AFM扫描参数对表面粗糙度测量的影响分析

原子力显微镜(AFM)是纳米科技研究中一个重要工具.影响AFM测量图像质量的因素很多,本文从AFM扫描参数选择的角度,研究扫描参数对样品表面均方根粗糙度的影响.实验和理论分析表明,扫描速度、反馈控制参数中的比例常数P和积分常数I的选择均对样品的表面粗糙度测量及评定产生影响.     

基于DSP的高速原子力显微镜系统

传统的以PC机为控制核心的AFM(atomic force microscope)越来越无法满足快速成像的要求,具有先进控制系统的高速AFM正成为国内外的一个研究热点.本文介绍了一种以DSP(digital signal processor)为控制核心的AFM系统.在该系统中,自动进针/退针、扫描电压的产生、A/D采样、D/A输出以及数字闭环反馈控制等任务均在DSP控制下完成;在分辨率为512×512时,可以获得行频55 Hz的扫描速度.实验表明,即便在这样高速扫描的情况下,该系统仍具有良好的成像性能.     

AFM反馈系统仿真模型的建立及实验

原子力显微镜（ AFM）广泛应用于纳米尺度的成像和操纵,其较低的扫描速度严重影响了测试的效率。为此,许多研究人员通过设计先进的Z向控制算法改善系统的响应速度,达到提高扫描速度的目的,而先进的控制算法的实现首先需要对AFM的Z向反馈系统进行建模。为此,本文提出一种简单准确的系统辨识方法,通过对系统输入输出数据的分析,得到AFM的Z向反馈系统模型,并利用该模型验证先进控制算法的控制性能。实验表明该方法能为先进控制算法的设计和实现建立有效的仿真模型。     

基于PI迟滞模型的压电陶瓷复合控制算法研究

为减小压电陶瓷的迟滞非线性对系统跟踪精度的影响,该文采用经典的存在逆解析的PI迟滞模型对压电陶瓷的迟滞特性进行建模,将PI模型的逆模型用于压电陶瓷的前馈控制算法中,然后设计了神经元比例、积分、微分(PID)反馈控制算法,将前馈控制算法与神经元PID反馈控制算法结合得到了压电陶瓷的复合控制算法。将仅含前馈的控制算法和复合控制算法在压电陶瓷的控制器上执行,实验结果表明,仅含前馈的控制算法的跟踪误差为1.256μm,而复合控制算法的跟踪误差仅为0.092μm,该复合控制算法使跟踪精度提高了1.164μm。     

基于PI迟滞模型的压电陶瓷复合控制算法研究

为减小压电陶瓷的迟滞非线性对系统跟踪精度的影响,该文采用经典的存在逆解析的PI迟滞模型对压电陶瓷的迟滞特性进行建模,将PI模型的逆模型用于压电陶瓷的前馈控制算法中,然后设计了神经元比例、积分、微分(PID)反馈控制算法,将前馈控制算法与神经元PID反馈控制算法结合得到了压电陶瓷的复合控制算法。将仅含前馈的控制算法和复合控制算法在压电陶瓷的控制器上执行,实验结果表明,仅含前馈的控制算法的跟踪误差为1.256 μm,而复合控制算法的跟踪误差仅为0.092 μm,该复合控制算法使跟踪精度提高了1.164 μm。     

安捷伦推出下一代原子力显微镜

安捷伦科技公司日前宣布推出7500原子力显微镜（AFM）,它设定了新的性能、功能和易用性标准,以进行纳米级测量、表征和操作。Agilent7500可以使用90μmAFM闭环扫描器获得原子级分辨率成像。     

实验分析连续太赫兹反射扫描成像测量效果

实验分析连续太赫兹反射扫描成像测量效果。针对极端系统进行分辨率特性测量,根据方法的不同将其分为连续太赫兹反射扫描成像测量法与传统刀口法测量法,并比较两种测量的结果。在该次实验中,连续太赫兹反射扫描成像测量得出系统分辨率测量结果为1.237 lp/mm,其对应线宽为0.393 mm,这与刀口法测量结果一致,且与传统刀口法相比较可以简化测量过程,准确得出测量结果。应用连续太赫兹反射扫描成像测量技术,可以简化系统分辨率特性测量过程,直观、准确地得出系统分辨率上限,在测量中发挥积极测量效果。     

