Evaluation of coordinate measurement uncertainty with use of virtual machine model based on Monte Carlo method

Advances in modern manufacturing techniques implies more efficient production but also new tasks for coordinate metrology. The main of them is evaluation of accuracy of the measurement, because according to technological requirements, results of measurements are useful only when they are given with their accuracy. Currently used methods for uncertainty assessment are difficult and require knowledge and measuring experience. It is therefore important to implement correct and validated methods that will also be easy to implement and will not require broad metrological knowledge from the personnel. Presented here simulation method, based on Monte Carlo method is one of them. The article presents the conception, implementation and validation of this method.     

Measurement of form error of a probe tip ball for coordinate measuring machine (CMM) using a rotating reference sphere

This study presents a method of measurement of the form error of the tip ball in the tactile probing systems of a coordinate measuring machine (CMM) by using a rotating reference sphere. The measurement of the form error of the CMM probe tip was conducted without the use of additional external measuring instruments or sensors. The form errors of the probe tip ball and the reference sphere were separated from the probing coordinates of CMM by rotation of the reference sphere. The effectiveness of the proposed method was evaluated based on an uncertainty analysis. The uncertainty in measurement of diameter of the probe tip ball was estimated to be less than 0.5 μm.     

Verification of the positioning accuracy of industrial coordinate measuring machine using optical-comb pulsed interferometer with a rough metal ball target

An optical-comb pulsed interferometer was developed for the positioning measurements of the industrial coordinate measuring machine (CMM); a rough metal ball was used as the target of the single-mode optical fiber interferometer. The measurement system is connected through a single-mode fiber more than 100 m long. It is used to connect a laser source from the 10th floor of a building to the proposed measuring system inside a CMM room in the basement of the building. The repetition frequency of a general optical comb is transferred to 1 GHz by an optical fiber-type Fabry–Pérot etalon. Then, a compact absolute position-measuring system is realized for practical non-contact use with a high accuracy of measurement. The measurement uncertainty is approximately 0.6 μm with a confidence level of 95%.     

Use of coordinate measuring machines and digital optical machines for the geometric characterization of circumference arcs using the minimum zone method

This paper presents an optimised method for the characterization of circular features of any amplitude, which includes the capture of geometric data, by means of the use of three-coordinate measuring machine or digital optical machines with a CCD camera, and its subsequent mathematical processing. The proposed model determines the radius and the circularity error, based on the minimum zone method, and to this end it uses linear programming techniques, the Simplex programming principles and the limaçon approximation. An experimental study on ring gauges and reference disks is provided, including a comparative analysis using the Chauvenet and Grubbs filtering procedures. Last of all, an uncertainty estimation method is proposed by means of the Monte Carlo simulation. The experimental analysis carried out on ring gauges and reference disks accredit that the algorithm developed, implemented in a Matlab® environment, gives reliable results for any circumference arc considered, regardless of its amplitude.     

基于多体系统运动学理论的坐标测量机误差自动建模

研究分析了运用多体系统运动学理论对复杂机械如坐标测量机进行误差建模的基本原理,介绍了误差自动建模过程。以FXYZ型立式三坐标测量机为例进行了误差建模,给出了空间误差模型具体数学表达式。理论分析和实际应用显示所述方法很好地解决了误差建模的通用性问题,为精度分析和误差补偿等提供了一个理想的误差建模方式。     

Multiple orientation technique for the calibration of cylindrical workpieces on CMMs

Coordinate measuring machines (CMMs) are widely used in various fields of precision engineering and science. Although they are highly accurate instruments, for some tasks, e.g. calibration of reference artifacts, the accuracy even of the best available instruments is not sufficient.In this paper, we describe a highly accurate technique using a CMM for the measurement of cylindrical workpieces. The proposed method is a combination of multiple orientation and substitution techniques and compensates for all geometrical errors of a CMM, systematic probing effects and the bending of the workpiece due to gravity. We demonstrate the method on a cylinder gauge with flat ends that incorporates a number of different geometrical features. The evaluation of the measurement uncertainties for each characteristic was performed manually and using the Virtual CMM (VCMM) [Trapet E, Franke M, Haertig F, Schwenke H, Waeldele F, Cox M, et al. Traceability of Coordinate Measurements According to the Method of the Virtual Measuring Machine: Final Project Report MAT1-CT94-0076, PTB-Report F-35, Parts 1 and 2; 1999; Haertig F, Trapet E, Waeldele F, Wiegand U. In: Proceedings of the 5th IMEKO TC-14. Traceability of coordinate measurements according to the Virtual CMM concept; 1995. p. 245–54.]. The results show, that very low uncertainties can be achieved by the proposed measurement techniques. It is also demonstrated that the VCMM approach considers reversal effects correctly for the calculation of measurement uncertainties.     

