitation

Imbalance vibration is a typical failure mode of rotational machines and has significant negative effects on the effii-ciency,accuracy,and service life of equipment.To automatically reduce the imbalance vibration during the opera-tional process,different types of active balancing actuators have been designed and widely applied in actual produc-tion.However,the existing electromagnetic-ring active balancing actuator is designed based on an axial excitation structure which can cause structural instability and has low electromagnetic driving efficiency.In this paper,a novel radial excitation structure and the working principle of an electromagnetic-ring active balancing actuator with a combined driving strategy are presented in detail.Then,based on a finite element model,the performance param-eters of the actuator are analyzed,and reasonable design parameters are obtained.Self-locking torque measurements and comparative static and dynamic experiments are performed to validate the self-locking torque and driving effi-ciency of the actuator.The results indicate that this novel active balancing actuator has sufficient self-locking torque,achieves normal step rotation at 2000 r/min,and reduces the driving voltage by 12.5％.The proposed novel balancing actuator using radial excitation and a combination of permanent magnets and soft-iron blocks has improved electro-magnetic efficiency and a more stable and compact structure.     

Numerical estimation of dynamic behavior of viscoelastic elastomer specimen

Dynamic deformation behavior of a cylindrical specimen made of viscoelastic elastomers was investigated numerically by solving the two-dimensional elastic wave equations. In order to enhance the accuracy of the viscoelastic property calculations, a pseudospectral analysis of two-dimensional elastic wave equation was employed. This allowed us to exclude the use of the form factor derived from the conventional one-dimensional model. Using the present method, an assessment of the conventional form factor concept was attempted. The present two-dimensional method was then utilized to predict a forced vibration response of the elastomer samples under periodic excitation. Obtained numerical results were compared with those using the simplest one-dimensional model. Applicable range of the form factor was examined. Empirical formulas to correct static and dynamic form factors for elastic deformation mode, which are suitable for engineering applications, are suggested.     

Effects of structural configuration on vibration control of smart laminated beams under random excitations?

The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation coefficient is higher than that for harder configurations. The study on the effect of sensor/actuator collocation pairs on optimal vibration control reveals that as the actuator shifts away from the sensor location, the peak of power occurs at higher frequency and becomes more distributed through all the frequencies in the domain.     

Thermally induced vibration control of cylindrical shell using piezoelectric sensor and actuator

Shell type components and structures are very common in many mechanical and structural systems. Modeling and analysis of adaptive piezothermoelastic shell laminates represent a high level of sophistication and complexity. In this paper a finite element model is developed for the active control of thermally induced vibration of laminated composite shells with piezoelectric sensors and actuators. The present model takes into account the mass, stiffness and thermal expansion of the piezoelectric patches. A C_o continuous nine-node degenerated shell element is implemented to model the structure. The piezoelectric sensing layer senses the structural vibration and a suitable voltage applied in the piezoelectric actuator layer suppresses the oscillation. Actuator and sensor are coupled together with a control algorithm so as to actively control the dynamic response of the structure in a close loop. Numerical results are generated for a cylindrical shell and it is observed that thermally induced vibration of a laminated cylindrical shell can be suppressed through the application of piezoelectric sensor and actuator. Effects of variation in control gain and piezoelectric layer area coverage (PAC) have been studied. Higher control gain is more effective in damping out the vibration. Although the damping is enhanced by increase in PAC, increase beyond a certain level may not be useful in view of smaller efficacy and increased weight.     

考虑局部故障边缘形态的球轴承振动特征

在分析球与不同边缘形态的局部故障之间接触关系的基础上,根据赫兹接触理论建立了球与局部故障光滑圆柱型边缘之间的接触刚度模型,以及球进入故障区域时的时变位移激励模型。考虑弹性流体动力润滑油膜的影响,提出时变冲击激励耦合的球轴承圆弧边缘型局部故障动力学模型。该模型考虑了故障边缘形态特征变化引起的球进入故障时的时变额外位移激励,以及球与故障边缘之间的时变接触刚度。研究滚道表面圆弧型边缘型局部故障激励下的球轴承振动响应特征,并分析故障边缘形态变化对球轴承振动响应特征的影响规律,解决了尖锐边缘型局部故障模型无法描述其边缘形态变化的问题,为获得可靠的局部故障球轴承的动力学响应特征提供新的手段和方法,也为球轴承局部故障的准确识别与定量诊断提供一定的理论依据。     

Non-contact electromagnetic exciter design with linear control method

A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for identifying the dynamic coefficients of journal bearings in high-speed grinding spindles. A linear force control method is developed based on PID controller. The influence of amplitude and frequency of current, misalignment and rotational speed on magnetic field and excitation force is investigated based on two-dimensional finite element analysis. The electromagnetic excitation force is measured with the auxiliary coils and calibrated by load cells. The design is validated by the experimental results. Theoretical and experimental investigations show that the proposed design can accurately generate linear excitation force with sufficiently large amplitude and higher signal to noise ratio. Moreover, the fluctuations in force amplitude are reduced to a greater extent with the designed linear control method even when the air gap changes due to the rotor vibration at high-speed conditions. Besides, it is possible to apply various types of excitations: constant, synchronous, and non-synchronous excitation forces based on the proposed linear control method. This exciter can be used as linear-force exciting and controlling system for dynamic performance study of different high-speed rotor-bearing systems.     

随机内外激励对齿轮系统动态特性的影响分析

考虑时变啮合刚度、齿侧间隙等因素的影响,建立了单对齿轮系统纯扭转非线性动力学模型。将齿轮综合传递误差波动和外部载荷作为随机变量,利用数值仿真方法对系统模型进行了求解,通过统计分析得到了系统各响应量和动态啮合力的统计特征。结果表明:外部激励的随机性对齿轮系统振幅和动态啮合力的影响比综合传递误差波动随机时明显;综合传递误差及外部激励随机波动离散程度的增加会导致系统振幅和动态啮合力不稳定性加剧。     

介电型EAP驱动的伸缩移动机器人研究

以介电型EAP为驱动材料,设计、制作了一种结构紧凑的圆柱形驱动器.模仿自然界无足爬行生物的运动机理,设计了基于该驱动器的可伸缩移动机器人,实现机器人的向前伸缩运动,验证了该介电型EAP驱动器在该类型机器人中的实用性.     

激励幅值慢变转子系统的动力学研究

建立了激励幅值慢变转子系统的动力学模型,利用渐近法对其动力学行为进行解析研究,得到了用显式形式表示的近似解析解,给出了系统响应的时域波形图和轴心轨迹图,分析了激励频率和系统阻尼对最大轴心位移的影响。结果表明:激励幅值慢变转子系统的振幅会产生相应的慢变波动,此类转子系统为多周期运动,周期数取决于激励频率和幅值慢变系数组合关系,且振动周期具有参数慢变敏感性等。