一种转子位置传感器无刷直流电机速度检测方法

本文提出了一种利用转子位置传感器发出的信号测量无刷直流电机（BLDC）转速的方法,并设计了相应的转动方向测定电路和数字PI速度控制器模块。通过利用比例积分控制器计算半个转动周期内的两次连续测量值,结合提出的转动方向测定电路和数字PI速度控制器,可以得出具有双倍测量频率的转子转动周期的准确值。最后将提出的方法在FPGA平台进行了实现,并与真实数据的对比表明,该算法在无换向器直流电机上可以获得具有高精度及高频率的速度测量值（每转动1周至少测量6次）。     

频域偏振敏感光学相干层析系统的研制及应用研究

偏振敏感光学相干层析(PS-OCT)是在OCT技术基础上发展起来的一种可以测量样品偏振特性的层析测量方法.本文将具有更快扫描速率及更高灵敏度的频域OCT技术与偏振特性测量相结合,研制了频域PS-OCT系统,纵向分辨率达到了11 μm,实现了高于260 Hz的扫描速率,获得了样品双折射、Stokes向量的偏振信息图像.该实验系统对肌腱、肌肉纤维等生物组织样品进行的应用实验显示了PS-OCT成像方法在生物医学成像中的独特优势和发展潜力.     

激光光路跟踪型原子力显微镜研究

提出和发展了一种激光光路跟踪型原子力显微镜(AFM)技术及系统。研制了新型AFM探头,设 计了与XY扫描器联动的跟踪透镜及扫描跟踪光路,实现激光束对微探针(微悬 臂)的XY扫描的实时跟踪;研 究设计了独特的反馈跟踪光路,既可实现微悬臂偏转量的精确检测,又可巧妙地消除因微探 针的Z向反馈运动 造成的干扰噪声。利用研发的AFM系统对多孔氧化铝纳米孔等具有不同横向与 纵向结构尺寸的微纳米样品进行了扫 描成像,得到了理想的实验结果,表明研发的系统具有优良的XY扫描跟踪特性 和Z向反馈跟踪性能。本文研发的 AFM系统原理新颖、方法巧妙、扫描成像性能好和分辨率高,克服了常规样品 扫描型AFM的局限性,能够以 微探针扫描的方式实现不同大小、不同重量的样品的AFM扫描成像,可望在微纳米技术领 域获得广泛应用。     

Design of incremental fuzzy PI controllers for a gas-turbine plant

In this paper, incremental fuzzy proportional integral (PI) speed and temperature controllers for a heavy-duty gas-turbine plant are presented. To improve performance, an analysis of incremental fuzzy PI control is provided, and new fuzzy control rules are proposed. In applying the fuzzy PI control to a gas-turbine plant, all gains are optimized by an adaptive genetic algorithm. We show the performance improvement of the proposed controller compared with conventional PI controller via simulations.     

A high-performance sensorless indirect stator flux orientation control of induction motor drive

A new method for the implementation of a sensorless indirect stator-flux-oriented control (ISFOC) of induction motor drives with stator resistance tuning is proposed in this paper. The proposed method for the estimation of speed and stator resistance is based only on measurement of stator currents. The error of the measured q-axis current from its reference value feeds the proportional plus integral (PI) controller, the output of which is the estimated slip frequency. It is subtracted from the synchronous angular frequency, which is obtained from the output integral plus proportional (IP) rotor speed controller, to have the estimated rotor speed. For current regulation, this paper proposes a conventional PI controller with feedforward compensation terms in the synchronous frame. Owing to its advantages, an IP controller is used for rotor speed regulation. Stator resistance updating is based on the measured and reference d-axis stator current of an induction motor on d-q frame synchronously rotating with the stator flux vector. Experimental results for a 3-kW induction motor are presented and analyzed by using a dSpace system with DS1102 controller board based on the digital signal processor (DSP) TMS320C31. Digital simulation and experimental results are presented to show the improvement in performance of the proposed method.     

基于超声电机的力矩补偿装置控制方法研究

为补偿卫星载荷运动产生的干扰力矩,设计了一种基于超声电机的力矩补偿机构。基于传统控制策略的比例、积分、微分(PID)闭环负反馈控制系统调速效果难以令人满意,在这种情况下建立了系统的数学模型,设计了基于模糊PI控制的闭环调速控制系统,并与传统的PI控制进行了对比。根据干扰力矩的给定形式,设计了飞轮运行的正弦速度给定曲线,仿真结果表明,该方法能够有效补偿载荷干扰力矩。此外,设计了以数字信号处理器(DSP)芯片为核心的硬件驱动控制电路,并进行了实验验证。结果表明,该算法比传统的PI控制效果更好,速度曲线跟踪精度明显提升。     

