A Fast Tool Servo System for Fabrication of Micro-structured Surfaces on A Diamond Turning Machine

A fast tool servo (FTS) system is developed for the fabrication of non-rotationally symmetric micro-structured surfaces using single-point diamond turning machines.The constructed FTS employs a piezoelectric tube actuator (PZT) to actuate the diamond tool and a capacitive probe as the feedback sensor.To compensate the inherent nonlinear hysteresis behavior of the piezoelectric actuator,Proportional Integral (PI) feedback control is implemented.Besides,a feed-forward control based on a simple feed-forward predictor has been added to achieve better tracking performance.Experimental results indicate that error motions in the performance of the system caused by hysteresis can be reduced greatly and the micro-structured surface is successfully fabricated by implementing the FTS.

Diamond machining of sinusoidal grid surface using fast tool servo system for fabrication of hydrophobic surface

Ultra-precision diamond machining with piezoelectric-assisted fast tool servo (FTS) was used to produce various free-form surfaces.A low cost,rapid and large area fabrication of uniform hydrophobic surface at room temperature which transfers the FTS fabricated sinusoidal grid surface to the flat film with UV-moulding process was described.A piezoelectric-assisted FTS with high band width of 2 kHz,travel range up to 16 μm and the compact mechanism structure was designed for the sinusoidal grid surface machining and the dynamic performance testing of FTS was described in detail.Machining results indicate that the dimensions of sinusoidal grid change with the variation of the FTS machining condition.Wetting properties of UV-moulded surface were evaluated,the best contact angle was measured to be 120.5° on the sinusoidal grid surface with profile wavelength of 350 μm and peak-to-valley amplitude of about 16 μm.

Tool path generation and optimization for freeform surface diamond turning based on an independently controlled fast tool servo

Diamond turning based on a fast tool servo(FTS)is widely used in freeform optics fabrication due to its high accuracy and machining efficiency.As a new trend,recently developed high-frequency and long-stroke FTS units are independently driven by a separate control system from the machine tool controller.However,the tool path generation strategy for the independently controlled FTS is far from complete.This study aims to establish methods for optimizing tool path for the independent control FTS to reduce form errors in a single step of machining.Different from the conventional integrated FTS control system,where control points are distributed in a spiral pattern,in this study,the tool path for the independent FTS controller is generated by the ring method and the mesh method,respectively.The machined surface profile is predicted by simulation and the parameters for the control point generation are optimized by minimizing the deviation between the predicted and the designed surfaces.To demonstrate the feasibility of the proposed tool path generation strategies,cutting tests of a two-dimensional sinewave and a micro-lens array were conducted and the results were compared.As a result,after tool path optimization,the peak-to-valley form error of the machined surface was reduced from 429 nm to 56 nm for the two-dimensional sinewave by using the ring method,and from 191 nm to 103 nm for the micro-lens array by using the mesh method,respectively.

用可视工具sisotool设计电液伺服系统的补偿器

MATLAB6 .0的控制系统工具箱提供了设计SISO系统补偿器的可视工具sisotool。本文提出了利用该工具设计电液伺服系统补偿器的方法 ,使补偿器的设计变得更加简便、直观 ,大大减少了设计的复杂性和重复性 。

Robust tracking control for micro machine tools with load uncertainties

The quality of the micro-mechanical machining outcome depends significantly on the tracking performance of the miniaturized linear motor drive precision stage. The tracking behavior of a direct drive design is prone to uncertainties such as model parameter variations and disturbances. Robust optimal tracking controller design for this kind of precision stages with mass and damping ratio uncertainties was researched. The mass and damping ratio uncertainties were modeled as the structured parametric uncertainty model. An identification method for obtaining the parametric uncertainties was developed by using unbiased least square technique. The instantaneous frequency bandwidth of the external disturbance signals was analyzed by using short time Fourier transform technique. A two loop tracking control strategy that combines the p-synthesis and the disturbance observer （DOB） techniques was proposed. The p-synthesis technique was used to design robust optimal controllers based on structured uncertainty models. By complementing the/z controller, the DOB was applied to further improving the disturbance rejection performance. To evaluate the positioning performance of the proposed control strategy, the comparative experiments were conducted on a prototype micro milling machine among four control schemes： the proposed two-loop tracking control, the single loop μ control, the PID control and the PID with DOB control. The disturbance rejection performances, the root mean square （RMS） tracking errors and the performance robustness of different control schemes were studied. The results reveal that the proposed control scheme has the best positioning performance. It reduces the maximal errors caused by disturbance forces such as friction force by 60% and the RMS errors by 63.4% compared with the PID control. Compared to PID with DOB control, it reduces the RMS errors by 29.6%.

