Micro/nano sculpturing of hardened steel by controlling vibration amplitude in elliptical vibration cutting

A new ultra-precision sculpturing method in micro/nano scale for difficult-to-cut materials is proposed in the present research. Elliptical vibration cutting technology is well-known for its excellent performance in achieving ultra-precision machining of steel materials with single crystal diamond tools. Elliptical vibration locus is generally controlled and held to a constant in practice. On the contrary, the proposed method utilizes the variations of the elliptical vibration locus in a positive manner. Depth of cut can be actively controlled in elliptical vibration cutting by controlling vibration amplitude in the thrust direction. By utilizing this as a fast tool servo function in elliptical vibration cutting, high performance micro/nano sculpturing can be attained without using conventional fast tool servo technology. A high-speed amplitude control system is developed for elliptical vibration, with a bandwidth of more than 300 Hz, where the vibration amplitude can be controlled within 4 μm_p-p. The developed control system is applied to sculpturing ultra-precision nano textured grooves on hardened steel with single crystal diamond tools. It is confirmed that the textured grooves have the desired shapes, and their profiles agree well with the vibration amplitude commands input to the control system. Further, a high performance micro/nano sculpturing system for plane surfaces is developed, where the vibration amplitude is controlled in synchronization with the planing motion of an ultra-precision machine tool. Nano sculpturing experiments on hardened steel, carried out by the developed system, are reported, as well as consequent picture images and a variety of dimple patterns that were formed successfully on the hardened steel as nano-scale sculptures.     

亚微米级微位移工作台及其微计算机数字闭环控制系统

本文介绍一种单尾X-Y强性微动工作台及其微计算机数字闭环控制系统,采用自适应P-PID选择控制算法,达到了±0.03μm的位置控制精度和优良的动态品质.     

一种宏微双重驱动精密定位机构的建模与控制

提出一种宏微双重驱动精密定位机构,采用高性能直线电机直接驱动宏动平台,实现系统大行程微米级精度定位;安装在宏动平台上的压电陶瓷驱动微动平台,实现纳米级的分辨率和定位精度,以高频响动态补偿系统的定位误差;采用精密光栅尺反馈微动平台输出端的位置信号,实现定位机构的全闭环反馈控制。在分别建立宏动、微动、宏微机构模型的基础上,提出复合型宏动控制和模糊自校正PID微动控制的宏微控制策略。实验研究表明:系统的动态和稳态性能良好,该定位机构的最大工作行程100 mm,稳定时间小于40 ms,重复定位精度10 nm。     

X-Y精密定位平台的敏感函数逆前馈补偿控制

针对音圈电机驱动的X-Y定位平台中稳态误差导致的系统定位精度较低的问题,提出了基于敏感函数逆的前馈补偿控制方法。首先,采用频域辨识方法建立了系统模型,基于终值定理推导出系统扰动和稳态误差的关系,并由此设计了敏感函数的逆模型来补偿扰动对稳态误差的影响,从而提高系统精密定位性能。最后,在搭建的音圈电机驱动X-Y定位平台上进行了不同运动行程的实验研究。实验结果表明:在行程为10μm,最大加速度为6mm/s2的微定位运动条件下,补偿后的定位误差可由2μm降低到0.2μm;在行程为10mm,最大加速度为6m/s2的宏定位运动条件下,定位误差可由2μm降低到0.4μm。实验结果验证了本方法的有效性,为后续高精密伺服系统的研制提供了重要参考和设计依据。     

基于电流变阻尼超精密气浮工作台建模及控制研究

随超精密装备加工精度和生产率的不断提高,直线气浮系统得到广泛重视和研究。为解决直线气浮系统抗干扰能力较差等问题,针对已开发的超精密直线气浮工作台,设计了电流变剪切模式阻尼器;建立了气浮工作台整体模型并基于屈服前后平滑过渡的Eyring连续本构模型通过辨识得出电流变剪切阻尼器类稳态模型;分别对零电场线性及高电场非线性电流变阻尼2种情况下的气浮工作台应用误差积分LQR控制器;为达到综合最优,进一步提出开关及滑模控制器,实验证实这2种控制策略均能同时提高系统的响应速度、减少建立时间,降低跟踪误差及纹波。     

精密隔振平台振动的模糊控制

采用混合隔振技术建立了以空气弹簧作为被动隔振元件、超磁致伸缩致动器作为主动隔振元件的精密隔振平台隔振系统，并采用模糊控制理论设计其主动控制器。应用MATLAB软件进行了仿真分析以验证系统的振动控制效果。仿真分析结果表明，该振动控制系统在较宽的频率范围内具有良好的减振效果，该系统可应用于超精密测量．制造设备的隔振领域。     

双维精密定位工件台数控系统的研究

X-Y两维精密定位工件台是以光栅干涉仪为位置检测元件的精密定位系统,其数控系统是以8031单片机作为位置控制的闭环系统。本文在对系统深入分析的基础上,设计了数控系统的硬件,用Turbo C、8088汇编语言及Mcs51汇编语言编制了相应的软件,采用细分方法提高了系统的分辨率,并对如何提高系统精度做了详细的讨论。结果表明,数控系统达到了预定的精度.     

