Digital closed-loop nanopositioning using rectilinear flexure stage and laser interferometry

To enhance the accuracy of nanopositioning and the metrological capability of scanning probe microscopy, we construct a two-dimensional interferometric nanopositioning system consisting of rectilinear flexure stage, calibrated laser interferometer, and digital feedback control system. We implement a correlation matrix, determined by the piezoelectric constant and the crosstalk between two axes, into the closed-loop control algorithm to compensate the nonlinearity and the crosstalk of the PZT-driven stage. In the tests on nanopositioning, the 1-nm-step motion and the tracking along a 1-nm-radius circular target path are accomplished to verify the short-term repeatability and the subnanometer-level precision. Additionally, a scanning tunneling microscope equipped with the interferometric nanopositioning system is built up to demonstrate the metrological functions of scanning probe microscopy.     

压电定位系统的自抗扰控制设计

纳米定位系统中广泛采用的压电驱动器因存在非线性、多映射的迟滞特性而严重影响了纳米定位系统的定位精度.为消除迟滞对定位精度的影响,将其视为干扰,设计不基于迟滞及定位系统精确数学模型的自抗扰控制算法,利用扩张状态观测器实时估计迟滞,进而补偿其对定位精度的影响,获得了良好的定化系统控制仿真效果.仿真结果表明,自抗扰控制器能够仃效消除迟滞、提高纳米定位系统的定位精度.     

A Survey of Methods Used to Control Piezoelectric Tube Scanners in High‐Speed AFM Imaging

In most nanotechnology applications, speed and precision are important requirements for obtaining good topographical maps of material surfaces using atomic force microscopes (AFMs), many of which use piezoelectric tube scanners (PTSs) for scanning and positioning at nanometric resolutions. For control engineers, the PTS is particularly interesting since its ability to enable the AFM to undertake 3D imaging is entirely dependent upon the use of a feedback loop. However, it suffers from various intrinsic problems that degrade its positioning performance, such as: (i) lightly damped low‐frequency resonant modes due to its mechanical structure; (ii) nonlinear behavior due to hysteresis and creep; (iii) the cross‐coupling effect between its axes (in 3D positioning systems such as AFMs); and (iv) effect of thermal drift. This article presents a survey of the literature on the PTS, an overview of a few existing innovative solutions for its nanopositioning and future research directions. This article will help the reader to walk around the present development of the PTS aimed at meeting the requirements for high‐speed AFM imaging.     

超精密伺服系统控制与应用

随着智能微纳器件和高性能数字系统的飞速发展,超精密伺服技术已逐步成为信息存储、精密成像、半导体装备等新兴行业的核心技术.本文从微纳操控领域的设计和控制问题着手,首先介绍了超精密伺服系统的设计及分析方法,进而阐述了超精密伺服系统对控制理论提出的诸多挑战.特别针对这类系统中广泛存在的模型不确定性及高阶未建模动态特性,非线性迟滞特性及执行机构饱和非线性,多源复杂干扰并存情况的抗干扰控制问题,以及面向复杂轨迹的高精度跟踪控制问题,给出了具有代表性的控制算法和应用实例.本文最后以高精度直写式真空蒸发系统为例,介绍了超精密伺服技术在现代精密仪器设备中的重要应用.     

Feature scalability for a low complexity face recognition with unconstrained spatial resolution

Automatic face recognition (FR) based applications in low computing power constrained systems, such as mobile and smart camera, have become particularly interesting topic in recent years. In this context, we present computationally efficient FR framework underpinning the so-called feature scalability algorithm. The proposed framework aims at implementing robust FR systems under low-computing power restriction and varying face resolution. Key beneficial property of our proposed FR framework based on feature scalability is to require low computational complexity without sacrificing a level of FR performance. To do this, using feature scalability algorithm enables to directly estimate the features (from pre-enrolled gallery images) that are well matched with the feature of an input probe image with different resolution (generally lower resolution) without any complex process. In addition, our method is helpful for relieving storage shortage problem as it does not require a large amount of training and gallery images with different face resolutions. Results show that our proposed feature scalability algorithm can be seamlessly embedded into state-of-the-art feature extraction methods extensively used for FR by achieving impressive recognition performance. Also, according to the results on computational complexity measurement, the proposed method is proven to be useful for substantially saving FR operation time.     

