一种并联机床的位置、速度和加速度逆解

本文针对一种混合结构的并联机器人机床,采用串并联运动学等效的方法,进行了运动学研究,推导了系统的位移、速度和加速度逆解的表达式,这可用于机床在加工时的运动规划及插补算法的实现。本文还进行了运动学仿真研究,机床的实际加工操作应用的结果表明,推导的运动学算法的正确性。

串并联数控机床的作业空间分析

鉴于并联机床普遍存在有效作业空间小、运动控制复杂和实用刚度还不理想等不足．采用了串并联混合式机床运动结构．针对所研究的4—4构型串并联机床,分析了影响作业性能的几何约束条件,采用基于位置逆解模型的极限边界数值搜索法,确定了机床作业空间,并通过数值仿真研究获得了机床运动参数和结构参数对作业空间的影响规律，为优化机床结构尺寸以获得尽可能大的有效作业空间奠定了基础。

一种新型四自由度并联机器人

提出一种用铅垂导轨上 4个滑块作为原动件的新型四自由度并联机器人 .该并联机器人的动平台能够实现两个方向的移动以及绕两个方向轴线的转动 .研究了该并联机器人的运动学建模方法 ,给出了运动学正、逆解 ,用 Grassmann几何法分析了该并联机器人在其工作空间内不会出现奇异形位 .基于该四自由度并联机器人可以非常方便地开发具有大工作空间的五轴联动数控机床

五轴并联铣床特征参数误差灵敏度分析

将并联机构等效为由串联机构构成的空间闭环机构，运用 D－ H方法系统研究了五轴并联铣床的特征参数误差对运动平台位姿误差的影响，揭示出特征参数沿机床各位姿方向误差灵敏度变化规律。仿真结果不仅证实了现有机床机构设计合理，而且为今后并联机床进一步精度设计提供了可靠依据。

并联机床平面约束机构误差分析与建模

针对五轴数控机床平面约束机构进行了误差分析 ,指出了并联机床平面约束机构误差主要影响因素为机构的制造误差和安装误差·前者与由其引起的约束机构顶边中点沿x方向的位移成非线性关系 ,而后者则成线性关系·提出了一种依据测量数据反演非线性误差模型的建模方法 ,给出了五轴并联机床约束机构实测信息与模型输出间的多项式误差模型·比较仿真结果与测量结果可知 ,基于上述方法建立的误差模型精确 ,进而利用该模型对机床进行实时精度补偿 ,可使机床x方向定位精度大为提高

并联机床的发展现状与展望

论述并联机床的发展现状及与传统机床的区别。在对国内外典型并联机床样机的工作原理分析的基础上，指出目前并联机床研究中所面临的主要问题，并对并联机床的研究发展方向进行了展望。

基于测量数据反演并联机床非线性位姿误差模型

利用最小二乘技术识别模型参数 ,将非线性问题作线性化处理 ,提出了一种基于测量数据反演非线性误差模型的建模方法。结合算例 ,指出了此类模型设计应注意的问题。五轴并联机床约束机构误差模型仿真结果表明 ,由此得到的误差模型精度高。利用所得模型对机床位姿进行补偿 ,即可提高机床沿该位姿方向的定位精度

基于四自由度并联机构的数控机床研究

介绍一种基于混合型四自由度并联平台机构开发的五坐标并联机床 .由于其独特的机构设计 ,与基于 Stewart平台的并联机床相比 ,X方向的进给运动与运动平台分离 ,改由工作台单独进给 ,因而其工作空间成倍增大 .采用龙门框架结构和滚珠丝杠支承方案使机床获得更高的刚度 .给出了该机床运动学逆解 ,控制系统采用基于 PC的数控系统进行五轴联动控制

一种并联机床运动平台位姿测量方法

提出一种采用附加测量机构直接测量并联机床运动平台位姿精度的方法。其基本思想是根据运动平台的运动特性在固定平台和运动平台之间增设附加测量机构，当运动平台运动时带动测量机构运动，通过安装在测量机构上的传感器测得广义坐标参量， 经运动学建模即可得到运动平台的位姿。当测量机构位姿正解求解速度满足实时控制要求时，利用该反馈信息对机床进行实时精度补偿和控制。基于上述思想建立的并联机床位姿测量系统可部分排除机床切削力变形和运动副间隙等误差， 从而提高机床的位姿测量精度。以一种五坐标并联机床为例，介绍采用附加测量机构直接测量运动平台位姿精度的建模方法。其中， 测量机构的综合十分重要。测量机构的组成决定了运动学模型的复杂程度， 即决定了运动学模型的计算效率。

并联机器人机床运动学正、逆解

基于一般ＳＴＥＷＡＲＴ机构研制的并联机器人机床是新一代智能化金属切削加工机床．然而，机床的运动学位置正、逆解呈强非线性，求解困难．出于机床精度的需要，本研究的模型样机在结构上采用了滚珠丝杠传动，因此又带来了关节运动耦合，导致机床运动学位置正、逆解求解更加复杂．利用运动学等效的原则，引入整机等效串联机构及分支等效串联机构，以等效广义坐标为中间变量建立机床运动学正、逆解求解迭代算法．仿真与控制实验表明，该算法具有收索速度快便于实际应用等特点。

