并联机器人胡克铰工作空间的研究与应用

提出了胡克铰在并联机器人应用中的关键问题。通过对胡克铰工作空间详细地仿真和研究,建立了分析此类问题的模型拟合法和更加精确的模型解析法,并运用这两种方法分析成对胡克铰的工作空间。研究结果应用于6-PTRT并联机器人的参数设计和干涉检验,使得该并联机器人的工作空间体积增大、并成功避免机器人发生铰链干涉。得到并联机器人胡克铰的工作空间对机器人优化设计,简化运动控制算法,提高其机构性能和安全性有着重要意义。     

并联机床数控加工碰撞干涉检验算法研究

由于并联机床与通用数控机床在结构上差别较大 ,因此在开发与其配套的CAD/CAM系统时 ,考虑到并联机床的结构特点 ,针对哈尔滨工业大学研制的并联机床BJ -30的结构形式 ,提出了并联机床的数控加工碰撞干涉检验算法。该算法较好地解决了刀具过切、少切 ,以及动平台与工件、刀具夹具与工件的碰撞等数控加工中较难解决的问题。仿真结果证明了该算法具有运算速度快、检验效率高等优点     

并联杆系机床结构干涉

通过对并联杆系机床结构干涉问题的研究 ,分析影响机床加工尺寸范围的因素 ,建立了并联机床支承腿之间及虎克铰结构干涉的数学模型 ,为并联机床的结构系列化设计提供了依据 ,并做了实例计算。     

并联杆系机床结构干涉

通过对并联杆系机床结构干涉问题的研究,分析影响机床加工尺寸范围的因素,建立了并联机床支承腿之间及虎克铰结构干涉的数学模型,为并联机床的结构系列化设计提供了依据,并做了实例计算。     

基于OpenGL的并联机床建模与运动仿真技术

介绍了基于OpenGL的并联机床实体建模和运动仿真技术。对一种新型五自由度并联机床的机构特点进行了简单描述,并建立了机床运动的数学模型。利用OpenGL的图形库和矩阵堆栈建立了该机床整体结构的实体模型,利用坐标变换对机床进行了运动仿真,对机床进行了干涉检验,分析了运动仿真的实时性策略,并开发了并联机床的仿真系统。对于同一轨迹运动分别进行轨迹绘制,仿真系统用时12秒,机床样机用时10·8秒,二者结果基本一致。     

Stewart平台式并联机床的干涉计算

并联机床是一种特殊的机床,类机器人的并联结构使得机床的干涉问题相对突出。为此对并联机床的干涉问题进行了分类,针对两类干涉问题。分别讨论了进行干涉计算及检验的方法,并给出了并联机床中连杆与连杆、连杆与主轴电机不发生干涉的条件,以及两种常用铰链不发生干涉的条件。     

基于遗传算法的3-PRS并联机床的运动学标定分析研究

针对并联机床运动中存在偏差的问题,提出了基于结构参数和遗传算法的逆向运动学标定方法,推导出了并联机床误差标定的模型。该方法不需要求并联主轴平台的正向解,避免了并联机构相对复杂的正向运动分析问题。计算表明:利用名义机床结构参数计算的逆向运动误差明显大于标定的结构参数得到的逆向运动误差;标定后的三个圆柱铰和球铰的位置更接近于名义位置,说明误差标定可以对机床结构进行校正。     

3-TPS(RRR)并联机床设计中的干涉分析

介绍了一种3-TPS(RRR)并联机床,对该机床平行约束机构的构件间、平行约束机构和并联机构间的干涉进行了详细分析,给出了相关构件间干涉判别的计算公式。通过对该机床虚拟样机的干涉检查,验证了干涉判别计算公式的正确性。这些判别公式为该机床原型样机的设计提供了依据。     

并联机床工作空间快速校验与仿真

根据并联机床工作空间的定义及几何约束条件 ,提出了工作空间快速定位校验算法和许用平台倾角[β]x ,y ,z 的概念 ,论述了用许用平台倾角 [β]x ,y,z 组成的工作空间文件描述并联机床不发生干涉的工作空间的思想。在此理论基础上 ,利用VC6 .0开发了并联机床刀具轨迹干涉校验模块 ,该模块实现了对UG的CAM模块产生的刀具路径进行快速校验的功能。同时 ,应用OpenGL ,实现了对并联机床工作空间和机床加工运动过程的三维仿真     

6-SPS并联机床工作空间分析

选用局部坐标系和球铰的转角描述了动平台的位置,分析了运动副转角、杆长、支链干涉等因素对并联机器人工作空间的影响。结合并联机床的加工要求,研究了工作空间及其随自转角的变化规律。     

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。     

非线性方程组解集边界求解方法及其在并联机构分析中的应用

并联机构的结构使其输入和输出运动之间具有复杂的非线性关系,在该类机构的运动学、动力学、作业空间、误差分析及运动控制中均涉及大量的非线性方程组求解。介绍一种含参数的非线性方程组的解集边界求解方法,基于流形理论和数值化连续算法,可直接搜索出一个非线性系统的解集边界,计算速度快、效率高。利用上述算法,对一台实际的4自由度并联机床进行了作业空间边界的求解和分析,验证了算法的实用性和有效性。     

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.     

Calibration of parallel kinematic machine tools using mobility constraint on the tool center point

In the application of parallel kinematic machine tools (PKM), because of errors in the geometric parameters, it is necessary to calibrate the PKM to improve the positioning accuracy. In existing self-calibration methods, either some redundant sensors on passive joints or some mobility constraints on the kinematic chains are used. However, the mobility constraints imposed on kinematic chains might apply large forces during the test on legs and passive joints. Also, these kinds of calibrating are applicable only on PKMs in which their actuated joints can be used as passive joints. To overcome weaknesses of existing methods, a novel approach to calibration based on imposing position constraints on the tool center point (TCP) is introduced. In this method, only the data of encoders installed on the actuated joints in some sets of configurations are required. In each set, the position of the TCP is fixed, but orientations of the tool are different. Simulations and experimental studies on a Hexaglide PKM built in Sharif University of Technology reveal the convenience and effectiveness of the proposed robot calibration method.     

混联数控机床虚拟加工系统的研究与开发

针对混联机床加工过程中干涉检查、空间刀具半径补偿及编程难等问题,分析了混联机床运动学逆解,提出了一种空间任意面内的刀具半径补偿方法,给出了干涉检查的判断条件。以V is-ual C++为开发环境,应用AutoCAD二次开发工具ObjectARX,建立了由NC代码驱动的混联数控机床加工仿真系统,实现了以真实加工条件为依据的加工过程实时动态模拟,预估加工的过程和结果,为检查NC代码的正确性提供了可靠的依据。     

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.     

3-RPS并联机构运动学标定方法的研究

针对六轴混联机床中因3-RPS并联机构结构参数误差引起的精度问题,分析了影响3-RPS并联机构几何精度的误差因素,给出了并联机构的误差模型;基于影响并联机构定平台运动精度较大的几何误差参数;建立了运动学标定模型.采用阻尼最小二乘法,经多次优化迭代实现了利用一组测量数据完成非线性超越矛盾标定方程组的求解.利用激光干涉仪完成了标定用数据的测量,通过3-RPS并联机构运动学逆解和各铰链的几何标定参数,得到动平台的实际位姿.通过对标定前后的Z轴定位精度的检测及实际零件加工试验,验证了3-RPS并联机构运动学标定模型和方法的正确性和有效性.     

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.     

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.