并联机床结构静刚度的有限元分析

通过对并联机床结构设计,利用ANSYS软件对其几种不同结构形式进行了单支路和机床整体静刚度有限元分析,优化出比较理想的结构,并对并联机床在结构设计中出现的问题提出改进意见,从而为进一步改进并联机床的结构设计与受力情况提供可靠的理论依据     

具有内力的3PRS/UPS冗余并联机床刚度分析

冗余结构可以提高并联机床的刚度,冗余机构在运动中由于各支链的误差使得机构会产生干涉内力,旨在研究内力对冗余并联机床刚度的改善作用,为靠内力提高并联机床性能提供理论基础.首先采用能量法推导了3PRS/UPS冗余并联机床的刚度模型,然后对具有内力的3PRS/UPS冗余并联机床刚度进行了分析.最后给出了特定位姿下的两种形式的刚度计算实例.结果表明内力对机床刚度的影响很小.     

并联机床静刚度研究

常见的并联机床静刚度分析理论发展尚未完善。本文在研究并联机床静力学的基础上,使用能量法分析在外载荷作用下的并联机床变形量,从而获得在不同位姿下并联机床的静刚度。利用上述方法,针对一台五自由度的并联机床进行了分析,获得了其静刚度。为并联机床静刚度研究及其设计提供了理论依据和方法支持。     

基于Stewart平台的并联机床刚度分析

刚度在机床设计中至关重要。讨论BKX-I型并联机床的刚度问题,通过采用结构矩阵分析方法和有限元分析方法,分别建立BKX-I型并联机床的刚度模型,并进行分析和比较。在此基础上,分析BKX-I型并联机床的刚度在工作空间中的分布规律。     

6-UPS并联机床静刚度的有限元分析和实验研究

用有限元方法分析一种6-UPS并联机床的静刚度，基于AN—SYS建立该机床的有限元模型，考虑了并联机床的支链和机架的变形，并利用Matrix27单元来模拟铰链；通过APDL语言实现有限元模型的参数化设计，计算出并联机床在工作空间内的刚度分布。静刚度实验表明了该模型的有效性。通过该有限元模型还可以对并联机床的动态性能做进一步分析。     

一种新型并联机床的刚度和固有特性的有限元分析

建立了一种新型并联机床刚度分析和弹性动力学分析的有限元模型，研究了参数变化对主进给机构刚度和固有频率的影响，计算结果表明：该新型并联机床与基于Stewart平台的并联机床相比，Z方向刚度与相当而X、Y方向的刚度优于后者；加大中间腿的截面积可以大大提高并联机床的刚度，研究结果为优化并联机床的结构参数，提高其结构搞震性和切削稳定性奠定了基础。     

6-PUS并联机床的动态特性分析

叙述了模态分析的基础理论,利用有限元分析软件ANSYS/Workbench对处在初始位姿下的6-PUS并联机床进行模态分析,根据得到的并联机床的六个主自由度对应的共振频率和振型,总结了该机床的振动特性和刚度分布特点。并在模态分析的基础上对其进行谐响应分析,得到了机床动平台沿X、Y、Z三个主运动方向的位移谐响应曲线,探讨了机床的谐响应特性,进一步验证并联机床在外力作用下的抗振性能,为对并联运动机床结构的动态设计和优化设计提供了一定的参考。     

3-(2SPS)并联机床设计及刚度分析

以3-(2SPS)型并联机床为主要研究对象,利用SolidWorks软件建立其三维实体模型,在此基础上首先建立机床坐标系,求得力雅可比矩阵和并联机床刚度矩阵,利用MATLAB编程,得到3种工况下并联机床的仿真刚度随动平台位置的分布规律,再利用ANSYS Workbench软件对机床进行有限元分析,在同样工况下得到机床的整体位移云图及有限元仿真刚度,结合两种分析结果,证明了仿真结果的有效性,为机床后续的优化以及良好的动态性能奠定了基础。     

基于Raleigh-Ritz的五自由度并联机床刚度分析及仿真

针对软件模拟方法适合某一固定位置的刚度分析,不适合对并联机构的工作空间刚度分析的问题,提出了一种基于raleigh-ritz的五自由度并联机床刚度分析方法。首先利用有限元基本原理对并联机床的机构分析离散出基本单元,然后利用raleigh-ritz方法计算出基本单元的刚度矩阵,装配后得到系统刚度矩阵,最后通过系统刚度矩阵对并联机床的刚度进行了分析,得到了并联机床工作空间内的刚度分布,并利用刚度分析软件进行了仿真实验,对分析结果进行了对比分析,为并联机床的优化设计提供了理论依据。     

VMC-1000主轴箱模态分析及改进设计

机床主轴箱的固有动态特性直接影响到机床的加工精度,以VMC-1000立式加工中心主轴箱为研究对象,应用有限元软件对其进行模态分析,提出了该主轴箱的薄弱环节。针对薄弱环节对箱体进行改进设计,通过比较分析,验证了改进的有效性。同时对两种结构刚度分析,得出主轴箱的最大变形量和最大应力,证实了改进的箱体结构具有较高的刚度。     

A Machine Tool with Parallel Two-Level Kinematics

A triaxial machine tool with parallel kinematic structure is described. Equations for solving inverse and direct kinematics problems in terms of the position are presented. The influence of the drives’ positioning errors on the maximum tool deviation from the intended position at characteristic points of the working space is analyzed.     

