6-DOF并联坐标测量机结构参数的识别与修正

首先对6-DOF并联机构坐标测量机的组成结构及工作原理进行了介绍,然后针对该坐标测量机的运动特点,提出了一种基于逐次逼近算法的结构参数识别与修正方法.该方法以最小二乘逐次逼近算法为基础,以寻找6自由度并联机构坐标测量机的43个主要结构参数为目的.文中对所提算法的求解过程进行了详细的论述,并通过计算机仿真计算,对结构参数的识别与修正结果进行了验证.仿真结果表明,所提出的逐次逼近算法能够充分利用目标函数值的信息,优化搜索过程具有较强的方向性和目标性,且收敛速度较快.采用该方法对6自由度并联机构坐标测量机的结构参数进行识别与修正以后,可使该坐标测量机的测量精度得到明显改善.     

并联坐标测量机建模理论及其虚拟原型设计

并联运动机构具有结构刚性大、运动速度高、误差不叠加等独特特性,因而若将其应用于坐标测量机中,将有可能使坐标测量机的测量精度及测量效率等综合性能得到很大程度的改善。本文首先介绍了一种基于并联运动机构的新型坐标测量机的结构、特点及工作原理,然后建立了该坐标测量机的测量模型,最后,在Windows 98(Windows NT)开发环境下,通过VC＋＋6．0调用OpenGL图形库中的图形函数,对该坐标测量机的虚拟原型进行了参数化三维建模与仿真,从而为真实样机的制作奠定了基础。     

并联六坐标测量机及其结构

提出了发展我国并联坐标测量机来克服直角坐标测量机在原理上对刚度、精度、速度和灵活性的限制。讨论了已有坐标测量机的结构和实现六坐标运动的并联机构。为简化位置求解的难度，确定以演化的Stewart平台作为并联六坐标测量机的结构，并按空间才环机构分析了该结构的自由度。     

ADAMS环境下并联坐标测量机运动分析与仿真

并联机构的运动学分析即是求解并联机构的输入与输出构件的位移、速度、加速度之间的关系。文章以基于Stewart平台的六自由度并联机构坐标测量机为研究对象,在ADAMS软件环境下建立了六自由度并联坐标测量机的虚拟样机模型,然后基于虚拟样机对所研究的并联坐标测量机进行了运动学仿真。通过软件仿真,可以对并联坐标测量机各种运动性能产生直观的了解,从而为并联坐标测量机的设计与开发提供软件验证方法,为建立物理样机打下坚实的基础。同时利用虚拟样机技术还可以大大简化并联坐标测量机的运动学逆解和正解,为进一步对并联坐标测量机的系统优化创造了有利条件。     

圆筒型直线电机及其在机床上的应用

介绍了圆筒型直线电机的工作原理、结构与特点，讨论了圆筒型直线电机在冲压机、并联机床以及并联机构坐标测量机等机床上的应用情况与进展。     

基于VC的可移动三坐标测量机

文章介绍了一种适用于现场测量的可移动三坐标测量机的机械结构及其基于VC的测量软件设计,并重点讨论了该测量机主要测量对象--工字钢结晶器内腔尺寸的测量原理,该测量机具有结构紧凑、测量范围大、可移动、成本低、有较高测量精度、实现自动化测量等特点.     

并联坐标测量机神经网络滑模控制

研究了6-TPS型并联坐标测量机的基于RBF神经网络的直接自适应滑模控制方法.根据测量机的系统动力学模型特点,基于Lyapunov函数的综合设计方法和滑模控制理论,利用RBF神经网络与自适应技术相结合,设计了一种控制律,然后利用MATLAB进行了系统控制仿真.结果表明,测量机在有周期干扰的情况下,采用这种直接自适应神经网络滑模控制方法达到了较高的控制精度,其闭环系统具有较强的自适应性和鲁棒稳定性.     

四面体三坐标测量机精度分析

并联式三坐标测量机具有测量范围大和精度高的特点。针对这些特点,介绍了一种四面体坐标测量机,可对机床或空间某一点位置进行测量。由于机构的几何误差以及各级伸缩杆之间的不可避免的间隙所带来的误差使得测量机存在一定的测量误差。文中针对伸缩杆杆长误差建立了测量机的测量误差模型,并通过MATLAB软件对测量机测量空间进行误差仿真分析,得到了测量机在机床工作空间的误差缩放规律。通过计算分析得出杆长误差及被测点初始位置误差对测量机测量误差的影响仅在0.2%~1.5%之间,满足测量要求。     

结晶器坐标测量机不确定度分析及精度保证

文章对影响结晶器专用坐标测量机测量精度的各项误差进行了详细分析，用齐次坐标理论建立了误差修正模型，对影响测量精度比较大的21项几何误差进行修正，并给出各项几何误差的传递系数。通过对误差修正后的测量机各轴不确定度进行评定，找出影响测量精度的瓶颈因素，分析了存在的问题并给出改进措施，最后通过实验验证了该方法的正确性和实用性，为保证测量机的精度提供了理论指导。     

