Dynamics and Control of Grinding Machine with Micropositioning Workpiece Table

To improve the machining precision of a surface grinding machine, a micropositioning workpiece table with high performance was used as auxiliary infeed mechanism to implement nanometer level positioning and dynamic compensation. To better understand the characteristics of the grinding machine modulated with micropositioning workpiece table, the dynamic model of the grinding system was established with modal synthesis and Lagrange's equation methods. The grinding system was divided into five subsystems. For each subsystem, the generalized kinematic and potential energies were obtained. Accordingly the dynamic model of the grinding system was given in the modal domain. The waviness of the grinding process was achieved based on the wheel and workpiece vibration. A nonlinear proportional integral derivative (PID) controller with differential trackers was developed to realize dynamic control. The simulation results show that the machining accuracy of the workpiece can be effectively improved by utilizing the micropositioning workpiece table to implement dynamic compensation. An experimental test was carried out to verify the proposed method, and the waviness of the workpiece can be reduced from 0.46 μm to 0.10 μm.     

基于改进TDOA算法的设计与仿真

为减弱信号传播中非视距等因素的影响,提高定位精度,提出改进到达时间差(TDOA)算法,给出了算法实现方案的流程和仿真对比结果.该算法在TDOA算法的基础上,融入了速度和区域约束,以此判断目标是否超出移动距离阈值或者区域边界,对定位结果进行优化.建模后对TDOA算法、速度受限定位算法、区域受限算法和改进TDOA算法进行了...     

光固化成型中曝光时间对成型质量的影响

A novel stereolithgraphy system with conventional UV light as a light source uses the 2D worktable as moving components, whose characteristics determine the accuracy of the prototyping parts. Many factors including mass of the worktable, elasticity and damp coefficients, speed and acceleration affect the non-uniform exposure time of the resin, and eventually influence the cured line shape and the curing accuracy. A light shuttle is used to eliminate the cure errors, greatly improving accuracy of the parts.     

电液伺服土工离心机振动台数据采集系统开发

清华大学电液伺服控制土工离心机振动台系统最近研制成功,并已应用于土工结构物动力反应模型试验.该文首先简要介绍了振动台数据采集系统的性能要求和组成,然后详述了数据采集系统静动力性能测试的过程.测试结果表明,数据采集系统采样频率高、受电磁干扰小、在1 g和N g离心加速度条件下均能实时采集与传送数据,满足试验要求.     

Modelling and Simulation of System Dynamics of Hybrid-Driven Precision Press

Different from conventional mechanical systems with single degree of freedom (DOF),the main idea of the system of hybrid-driven precision press is to combine the motion of a constant speed motor with a servomotor via a two-DOF mechanism to provide flexible output. In order to make the feasibility clear, this paper studies theoretically the dynamic characteristics of this hybriddriven mechanical system. Firstly,the dynamics model of the whole electromechanical system is set up by combining dynamic equations of DC motors with those of two-DOF nine-bar mechanism deduced by the Lagrange‘s formula. Secondly through the numerical solution with the fourth Runge-Kutta, computer simulation about the dynamics is done, which shows that the designed and optimized hybrid-driven precision press is feasible in theory. These provide theoretical basis for later experimental research.     

力矩控制模式在高速钻铣床控制中的应用

高速定位系统中,电机工作在力矩控制模式下不但克服了位置模式下的低响应特性,又克服了速度模式下调试PID参数耗时长,难以获得最佳效果的不足,通过引入和实施改进的PID和加速度前馈等高级控制算法,能给控制系统带来更好的高速、高精度响应特性。     

数控机床伺服系统性能分析

数控机床是一种高科技的机电一体化设备,能实现机械加工的高速度、高精度和高度自动化,在现代企业生产中占有非常重要的地位。而伺服系统的静态、动态性能直接关系数控机床的定位速度、定位精度和加工精度。     

Adaptive Controller for Vehicle Active Suspension Generated Through LMS Filter Algorithms

The least means squares (LMS) adaptive filter algorithm was used in active suspension system. By adjusting the weight of adaptive filter, the minimum quadratic performance index was obtained. For two-degree-of-freedom vehicle suspension model, LMS adaptive controller was designed. The acceleration of the sprung mass,the dynamic tyre load between wheels and road,and the dynamic deflection between sprung mass and unsprung mass were determined as the evaluation targets of suspension performance. For LMS adaptive control suspension, compared with passive suspension, acceleration power spectral density of sprung mass acceleration under the road input model decreased 8-10 times in high frequency resonance band or low frequency resonance band. The simulation results show that LMS adaptive control is simple and remarkably effective. It further proves that the active control suspension system can improve both the riding comfort and handling safety in various operation conditions, and the method is fit for the active control of the suspension system.     

基于直流减速电机的内镜缝合器电控系统研制

旨在设计以直流减速电机为动力元件,利用编码器精准控制的闭环控制系统。研究霍尔编码器控制原理,利用霍尔编码器实现电机转动圈数控制、调速以及定位功能|研制内镜缝合器电动控制系统,阐述系统驱动机构组成部分,以及器械运动控制算法,利用参数调节合适的PWM波占空比,以实现对器械运动的精准控制,并通过外部传感器进行验证。结果表明,当PWM波占空比在80%～100%之间时,运动速度合理,电机测试精度变化范围大致为-0.007%～0.567%,精度较高。该研究为内窥镜器械的电动控制系统开发提供了理论基础,且具有良好的应用前景。     

基于改进PID算法的运动控制器的设计

构建了以DSP为基础的运动控制器系统平台。该平台集成度高、稳定性强,能实现生产过程的高速度、高精度要求,实现了基于CPLD的可重构设计,提高了系统的柔性。在控制算法上,采用单神经元PID及cMAc相结合的伺服运动控制算法,仿真及实验结果显示较常规PID控制有更好的动态特性、控制精度、抗干扰能力。     