基于机器视觉的激光植球系统标定

构建了一个基于机器视觉辅助定位的激光植球系统。通过试验发现，整个系统的定位误差主要由机器视觉中透镜畸变和X—Y定位平台的装配误差引起。对于透镜畸变，引入了基于直线方法的图像畸变校正算法进行校正；对于非垂直的X—Y定位平台，通过基于机器视觉的软件补偿算法来校正X—Y定位平台的装配误差。最后，给出了试验对比数据和试验结果，验证了整个系统的标定效果。     

基于静压气浮导轨的直线电机高性能工作台的研制

精密定位技术是精密工程领域的关键技术,由直线电机驱动的气浮直线导轨工作台在超精密运动领域得到广泛应用。本文介绍了静压气浮导轨的设计方法,开发了止推气浮轴承设计软件;为了提高气浮导轨的承载能力和刚度,总结提出了几种适用于不同结构气浮导轨的预加载技术;运用气浮轴承设计系统和适合的预加载技术,研制了能满足大惯量、高速度、高精度要求的H型直线电机气浮工作台。     

基于体硅工艺的集成式定位平台

针对纳米定位平台的构型和定位精度问题,采用体硅加工技术成功地研制出了一种基于单晶硅并带有位移检测功能的新型二自由度微型定位平台,定位平台采用侧向平动静电梳齿驱动.利用力电耦合和能量守恒原理分析了静电致动器的致动机理,对定位平台的主要失效模型、静态和动态特性进行详细建模分析,证明了静电梳齿力电耦合所导致的侧壁不稳定以及驱动器的最大稳定输出位移,给出了平台稳定工作条件下梳齿间隙、梳齿初始交错长度以及复合柔性支撑梁的弹性刚度比之间的关系.动态分析时考虑空气阻尼对平台的影响,给出了平台最大运行速度、位移及动态条件下的临界驱动电压并把分析结果应用于平台闭环控制.实验结果表明:驱动电压30 V时,平台稳定输出位移达10 μm,机械稳定时间仅为2.5 ms.     

Piezo微步进工作台主框架研究

为了扩大微动工作台的有效行程,提出一种新型的基于Piezo驱动的微步进X-Y工作台,通过机构仿真确定了微步进工作台主框架中各柔性铰链的转角参数,并据此确定了主框架中各柔性铰链的结构参数,最后通过非线性有限元对整个微步进工作台主框架的变形情况进行了分析.     

Control of a dual stage magnetostrictive actuator and linear motor feed drive system

A dual stage feed drive system is well suited to satisfying current demands of high performance machining with tight position control under high feed rates in the presence of disturbances. It does this by integrating an actuator with high position resolution and fast response together with a conventional linear drive. A magnetostrictive actuator (MA) with a bandwidth in the kHz range capable of several kN of force output is an ideal candidate for use as the fine positioning element in such a dual stage system. However, MAs display significant hysteresis in their performance. This makes the effective implementation of real-time fast servo control challenging. In this paper, a dynamic Preisach model is utilized to reduce the undesired nonlinearity. A sliding mode controller (SMC) is designed to deal with uncertainties such as the Preisach modeling error as well as external disturbances so as to ensure a robust stable system. Experimental results show the servo performance improvement during a feed step test for single axis control and a single axis component of a sharp path interpolation test.     

压电陶瓷驱动的铰链放大式微动工作台研究

研制了一种新的压电陶瓷驱动的铰链放大式微动工作台。介绍了该微动工作台的基本原理,利用原子力显微镜技术测定了压电陶瓷与铰链放大臂的微位移和微振动,确定了铰链机构的放大比及微动工作台的时间响应频率。结果表明,该微动工作台能以0.5μm～5μm的步长实现平稳的微位移,最大速度达到250μm/s。     

高速高精度叠层直线运动控制系统

在分析粗精动控制系统的耦合及轨迹分配等问题的基础上,介绍叠层试验台高速高精度直线运动的实现: 采用永磁直线交流电动机驱动粗动台,粗动台行程大但带宽较低;音圈电动机驱动精动台,精动台带宽高但行程较小。用绝对空间闭环方式实现试验台的粗精运动控制,这种方法可以忽略粗动台对精动台的惯性力扰动,精动台直接跟踪给定轨迹,粗动台跟踪精动台的运动轨迹防止精动台发生运动饱和。试验结果表明,精动台显著提高了系统的定位和跟踪精度,该控制方法使叠层试验台的高速高精度运动得以方便实现。     