Development of Integrated Precision Vibration-Assisted Micro-Engraving System

A novel precision vibration-assisted micro-engraving system was developed by the integration of fast tool servo and ultrasonic elliptical vibration system, in which the flexure hinge was designed to avoid backlash and PID control algorithm was established to guarantee specific precision. Apart from experimental validation of the performance of the system, various micro-V-grooves cutting experiments on aluminum alloy, ferrous material and hard cutting material were performed, in which Kistler force sensor was used to measure cutting force. Through experiments, it was clear that the vibration-assisted micro-engraving system can ensure good quality of micro-V-grooves and reduce cutting force by about 60% compared with traditional removal process without ultrasonic vibration.

基于改进灰狼算法的非线性摩擦力辨识与补偿方法研究

为减小非线性摩擦力对机床伺服系统运动控制精度的影响,对机床伺服系统摩擦特性进行研究,将改进灰狼算法应用于LuGre摩擦模型参数辨识,通过搭建伺服系统动力学模型进行摩擦前馈补偿仿真,并在三轴数控雕铣机试验平台进一步完成摩擦前馈补偿验证。结果表明:应用基于改进灰狼算法辨识的LuGre摩擦模型前馈补偿方法,在两轴联动圆轨迹运动跟随过程中,低速运动换向时最大跟随误差下降幅度为67.7%,高速运动条件下误差下降幅度为84.0%,有效消除了非线性摩擦在速度换向过程中产生的负面影响,证明该方法在非线性摩擦力辨识方面具有优异的效果,有助于提高机床伺服系统的运动控制精度。

数控机床伺服驱动系统的多电机同步控制策略

以数控机床伺服驱动系统的多电机同步控制为研究对象,提出了一种基于多交流伺服电机的同步控制策略。此策略将虚拟主轴和偏差耦合的同步控制方式相结合,并加入反向传播神经网络比例积分微分控制以及自适应鲁棒控制。通过搭建Matlab/Simulink仿真平台模拟了系统的运行状态。结果表明,所提同步控制策略具有良好的同步性能和伺服效果,在提高多电机联动系统的控制精度和响应速度、减少摩擦和齿隙的影响以及增强系统鲁棒性方面表现出优越性。

非最小相位法向电磁应力驱动快速刀具伺服系统轨迹跟踪控制

基于快速刀具伺服(FTS)的金刚石车削是复杂光学表面超精密制造的一种高效手段。为进一步提高具有非最小相位特征的电磁法应力驱动FTS的控制性能,将系统逆动力学补偿嵌入主控制回路中以改善被控对象动力学特征。对改善后的被控系统以比例微分积分(PID)和前馈补偿作为主控制器,并以基于内模原理的并联谐振控制器实现周期性轨迹的超高精度跟踪。考虑系统非最小相位特征,结合因子分解和镜像极点配置方法获得了系统稳定逆动力学模型。实验测试结果表明:该文所设计的控制方法,获得了1070 Hz(-3 dB)闭环带宽;100 Hz正弦轨迹实际跟踪误差小于±0.375%,并可对5 nm台阶轨迹进行稳定闭环跟踪,证明所设计的FTS控制系统可有效实现nm精度切削。

利用置信规则库的数控机床伺服系统故障诊断

为了诊断数控机床伺服系统故障,针对数控机床伺服系统故障原因和征兆之间存在的复杂非线性关系,提出利用置信规则库(belief rule base,简称BRB)对伺服系统进行故障诊断。该方法能够利用各种类型的信息,建立输入和输出之间的非线性模型,通过优化模型对系统进行故障诊断。为了解决专家给定的初始BRB中参数不精确的问题,结合可以获得的伺服系统发生故障时的信息类型,基于数值观测值的优化学习模型对由专家给定的初始BRB系统中的参数进行训练,对数控铣床伺服系统中工作台的故障进行诊断。实验结果表明,利用该方法训练后的BRB系统能够准确反映系统的行为,可充分利用各种不确定信息,提高故障诊断精度。

数控机床用直线电机伺服试验平台开发及应用

在分析数控机床用直线电机驱动伺服系统动态特性的基础上,概括了直线伺服系统抑制外部扰动、提高稳态精度、提高动态响应速率以及增强鲁棒性的先进控制策略,研制了数控机床用直线电机驱动伺服系统综合试验平台及其调试软件,最后,指出了直线电机在使用过程中其他一些值得关注的技术问题。

考虑摩擦和间隙影响的机床进给伺服系统建模与分析

进给伺服系统的性能对数控机床的跟踪及定位精度、加工质量等有着重要的作用。摩擦和间隙的非线性会导致系统的爬行、振荡等不稳定行为。针对闭环控制的直联式进给伺服系统,建立了考虑摩擦和间隙的综合力学模型和数学模型。研究了低速进给条件下摩擦和间隙非线性对工作台输出的影响,得出了工作台产生爬行现象的几种可能条件,并给出消除进给系统爬行现象的几种常见措施。所得结论为进给伺服系统的优化设计和性能预测提供了理论支持。

