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.     

Information model for the integration of inspection activity in a concurrent engineering framework

The basis of the integration of activities related to the product life cycle is, mainly, the creation of a unique and coherent information model along all the stages in the cycle. Up to date, dimensional inspection activities have not been deeply analysed, possibly due to the fact that, their work influences are smaller than others, such us numerical analysis, materials or numerical control. However, the integration of dimensional inspection is very important for several reasons: the need of specifying the design and planning of the inspection process from the conceptual part design; the increase of use of high speed coordinate measuring machine (CMM) in the production lines; and finally, for the interest of a feedback between data inspection and manufacturing processes. This paper is a detailed proposal of an information model for inspection based on operations for CMM, which represents a consistent structure of the necessary data in an integrated product setting.     

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.     

Computer-Aided Planning of Laser Scanning of Complex Geometries

A computer-aided planning method for laser scanning based on the CAD model has been developed. It integrates three planning criteria, visibility, accuracy, and efficiency and detects deep concave features that would be more suitable for CMM probing. Clustering, based on the view angle and depth of view, is used to plan an optimal scanner placement and motion path. Simulation studies on complex auto-parts demonstrate the effectiveness of the generated plans. The integration of the scanning plan with CMM controls was also demonstrated. The benefits of the CAD-based automated laser inspection planning have been demonstrated.     

面向自由曲面零件的在线检测技术研究现状

数控机床在线检测系统是集数控机床、测头及计算机等为一体的高度集成化系统.高精度在线检测是实现柔性制造系统连续可靠工作的重要手段,是保证数控机床加工精度和效率的重要措施.在航空、汽车、模具等现代工业生产中出现了越来越多的自由曲面零件,这对测量系统提出了更高的要求,因而对具有自由曲面的零件进行高精度高效率的检测将是当前的一个重要研究方向.本文主要介绍自由曲面零件的在线检测技术在国内外的研究现状与进展,包括检测系统开发、自由曲面零件的接触式测量及路径规划和误差补偿等3部分,指出了目前在该领域存在的有待于进一步解决的关键问题.     

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。     

CMM离线检测在逆向设计模型改进中的应用

目前逆向工程主要采用逆向设计软件和CAD系统（如Geomagic，UG等）对点云进行拟合，并以此来评估几何型面拟合误差，而对设计模型的配合型面位置约束检测方法的研究则相对缺乏。为了在设计早期就能提前发现逆向设计模型的缺陷并进行改进，提出用精密三坐标测量软件离线检测逆向设计模型配合型面间空间约束的方法，讨论了逆向设计B-Rep模型的几何封闭性问题和制造工艺性（特别是装配要求）问题场景，给出装配约束型面间位置约束检测与缺陷改进的方法，最后用实例进行了说明，为现有的逆向设计模型质量检验和改进方法提供了一种有益补充。     

基于改进遗传算法的工厂AGV安全路径规划

为了避免危害事故的发生,在复杂的加工制造工厂中规划AGV小车安全无碰撞的行驶路径,不能简单地将AGV看成一个质点。首先在传统的障碍物栅格地图中叠加了环境安全信息,构建了融合信息栅格地图,提出了一种改进的遗传路径规划算法,在其适应函数中加入安全信息,并采用A*算法产生的初始路径为基准进行安全优化,减少了算法的搜索空间和复杂度。在MATLAB中对算法进行了验证,并在Gazebo中模拟了制造工厂AGV路径规划过程,验证了该方法具有较快的收敛速度及有效性。     

Characterization on Laser Melting Deposition of Metallic Components

Laser melting deposition process (LMD) is an advanced computer-aided laser additive manufacturing process (LAM). This process can produce net-shape components with fully dense microstructure and good properties based on a computer aided design (CAD) model by using a high power laser to melt the injected powders and re-solidify them in a layered way. It presents obvious superiority in direct manufacturing components with small-lot, repairing high-value components with good performance, and integrated fabrica...     

Tool path generation for NC grinding

A new method for tool path generation for grinding is proposed. This method for tool path generation is based on a conceptually simple yet fundamental representation of the manufactured surface. Such representations of the manufactured surface, which are derived analytically, were traditionally derived by measurement based methods. The representation of the manufactured surface is also advantageous in developing analytical estimates of surface roughness. These analytical estimates provide a starting point for the measurement or inspection operations which are usually data intensive and often times expensive for free-form surfaces. This paper thus presents an integrated approach to tool path generation which takes into account the manufacturing and measurement activities.     

Selection of sampling points for accurate evaluation of flatness error using coordinate measuring machine

Dimensional inspection, in integrated manufacturing environments, requires accurate inspection while minimizing the cost and time of inspection. The selection of sampling plan—sample size and sample point locations, the method of evaluating the form error and the nature of the manufactured surfaces will play an important role in deciding the best inspection strategy to be adopted. This paper deals with the strategy for evaluation of flatness error which is one of the most commonly used form tolerances for control of manufactured surfaces. Investigations have been carried out to ascertain the influence of surface quality (surface roughness) in determining the sampling strategy for accurate determination of flatness error while inspecting on a coordinate measuring machine (CMM). The sampling plan utilizes the Hammersley sequence for point location and the flatness error is evaluated using the minimum zone method (MZM) based on computational geometry techniques. Results indicate that the surface roughness influences the accuracy of inspection and can be used as a parameter for determining an initial sample size for the determination of flatness error.     

