Deflection of coupled elasticity–electrostatic bimorph PVDF material: theoretical,FEM and experimental verification

Piezoelectric materials have wide applications in the field of mechanical, aerospace and civil engineering because of its voltage dependent actuation. Piezoelectric material goes through voltage generation whenever deflection is induced in it and vice versa. Piezoelectric bimorph beam has been widely used for sensing and actuating. In the actuation mode, an electric field is applied across the beam thickness, one layer contracts while the other expands. This results in the bending of the entire structure and tip deflection. In the sensing mode, the bimorph is used to measure an external load by monitoring the piezoelectric induced electrode voltages. In this research work, a 2D bimorph piezoelectric actuator model having two layers made of polyvinylidene fluoride (PVDF) material was developed to examine the inverse piezoelectric effect. Finite element analysis (FEA) was carried out on specially designed actuator model by using MATLAB Partial Differential Equation (PDE) Toolbox™. Theoretical analysis has been carried out to measure the tip deflection under applied electric field. The laboratory test was performed to investigate the deformation behavior of piezoelectric actuator. It is observed that, more the electric field applied, more the material would be deformed in a particular direction. The experimental results are in good agreement with numerical results.

     

双晶片悬臂梁式压电传感器的有限元仿真研究

压电传感器作为一种便捷、高效的传感器类型,越来越受到人们的青睐.为研究压电传感器机电耦合能力,将压电高聚物聚偏氟乙烯(PVDF)黏结而成的压电双晶片悬臂梁作为研究对象,利用有限元分析软件ANSYS Workbench,首先完成对模型的构建和模态分析,得出模型的固有频率和固有振型,再建立压电材料的压电本构方程,对压电双晶片悬臂梁模型发电量进行模拟仿真,最后将仿真结果与前人研究结果相对比.分析得出:在10 mm的形变量下,能够产生最大320 V左右的瞬时电压,这与前人的研究结果相近,验证了仿真结果的准确性,同时也证实了压电双晶片悬臂梁作为压电传感器的可行性.     

Design and static modeling of a semiconductor polymericpiezoelectric microactuator

The design of a semicircular polymeric piezoelectric actuator is presented, the models for its deflection and force are derived, and the results of the experiments used to verify the models are reported. The design is a polymeric piezoelectric bimorph formed in a semicircular shape instead of the standard straight cantilever beam bimorph design. The deflection model is adopted from the straight cantilever beam model and relates the free deflection as a function of the applied voltage field. The force model is developed using Castigliano's second theorem. Two experiments were conducted to verify the model: force-voltage and force-deflection. The models show that a bimorph formed in a semicircular shape produces significantly more force than a straight cantilever beam bimorph of the same length without a significant sacrifice in deflection     

Myriapod-like ambulation of a segmented microrobot

Segmented myriapod-like bodies may offer performance benefits over more common fixed body morphologies for ambulation. Here, the design of a segmented ambulatory microrobot with a flexible backbone is presented. A dynamic model describing the motion of the microrobot is used to determine body parameters. A three-segment microrobot was fabricated using the Smart Composite Microstructures process and piezoelectric bimorph actuators, and forward locomotion on a flat surface was demonstrated. The footprint of the 750 mg microrobot is 3.5 by 3.5 cm, and it has potential advantages over rigid body hexapedal microrobots in climbing, versatility, and stability.     

一种集成微力检测的压电式微夹钳

针对微装配任务设计了一种双悬臂梁结构的压电双晶片微夹钳,该微夹钳由两个压电双晶片驱动．建立了压电双晶片的复合梁模型,并对它的微位移—电压特性、夹持力—应变特性进行了数学分析．通过检测悬臂梁根部的应变信号实现对微夹钳夹持力的检测．实验证明该微夹钳工作可靠,能够满足微装配机器人装配任务的要求．     

Application of piezoelectric layers in electrostatic MEM actuators: controlling of pull-in voltage

In this paper, a novel method has been developed to control the pull-in voltage of the fixed-fixed and cantilever MEM actuators and measure the residual stress in the fixed-fixed model using of the piezoelectric layers that have been located on the upper and lower surfaces of actuator. In the developed model, the tensile or compressive residual stresses, fringing-field and axial stress effects in the fixed-fixed end type micro-electro-mechanical systems actuator have been considered. The non-linear governing differential equations of the MEM actuators have been derived by considering the piezoelectric layers and mentioned effects. The results show that due to different applied voltage to the piezoelectric layers, the pull-in voltage can be controlled and in the fixed-fixed type the unknown value of the residual stress can be obtained.     