云控制系统及其面临的挑战

本文提出的云控制系统(Cloud control systems, CCSs)是对之前的网络化控制系统(Networked control systems, NCSs)的进一步扩展.目前,物联网(Internet of things, IOT)已经成功应用于实际中,网络化控制技术在其中发挥了关键作用.与此同时,云计算的迅速发展为大数据存储与处理、控制器设计和控制系统性能优化提供了一个完美的平台.可以预见,虽然当前云控制技术的研究和应用还存在许多挑战,但在不久的将来,云控制系统的深入研究将对控制理论的发展和各种实际应用起到积极推动作用.     

Accounting for hysteresis in repetitive control design: Nanopositioning example

This paper deals with designing a repetitive controller (RC) for tracking periodic reference trajectories for systems that exhibit hysteresis, such as piezoelectric actuators used in nanopositioning systems. Hysteresis can drastically limit the performance of an RC designed around a linear dynamics model, and thus the effect of hysteresis on the closed-loop stability of RC is analyzed and the allowable size of the hysteresis nonlinearity for a stable RC is quantified. But when the hysteresis effect exceeds the maximum bound, an inverse-hysteresis feedforward controller based on the Prandtl–Ishlinskii hysteresis model is used to compensate for the nonlinearity. The control method is implemented on a custom-designed nanopositioning stage. Experimental results show that by incorporating hysteresis compensation the stability margin and the rate of error reduction improve. Likewise, the maximum tracking error reduces by 71%, from 13.7% (using industry-standard integral control) to 3.9% (using RC with hysteresis compensation), underscoring the benefits of RC with hysteresis compensation.     

超分辨率技术的实现——一种改善的小波插值方法

由于成像系统内部和外部的因素 ,使得获取的图象产生退化 .为提高图象的质量 ,发展了一种基于小波插值方法的超分辨率技术 .在简要分析若干典型插值算法的基础上 ,考虑到 Bézier曲面插值方法的精确性和可快速实现性 ,提出了基于 Bézier曲面插值的小波变换方法 .该方法不仅克服了传统插值方法使图象细节退化的缺点 ,同时由于 Bézier曲面插值的快速实现使算法的复杂性得以有效的控制 .实验结果表明了采用 Bézier曲面插值的小波方法对于改善图象分辨率的有效性和可行性 .     

混合类型多媒体负载访问存储系统的统计学访问控制算法

混合类型多媒体负载访问存储系统是一个复杂的过程，不同类型的多媒体应用要求存储系统提供不同的服务质量保证．存储系统需要一个有效的访问控制算法，为尽可能多的多媒体应用提供保证服务质量的服务．对混合类型多媒体负载访问存储系统的访问控制问题进行了系统的研究：定义多媒体应用访问存储系统的服务质量参数；建立并发多媒体应用的汇聚负载模型；推导出混合类型多媒体负载的访问控制约束条件；实现相应的统计学访问控制算法．仿真实验的结果表明，新的存储系统访问控制算法是有效的，并具有相当高的精确度．     

Nanofabrication using near-field optical probes

Nanofabrication using near-field optical probes is an established technique for rapid prototyping and automated maskless fabrication of nanostructured devices. In this review, we present the primary types of near-field probes and their physical processing mechanisms. Highlights of recent developments include improved resolution by optimizing the probe shape, incorporation of surface plasmonics in probe design, broader use in biological and magnetic storage applications, and increased throughput using probe arrays as well as high-speed writing and patterning.     

