《智能材料与结构技术》专题文章导读：半电极含金属芯压电纤维的驱动性能

建立了悬臂梁结构半电极含金属芯压电纤维新型压电弯曲驱动器的理论模型。根据第一类压电方程,推导出自由端位移、夹持力和弯曲共振频率的解析表达式,分析了金属芯性能和半径对这3个参数的影响,并把理论计算结果和有限元分析结果进行了比较。实验结果表明,悬臂梁结构半电极含金属芯压电纤维弯曲驱动器的自由端位移可达589um,央持力可达427uN,一阶弯曲共振频率为28Hz,有限元分析结果和理论值基本吻合,说明这种驱动器有较大的端部位移、较小的夹持力和较低的弯曲共振频率。     

半电极含金属芯压电纤维的驱动特性研究

半电极含金属芯压电纤维是一种新型的压电传感器和驱动器。金属芯位于纤维的中心位置,外面包裹着压电陶瓷部分。金属芯可以用作一个电极,覆盖在纤维一半表面上的金属层作为另一个电极。在表面电极和金属芯上外加电压后,由于压电效应,整个压电纤维将产生弯曲变形。建立了这种悬臂梁结构压电弯曲驱动器的理论模型,导出了自由端位移、夹持力和弯曲共振频率的解析表达式;并用理论计算和有限元分析方法研究了金属芯对这三个参数的影响。结果表明：这种驱动器有较大的端部位移、较小的夹持力、较低的弯曲共振频率。最后用实验方法验证了理论结果。     

含金属芯压电纤维的驱动特性研究

针对含金属芯压电纤维这种新型驱动器的确定特性,建立了悬臂杆结构含金属芯压电纤维驱动器的理论模型.根据第一类压电方程,推导出了自由端位移、夹持力和纵向共振频率的解析表达式,分析了金属芯性能和半径对这3个参数的影响;并把理论计算结果和有限元分析结果进行了比较.通过实验测量了自由端位移和夹持力.理论和实验结果表明,这种驱动器...     

半电极含金属芯压电纤维的弯曲振动模型

建立了悬臂梁结构的半电极含金属芯压电纤维(HMPF)的弯曲振动模型和动态测试模型。基于外加电压时的等效弯矩,推导了悬臂梁结构的HMPF的弯曲振动模型;用第一类压电方程,推导了外加简谐激励电压时,HMPF的表面电位移、电荷和导纳,建立了动态测试模型,通过测量共振频率fr、反共振频率fa和低频电容CLF,得到HMPF的弹性柔顺系数s1E1、机电耦合系数k31、介电常数ε3T3和压电常数d31。叙述了弯曲振动模型和动态测量模型的建立过程和测试步骤,测试了3根HMPF样品,得到各参数的平均值,s1E1为16.856×10-12 Pa-1,k31为0.179,ε3T3为2 251,d31为-103.621pC/N。测试结果表明所建立的动态测试方法可以快速、准确地测量HMPF的主要参数。     

阶梯结构微梁传感器优化设计

为了实现微悬臂梁传感器的自驱动自感知功能,设计了嵌套式阶梯结构微悬臂梁传感器。采用有限元分析的方法对其微梁的自由端弯曲位移和固有频率进行了仿真,研究了阶梯结构对微悬臂梁传感器性能的改善,确定了微悬臂梁传感器的阶梯结构参数。结果表明,经优化设计后的微梁传感器,微悬臂梁自由端弯曲位移可达566 nm,提高了2倍;固有频率可达385 k Hz,提高了1. 45倍。阶梯式微梁的成功设计为传感器的集成与小型化奠定了基础。     

功能梯度压电驱动器的结构设计、制备与功能验证

本文作者在以前的研究中,提出了一种新型的功能梯度驱动器。在此基础上,本文设计并制备了该驱动器,建立了理论模型,并对驱动器的性能进行了测试。这种新型功能梯度驱动器由4种基于Pb(Ni1/3Nb2/3)O3－PbZrO3－PbTiO3系列的材料复合而成,且四层材料的压电常数和介电常数在厚度方向上的梯度变化相反,这种梯度结构能够使得驱动器结构内部的应力分布优于传统弯曲驱动器。为了对驱动器进行优化设计,作者利用经典复合材料力学和压电方程建立了功能梯度压电驱动器的理论模型,并计算了不同厚度配比的驱动器受电压和自由端集中力单独作用时的准静态变形和应力分布。通过分析驱动器的内部应力确定了最优厚度配比。根据优化结果成功制备了功能梯度压电驱动器,并测量了驱动器自由端输出位移与输出力的关系。测量结果表明：功能梯度压电弯曲驱动器的输出位移和输出力呈线性关系,并且频率越低,输出位移和力就越大。     

