Integrated approach to electrode and AlN depositions for bulk acoustic wave (BAW) devices

This paper investigates the (002) texture of AlN films deposited by reactive pulsed direct current sputtering on Al, Al–Cu, W and Mo metal electrodes. X-Ray diffraction and atomic force microscopy studies show that the AlN texture is dependent on the deposition conditions and nature of the underlayers. A smooth underlayer with a sharp texture represents the best combination of properties. AlN films with a full width at half maximum less than 1.5 have been deposited on the electrodes studied. It is also possible to deposit well-textured electrodes with a roughness less than 2.5 nm.     

Improved direct inverse tracking control of a piezoelectric tube scanner for high-speed AFM imaging

For a piezoelectric tube scanner (PTS), this paper proposes an improved direct inverse tracking control algorithm and apply it to an atomic force microscope (AFM) to accomplish high-speed scanning tasks. That is, to enhance the high-speed tracking control performance of a PTS, an improved direct inverse rate-dependent Prandtl–Ishlinskii (P–I) model is firstly constructed, which includes a polynomial module to eliminate the structure nonlinearity. Based on the model, a practical feedforward control law is then designed to implement high-speed tracking control for a high-frequency trajectory with strong robustness, which presents the advantages of high-speed response, simple structure and convenient implementation. Subsequently, the designed feedforward law is combined with a feedback component, and the combined control strategy is employed in an AFM to accomplish fast imaging tasks. Numerous experimental results are then collected, which convincingly demonstrate the superior performance of the proposed practical model/control scheme.     

A miniature generator using piezoelectric bender with elastic base

Nowadays green energy devices such as vibration generators attempt to harvest energy from environment. A lot of studies dealing with vibration generators put emphasis on mechanism designs or power generation methods, but few on lowering the resonant frequency of power generation systems. This study proposes that elastic bases attached to vibration generators can lower natural frequencies, so as to make natural frequencies closer to ambient vibration frequency. Therefore, this study investigates miniature electric generators consisting of piezoelectric benders and elastic bases. To install the elastic base, this work uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and a vibration source to make the resonant frequency of piezoelectric benders close to the frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. Accordingly, more electric power can be generated from piezoelectric generators using an elastic base with appropriate mass and stiffness. According to experimental results, using an elastic base increases 376 times generated power compared with no elastic base. In the presence of the elastic base, the power increases 132% when a point mass is added.     

Identification of bulk microwaves and detection of Pseudo-singularities by wavelet technique in piezoelectric medium

In this paper, the analysis of pseudo-singularities (corresponding to rapid variations) which appear in some parameters during the propagation of acoustic microwaves in a piezoelectric substrate is considered. These pseudo-singularities have a major importance because they can inform of the presence of bulk waves. However, there is a problem for the detection of the waves when the pseudo-singularities exist but is unobservable with the classical methods. To solve this problem, it is proposed that a new technique of detection based on the famous wavelet transform. This transform insures the detection of pseudo-singularities because it has the property of being locally maximal around the points where the signal is singular (or pseudo-singular).     

Measuring and predicting resolution in nanopositioning systems

The resolution is a critical performance metric of precision mechatronic systems such as nanopositioners and atomic force microscopes. However, there is not presently a strict definition for the measurement or reporting of this parameter. This article defines resolution as the smallest distance between two non-overlapping position commands. Methods are presented for simulating and predicting resolution in both the time and frequency domains. In order to simplify resolution measurement, a new technique is proposed which allows the resolution to be estimated from a measurement of the closed-loop actuator voltage. Simulation and experimental results demonstrate the proposed techniques. The paper concludes by comparing the resolution benefits of new control schemes over standard output feedback techniques.     

基于压电效应的智能控制广场自发电系统

本文介绍了一种基于压电效应的智能控制广场自发电系统,核心技术是通过压电材料的压电效应将机械能转化为电能,并通过能量转换模块和能量储存模块将电能储存于锂电池中,给主控制器模块即Arduino供电,主控制器模块驱动灯光和音频输出模块.整个装置所需的电能都通过压电效应产生,起到节能环保的作用.     