New self-tuning fuzzy PI control of a novel doubly salient permanent-magnet motor drive

In a doubly salient permanent-magnet (DSPM) motor drive, it is difficult to get satisfied control characteristics by using a normal linear proportional plus integral (PI) controller due to the high nonlinearity between speed and current or torque. Hence, a new self-tuning fuzzy PI controller with conditional integral, which is performed by a single-chip N87C196KD, is proposed. The initial parameters of the controller are optimized by using genetic arithmetic. Simulation and experiments on the newly proposed 8/6-pole DSPM machine have shown that the proposed new self-tuning fuzzy PI controller offers better adaptability than the normal linear PI control and that the developed motor drive offers better steady-state and dynamic performances.     

AFPI:一种基于模糊控制的队列管理新算法

以PI算法为基础提出了一种模糊自适应PI算法AFPI,可通过利用模糊控制动态设置PI算法中的有关参数。ns-2模拟实验表明,相对于PI算法,AFPI具有更快的收敛速度和更小的队列抖动。     

Fuzzy-PI-based centralised control of semi-isolated FP-SEPIC/ZETA BDC in a PV/battery hybrid system

Multiport converters with centralised controller have been most commonly used in stand-alone photovoltaic (PV)/battery hybrid system to supply the load smoothly without any disturbances. This study presents the performance analysis of four-port SEPIC/ZETA bidirectional converter (FP-SEPIC/ZETA BDC) using various types of centralised control schemes like Fuzzy tuned proportional integral controller (Fuzzy-PI), fuzzy logic controller (FLC) and conventional proportional integral (PI) controller. The proposed FP-SEPIC/ZETA BDC with various control strategy is derived for simultaneous power management of a PV source using distributed maximum power point tracking (DMPPT) algorithm, a rechargeable battery, and a load by means of centralised controller. The steady state and the dynamic response of the FP-SEPIC/ZETA BDC are analysed using three different types of controllers under line and load regulation. The Fuzzy-PI-based control scheme improves the dynamic response of the system when compared with the FLC and the conventional PI controller. The power balance between the ports is achieved by pseudorandom carrier modulation scheme. The response of the FP-SEPIC/ZETA BDC is also validated experimentally using hardware prototype model of 500 W system. The effectiveness of the control strategy is validated using simulation and experimental results.     

A genetic algorithm for the design of a fuzzy controller for active queue management

Active queue management (AQM) policies are those policies of router queue management that allow for the detection of network congestion, the notification of such occurrences to the hosts on the network borders, and the adoption of a suitable control policy. This paper proposes the adoption of a fuzzy proportional integral (FPI) controller as an active queue manager for Internet routers. The analytical design of the proposed FPI controller is carried out in analogy with a proportional integral (PI) controller, which recently has been proposed for AQM. A genetic algorithm is proposed for tuning of the FPI controller parameters with respect to optimal disturbance rejection. In the paper the FPI controller design methodology is described and the results of the comparison with random early detection (RED), tail drop, and PI controller are presented.     

An optimal fuzzy PID controller

This paper introduces an optimal fuzzy proportional-integral-derivative (PID) controller. The fuzzy PID controller is a discrete-time version of the conventional PID controller, which preserves the same linear structure of the proportional, integral, and derivative parts but has constant coefficient yet self-tuned control gains. Fuzzy logic is employed only for the design; the resulting controller does not need to execute any fuzzy rule base, and is actually a conventional PID controller with analytical formulae. The main improvement is in endowing the classical controller with a certain adaptive control capability. The constant PID control gains are optimized by using the multiobjective genetic algorithm (MOGA), thereby yielding an optimal fuzzy PID controller. Computer simulations are shown to demonstrate its improvement over the fuzzy PID controller without MOGA optimization     

Digital control of active magnetic bearings

Theoretical relationships are developed to relate the characteristics of a controller transfer function to the stiffness and damping properties of an active magnetic bearing for machine rotors. Both proportional and derivative feedback are shown to be necessary for closed-loop system stability, and, for the ideal case, bearing stiffness and damping properties are shown to be simple linear functions of the proportional and derivative feedback gain constants, respectively. The flexibility of a digitally controlled magnetic bearing is demonstrated by the implementation of algorithms which include second-derivative and integral feedback. Second-derivative feedback is shown to be effective at extending the usable bandwidth of the digital controller, and integral feedback rejects rotor position error in the presence of static loads. The relationship between controller sampling rate and bearing performance is investigated, and it is shown that increased sampling rate and increased amounts of second-derivative feedback have similar effects on the bearing properties