Monolithically cascaded micromirror pair driven by angular vertical combs for two-axis scanning

In this work, monolithically cascaded one-axis micromirrors driven by angular vertical comb drives are designed and fabricated. Using W-shaped folded-beam optics, we demonstrate two-axis scanning covering /spl plusmn/6.0/spl deg/ two-dimensional area at resonant modes of 7.5 kHz, /spl plusmn/17 V for a fast-scanning mirror and 1.2 kHz, /spl plusmn/7 V for a slow-scanning mirror. The experimental results satisfy the requirements for a surveying instrument.     

Analysis of primary-on-slider ultrasonic piezoelectric actuators and experiments on multidegree of motion freedom plane actuator

Recently, various machines and tools have been miniaturized, and with this trend, the size of an actuator becomes a very important factor. An ultrasonic actuator is different from other actuators using electromagnet force in the driving principle. The structures of an ultrasonic piezoelectric actuator is simple. An ultrasonic actuator converts the ultrasonic mechanical energy to mechanical thrust force by a friction force. Based on this idea, various ultrasonic actuators have been proposed and experimentally constructed. In this paper, the basic characteristics of a piezoelectric actuator are analyzed theoretically. The relationship between the thrust force and the weight force is clarified and verified by experiments. Various prototypes of plane ultrasonic piezoelectric actuators are constructed experimentally, and the fundamental characteristics are measured.     

Low cross talk design and simple fabrication process of electrostatic vertical comb‐drive actuators for positioning application

In this paper, different types of vertical electrostatic comb‐drive actuators are proposed. The aim of design is to minimize the cross talk between vertical and lateral motions with a relatively simple fabrication process, namely, with only two ICP‐RIE steps from the front side with layered masks. Three designs are analyzed by MEMCAD, a finite‐element modeling package, combined with a micromachining process simulator. After optimization based on the calculation, all types were fabricated and tested. The experimental results are qualitatively in good agreement with the calculations. Because of the excess undercutting in our ICP‐RIE machine, the supports were softer than designed. The displacement was larger than expected. According to obtained results, we can expect to generate a vertical force of 0.5 µN per tooth at around 50 V. The measured cross talk between vertical motion and the horizontal motion was 20%. The resonant frequency of a typical device is 9 kHz and the displacement is 1.5 µm at 50 V. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Development of piezoelectric actuators for active X-ray optics

Piezoelectric actuators are widely utilised in adaptive optics to enable mirrors having an actively controlled reflective surface for the purpose of the wavefront correction by reducing the effects of rapidly changing optical distortion. Two new prototype adaptive X-ray optical systems are under development with the aim of approaching the fundamental diffraction limit. One proposed technology is microstructured optical arrays (MOAs) involving two or four piezoelectric strips bonded to a silicon wafer to produce a micro-focused X-ray source for biological applications, and which uses grazing incidence reflection through consecutive aligned arrays of channels obtained using deep silicon etching. Another technology is large scale optics which uses a thin shell mirror bonded with 20?C40 piezoelectric actuators for the next generation of X-ray telescopes with an aim to achieve a resolution greater than that currently available by Chandra (0.5"). PZT-based piezoelectric actuators are being developed in this programme according to the design and implementation of the proposed mirror and array structures. Viscous plastic processing is chosen for the preparation of the materials system, which is subsequently formed and shaped into the suitable configurations. Precise controls on the thickness, surface finish and the curvature are the key factors to delivering satisfactory actuators. Unimorph type piezoelectric actuators have been proposed for the applications and results are presented regarding the fabrication and characterisation of such piezo-actuators, as well as the related design concepts and comparison to modelling work.     

A parallel prefiltering approach for the identification of a biased sinusoidal signal: Theory and experiments

The problem of estimating the amplitude, frequency, and phase of an unknown sinusoidal signal from a noisy‐biased measurement is addressed in this paper by a family of parallel prefiltering schemes. The proposed methodology consists in using a pair of linear filters of specified order to generate a suitable number of auxiliary signals that are used to estimate—in an adaptive way—the frequency, the amplitude, and the phase of the sinusoid. Increasing the order of the prefilters improves the noise immunity of the estimator, at the cost of an increase of the computational complexity. Among the whole family of estimators realizable by varying the order of the filters, the simple parallel prefilters of orders 2 + 2 and 3 + 3 are discussed in detail, being the most attractive from the implementability point of view. The behavior of the two algorithms with respect to bounded external disturbances is characterized by input‐to‐state stability arguments. Finally, the effectiveness of the proposed technique is shown both by comparative numerical simulations and by a real experiment addressing the estimation of the frequency of the electrical mains from a noisy voltage measurement. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimisation of interdigitated electrodes for piezoelectric actuators and active fibre composites

