混联机床的静刚度实验测量

机床的静刚度是保证其工作性能的重要指标,用理论模型对机床静刚度进行研究难免产生偏差,因此有必要对其进行实验研究.文中针对一台近期研发成功的混联机床,利用力传感器和千分表对其进行静刚度的实验研究.对实验数据进行最小二乘直线拟合,得到该机床在工作空间内9个位姿的各方向静刚度.为了研究该机床静刚度的变化情况,计算同一水平面或竖直面内的静刚度变化率.文中方法和结论为该类型机床的静刚度理论研究和仿真提供实验依据.     

基于RGRR-Ⅰ并联双自由度转动机构的混联五轴机床研究

传统的串联式数控机床存在刚度低的缺点.并联双自由度转动机构RGRR-Ⅰ刚度高,且有着工作空间/机构尺寸比大、耦合为零、制造容易等一系列的优点.运用RGRR-Ⅰ构造的并联双自由度转动刀头摆动精度高、工作空间大.基于混联五轴联动车床的工作要求,研究能实现绕xyz三个直线运动坐标移动,两个运动轴坐标回转的混联五轴联动机床,分析其工作机理,建立有关模型.该研究也可为其他混联机床的设计与制造提供借鉴.     

混联机床并联机构的逆动力学分析

采用Lagrange方法建立了VC80混联机床两自由度并联机构封闭形式的逆动力学模型,并用ADAMS建立的虚拟样机验证了该模型的正确性。对给定的加工轨迹下并联机构所需的驱动力进行了计算和分析,结果表明,该混联机床并联机构的动平台和连杆重力需要的驱动力分量最大,其次是切削力和惯性力,而动平台速度的不同对驱动力的影响较小。
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一种新型混联机床的机构设计与运动学分析

提出了以四自由度1PS+4TPS型混联机构为主进给机构,辅以双向移动工作台实现多坐标数控加工的一种新型混联机床的布局设计方案。该混联机床方案中定平台通过4个结构完全相同的TPS驱动分支以及一个PS约束分支与动平台相联,动平台可以实现一维平动和三维转动,该方案具有可实现姿态角大、工作空间大等优点。对主进给机构进行了机构设计,推导出了主进给机构一、二阶运动影响系数矩阵,建立了主进给机构封闭形式的运动学方程。文中给出了运动学分析的数值实例。     

新型并联机床的刚度计算模型

本文建立了并联机床的有限元刚度模型,通过实例计算得出机床的动平台中心距定台中心Ｚ坐标较小及动平台姿态角较小时可获得高刚度;根据实例计算结果和机床倒锥状的结构特点,提出了并联机床主刚度的概念,建立了主刚度简化模型,并以此作为衡量机床刚度的准则。     

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。     

2RPU/UPR+RP五自由度混联机器人静刚度分析

为快速建立基于三自由度并联机构2RPU/UPR构造出的五自由度混联机器人的解析刚度模型,首先对混联机器人的结构进行了描述;然后基于串联和并联结构独立求解思想,建立了混联机器人的位置反解模型;再对混联机器人的结构进行简化处理,分别求解并联部分与串联部分两子系统的静刚度模型,从构造系统的力旋量系和弹性变形协调条件入手,简单且快速地建立了混联机器人的整体刚度模型;最后构造混联机器人的等效三维模型,运用有限元和MATLAB软件,对典型位姿下混联机器人受外力/力矩产生的微位移进行仿真验证,并给出了整机静刚度在任务空间中随位形变化分布图。通过仿真与理论计算的对比分析,验证了该混联机器人理论刚度模型的正确性。     

一种3自由度并联机床的性能分析

混联机床同时兼顾了串、并联机构的优点,已越来越多的应用于复杂零部件的生产加工;提出一种3-RPS构型的三自由度并联机床,基于杆长条件建立了该机床位置反解方程,利用运动副速度投影求解了驱动杆速度输入变化规律,并推导了系统的雅克比矩阵;利用拉格朗日方程,求解了机床动力学模型;为后续对机床的运动学和动力学性能研究奠定了基础。最后结合原型机模型和Matlab对推导结果进行仿真,绘制了运动学和动力学曲线,总结出该机床运动学、动力学性能,结果表明该机床完全满足混联机床中并联模块的性能要求,并能满足航空、航天等复杂零部件和异形曲面的加工需求。     

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。     

并联机床研究

并联机床是基于并联机构的新型机床，介绍了并联机构和并联机床的特点和国内外取得的一些研究成果，最后介绍了课题组在三杆并联机构方面的研究成果。     

新型串并联结构数控机床

介绍了一种新型串并联结构数控机床,对其机械结构、数控系统、虚实轴转换作了论述.该串并联结构数控机床采用了先进的虚拟样机在线仿真数控加工软件ILP技术,具有更大的工作空间,更好的刚度性能.并对串并联结构数控机床的发展趋势进行了展望.     