A decoupled inversion-based iterative control approach to multi-axis precision positioning: 3D nanopositioning example

System inversion provides a nature avenue to utilize the priori knowledge of system dynamics in iterative learning control, resulting in rapid convergence and exact tracking (for nonminimum-phase systems). The benefits of system inversion, however, are not fully exploited in the time-domain ILC approach due to the lack of uncertainty quantification. This critical limit was alleviated in the frequency-domain formulated inversion-based iterative control (IIC) techniques. The existing IIC techniques, however, are for single-input–single-output (SISO) systems only, and the time-domain properties of the IIC techniques are unclear. The contributions of the proposed multi-axis inversion-based iterative control (MAIIC) approach are twofold: First, the IIC technique is extended from SISO systems to multi-input–multi-output systems and is easy to implement in practice. The iterative control law is optimized by using the quantification of the system uncertainty. Secondly, the time-domain properties of the MAIIC law are discussed. The proposed MAIIC technique is illustrated through 3D nanopositioning experiments using piezoelectric actuators. The experimental results clearly demonstrated that by using the proposed technique, precision tracking in all 3D axes can be achieved in the presence of a pronounced cross-axis dynamics coupling effect.     

Design of high-bandwidth high-precision flexure-based nanopositioning modules

This paper presents the design of a single degree-of-freedom high-bandwidth high-precision nanopositioning module for high-throughput nanomanufacturing applications. Compared with widely used lumped-compliance mechanisms (using notch-flexure hinges) and distributed-compliance mechanisms (using compliant flexure beams), this nanopositioning module adopts a hybrid compliant-notch-flexure-based structure. This flexure design decouples the performance requirements for the structural bandwidth and parasitic accuracy that are correlated in the lumped-compliance mechanisms and distributed-compliance mechanisms. The parallelogram hybrid compliant-notch-flexure-based structure enables simultaneous achievement of a higher structural bandwidth and a smaller parasitic motion. The behavior of the nanopositioning module is analyzed theoretically with respect to its design parameters and performance objectives. Finite element analysis is adapted to study the dynamic responses and parasitic displacement of the designed nanopositioning module. The results from the theoretical and FEA analysis demonstrate the effectiveness of the hybrid compliant-notch-flexure design over commonly used lumped-compliance mechanisms and distributed-compliance mechanisms, especially when a high structural bandwidth is required for high-throughput nanomanufacturing applications.     

A cost effective fault-tolerant scheme for RAIDs

The rapid progress in mass storage technology has made it possible for designers to implement large data storage systems for a variety of applications.One of the efficient ways to build large storage systems is to use RAIDs only when one error occurs .But in large RAIDs systems ,the fault probability will increase when the number of disks increases ,and the use of disks with big storage capacity will cause the recovering time to prolong,thus the probability of the second disk‘‘‘‘‘‘‘‘s fault will incerease Therefore,it is necessary to develop methods to recover data when two or more errors have occurred In this paper,a fault tolerant scheme is proposed based on extended Reed-Solomon code,a recovery procedure is designed to correct up to two errors which is implemented by software and hardware together,and the scheme is verified by computer simulation,In this scheme,only two redundant disks are used to recover up to two disks‘‘‘‘‘‘‘‘ fault .The encoding and decoding methods,and the implementation based on software and hardware are described.The application of the scheme in software RAIDs that are builit in cluster computers are also described .Compared with the existing methods such as EVENODD and DH ,the proposed scheme has distinct improvement in implementation and redundancy.     

多光谱图像的无损压缩方法

利用多光谱传感器对同一观测对象在多个窄光谱范围上获得的图像,称为多光谱遥感图像。这类具有高空间和谱间分辨率的谱图像数据量大,其存储和传输都比较困难。因此,对海量数据进行有效的数据压缩便成了遥感资料应用中迫切需要解决的问题之一。为了防止有用信息的丢失而影响图像的进一步处理和应用,采用无损数据压缩方法是解决该问题的有效途径之一。本文分析了多光谱图像的空间和谱间相关性等特点,从多光谱图像预处理、预测和变换无损压缩方法等方面介绍了目前主要的多光谱图像无损压缩方法,并对其特点进行了对比分析。     

Automated Software Engineering Through Structured Data Management

The Software Engineering Facility (SEF) is a system for software engineering which is specifically designed to support the development of well-engineered software. However, it is not an operating system. Unlike operating systems such as OS/370, EXEC 8, and others, the SEF is not meant to support the execution of applications programs, just as the ordinary operating systems are not intended to specifically support the development of well-engineered applications programs. The SEF, in fact, will run under and use the facilities of such operating systems. It, then, is easily transferable and can be used with vaxious hardware/operating system configurations where it will provide a host-independent software development system. In such a role it will provide to the software developer standard facilities across a variety of host systems.     