Swing-arm-type PZT dual actuator with fast seeking for optical disk drive

 In this paper, a swing-arm-type dual positioning mechanism using a voice coil motor (VCM) and bimorph PZT actuators is proposed for the possible application to the future optical disc drive actuator. A VCM is used as a coarse motion actuator, and a set of piezoelectric actuators is used for fine motion. The two pairs of PZT actuators are arranged in parallel and are carefully designed to deflect in `S' shape such that tension and compression forces are generated simultaneously and thus the hysteresis is minimized. The static and dynamic analyses are performed and the parameter studies on the key dimensions of the set of PZT actuators are investigated. For fast seeking motion, time optimal control scheme combined with PD algorithm is adopted for the fast seeking motion of VCM. Positive position feedback (PPF) control is used to suppress residual vibration for the PZT actuator beams by activating it at the end of VCM swing motion. The feasibility of the suggested actuator system and the control scheme is demonstrated through simulations and experiments. Received: 5 July 2001/Accepted: 21 December 2001     

基于压电双晶片的微型无人机增稳驱动系统研究

研究了一种,基于压电双晶片的微型无人机增稳驱动系统,并设计了一种基于升压电路原理的压电驱动电源,该驱动电源采用机载电池供电,通过 0～5V 控制信号控制其运动,对驱动电源的动态特性进行了测试.同时为实现对整个驱动系统的自适应控制,采用光纤 Bragg 光栅(FBG)传感器对压电双晶片的位移变化特性进行了测量.研究结果表...     

Electromechanical coupling correction for piezoelectric layered beams

This paper deals with the bending of layered piezoelectric beams (multimorphs) subjected to arbitrary electrical and mechanical loading. Weinberg (1999) obtained a closed-form solution to this problem using Euler-Bernoulli beam theory and integrated equilibrium equations. In his analysis, Weinberg assumes that the electric field is constant through the thickness of the piezoelectric layers. This approximation is valid for materials with small electromechanical coupling (EMC) coefficients. In this paper, we relax this constraint and obtain a solution which accounts for the effect of strain on the electric field in the layers. We find that Weinberg's solution can be extended to arbitrary EMC with a simple correction to the moment of inertia I of the piezoelectric layers. The EMC correction amounts to replacing I with (1+/spl xi/)I, where /spl xi/ is the square of the expedient coupling coefficient. The error in beam curvature introduced by neglecting the effect of EMC is shown to be proportional to /spl xi/. This effect can be quite significant for modern piezoelectric materials which tend to have large EMC coefficients. The formulation is applied to three example cases: a cantilever unimorph, an asymmetric bimorph and a three-layer multimorph with an elastic core. The theoretical predictions for the last two examples are compared to simulations using the finite-element method (FEM) and found to be in excellent agreement.     

Micron-scale polymer-metal cantilever actuators fabricated by focused ion beam

Polymer-metal microcantilever actuators have been fabricated using an innovative approach based on focused ion beam micromachining technology. The fabrication involves depositing a thin metal film onto the surface of the polymer and machining using the ion beam. The microcantilever created is then extracted and transferred to a desirable support using a micromanipulator. This approach demonstrates the potential for maskless and resistless prototyping of cantilevers that can be evaluated for use as MEMS/NEMS actuators. Nanometer-scale displacement of the resulting polystyrene-platinum bimorph microactuator with respect to temperature change is demonstrated via visual monitoring in a scanning electron microscope with a heating stage. The performance of the bimorph cantilever microactuators is verified using both analytical and finite element modeling.     