The optimisation of the interdigitated electrode (IDE) design for active fibre composites was performed using finite element analysis. The effect of the IDE geometry (electrode width and spacing) and electroceramic substrate thickness on the developed strain for bulk PZT substrates was modelled. The modelling results show that the highest strain is generated when the electrode width equals half the substrate thickness and for thin substrates the electrode finger spacing can be reduced to enable lower driving voltages. Approximately 80% of the maximum d ₃₃ strain can be achieved with an electrode separation to substrate thickness ratio greater than 4. The results present simple coherent guidelines for the optimisation of electrode geometry for piezoelectric actuators and active fibre composites.     

Comparison with film substrates of polyimide and Ni for cantilevered magnetic actuators

This paper describes a cantilevered actuator driven by magnetostriction in a low magnetic field. The dimensions of the two‐layer actuator were 1 mm × 5 mm, and amorphous FeSiB was used as the positive magnetostrictive material. The theoretical formulas for the amount of displacement and force of the actuator were obtained. In the experiment, a nonmagnetic polyimide film material and a negative magnetostrictive Ni film material were used as the substrates. The change in the characteristics of the actuator caused by changing the substrate was examined with theoretical formulas and experiments. It is shown that the actuator with Ni as the substrate was designed to obtain the largest displacement and the largest force. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Adaptive tracking for pneumatic muscle actuators in bicep and tricep configurations

Adaptive tracking techniques are applied to pneumatic muscle actuators arranged in bicep and tricep configurations. The control objective is to force the joint angle to track a specified reference path. Mathematical models are derived for the bicep and tricep configurations. The models are nonlinear and in general time-varying, making adaptive control desirable. Stability results are derived, and the results of simulation studies are presented, contrasting the nonlinear adaptive control to a nonadaptive PID control approach.     

Nonlinear model accounting for minor hysteresis of embedded SMA actuators

A quantitative index martensite fraction was used to describe the phase transformation degree of shape memory alloy (SMA). On the basis of the martensite fraction, a non-linear analysis model for major and minor hysteresis loops was developed. The model adopted two exponential equations to calculate the martensite fractions for cooling and heating, respectively. The martensite fractions were derived as the relative parameters were adjusted timely according to continuous, common initial and common limit constraints. By use of the linear relationship between the curvature of embedded SMA actuator and SMA’s martensite fraction, the curvature was determined. The results of the simulations and experiments prove the validity and veracity of the model. Translated from Journal of Huazhong University of Science and Technology (Natural Science Edition), 2006, 34(2): 42–43 [译自: 华中科技大学学报(自然科学版)]     

Study and implementation of a 15‐W driver for piezoelectric actuators

This paper studies and implements a 15‐W driver for piezoelectric actuators. The discussed driver is mainly composed of a flyback converter and a power operational amplifier (P‐OPA). The flyback converter produces a variable DC voltage to supply the P‐OPA, which outputs an amplified sinusoidal signal with a DC bias of 100 V to drive the piezoelectric actuator. The power losses can be reduced because the supply voltage of the P‐OPA varies with the peak of the input signal. The power conversion efficiency of the driver can thus be promoted up to more than 30%. From the experimental results, the implemented prototype possesses some advantageous features, such as a nearly constant output‐to‐input voltage gain, a high slew rate, a high input impedance, a low output impedance, and low output voltage ripples. Copyright © 2016 John Wiley & Sons, Ltd.     

Comparative analysis and design criteria of permanent magnet tubular actuators

The adoption of an adequate methodology of analysis of permanent magnet (PM) tubular actuators allows one to formulate effectively the problem of improving their performance. A proper dimensioning strategy is then envisaged to increase the force density yielded by a tubular linear PM actuator. The strategy must be calibrated on the geometrical and mechanical constraints. This paper takes into consideration the most frequently adopted configurations of tubular actuators, presents a novel model and suggests two one-step design procedures.     