基于微分几何理论的感应电机输入输出解耦控制

感应电动机是一个多变量、强耦合、非线性的控制对象。微分几何理论是目前分析非线性系统的一种很有效的数学工具。文章介绍了应用微分几何理论对感应电机转速和磁链进行解耦控制的方法,并对解耦控制系统进行了仿真,仿真结果验证了理论分析的正确性。     

基于双目机器视觉的高速高精度自动贴屏机设计

针对目前智能手机人工贴屏精度差、效率低、成本高的现状,文章提出了一种基于双目机器视觉的高速高精度自动贴屏解决方案。该方案采用两个CCD相机分别采集手机机身和手机屏幕图像,经图像采集、图像预处理后,快速提取图像边缘信息,准确快速计算XY轴向偏差和R向角度偏差,并由XYR对位平台快速完成对位调整。经测试,该设备定位精度≤±0.005mm,重复定位精度≤±0.005mm,贴屏速度≥300片/小时,屏幕贴合平整度≤±0.005mm,能大幅提升贴屏精度和效率,具备一定的应用和推广价值。     

Automatic target tracking on multi-resolution terrain

INTRODUCTION In this paper, we propose an automatic target tracking method in our real-time simulation and animation system of large-scale terrain field. Our system supplies autonomous guidance, navigation and control of moving objects, in order to efficiently perform related challenging missions in manufacture, entertainment, and other real-world applications. Our goal is to deploy a large number of moving vehicles upon a large-scale virtual terrain (essentially a 2D curved terrain surfa…     

基于有限元分析的纳米级微进给平台设计

设计了一种利用弹性铰链作为预紧机构、高精度滚动导轨作为导向机构的单PZT驱动的微进给平台。利用有限元方法对微进给平台的结构和静、动态特性进行了研究。在静态特性中着重分析了微进给平台的静态刚度,得出整个动平台的工作平面上的刚度分布图。在动态特性分析中着重研究了微进给平台的模态振型、固有频率和谐波激励响应,得出了激进给平台在动态激振力作用下的特性。最后分析了微进给平台工作平面上静态刚度和动态刚度变化很大的原因,并提出一些改进的措施。     

基于声发射及时延估计的风源系统泄漏定位

动车风源系统专门用于为动车整车制动系统供风,而漏风问题会影响供风效率乃至整个制动系统。旨在利用声发射传感器技术,针对风源系统中最常见的漏风问题进行检测,并利用时延估计技术进行泄漏点定位,从而及时发现泄漏点并采取措施解决问题,以降低风源系统发生故障的风险,减少故障带来的损失。采用小波包分析对传感器采集的数据进行分解重构,以减小外界环境噪音对结果的干扰,最后利用互相关分析及定位公式对漏风点进行定位。仿真实验结果表明,该方法具有较强的抗干扰能力与较高的精度,精度可达到95%左右,因此能较好地解决风源系统漏风定位问题。     

一种失真或旋转QR码的定位算法

为了解决传统算法QR码定位中出现QR码失真,或旋转时出现较弱鲁棒性的现象,提出一种新型QR码自适应定位算法。在算法研究过程中,首先使用自适应阈值算法解决不均匀照明的影响,在此基础上提出一种基于轮廓跟踪与轮廓筛选的定位方法。实验结果表明,与传统QR码定位算法相比,该算法定位准确率提高了30%,且定位速度提升了17%,可见该定位算法能够很好地应用于QR码定位。     

基于Pro/E的曲柄摇杆机构运动仿真

利用Pro/E建立了曲柄摇杆机构的3D模型,并对该模型进行了动态仿真,仿真结果实现了对机构运动的可视化研究。最后得出了分析点的速度、加速度、角位移等随时间变化的曲线。仿真结果表明:在不同的速度模式下,分析点的速度、加速度、角位移随时间而变化,运动过程中分析点存在着抖动现象。仿真结果实现了对机构的全面可靠的动态分析,大大提高了机构的分析效率,对于优化机构设计有重要的指导意义。     

考虑电磁力作用下磁浮三跨刚构桥振动分析

研究了磁浮车辆与三跨刚构桥之间的耦合振动.考虑主动控制电磁悬浮力的作用,建立了磁浮车辆-桥梁耦合振动分析模型.使用数值方法对车辆通过时桥梁的动力反应进行了分析.结果表明桥梁的梁墩线刚度比宜在2.0到3.0之间.桥梁的动力反应随着桥梁刚度的降低、车速和跨度比的增加而加剧.建议桥梁动力设计中以控制桥梁的冲击系数和振动加速度为主.移动荷载模型和移动质量模型在磁浮桥梁动力设计中均不适用.所得结论可为高速磁浮三跨刚构桥设计提供理论依据.     

激光多普勒定位X-Y工作台单向运动系统精度分析

本文首先介绍了所研究的激光多普勒定位X-Y工作台单向运动系统的组成,同时简单介绍了达到目前的精度所采取的前馈螺距误差补偿措施等办法,然后详细分析了采取补偿措施后激光多普勒定位X-Y工作台单向运动系统的各个误差组成,特别指出了由摩擦力引起的误差的影响,最后分析计算了目前系统的综合定位精度,指出了下一步通过摩擦力的补偿控制来减少滚珠丝杠重复定位误差和滚珠丝杠螺距误差,提高系统的定位精度.     

一种无耦合微步进机构的误差分析

提出一种新型二维解耦的微步进定位机构,并对该机构的解耦性进行了证明,针对该机构制造过程中存在的误差分配问题,分析了该机构杆件的制造误差对机构输出的影响,结果证明杆长L1制造误差对输出角的影响大于L5制造误差的影响。