大位移压电陶瓷驱动器的有限元分析

为研究压电陶瓷驱动器的驱动效能,制作了大位移压电陶瓷驱动器.基于压电陶瓷材料的机电耦合特性,应用动力学有限元分析方法,将大位移压电陶瓷驱动器离散成一系列四面体单元,分别进行了力学和电学分析.根据压电陶瓷的基本压电方程,耦合了位移模式与电场模式的有限元模型,建立了压电陶瓷驱动器的有限元动力学模性.利用有限元分析软件ANSYS中的直接耦合场进行分析求解,分析结果与试验测量值取得了良好的一致,证实了利用压电陶瓷双晶片弯曲变形,制作的大位移压电陶瓷驱动器结构设计的合理性.该分析方法对压电陶瓷驱动器的设计、制造与测试具有理论指导意义.     

Unimorph and bimorph piezoelectric energy harvester stimulated by β-emitting radioisotopes: a modeling study

We use energy methods and lumped-element modelling in the analysis and optimization of a miniaturized aluminum nitride based piezoelectric energy harvester which utilizes tritiated silicon as an uninterrupted energy source. Tritiated silicon serves as a radioisotope source which emits energetic β particles that results in an electrostatic force between the radioactive source and collector that traps the emitted particles. The generated electrostatic force will drive the charging and actuating cycles of the piezoelectric cantilever leading to a continuous charge–discharge cycles, thus inducing vibrations in the piezoelectric cantilever. The energy generated from the piezoelectric thin-film is appropriately rectified and stored to provide continuous and uninterrupted electrical power to a low-power devices. The modelled results have been benchmarked against available experimental data for a unimorph piezoelectric harvester with very good agreement. Furthermore, the model was applied to a bimorph piezoelectric harvester, showing that the output power can be doubled in relation to a unimorph design. Moreover, the model accounts for the entire range of design and operating factors such as the ambient medium and associated damping losses, current leakage, and device scaling.     

供能于无线传感器网络的微型振动发电机结构性能研究

应用微机电加工技术制造的振动发电机可以无限、持续地为无线传感器网络提供能源。为了提高发电能力,通过有限元仿真与实验分析了单压电片型式、双压电片并联型式和双压电片串联型式振动发电机的结构参数对发电能力的影响规律。结果表明,厚度比小的双压电片串联型式发电机输出开路电压较高;存在某一最优负载,在给定的激励频率下,使得输出功率最大;相同材料、结构参数下,双压电片串联和双压电片并联型式发电机的输出功率基本相同且高于单压电片型式发电机。     

Two-Axial Piezoelectric Actuator Controller Using a Multi-Layer Artificial Neural Network Featuring Feedback Connection for Tactile Displays

Although some compensation method is required when using a piezoelectric actuator because of hysteresis, a sensor feedback method is not suitable for an actuator array. In this study, we design a controller using a neural network to apply it to a tactile display composed of two-axial miniature actuators. This paper describes the two-axial miniature actuator, which is composed of two bimorph piezoelectric elements and two small links connected by three joints. A control system for the two-axial miniature actuator is designed based on a multi-layered artificial neural network to compensate for the hysteresis of piezoelectric elements. The output neuron emits the time derivative of voltage, a two-bit signal expressing increment or decrement condition is generated by two input neurons, and two input neurons calculate current values of voltage and displacement, respectively. The neural network is outfitted with a feedback loop including an integral element to reduce the number of neurons. In the experiment, if the result of the left piezoelectric element is compared to that of the right element, the displacement amplitudes and the inclinations coincide on the right and left piezoelectric elements. Although precise hysteresis characteristics such as loop width are considerably different, the present neural system can follow the difference.     

Design,kinematic modeling and sliding mode control with sliding mode observer of a novel 3-PRR compliant mechanism

Compliant mechanisms have great advantages to be used as micropositioning stages for high-precision applications but they are very sensitive to manufacturing tolerances and assembling errors. In this work, a novel compliant stage having 3-PRR kinematic structure and actuated by piezoelectric actuators is introduced. A kinematic modeling based on compliance of the flexible elements and finite element analysis based model have been extracted. It is found out that the experimental results are not compatible with the theoretical results due to the manufacturing, actuator assembly errors. The position control of the mechanism has been achieved using sliding mode control which is a great method for unpredictable varying parameters in the system. Sliding mode observer has also been used for the hysteresis and nonlinearities of the piezoelectric actuators. Experimental models for each actuation axis have been used as the nominal models for the sliding mode observer. In order to see the advantage of the control method simple PID control has also been implemented. It is seen that sliding mode control with sliding mode observer using experimental models reduces the position tracking errors to the range of the accuracy of our available measurement.     