基于压电悬臂梁的驱动器与传感器性能分析的精确解析模型

三层压电梁结构在电场作用下发生变形后会产生诱发电势,进而改变材料整体电势分布,本文考虑此变形和电势耦合效应,基于欧拉-伯努利梁变形理论,推导出能够准确预测压电智能悬臂梁传感器与驱动器性能的解析表达式。考虑压电梁结构弯曲变形后产生的电场影响,建立了三层压电梁结构的控制方程;建立了压电梁作为驱动器时端部输出位移、驱动力矩与输入电压之间联系的解析表达式,以及作为传感器时输出电压与端部作用力之间联系的解析表达式。通过与ANSYS有限元模拟结果以及传统的驱动器和传感器性能表达式的对比,验证了所推导的解析表达式的准确性。     

表面半电极含金属芯PVDF纤维振动传感特性研究

模仿蜘蛛等昆虫的毛发感受器结构,在制备好的含金属芯PVDF纤维的一半纵向表面均匀涂镀导电银浆用作表面电极,极化之后制备成表面半电极含金属芯PVDF纤维(HMPF)振动传感器。将HMPF粘贴在基体上形成悬臂梁结构的HMPF振动传感器。建立悬臂梁结构HMPF的振动传感模型,并搭建实验系统进行验证。理论和实验结果表明,HMPF可以感知基体振动的幅值和频率,并具有明显的振动方向感知能力,具有广泛的工程应用前景。     

四自由度压电微夹钳的设计

为降低微夹钳前端执行机构的复杂度,探索四自由度压电微夹钳的实现问题。通过在被设计成夹钳形状的两个压电单晶片的非黏结面上制作相互绝缘的驱动电极,且使两个非黏结面上驱动电极相互对齐的方法,设计出了可同时产生夹持方向与垂直于夹持方向位移的四自由度压电微夹钳;采用压电悬臂梁变形理论,推导出了钳指位移同钳指几何参数、驱动电压的关系,进而在对钳指进行尺寸优化的基础上,采用有限元方法分析了其静动态特性;最后,对微夹钳的静动态特性进行了测试,结果表明：当驱动电压为60 V时,左钳指、右钳指在夹持方向上的位移分别为25.7 μm、26.1 μm,左、右钳指在垂直于夹持方向上的位移分别为33.5 μm、32.8 μm,钳指位移具有很好的重复性;微夹钳在夹持方向和垂直于夹持方向的固有频率分别为2.35 kHz、0.62 kHz;在15 V的阶跃电压作用下,微夹钳在夹持方向和垂直于夹持方向的响应时间均为0.23 s。     

悬臂梁压电弯曲效应研究与验证

采用各向异性弹性理论和电磁理论计算压电石英悬臂梁的弯曲应力和弯曲束缚电荷密度,并利用有限元方法模拟出极化电场分布。理论分析表明,采用分割电极法在压电梁表面合理布置检测电极可测量弯曲效应。对该悬臂梁压电弯曲效应进行了实验验证,实验结果表明电极检测的电荷量与外力成线性关系,理论分析与实验结果基本一致。悬臂梁压电弯曲效应研究将为新型压电谐振器或执行器的开发奠定理论和实验基础。     

Dynamic responses and fuzzy control of a simply-supported beam subjected to a moving mass

This paper deals with the active vibration control of a simply-supported beam traversed by a moving mass using fuzzy control. Governing equations for dynamic responses of a beam under a moving mass are derived by Galerkin’s mode summation method, and the effect of forces (gravity force, Coliolis force, inertia force caused by the slope of the beam, transverse inertia force of the beam) due to the moving mass on the dynamic response of a beam is discussed. For the active control of dynamic deflection and vibration of a beam under the moving mass, the controller based on fuzzy logic is used and the experiments are conducted by VCM (voice coil motor) actuator to suppress the vibration of a beam. Through the numerical and experimental studies, the following conclusions were obtained. With increasing mass ratioy at a fixed velocity of the moving mass under the critical velocity, the position of moving mass at the maximum dynamic deflection moves to the right end of the beam. With increasing velocity of the moving mass at a fixed mass ratioy, the position of moving mass at the maximum dynamic deflection moves to the right end of the beam too. The numerical predictions of dynamic deflection of the beam have a good agreement with the experimental results. With the fuzzy control, more than 50% reductions of dynamic deflection and residual vibration of the tested beam under the moving mass are obtained.     