An experimental method for assessing the contribution of the production process variations to the task-specific uncertainty of coordinate measurements

The present paper deals with an important source of variation often neglected in uncertainty estimates of coordinate measurements: the between-sample variation. This source of variation becomes relevant to the measurement uncertainty when significant interactions occur between variations in the production process and specific limitations in the measurement process. This paper discusses some particular types of interaction which usually lead to between-sample variation in coordinate measurements. For analysing the statistical significance of the between-sample variation and for assessing its contribution to the measurement uncertainty, an experimental method using multiple calibrated workpieces is described. A case study involving the uncertainty estimation of a roundness measurement process using a coordinate measuring machine is presented. The results show the importance of considering the between-sample variation in uncertainty evaluations of coordinate measurements.     

加工中心工件坐标系原点确定方法及应用

结合生产实践中的零件,对其在加工中心上进行工件坐标系原点确定的几种主要方法及其应用进行了探讨.这些方法经实践证明生产可靠性强,且便于操作,对生产有积极的指导意义.     

Modelling of pretravel for touch trigger probes on indexable probe heads on coordinate measuring machines

This paper presents a pretravel model for touch trigger probes mounted on indexable probe heads, which can rotate and tilt the probe into a number of orientations for coordinate measurements on coordinate measuring machines (CMMs). Pretravel accounts for the majority of touch trigger probe errors and is caused by bending deflection of the stylus shaft. A trigger force model is derived and used to model bending deflection of the stylus shaft at the trigger instant. Only one model parameter needs to be calculated using the probe calibration data. Experimental data associated with thirteen probe orientations were used to validate the model. It is shown that the model can effectively predict pretravel distances associated with various probe approach directions. The standard deviations of prediction errors are less than 0.71 µm, indicating that the proposed model can be used to compensate for pretravels occurring in touch trigger probe applications.     

A developed algorithm for simulation of blades to reduce the measurement points and time on coordinate measuring machine (CMM)

A 3D Coordinate Measurement Machine Facility (CMM) of the latest technology enables both researchers and industrial manufacturers to evaluate the precision of the different manufacturing techniques that are usually applied for the production of the mechanical component. Especially when the examined component is a blade, due to the geometrical complexity, larger errors can occur during the manufacturing procedure. These errors have a strong impact on the final performance. The high precision measurement with a CMM requires scanning with small steps, which means measuring several points that need long-time measurement.The aim of this paper is to develop a method for simulating objects by three-dimensional scanning, with a small number of points, while achieving the goal of a certain allowable deviation. The curves used are of a 3rd degree polynomial form.     

Kinematic analysis of the wire parallel mechanism for full coordinate measuring of industrial robot

This paper presents a wire parallel mechanism for full coordinate measuring of industrial robot. The mechanism is constructed with six parallel wires that act as links. The position and orientation of a robot end-effector are obtained from the wire lengths. The equations of the forward kinematics are solved by a Newton-Raphson method, and the unique solution is determined from the geometric configuration of the mechanism. A method to estimate the workspace is presented. Through simulations, it is verified that the proposed mechanism can measure a robot pose over a large workspace, and can be used effectively for full coordinate measuring of a robot with little cost and effort.     