三坐标测量机测头的正确使用

测头是坐标测量机的一部分，主要用来触测工件表面。本文对坐标测量机的测头探针的正确使用进行了探讨。为了确保坐标测量机的测量精度、测量范围和测量效率，选用测头时测头长度，应尽可能短、连接点最少、测球尽可能大，使测头的刚性和测尖的形状达到尽可能最佳的程度；测量过程中避免杆的碰撞；对工件进行检测之前，需对所使用的测杆进行校验。     

并联运动机床数控加工后置处理

在分析研究了并联机床的结构和坐标转换关系的基础上，针对清华大学研制的6—PSS型并联机床，提出了刀位后处理计算方法，包括刀轴矢量与机床坐标夹角的计算和NC数据的计算；为编制并联机床数控后处理程序提供一条捷径。     

Application of homogenous transformation matrix to measurement of cam profiles on coordinate measuring machines

A kinematic model is presented to aid the cam profile design task and to determine the NC data required to move an inspection probe to the necessary locations to inspect the surface profile of a spatial cam on a coordinate measuring machine (CMM). The cam profile is designed in accordance with the principles of conjugate surface theory. Homogenous transformation matrices are then employed to derive the CMM ability function matrix and the measuring probe location matrix. The required NC data are obtained by equating the elements in the ability function matrix with the corresponding elements in the probe location matrix in order to solve the CMM link variables. The validity of the proposed approach is verified by carrying out the automatic inspection of a machined cam on a CMM using the NC data computed by the developed algorithm. The methodology presented in this study combines the cam design, machining and inspection activities, and makes possible a flexible and automatic spatial cam design and manufacturing process.     

CAD系统在CMM测量中的应用

对CAD系统在三坐标测量机测量中的应用进行了介绍。通过CAD系统可以完善和扩大测量机的功能，实现曲面测量时的测头半径补偿，并能对测量数据进行处理。文中对实现这些功能的方法和步骤进行了说明。     

Towards a haptic virtual coordinate measuring machine

In this paper, a novel coordinate measuring machine (CMM) inspection path planning environment, named haptic virtual coordinate measuring machine (HVCMM), is proposed, which makes use of haptic modeling technique for CMM off-line programming. HVCMM is an accurate model of real CMM, simulating a CMM’s operation and its measurement process in a virtual environment with haptic perception. It enables CMM off-line programming to take place exactly as if an operator were in front of a real CMM and moving a real CMM probe. To generate the inspection path of a part, teach pendant programming is made by pointing a probe at the 3D computer-aided design (CAD) model of a part using a haptic device. With the HVCMM system, it is much easier to generate collision-free probe path than using other off-line inspection planning methods. Furthermore, when a contact occurs between the CMM and the object, a force is generated based on a proposed mechanics model besides visually showing the contact in the HVCMM environment. Surface voxel is used for quick collision detection. The HVCMM not only facilitates the inspection path planning, but also speeds it up. The proposed HVCMM can also be used for the training of CMM operation.     

大批量产品加工质量过程控制技术的研究

文章针对大批量产品加工的特点和现在质量控制中所存在的问题,详细阐述了大批量产品加工质量过程控制中涉及的多项技术和解决方法.重点介绍了质量保证工艺在质量过程控制中发挥的重要性.     

基于CAD点云模型的CMM离线编程技术研究

三坐标测量机(CMM)的离线编程较复杂,尤其针对未知三维CAD模型的工件更加难于实现离线编程。为此提出基于CAD点云模型,针对工件中常见的平面和圆柱面等特征,通过编程方式完成特征异常点删除和提取特征点操作,编制DMIS自动测量程序,模拟仿真检验后进行CMM在线测量。实例验证:该方式较易编制CMM离线程序,实现了CMM的自动稳定测量。     

Relationships between straightness and angular kinematic errors in machines

The software compensation approach for the improvement of machine tool and coordinate measuring machine accuracy depend to some extent on machine error modelling and measurement methodologies. The currently established methodology is based on the derivation of tool position error (for machine tools) or stylus tip position error (for coordinate measuring machines) by the combination of individual axis joint kinematic error parameters. The purpose of this paper is to propose a machine error analysis based on error classification. This taxonomic approach forms a conceptual basis for an analysis of machine errors with a deeper understanding of error mechanisms at more fundamental levels. The relevance of this approach is investigated through the case study of the coupling mechanism between joint kinematic angular and straightness errors of machine linear axes. The limitations of the joint kinematic straightness and angular error modelling based on purely abstract mathematical dependence principles are explored through simulations and experiments.     

Complete 3D measurement in reverse engineering using a multi-probe system

To meet the demand of measuring the complex prototypes completely in reverse engineering, a multi-probe measurement system integrated with a coordinate measuring machine (CMM), a structured-light sensor, a trigger probe and a rotary table is presented in this paper. The structured-light sensor is designed with optimal structure, and its model is established based on the CMM to simplify its parameters, this enables the sensor to be calibrated expediently at any condition. Three measuring modes are proposed considering the efficiency of the structured-light sensor, the high accuracy and flexibility of the trigger probe and the rotation of the table for finding proper scanning views. The structured-light sensor is usually applied to scan the profile of a part from different views, while the trigger probe is used to measure the edge and key features of the part. The data generated by different modes can be merged into a whole data body. The system possesses the function of obtaining the coordinate of nearly any point on a complicated part. Experiment studies on the accuracy of the structured-light sensor, data patch assembling and data merging show that the total accuracy of the system is ±0.033 mm.