Modeling and compensation for angular transmission error in harmonic drive gearings

This paper presents a novel modeling and compensation approach for the angular transmission error in harmonic drive gearings. In the modeling, physical phenomena of the transmission error due to nonlinear elastic deformations in micro-displacement region are especially dealt with, as well as the synchronous component which has been discussed in a variety of conventional studies. On the basis of the analyses of the phenomena, the nonlinear elastic component is mathematically modeled by applying a modeling framework for the rolling friction with hysteresis attributes. The proposed transmission error model has been adopted to the positioning system as a model-based feedforward compensation manner. Experimental results using a prototype show the effectiveness of the proposed modeling and compensation. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

改进的着陆引导雷达天线角基准校验仪

针对传统的着陆引导雷达天线角基准校验方法的电磁辐射量大、抗环境干扰能力弱、工作效率低等缺点,提出并实现了一种改进的校验仪。改变被测天线主动发射大信号方式为被动接收小信号,校验仪远端采用三轴程控转台加伺服控制机构实现对标准源天线的精确控制,配合近端的操作软件,在天线测试外场150～250 m遥控源天线动作,具有自动寻峰、数据判断存储功能。改进后对人体辐射量仅为原来的1/850 000,测试人员数量从4人减少为2人,时间从2 h缩短到30 min以内。实验证明改进的雷达天线角基准校验仪完全可以替代传统的校验仪。     

The potential of dielectrophoresis for single-cell experiments

In this article, a microfluidic system was developed for sorting and high-content analysis of single cells using dielectrophoresis. It makes high-resolution imaging of suspended cells feasible immediately before depositing them into a microtiter plate. The microfluidic devices contain three-dimensional arrangements of radio-frequency driven electrodes and are used to gently manipulate suspended cells in flow. Viability of sorted and deposited cells is comparable to a control group. The influence of RF electric fields is studied using (a) calcium flux measurements and membrane potential dependent fluorescence dye on suspended human cells and (b) cultivation of yeast trapped for several days in dielectric field cages driven at field strengths up to 100 kV/m and 7 MHz.     

Selection and installation of a vertical roller mill for clinkerpregrinding

A vertical roller mill has been installed in a Canadian cement plant for the pregrinding of Portland cement clinker. It is the first application of this type of technology in the Western Hemisphere. The process of selection of the technology and the development of the engineering project are described     

Fabrication and evaluation of PZT/Ag composites and functionally graded piezoelectric actuators

Metallic Ag as the second phase was added into PZT ceramic matrix to fabricate piezoelectric composites and functionally graded actuators by gradually altering Ag concentration, aimed to improve mechanical properties and to solve possible interfacial debonding usually observed in conventional bimorph-type piezoelectric actuator. The PZT/Ag composites were obtained by directly co-firing PZT and Ag powders at 1200^∘C for 1 h. The fracture strength σ _f and fracture toughness K _IC , as well as the corresponding piezoelectric properties, were firstly evaluated upon the PZT/Ag composites for Ag concentrations of 0–30 vol%. The mechanical properties for the PZT/Ag composites were found to be greatly enhanced compared with pure PZT ceramics: from 69 to 129 MPa for σ _f and from 1.0 to 3.7 MPa.m^1/2 for K _IC . With increasing Ag concentration, the piezoelectric constant d ₃₃ of PZT/Ag composites was found to decrease from 419 to 86 pC/N. Then, a functionally graded actuator was fabricated and evaluated in terms of electric-induced curvature k. The PZT/Ag FGM actuator with size of 12 mm × 3 mm × 1 mm has a curvature k of 0.03–0.17 m⁻¹ that corresponds to applied voltages of 100–500 V. A comprehensive comparison was made on the mechanical property enhancements by the metal particles dispersion, and the bending displacements produced by the FGM actuators between the PZT/Ag and previously fabricated PZT/Pt systems.     

球铰链的多维回转角度测量方法研究综述

球铰链具有结构紧凑、运动灵活和承载能力强等优点,是一种应用较普遍的多自由度机械关节,其回转角度的检测对系统运动误差预测分析、反馈和控制具有十分重要的意义。首先介绍球铰链的应用与结构特点,然后分析球铰链多维回转角度的测量需求,对国内外球铰链多维角度检测的相关研究发展进行综述,主要包括基于结构解耦测量、基于光学原理测量和基于磁场理论测量等方法。最后,对球铰链多维回转角度测量的研究现状进行总结,指出了其研究的重点、难点以及关键技术突破面临的挑战。     

Lifetime of piezoceramic multilayer actuators: Interplay of material properties and actuator design

We report an investigation into factors limiting the functional lifetime of multilayer piezoceramic actuators. The study consists of a combination of lifetime experiments by means of an accelerated lifetime test, inspection of the actuator microstructure at different stages of the accelerated lifetime test, and numerical simulation of the displacements and mechanical stresses that arise during actuator performance. During the lifetime test, both displacement and electrical properties were measured. The results show a clear correlation between the microstructure and the mechanical stresses in the actuator, giving evidence that crack initiation starts early in actuator lifetime and humidity effects accelerate degradation. The numerical simulations performed provide clues for optimization of the actuator design with respect to stress development and performance. Attention is paid to the choice of adhesive interlayer and its effect on the performance and lifetime of the actuator.