Studies on dielectric and magnetoelectric behavior of 25% CMFO ferrite and 75% BZT ferroelectric multiferroic magnetoelectric composites

In the present work, multiferroic magnetoelectric (ME) composites of ferrite and ferroelectric phases are prepared. Here, the magnetostrictive (ferrite) phase, Co_1.2 − yMn_yFe_1.8O₄ (y = 0.0 to 0.4) i.e. CMFO is synthesized by chemical combustion route and the piezoelectric (ferroelectric) phase, BaZr_0.08Ti_0.92O₃ i.e. BZT is synthesized by conventional ceramic method. Frequency dependent dielectric constant measurement from 20 Hz-1 MHz at room temperature shows usual dielectric dispersion behaviour, which may be attributed to the Maxwell-Wagner type interfacial polarization. Temperature dependent dielectric constant measurement shows two dielectric maxima, one below 100 °C and the second above 500 °C. The dielectric maxima below 100 °C corresponds to the transition temperature of the ferroelectric phase and that of above 500 °C corresponds to the transition temperature of the ferrite phase of the ME composites. It is observed that as Mn content increases in the cobalt ferrite, the phase transition temperature of the ferrite phase decreases. The static magnetoelectric voltage coefficient was measured as a function of intensity of the applied dc magnetic field. These magnetoelectric composites may have possible applications in magnetic field sensing probes and linear ME devices.     

Modified Eshelby tensor for an ellipsoidal inclusion imperfectly embedded in an infinite piezoelectric medium

The modified Eshelby tensor for predicting the effective moduli of particle-reinforced piezoelectric composites is derived for the problem of an ellipsoidal inclusion which is imperfectly bonded to the matrix. A linear interface relation is adopted, which involves discontinuities of the mechanical displacements and electric potential across the interface, and assumes that the corresponding jumps are proportional to the continuous stresses and electric displacements at the interface. The piezoelectric field induced by a uniform eigenstrain given only in the inclusion is deduced analytically. As the induced piezoelectric field is no longer uniform, the average strains and electric displacements are calculated, and the modified piezoelectric Eshelby tensor is evaluated by both an iterative method and a direct method. By comparison, it is shown that the iterative method yields rapidly convergent results.     

压电陶瓷执行器迟滞补偿及复合控制

快速倾斜镜是星间激光通信终端精瞄系统的核心部件,其驱动装置为压电陶瓷执行器,而压电陶瓷具有迟滞特性,其严重影响了快速倾斜镜的定位精度,进而对星间通信链路的稳定性造成不利影响。为解决这一问题,本文设计了一种改进Prandtl-Ishlinskii(P-I)模型对压电陶瓷执行器进行建模。在此基础上,提出了压电陶瓷执行器前馈线性化方法,以对迟滞特性进行前馈逆补偿。接着,提出了一种结合改进的P-I模型与增量式PID算法的复合控制算法,并在DSP中实现了该复合控制算法。最后,在试验平台上对该算法进行了验证。结果显示:当分别对系统输入10Hz和100Hz减幅正弦、等幅正弦曲线时,模型误差在0.59%以内,在输入同频100Hz以下的减幅正弦曲线时,传统PID算法的最大误差为59.31μrad,而该复合算法的最大误差为14.22μrad。实验数据表明,本文复合控制方法的动态跟踪性能明显优于传统PID方法,改进Prandtl-Ishlinskii(P-I)模型可以精确描述压电陶瓷的迟滞特性。本文设计的复合控制方法满足实际应用对快速倾斜镜的要求。     

采用喷墨打印机进行低成本微阵列印刷的可行性研究

根据网点形成技术,微阵列制作方法可归结为接触式印刷和非接触式印刷.接触式印刷中,如印刷生物样本时,设备与基底是直接接触.而非接触式印刷中,设备与基底之间不会直接接触.在非接触式印刷中,喷墨印刷技术是相对灵活、简便、便宜的一种方式,同时还减少了污染且避免了更高的数据吞吐量.但是,喷墨印刷需要有能喷射儿微微升墨滴的喷嘴和能够精确喷射墨滴的喷嘴位置控制单元.若使用喷墨方法制作微阵列就需要复杂的机构系统,以致成本增加.因此,本论文提出使用已具有喷墨系统的商用喷墨打印机来制作微阵列.