大行程高精度驱动系统的研究

首先对大行程高精度驱动系统结构研究进展进行介绍和评述,其次针对目前大行程高精度宏微两级定位系统结构复杂,体积大,驱动控制困难等问题,提出研究具有宏微双重运动功能的单一驱动结构将是大行程高精度驱动定位系统的发展方向;指出将超声电机与压电微驱动器结合成为单一驱动器将是大行程高精度驱动系统的一个发展方向;最后对单级超声电机宏微驱动系统建模方法、位置控制策略的研究进展进行了综述,指出了单级宏微驱动的超声电机研究的主要难点。     

基于电流变阻尼超精密气浮工作台研究

为解决直线气浮系统抗干扰能力较差等问题，针对已开发的超精密直线气浮工作台，设计了电流变剪切模式阻尼器；基于屈服前后平滑过渡的Eyring连续本构模型通过辨识得出电流变剪切阻尼器类稳态模型；从仿真和实验研究了电流变阻尼及高电场强度对直线气浮工作台模态的影响，实验模态结果验证了仿真方法的有效性，同时证实设计的电流变阻尼器及电场强度的提高不会造成模态频率的下降，只会引起阻尼比的大幅度提高，甚至减少模态阶数。     

The long-range scanning stage: a novel platform for scanned-probe microscopy

This paper describes a magnetically suspended six degree-of-freedom precision motion control stage with a horizontal positioning noise of less than 0.6 nm three sigma. The vertical positioning noise is less than 2.2 nm three sigma. The stage utilizes four levitation linear motors to suspend and servo the moving element (platen) throughout its 25 mm × 25 mm × 0.1 mm range of travel. Position feedback is provided by three plane mirror interferometers and three capacitance probes. The suspended platen (12 kg mass) is floated in oil to enhance the stage’s disturbance rejection and to reduce power dissipation in the actuators. The stage has been designed to achieve a positioning accuracy of 10 nm and is used to position samples beneath a scanned probe microscope. The ultimate purpose of this measuring machine is to provide a means of measuring submicron-scale features with nanometer-scale accuracy. The technology can easily be scaled to larger travels, with accuracy limited primarily by the wavelength instability of the HeNe light source. This article gives an overview of the LORS project, emphasizing the system error terms, tolerancing, and experimental results.     

Development of a novel 3-degrees of freedom flexure based positioning system

Flexure mechanisms have been widely used for nanometer positioning systems. This article presents a novel conceptual design of an ultra-precision 3-degrees of freedom (XYθ(Z)) positioning system with nanometer precision. The main purpose of this novel stage design is for the application of measurement equipment, in particular biological specimens. The stage was designed as a hollow type and with a compact size for the inverted microscope. This stage includes piezoelectric transducer actuators, double compound amplification mechanisms, moving plate, and capacitor sensors. The double compound amplification mechanism was designed using a mathematical model and analyzed by the finite element method. Since the relationship between the variables of the hinge parameters and system performances are complicated, an optimization procedure was used to obtain the optimal design parameters, which maximized the system bandwidth. Based on the solution of the optimization problem, the design of the stage and FEM simulation results are presented. Finally, the stage was manufactured and tested.     

Development of a linear electrostrictive servo motor

This paper presents a linear electrostrictive servo motor with high resolution and large stroke for ultra-precision motion control. High thrust force is obtained by making use of an electromagnetic clamping mechanism with force magnifying structure in the motor design. An operator alterable iterative learning control algorithm is proposed for the motion control of the motor. A prototype is designed, fabricated and tested. Experimental results show that the prototype has a mechanical resolution of 0.02 μm, yaw error less than 2 μm and maximum thrust force of 30N. Applications of the motor include producing the servo feed motions required in micro electrical discharge machining (micro-EDM) system or as a motion control device for other precision machining systems.     

微结构自由曲面的超精密单点金刚石切削技术概述

回顾了超精密加工技术的发展,主要包括超精密加工设备的开发历程,以及超精密单点金刚石切削技术基础,并对微工程技术作一简要介绍;重点论述微结构自由曲面的微纳切削技术,包括单点金刚石车削(Single point diamond turning, SPDT),快刀伺服加工(Fast tool servo, FTS),金刚石微凿切(Diamond micro chiseling, DMC),光栅铣削等技术。指出微结构自由曲面测量领域面临的挑战和存在的问题,包括接触式测量和非接触式测量。通过几个典型微结构自由曲面的加工及测量的应用进行举例说明;最后介绍我国在超精密加工机床领域内的研制情况,展望了超精密切削技术未来发展趋势。