Electrostrictive polymers for mechanical energy harvesting

This article reviews the developments in electrostrictive polymers for energy harvesting. Electrostrictive polymers are a variety of electroactive polymers that deform due to the electrostatic and polarization interaction between two electrodes with opposite electric charge. Electrostrictive polymers have been the subject of much interest and research over the past decade. In earlier years, much of the focus was placed on actuator configurations, and in more recent years, the focus has turned to investigating material properties that may enhance electromechanical activities. Since the last 5 years and with the development of low‐power electronics, the possibility of using these materials for energy harvesting has been investigated. This review outlines the operating principle in energy scavenging mode and conversion mechanisms behind this generator technology, highlights some of its advantages over existing actuator technologies, identifies some of the challenges associated with its development, and examines the main focus of research within this field, including some of the potential applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

变形镜驱动器位置偏差对低频相位拟合能力的影响

基于最小二乘法,数值分析了变形镜驱动器位置偏差与驱动器排列方式、数量及交连值等对变形镜相位拟合效果的影响。研究结果表明:对于随机产生的低频相位,在变形镜驱动器中心位置引入位置偏差后,方形排列变形镜的抗扰动能力优于三角排列方式;驱动器单元数越多,变形镜抗扰动能力也越强;交连值在一定范围增加时,变形镜的抗扰动能力随之增强。     

基于匹配光纤光栅法布里-珀罗干涉仪的应变解调方法

提出并实验验证了一种基于匹配光纤光栅法布里-珀罗干涉仪的应变传感器解调方法,该方法综合了光纤法布里-珀罗干涉技术和匹配光纤光栅滤波法的优点.通过半导体制冷片和压电陶瓷组成的闭环负反馈控制系统,精确调节匹配光栅法布里-珀罗干涉仪的温度和应变,有效解决了光栅法布里-珀罗干涉仪的失配问题,从而保证系统静态工作点处于最佳匹配位置,同时能够避免探头因环境温度波动导致的测量误差.实验结果表明,该系统能够响应50～800Hz的输入信号,应变最小分辨力至少为0.4nε/Hz1/2,解调灵敏度高,且不受环境温度波动的影响,因而在动态应变或振动测量中具有较高的实用性.     

Electrostrictive properties of thermoplastic polyurethane elastomer: Effects of urethane type and soft–hard segment composition

The electromechanical behavior of thermoplastic elastomer polyurethane (TPE-PU) is investigated under the effects of urethane type (ester and ether-types) and soft–hard segments at various electric field strengths and temperatures. The highest dielectric constant, electrical breakdown strength, and specific conductivity belong to the ester-type polyurethane (LPR matrix), while the lowest values are obtained from the ether-type polyurethane composing predominantly with the soft-segment (E 80A matrix). Under the electric field strength in the range between 0 and 2 kV/mm, the LPR matrix attains the storage modulus sensitivity (ΔG′/G′₀) up to 2 at 2 kV/mm. For the temporal response, the polyurethanes behave with good reproductively (number of cycles >10⁵ times) and with very good recoverability. The steady state behavior can be attained at the first actuation and at the electric field strength of 1 kV/mm. Furthermore, the storage modulus (G′) shows linearly negative responses with increasing temperature. In the deflection experiments, the deflection distance and the dielectrophoresis force increase monotonically with increasing electric field strength. All of the TPE-PU possesses very fast response times for activation (<10 s.) and deactivation (<5 s.). TPE-PU material is systematically shown here to be a potentially good actuator material with high efficiency based on the electrostrictive performance data obtained.     

An explicit exact analytical approach for free vibration of circular/annular functionally graded plates bonded to piezoelectric actuator/sensor layers based on Reddy’s plate theory

In the present study, a novel exact closed-form procedure based on the third order shear deformation plate theory is developed to analyze in-plane and out-of-plane frequency responses of circular/annular functionally graded material (FGM) plates embedded in piezoelectric layers for both close/open circuit electrical boundary conditions. Introducing a new analytical method, five governing partial deferential equations of motion beside Maxwell electrostatic equation are solved via an exact closed-form method. The high accuracy and reliability of the present approach is confirmed by comparing some of the present data with their counterparts reported in the literature. Finally, the effect of material properties, power law index and boundary conditions on the free vibration of the smart FGM plate are studied and discussed in detail.     

100kHz～500kHz压电复合材料标准水听器

本文介绍了一种我们制作的可应用于100kHz～500kHz频段的标准水听器,水听器敏感元件采用1-3型压电复合材料,通过对敏感元件及水听器结构进行合理设计,从工艺上保证水听器性能的稳定、可靠,制作完成的标准水听器满足高频标准的所有技术指标要求。测试结果表明,水听器的接收灵敏度大于-194dB,频段内灵敏度起伏为2.9dB,最高使用频率-3dB波束宽度大于20度;稳定性考核表明,水听器有良好的温度、时间稳定性,是一种比较理想的中高频标准水听器,适合于水声的校准和中高频声信号测试。     

Axial vibration characteristics of a cylindrical, radially polarized piezoelectric transducer with different electrode patterns

A circular cylindrical piezoelectric transducer with radial polarization is proposed. The axial vibration characteristics of the transducer are studied by three different methods: analytical calculation, FEM simulation and experiment. The symmetric and asymmetric excitation conditions are discussed in the Haskins and Walsh model. For the resonance frequencies of the transducer, the results from the above three methods coincide well with each other. For the vibration amplitude, there are some deviations between the FEM simulation and measurement results; some possible reasons for this are discussed. The influence of the electrode patterns on the excitation modes are also investigated in detail. Based on the study described in this paper, the research methodology for a cylindrical piezoelectric transducer is clarified.     

Hysteresis compensation of piezoelectric actuators: The modified Rayleigh model

In this study, we develop a novel modified Rayleigh model for hysteresis compensation in piezoelectric actuators. Piezoelectric actuators suffer from hysteresis, in large drive fields of more than 100 V, which can result in serious displacement errors. The typical phenomenological approach is to use the Rayleigh model; however, this model gives more than 10% difference with experiments at the large electric fields of more than 1 kV/mm. Furthermore, there are no studies that apply the Rayleigh model to the compensation of precision actuators, such as stack actuators; it has only been applied in the study of the physical properties of piezoelectric materials. Therefore, we propose a modified Rayleigh model, in which each coefficient is defined differently according to whether the field is increasing or decreasing to account for asymmetry at the high fields. By applying a computer-based control from an inverse form of this modified Rayleigh model, we show that we can compensate for hysteresis to reduce the position error to less than five percent. This model has the merits of reducing complicated fitting procedures and of saving computation time compared to the Preisach model. Specifically, this model cannot only predict the hysteresis curves in all local fields using only one fitting procedure, but also make it possible to control the displacement of various piezo-based actuators without expensive sensors, based on the charge-based model.