Geometric and quasi-static thermal error compensation for a laser digitizer equipped coordinate measuring machine

An emerging trend in dimensional inspection of manufactured parts is the use of coordinate measuring machines (CMMs) equipped with non-contact laser digitizers instead of traditional contact probes. Error mapping is generally proprietary to the CMM controller, and the accuracy of such a combined system is limited by the lack of integrated CMM/laser digitizer error compensation. This paper reports progress towards achieving such a system.Geometric error compensation measurements are made on a test machine at 20, 25 and 30 °C. Performance of the system was tested by measuring a special optically coated sphere ballbar artifact. The scan coordinates, the CMM axis scale positions and temperature were recorded simultaneously in real time. The CMM error compensation data was then used to post process the laser digitizer coordinates to obtain improved global part coordinates.Inclusion of the error compensation terms is shown to reduce the dispersion of results by 65 to 80%.     

基于改进D?Lite遗传算法路径规划研究

针对遗传算法在移动机器人路径规划中易产生早熟现象和收敛速度慢的问题,提出了改进的D~* Lite遗传算法。该算法将D~* Lite算法和遗传算法相结合,通过引入碰撞系数和可视检测技术以提高路径安全性,寻找最短路径。在遗传算法设计中加入动态调整交叉与变异概率,以解决算法在路径规划中因陷入局部最优值而不能到达目标点的问题。最后,通过实验仿真可知:与蚁群算法和免疫遗传算法相比,改进的D~* Lite遗传算法执行效率高,可以快速规划出全局最优路径。     

基于3D打印的CMM辅助测量技术

针对现阶段复杂零件在CMM上测量的不足,提出了采用基于3D打印的CMM辅助测量技术。为了能使产品在CMM探针精度最高的A0B0度方向测量,经常需要借助治具辅助。文中首先使用光学扫描技术获取产品表面数据,然后在Geomagic Studio软件进行数据处理,并将网格面导入到Rapidform软件对该产品的治具进行建模和设计,再将设计模型导入到3D打印机中得到治具模型,最后将测量的产品放置在治具中测量。通过试验证明,该方法可以很好地提升复杂零件在CMM下的测量效率。     

Applications of 3-D solid modelling to coordinate measuring inspection

This paper describes a set of algorithms for the automation of component inspection using coordinate measuring machines. Solid modelling techniques are used to describe the component, and this model is then used to generate a set of inspection points and a collision-free probe path. The model is also used in the analysis of the resulting measurements. The algorithms have been implemented in a system that will handle the range of form, location and attitude tolerances, as defined by BS 308, for planar, cylindrical, conical and spherical features.     

双机器人松协调焊接过程无碰路径规划

针对两台机器人在同一工作区间进行焊接工作可能发生碰撞的问题,提出一种基于"假设修正"策略和遗传算法的无碰路径规划方法. 利用球体和圆柱体建立机器人包络模型,根据空间几何理论求出包络模型之间最短距离解析式. 以理想约束条件,得到假设路径. 建立与弧焊焊接质量、点焊最短路径等相关的适应度函数,通过遗传算法搜索出无碰位形. 以螺柱焊接工位为实例,运用仿真软件进行无碰路径规划工作. 结果表明,方法正确可行,为双机器人规划出优质无碰焊接路径.     

三坐标测量机测头半径补偿的新方法

用三坐标测量机进行测量时,需要对测头半径进行补偿。在对现有的测头半径补偿方法进行分析的基础上,提出一种“四点共球法”,实现了对测头半径的补偿。在阐述四点共球法原理的同时,给出了它的运算量和采集数据点的方法。然后,对该方法的补偿精度做了初步分析,并给出保证补偿精度的注意事项及进一步提高补偿精度的方法,以一个补偿实例进行验证,结果表明四点共球法可以满足绝大多数工程测量,具有一定的实际应用价值。     

基于HPSO算法的CNC在线检测路径规划

CNC在线检测路径规划直接关系到在线检测效率,为生成最短的无干涉检测路径,文章提出一种基于混合粒子群算法(HPSO)的在线检测路径规划方法。采用先避障后优化的规划策略,规划出无干涉的初始检测路径,基于旅行商问题建立优化模型,使用HPSO算法优化测点间检测顺序及特征间检测顺序。针对典型工件进行在线检测路径规划及检测实验,相比于基本粒子群算法的优化结果和人工规划结果,该方法在保证测头安全的前提下,有效缩短检测路径长度,提高了检测效率。     

NGSA算法在不规则零件优化排样中的应用研究

对于二维不规则图形零件在排样区域上的最优排列,也就是对二维不规则图形的计算机自动排样算法进行优化问题.采用矩形包络算法、遗传模拟退火算法及小生境技术相结合,寻找排样件在排样时的最优次序及各自的旋转角度,然后采用基于"最低水平线"策略的启发式排样算法实现二维不规则图形零件自动排样,得到满意的优化排样结果.     

Integrated real time compensation system for errors introduced by measurement probe and machine geometry in commercial CMMs

In this paper, an integrated real time compensation system has been proposed for the errors introduced by the probe and machine geometry in commercial CMMS. For efficient probe error mapping, a compact notation (ε, θ) for probing direction and corresponding concentric diagram is proposed. A set of integrated volumetric error equations are also proposed for the volumetric error map integrating the probe error and the machine geometric error. For the real time error compensation scheme, an interface box and an appropriate software driver have been designed and implemented between the CMM and machine controller. The data flow is intercepted and corrected according to the integrated volumetric error map without the controller being noticed. Thus the real time error compensation system has been successfully implemented for the machine with minimum interference to the existing coordinate measurement system. The developed system has been applied to a commercial CMM on the shop floor, and the measurement accuracy has been improved remarkably.