一种基于MEMS技术的压电微泵的研究

介绍了一种基于MEMS技术的压电微泵。该微泵利用聚二甲基硅氧烷(PDMS)作为泵膜,使用了一个主动阀和一个被动阀,并利用压电双晶片作为驱动部件。压电双晶片和PDMS泵膜的组合可以产生较大的泵腔体积改变和压缩比,显著降低了加工成本,并提高了成品率。对压电微泵的输出流量进行了测试,结果显示:电压、频率以及背压对流量均有显著影响。在100 V,25Hz的方波驱动下,该压电微泵的最大输出流量为458μL/m in,最大输出压力为6 kPa。     

Sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner

This paper presents the sliding‐mode control of a three‐degrees‐of‐freedom nanopositioner (Z, θ_x, θ_y). This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. In order to design the feedback controller, the open‐loop characteristics of this nanopositioner are investigated. Based on the results of the investigation, each pair of piezoelectric actuators and corresponding gap sensors is treated as an independent system and modeled as a first‐order linear model coupled with hysteresis. When the model is identified and the hysteresis nonlinearity is linearized, a linear system model with uncertainty is used to design the controller. When designing the controller, the sliding‐mode disturbance (uncertainty) estimation and compensation scheme is used. The structure of the proposed controller is similar to that of a proportional integral derivative controller. Thus, it can be easily implemented. Experimental results show that 3‐nm tracking resolution can be obtained. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Self-sensing actuators with passive damping for adaptive vibration control of hard disk drives

A push–pull piezoelectrically actuated devices have been developed for higher bandwidth servo systems as microactuators for fine and fast positioning, while the voice coil motor functions as a large but coarse seeking. However, the current dual-stage actuator design uses piezoelectric patches only and therefore a dual-stage servo system using enhanced active–passive hybrid micro piezoelectric actuators is proposed to improve the existing dual-stage actuators for higher precision and shock resistance, due to the incorporation of passive damping in the design. In this paper, three different configurations of self-sensing actuators (SSAs) incorporating an adaptive mechanism for vibration control of suspensions in dual-stage hard disk drives (HDDs) are investigated. In the piezo-based SSA configuration, the signal sensed due to mechanical deformation is mixed with the control input signal, which would be corrupted due to the variation of the piezoelectric capacitance when a fixed bridge circuit is used. In this study, a self-tuning adaptive compensation is used to combine with the SSA technique to extract the true sensing signal for the vibration control of suspensions in HDDs. An assembled suspension with piezoelectric microactuators is tested to demonstrate the vibration suppression performance of this adaptive structure under an external shock disturbance such as hammer excitation. The experimental results show that the target vibration modes have been suppressed effectively with using the adaptive positive position feedback controller for the enhanced SSAs with passive damping in HDDs.     

Nonlinear dynamic characteristics of piezoelectric bending actuators under strong applied electric field

Dynamic characteristics of piezoelectric bending actuators under low and high electric fields are studied using the asymptotic theory of nonstationary vibrations. The proposed nonlinear model predicts the changes in fundamental resonant frequencies of the piezoelectric cantilever. The predicted resonance amplitude of the tip deflections of the piezoelectric actuators, which increases with the increase in the magnitude of the electric field, well agrees with the experimental results. Additionally, the decrease in the mechanical quality factor with the increase in the electric field, the tip deflection of piezoelectric actuators near resonance frequency,and the amplitude of the tip deflection at the fundamental vibration tone under an applied electric field varying with time have also been obtained using the present model.     

Piezoelectric bimorph microphone built on micromachined parylene diaphragm

This paper describes a novel bimorph piezoelectric microphone built on a micromachined parylene diaphragm with two ZnO films of opposite c-axis orientations. Both the sensitivity and signal-to-noise ratio (SNR) of the bimorph parylene-diaphragm microphone have been demonstrated to be much higher than those of a conventional unimorph silicon-nitride-diaphragm microphone.