Macroscopic and microscopic observations of needle insertion into gels

Needle insertion into soft tissue is one of the most common medical interventions. This study provides macroscopic and microscopic observations of needle-gel interactions. A gelatin mixture is used as a soft-tissue simulant. For the macroscopic studies, system parameters, such as insertion velocity, needle diameter, gel elasticity, needle tip shape (including bevel angle) and insertion motion profile, are varied, while the maximum insertion force and maximum needle deflection are recorded. The needle tip and gel interactions are observed using confocal microscopic images. Observations indicate that increasing the insertion velocity and needle diameter results in larger insertion forces and smaller needle deflections. Varying the needle bevel angle from 8 degrees to 82 degrees results in the insertion force increasing monotonically, while the needle deflection does not. These variations are due to the coupling between gel rupture and tip compression interactions, which are observed during microscopic studies. Increasing the gel elasticity results in larger insertion forces and needle deflections. Varying the tip shapes demonstrates that bevel-tipped needles produce the largest deflection, but insertion force does not vary among the tested tip shapes. Insertion with different motion profiles are performed. Results show that adding I Hz rotational motion during linear insertion decreases the needle deflection. Increasing the rotational motion from I Hz to 5 Hz decreases the insertion force, while the needle deflection remains the same. A high-velocity (250 mm/s and 300 mm/s) tapping during insertion yields no significant decrease in needle deflection and a slight increase in insertion force.     

压电双晶片的有限元分析及实验

采用有限元分析方法,分析了压电双晶片悬臂梁的位移形变特征.研究了金属弹性层、压电陶瓷片的材料属性及几何尺寸对双晶片偏转位移的影响;计算了双晶片的弹性模量、厚度以及加载电压与位移形变产生弯应力的关系;通过位移测试、弯应力测试等相关实验对有限元分析进行了验证.当加载电压为60 V(120 Vp-p)时,双晶片的偏转位移和弯应力分别为166/μm和34.7 m·N,实验结果证明本文所建的有限元模型是合理有效的.此外,测试了压电双晶片的振动特性,测得其谐振频率为310 Hz,在该频率下加载20 Vp-p电压,其端部位移输出即可达1.7 mm.有限元分析结果及实验验证为压电双晶片结构的优化设计提供了依据.     

一种微开关悬臂梁的静力变形分析模型及其应用

建立一种微开关悬臂梁的静力变形分析模型,该模型将微开关悬臂梁的受力变形分为三个阶段,受电场力作用的悬臂梁阶段,受电场力作用的一端固支、另一端铰支的单跨梁阶段以及受电场力和集中力联合作用而保持自由端有指定的位移和零转角阶段。第二阶段中铰支端支反力的大小以及第三阶段中集中力的大小和作用位置均与电场力的驱动电压有关;同时文中将求解微开关悬臂梁挠度的高阶微分方程问题转化为含有未知初始条件的一阶微分方程组问题。在实例中,设计一种求解未知初始条件的迭代方法,并给出部分计算结果,从中可得出一些有益的结论。     

Fibre-top atomic force microscope probe with optical near-field detection capabilities

We present a fibre-top probe fabricated by carving a tipped cantilever on an optical fibre, with the tip machined in correspondence of the fibre core. When approached to an optical prism illuminated under total internal reflection conditions, the tip of the cantilever detects the optical tunnelling signal, while the light coupled from the opposite end of the fibre measures the deflection of the cantilever. Our results suggest that fibre-top technology can be used for the development of a new generation of hybrid probes that can combine atomic force microscopy with scanning near field optical microscopy.     

Inverse estimation of the tapered probe-sample shear force of scanning near-field optical microscope

In this paper, the conjugate gradient method of minimization with an adjoint equation is successfully applied to solve the inverse problem in estimating the shear force between the tapered probe and sample during the scanning process of scanning near-field optical microscope (SNOM). While knowing the available deflection at the tapered probe tip, the determination of the interaction shear force is regarded as an inverse vibration problem. In the estimating processes, no prior information on the functional form of the unknown quantity is required. The accuracy of the inverse analysis is examined by using the simulated exact and inexact measurements of deflection at the tapered probe tip. Numerical results show that good estimations on the interaction shear force can be obtained for all the test cases considered in this study.     

CUTTING PROCESS DIAGNOSTICS UTILISING A SMART CUTTING TOOL

A new sensorised boring tool has been developed to enhance the flexibility and precision of line boring processes. A position sensor and tool tip actuator to control and its controller electronics were integrated into a cutting tool. To take further advantage of this highly sophisticated tool, a process diagnostic method based on cutting force measurement method was developed. An observer implemented in the tool controller estimates the disturbance to the actuator using the tool position sensing information. The estimated disturbance is the same as cutting force applied to the tool tip. The algorithm utilising the cutting force to detect cutting process faults, such as tool tip breakage and misalignment of workpiece has been designed and tested experimentally.     

弯曲型内嵌式SMA驱动器的设计与优化

在直线型内嵌式形状记忆和合金驱动器(ESMAA)的研究基础上,提出了弯曲型ESMAA结构。该驱动器工艺简单,循环寿命更长,运行可靠性更高。通过温控方式可实现驱动器的往复可逆弯曲运动,对外稳定输出力和位移。本文建立了驱动器的变形理论,结合实验结果,对丝半径、丝的预变形量和棒半径进行了优化设计,得出了这一驱动器设计的规律性结论。