立卧转换式混联机床及其平行机构的运动学分析

开发出一种能够实现立卧转换的3-TPS（RRR）型混联机床新构型。该机床在动平台与基座之间附加一个平行约束机构,可以限制平台的部分自由度,使动平台只能作三个方向的平移和一个派生的转动。着重对该机订泊平行约束机构进行运动学分析,得出了它的位置,速度,加速度以及雅可比矩阵的计算公式,并进行了仿真计算,为机床的结构设计和动力学计算奠定了基础。     

PRS-XY型混联数控机床误差建模及敏感度分析

以PRS-XY型混联数控机床为对象,以加工、装配精度为依据,建立该机床完整的误差模型.设计能反映机床运动精度的典型轨迹,利用该轨迹,通过对该模型的求解和分析,得出主要误差源对机床运动精度的影响.为指导该混联机床的精度设计和误差补偿提供了数据.     

基于有限元的并联机床整机静力特性分析

分析了并联机床承受静力时的受力特点.通过应用ANSYS有限元软件对并联机床整机进行了静力分析,研究机床在特定位姿时不同受力情况下的应力应变及其分布特性,得出了机床机架和整机在不同位姿时的应力应变图,分析了机床应力分布规律.并确定了机床的薄弱部位,为结构优化提供理论依据.     

并联机床主运动机构工作空间分析

针对一种新型模块化并联机床结构模型，给出了机床主运动模块平面二自由度机构的运动特性，分析研究了工作空间，机构的工作空间与机构滑鞍的行程以及机构的尺寸有关，分别给出了各种情况的工作空间几何形状，并以实例给出了工作空间的几何特性，为该并联机构的设计提供了有参考价值的方法和资料。     

Dynamic analysis of the 2-DOF planar parallel manipulator of a heavy duty hybrid machine tool

This paper focuses on the dynamic characteristics of the two degree-of-freedom (DOF) planar parallel manipulator of a heavy duty hybrid machine tool. The Newton-Euler approach is employed to derive the inverse dynamic equation of the parallel manipulator. According to the motion planning of the cutting tool, dynamic simulation without cutting force is performed, and the ratio of the masses of counterweights to that of moving parts (not including the counterweight) is optimized. It demonstrates that the manipulator which is designed with over constraint can improve the dynamic behaviour. Furthermore, the cutting force model for face milling is introduced and the dynamic simulation with the dynamic cutting force is carried out. Simulation shows that the oscillation of cutting force is one cause of the vibration of the machine tool in the milling process. In the detailed design, some modification in the structure of the machine tool is made to suppress the vibration.     

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.     

BKX-Ⅰ型并联机床的谐响应分析

应用有限元分析软件(ANSYS),对BKXⅠ型并联机床进行谐响应分析,分别得到了机床各节点沿机床的虚拟轴X、Y和Z向的位移谐响应曲线。在此基础上,还分析了该机床的谐响应规律,并明确了谐响应的特点,为改善此类机床的动态特性提供了一定的参考依据。     

Simultaneous tool posture and polishing force control of unknown curved surface using serial-parallel mechanism polishing machine

In automotive manufacturing, the repair polishing process of an automotive body is still manually performed by skilled polishing workers. This is because skilled workers can appropriately control the polishing motion and force according to the workpiece conditions based on their experience. However, the number of skilled workers has been decreasing. Additionally, the skill development of younger workers has not been satisfactorily conducted. To overcome such problems, in a previous research investigation, we developed a serial-parallel mechanism polishing machine that effectively reproduced the polishing motion and force of skilled workers. This replication system, however, had limited use because the acquired polishing techniques could not adapt to various workpiece conditions, such as shape and size. The present study aimed to expand the polishing method for application to curved surfaces, in other words, adapt the replication system to changes in the workpiece shape. In the past polishing methods for curved surfaces, the workpiece shape was acquired by using CAD data or external sensors that often led to an increase in process time and cost. However, the newly proposed method in this study requires neither CAD data nor external sensors, and was able to effectively achieve simultaneous posture and force control on unknown curved surface. The experimental results showed that the skilled polishing techniques were successfully replicated on an unknown curved surface and the surface roughness was greatly improved by integrating the newly proposed method into the skilled polishing replication system.