数控机床的轮廓误差的控制

本文在分析两轴数控系统轮廓误差的基础上，提出了基于神经元的自适应交叉耦合控制器。仿真结果表明，本文提出的轮廓误差控制方法可以有效地提高数控系统的轮廓加工精度。

数控机床伺服系统的模糊自整定PID仿真研究

以数控机床进给伺服系统为研究对象,结合模糊控制和PID调节的各自优点,分析研究模糊PID控制器的实现方法。运用MATLAB建立应用模糊PID控制的伺服系统仿真模型,对模糊PID控制器的设计方法与应用效果进行了研究探讨。仿真实验结果表明模糊PID控制器能够很好的弥补常规PID控制整定不良、性能欠佳和适应性差的缺点,有效地减少了系统响应的超调,具有良好的动态特性。

模糊PID控制在伺服系统中的应用

针对高速数控机床的应用需求越来越多,以交流永磁同步直线电动机为驱动元件的高速伺服系统是最为有效的解决途径。以数控机床直线交流伺服系统为研究对象,首先进行了主回路及配电的设计,然后对其中主要部件进行选型。然后针对核心部件永磁同步直线电机建立电流、速度、位置三闭环的PID控制模型,应用PID优化理论及模糊自适应理论,对PID参数进行整定优化,并用MATLAB/SIMULINK进行动态仿真、计算,仿真结果表明采用上述方法提高了数控机床交流伺服系统设计整定的效率和精度、改善了系统动态响应性能。

数控伺服进给系统中摩擦补偿控制研究进展

首先分析在高精度数控机床工作台伺服进给系统中进行摩擦补偿控制的必要性,其次介绍摩擦力模型研究方面的现状,然后着重总结数控机床工作台进给伺服系统领域采用的各种摩擦补偿技术研究成果。最后,指出了该领域研究存在的问题,展望了该领域的发展方向。

并联机床伺服系统双自适应模糊滑模控制

以并联机床的单通道对称阀控非对称液压缸为研究对象,提出一种适合该系统的将模糊控制、滑模控制、自适应控制三者有机结合的双自适应模糊滑模控制算法。仿真结果表明,采用所提方法使系统的输出渐进一致地收敛于参考输入信号,解决了对称滑阀控非对称液压缸系统存在的动态性能不对称、系统精度低、稳定性差等问题,可有效快速跟踪变化信号,对有界的干扰和参数摄动具有不变性。与常规PID控制相比,双自适应模糊滑模控制更适合于高阶非线性、强干扰的复杂系统,将此法应用于并联机床的液压控制系统可提高机床控制精度,改善机床动态性能,稳态误差仅为常规PID控制的20%。

基于SIMULINK的伺服进给系统仿真模型与分析

为了方便和准确的研究影响数控机床伺服进给系统性能的各种因素以及设计更加优良性能的系统,在分析一般数控机床伺服进给系统基础之上,依据经典机械动力学原理,建立了一种伺服进给系统的仿真模型。利用Matlab/Simulink仿真工具对影响该系统的系统刚度、工作台质量以及间隙、摩擦力、切削力等因素进行了综合的动态仿真,得到了工作台输出速度和输出位移的响应曲线。结果表明,采用所建模型,可以快速有效的对系统进行动态模拟仿真,并且能够很直观的观察和对比仿真结果,得到的相应结论对以后伺服进给系统的优化提升和设计改造具有一定的实用价值和参考价值。

CNC机床伺服系统特性对轮廓误差的影响机理

位置闭环控制的CNC机床在进行连续切削时,零件的轮廓精度与伺服驱动系统的稳态、动态特性有关。介绍了位置增益、跟随误差、轮廓误差,建立了位置闭环控制系统传递函数、跟随误差与轮廓误差数学模型,研究了直线和圆弧轮廓跟随误差与轮廓误差的关系,分析了CNC机床伺服系统特性对零件轮廓误差的影响机理,为提高零件轮廓的加工精度提供理论基础。

基于RTCP功能的五轴数控机床动态误差溯源方法

RTCP(Rotation tool center point)功能作为目前高档数控机床必备的功能之一,可以大幅减小由于旋转轴运动带来的非线性误差,有效提高机床加工精度。根据刀具刀尖点相对于加工工件相对静止的特点,设定刀具刀尖点不动,规划了有利于研究机床伺服系统动态性能的RTCP轨迹,并进行伺服系统仿真研究,得到刀尖点误差轨迹与机床伺服系统动态性能影响因素的对应关系,并依据此对应关系提出动态误差溯源方法,为数控机床伺服系统参数调整提供理论支持。