Distribution of control using active storage

Real-time control systems are often distributed, with complex data-sharing requirements. A method is proposed for the distribution of functions in such a control system using a distributed real-time database as storage, extended with an active mechanism based on event–condition–action rules that react to changes in the system. This database is fully replicated and nodes communicate using only the database distribution facilities. Critical temporal constraints at individual nodes may be met at the expense of introducing temporary inconsistencies in the database. This paper investigates the effects of using the active mechanism and the replicated storage as a distribution mechanism for certain classes of real-time systems. Particular attention is paid to the requirement of applications to tolerate temporary inconsistencies, assuming that eventual consistency is ensured.     

物联网情景感知技术在智能仓储领域的应用展望

智能仓储系统中最为关键的是对于仓储流程中的情景信息的应用,其中RFID等情景感知技术在仓储领域的应用已经帮助该领域得到了快速发展。文中对物联网和相关情景感知技术在仓储业的应用进行了分析和研究,给出了情景感知在智能仓储和物流系统中的应用现状和发展趋势。     

An energy-balancing perspective of interconnection and damping assignment control of nonlinear systems

Stabilization of nonlinear feedback passive systems is achieved assigning a storage function with a minimum at the desired equilibrium. For physical systems a natural candidate storage function is the difference between the stored and the supplied energies—leading to the so-called energy-balancing control, whose underlying stabilization mechanism is particularly appealing. Unfortunately, energy-balancing stabilization is stymied by the existence of pervasive dissipation, that appears in many engineering applications. To overcome the dissipation obstacle the method of Interconnection and Damping Assignment, that endows the closed-loop system with a special—port-controlled Hamiltonian—structure, has been proposed. If, as in most practical examples, the open-loop system already has this structure, and the damping is not pervasive, both methods are equivalent. In this brief note we show that the methods are also equivalent, with an alternative definition of the supplied energy, when the damping is pervasive. Instrumental for our developments is the observation that, swapping the damping terms in the classical dissipation inequality, we can establish passivity of port-controlled Hamiltonian systems with respect to some new external variables—but with the same storage function.     

A large-range compliant micropositioning stage with remote-center-of-motion characteristic for parallel alignment

Micro-/nanopositioning stage with remote-center-of-motion (RCM) plays a key role in precision out-of-plane aligning since it can eliminate harmful lateral displacement generated at the output platform. This paper presents the design, modeling and test of a novel large-range flexure-based micropositioning stage with RCM characteristic. The stage is composed of an outer RCM guiding mechanism and a inner output-stiffness enhanced lever amplifier (OELA). The outer RCM guiding mechanism is constructed by a symmetric double parallelogram mechanism which can guide the stage to perform a RCM movement with high rotational precision. The inner OELA is designed to amplify the output displacement of the adopted piezoelectric stack actuator (PSA). Compared with conventional lever amplifier, the proposed OELA possesses twice the output stiffness, which makes it more appropriate for actuating the outer mechanism and therefore, a large rotational range can be obtained. Based on the pseudo-rigid-body-model (PRBM) method, the analytical models predicting kinematics, statics, and dynamics of the RCM stage have been established. Besides, the dimensional optimization is conducted in order to maximize the first resonance frequency of the stage. After that, finite element analysis is carried out to validate the established models and the prototype of the stage is fabricated for performance tests. The experimental results show that the developed RCM stage has a rotational range of 6.96 mrad while the maximum center shift of the RCM point is as low as \(9.2\,{\upmu } \text {m}\), which validate the effectiveness of the proposed scheme.     

介电法小麦含水率检测试验研究

小麦从收割、收购到存储、加工都需要快速、准确获取其含水率,为此设计一种外边缘效应圆柱形电容传感器探头及相应测量电路.采用小麦样品对所设计的装置进行标定与温度特性测试.试验结果表明:该传感器具有较高的灵敏度和准确性,含水率在8%~20%之间,误差在0.5%以内;在14℃~32℃温度范围内,漂移量为0.19%/℃.