可重构车间管理系统的关键设计技术研究

介绍了一个基于组件的可重构车间管理系统,分别从建模方法、体系结构和组件设计等角度描述了系统的设计思想,并阐述了系统涉及的组件分类、组件粒度划分及XML的应用等关键设计技术。开发的可重构车间管理系统已经用于沈阳第一机床厂两个不同类型生产车间的管理,应用效果良好。

成批生产计划调度的集成建模与优化

针对多品种批量生产类型,建立了调度约束的生产计划与调度集成优化模型。模型的目标函数是使总调整费用、库存费用及生产费用之和最小,约束函数包括库存平衡约束和生产能力约束,同时考虑了调度约束,即工序顺序约束和工件在单机上的加工能力约束,保证了计划可行性。该模型为两层混合整数规划模型,对其求解综合运用了遗传算法和启发式规则,提出了混合启发式求解算法。最后,针对某机床厂多品种批量生产类型车间进行了实例应用,对车间零件月份作业计划进行分解,得到各工段单元零件周作业计划,确定了零件各周生产批量与投产顺序。

Enabling ultra high precision on hard steels using surface defect machining

This paper is an extension to an idea coined during the 13th EUSPEN Conference (P6.23) named "surface defect machining" (SDM). The objective of this work was to demonstrate how a conventional CNC turret lathe can be used to obtain ultra high precision machined surface finish on hard steels without recourse to a sophisticated ultra precision machine tool. An AISI 4340 hard steel (69 HRC) workpiece was machined using a CBN cutting tool with and without SDM. Post-machining measurements by a Form Talysurf and a Scanning Electron Microscope (FEI Quanta 3D) revealed that SDM culminates to several key advantages (i) provides better quality of the machined surface integrity and offers (ii) lowering feed rate to 5μm/rev to obtain a machined surface roughness of 30 nm (optical quality).

Molecular dynamics simulation (MDS) to study nanoscale machining processes

Molecular Dynamics Simulations (MDS) are constantly being used to make important contributions to our fundamental understanding of material behaviour, at the atomic scale, for a variety of thermodynamic processes. This chapter shows that molecular dynamics simulation is a robust numerical analysis tool in addressing a range of complex nanofinishing (machining) problems that are otherwise difficult or impossible to understand using other methods. For example the mechanism of nanometric cutting of silicon carbide is influenced by a number of variables such as machine tool performance, machining conditions, material properties, and cutting tool performance (material microstructure and physical geometry of the contact) and all these variables cannot be monitored online through experimental examination. However, these could suitably be studied using an advanced simulation based approach such as MDS. This chapter details how MD simulation can be used as a research and commercial tool to understand key issues of ultra precision manufacturing research problems and a specific case was addressed by studying diamond machining of silicon carbide. While this is appreciable, there are a lot of challenges and opportunities in this fertile area. For example, the world of MD simulations is dependent on present day computers and the accuracy and reliability of potential energy functions [109]. This presents a limitation: Real-world scale simulation models are yet to be developed. The simulated length and timescales are far shorter than the experimental ones which couples further with the fact that contact loading simulations are typically done in the speed range of a few hundreds of m/sec against the experimental speed of typically about 1 m/sec [17]. Consequently, MD simulations suffer from the spurious effects of high cutting speeds and the accuracy of the simulation results has yet to be fully explored. The development of user-friendly software could help facilitate molecular dynamics as an integral part of computer-aided design and manufacturing to tackle a range of machining problems from all perspectives, including materials science (phase of the material formed due to the sub-surface deformation layer), electronics and optics (properties of the finished machined surface due to the metallurgical transformation in comparison to the bulk material), and mechanical engineering (extent of residual stresses in the machined component) [110]. Overall, this chapter provided key information concerning diamond machining of SiC which is classed as hard, brittle material. From the analysis presented in the earlier sections, MD simulation has helped in understanding the effects of crystal anisotropy in nanometric cutting of 3C-SiC by revealing the atomic-level deformation mechanisms for different crystal orientations and cutting directions. In addition to this, the MD simulation revealed that the material removal mechanism on the (111) surface of 3C-SiC (akin to diamond) is dominated by cleavage. These understandings led to the development of a new approach named the “surface defect machining” method which has the potential to be more effective to implement than ductile mode micro laser assisted machining or conventional nanometric cutting.

Permutation entropy based real-time chatter detection using audio signal in turning process

Machine tool chatter is an unfavorable phenomenon during metal cutting, which results in heavy vibration of cutting tool. With increase in depth of cut, the cutting regime changes from chatter-free cutting to one with chatter. In this paper, we propose the use of permutation entropy (PE), a conceptually simple and computationally fast measurement to detect the onset of chatter from the time series using sound signal recorded with a unidirectional microphone. PE can efficiently distinguish the regular and complex nature of any signal and extract information about the dynamics of the process by indicating sudden change in its value. Under situations where the data sets are huge and there is no time for preprocessing and fine-tuning, PE can effectively detect dynamical changes of the system. This makes PE an ideal choice for online detection of chatter, which is not possible with other conventional nonlinear methods. In the present study, the variation of PE under two cutting conditions is analyzed. Abrupt variation in the value of PE with increase in depth of cut indicates the onset of chatter vibrations. The results are verified using frequency spectra of the signals and the nonlinear measure, normalized coarse-grained information rate (NCIR).