Process parameter definition with respect to the behaviour of complex kinematic machine tools

The definition of machining processes with respect to complex kinematic machine tool behaviour involves the control of machine accuracy and kinematic performances. The aim is to propose process settings and tool paths which guarantee the required machining quality while maximizing productivity. This article presents an experimental protocol which enables the determination of machine tool structure behaviours which have an influence on machining quality. In parallel, an experimental analysis of the different kinds of settings which can improve machining quality is carried out. Two kinds of settings appear: the first class of settings improves machining quality or machining time, and the second class has an antagonistic influence on machining quality and machining time. Thus, the definition of the second class of settings arises from an optimisation between first-order defects, second-order defects and machining time. The developed method is illustrated on a parallel kinematic machine tool, the Tripteor X7. Note that this study is a first step towards controlling machine tool behaviour during machining.     

Process definition of preformed part machining for taking benefit of parallel kinematic machine tool kinematic performances

In the automotive or aeronautical industries, few parallel kinematic machine tools (PKM) are used in high-speed machining (HSM). However, the dynamics of these machine tool structures could be relevant for HSM since their acceleration potential is much higher than serial kinematic machine tools. However, a particularity of PKM is to have kinematic performances depending on the tool pose in the machine workspace. Thus, this paper proposes a method to increase the productivity of performed part machining with PKM by taking advantage of their kinematic performances, with the aim of decreasing the time of the non-cutting tool movements. Process parameters defined by this method are the machined part setup, the planning of the machining operations, the control of potential redundant axis and the definition of the tool paths between cutting operations. The developed method is achieved in four successive steps based on a modelling of the kinematic behaviour of a given PKM. Each step leads to define one of the process parameters with regard to the decrease of non-cutting time. Thus, this method only requires common optimization algorithms that increase it robustness and its adaptability to different structures of PKM. It is illustrated with drilling operations on preformed parts with the Tripteor X7 machine tool developed by the PCI-SCEMM Company.     

Kinematic calibration of gantry hybrid machine tool based on estimation error and local measurement information

This paper presents the kinematic calibration of a four degrees-of-freedom (DOF) hybrid machine tool based on a novel planar 3-DOFs parallel mechanism and a long movement of the worktable. Closed-form solutions are developed for both the inverse and direct kinematics about the parallel mechanism. The error model is built and the mechanism accuracy is investigated. Two types of kinematic calibration method are proposed by a simple measurement device. The first type of calibration method is based on estimation error, and can easy improve the machine tool accuracy quickly by estimating the error trends. The second type of kinematic calibration method is based on local measurement information, which includes the position errors and does not include the pose errors of the machine tool. The calibration tests showed the effectiveness of the calibration methods, which can be useful for the similar types of parallel machine tool.     

Applications of equivalent components concept on the singularity analysis of TRR–XY hybrid parallel kinematic machine tools

The design of using a parallel kinematic mechanism as a structure of machine tools has several good points compared with the traditional machine tools. However, the problem of singularity is usually encountered during real applications. Therefore, singularity analysis is very essential for using a parallel kinematic mechanism in real machining applications. Screw theory based on the Plücker coordinate system is one of the effective methods for analyzing the singularity of a parallel kinematic mechanism. A TRR–XY five DOF parallel kinematic machine tool that was developed in this research is adopted as an example for investigating the feasibility of this method. A 6×6 matrix calculation is usually required in screw theory for analyzing a six DOF mechanism. For a three DOF mechanism, the analysis using the screw theory becomes more complicated. An equivalent component method is addressed in this research to simplify the singularity analysis for a three DOF mechanism. The effects of differently designed dimensions of machine tools on the singularity are also investigated in this research.     

并联机床不同位形下的运动精度评价指标

以6自由度6TPS型并联机床为模型,推导出机构输入和输出的误差传递方程,分析了单个支链和整个系统的误差传递情况。利用雅可比矩阵的奇异值分解,得到影响位形精度的三个误差敏感性指标,即误差综合敏感度、误差绝对敏感度和误差方向敏感度。定义了综合误差系数和综合误差度,并以此作为评价不同位形运动精度的指标。最后,利用一台实际的并联机床,对不同加工轨迹的运动精度进行了评价,确定最优的加工轨迹。     

面向新型并联机床的NURBS曲面直接插补算法研究

提出了以四自由度空间并联机构作为主进给机构 ,辅以双向移动工作台实现多坐标数控加工的一种新型并联机床的配置方案。推导了并联机床位置、速度逆解模型 ,设计了面向该并联机床的CNC系统方案。构造了由刀具轨迹计算、位置与速度逆解模型和PVT细插补模式相结合的NURBS曲面直接插补算法 ,并讨论了CNC系统方案实施中的关键技术     

A new machine tool with parallel kinematic structure

A new machine tool with parallel kinematic structure and a special Hooke’s joint of increased rigidity is described. The static rigidity of the machine tool is simulated. Nonuniformity of the rigidity distribution at characteristic points of the working space is analyzed with different directions of the cutting force.     

虚拟轴机床作业空间快速检验算法的研究

根据虚拟轴机床的结构和运动特点,提出在机床的运动学分析中运用单开链方法,只进行一次运动学逆解计算就可求出全部运动变量的值,包括从动铰的运动坐标,因此适合于作业空间的快速经验。基于一台实际的虚拟轴机床－－VAMT1Y,对该算法进行了应用和验证。     

并联机床快速干涉检验算法的研究

摘　要:为了解决并联机床的干涉检验问题,克服传统方法实时性不好的缺点,本文提出了利用单开链分析方法推导并联机床运动学方程的方法。这种方法在一次运动求解中就可以求出杆件的长度和各虎克铰、球铰的转角,适合于并联机床的快速干涉检验。给出了该方法的算法流程,对具体算法进行了实现和验证。实践表明,该算法能够完全满足数控系统实时性的要求。