基于LabVIEW的摆线齿轮误差虚拟测量仪的研制

提出摆线齿轮误差检测的评定指标,利用LabVIEW虚拟仪器软件平台,开发摆线齿轮误差检测的虚拟仪器,介绍仪器测试系统的构成及其程序设计。     

基于共视法的电压源远程校准方法及一致性评价研究

本文针对传统电压源校准方法存在的问题,提出了一种基于卫星共视法的电压源远程校准方法,该方法以非实物标准传递为基础,实现将标准器置于实验室而无需传递至现场进行远程校准,可解决引入附加误差的问题,通过设计基于共视法的电压源远程校准系统,建立校准模型,根据共视原理,实现标准端和被校端电压值远程比对,完成校准。本文对远程校准方法和传统校准方法在直流0～1 V校准点校准结果进行了对比,结果显示两种方法的校准结果差距在5.2×10^-5 V以内。本文给出了两种方法在直流1 V校准点的不确定度评定过程,并通过传递比较法对两种方法的校准结果进行了一致性评价,结果表明,远程法在1 V校准点的扩展不确定度为9.182 44×10^-5 V(k=2),且校准结果与传统法具有一致性。     

基于坐标测量机的轴向立体视觉测量方法研究

为了解决双目立体视觉测量过程中图像匹配计算量大、算法复杂、误匹配率高的问题,提出了一种轴向立体视觉测量方法。该方法由单个摄像机沿坐标测量机轴向先后捕捉被测物表面,利用同轴摄像机外极线相互平行的特性进行同源相点的逐个匹配,并根据视差原理反求三维坐标。着重论述了该方法的原理、同源点匹配及具体实现过程,并通过实验进行了验证,测量了一个塑料盘的边缘并进行了重建。研究结果表明该方法能提高匹配效率,减小误匹配几率,实现快速高效的非接触式测量。     

Development of a parametric model and virtual machine to estimate task specific measurement uncertainty for a five-axis multi-sensor coordinate measuring machine

Any combination of contact and non contact sensors on a single coordinate measuring machine makes it a multi-sensor or hybrid coordinate measuring machine. The ability to change the probing device without re-establishing the part coordinate system is a significant advantage and consequently the reason for their wide acceptance and usage. In addition to the existing three linear stages in a conventional or hybrid coordinate measuring machine, the number of axes can be augmented with two rotary stages in order to make them more versatile. This not only complicates the metrology loop but also adds more parametric errors to existing list of known 21 errors for a three stage conventional measuring machine. Also different probing sensors in the system have different metrology loops. Literature survey reveals that there is no previous or current work on estimation of task specific uncertainty for machines of this class with a wide potential for measuring complex parts quickly and with great ease. The current work focuses on developing a virtual measuring machine of this class which incorporates a parametric model of a five-axis multi-sensor coordinate measuring machine, techniques to estimate the parametric errors in the model and error correction strategies for the same. The virtual machine is used to mimic real time measurements in order to come up with estimates for task specific measurement uncertainty.     

Comparising measuring methods of pitch diameter of thread gauges and analysis of influences on the measurement results

In this article, the differences between three calibration methods of the thread ring pitch diameter are being presented. Two of these methods are classical methods (executed on a 1D-length measuring machine with a two-ball stylus for mechanical probing and on a coordinate measuring machine also with a two-ball stylus for mechanical probing); the third method is a modern one, executed on a profile scanner to calculate the pitch diameter with an adjustment technique (least square fit).     

基于制动力矩的ABS整车控制方法的研究

提出了一种基于整车的控制方法,首先根据制动压力进行道路自动识别,然后根据路况自动调整左右两侧车轮的制动力之差,以保证车辆制动时的方向稳定性.结合14自由度的虚拟样机整车模型,分别在对接路面和分离路面上进行基于ADAMS/Simulink的联合仿真制动模拟试验.结果表明该方法能够较好的识别路面状态,使车辆在兼顾其制动距离与时间的前提下提高其直线制动的方向稳定性,为一些基于路面状态的汽车主动控制策略提供了条件.     

Review of non-destructive measuring methods for the assessment of surface integrity: a survey of new measuring methods for coatings, layered structures and processed surfaces

Even though the near-surface areas of precisely manufactured parts represent only a few percent of the workpiece’s material volume, they influence its functional behaviour, quality and lifetime significantly. Therefore, sensors and measuring principles able to detect material changes, damage and process influences in the near-edge zone are of increasing importance. However, they have to meet industrial purposes concerning accuracy, measuring time, robustness and costs. In addition, they should work non-destructively and should offer the capability for integration in a production line.     

Force control of a piezoelectric actuator based on a statistical system model and dynamic compensation

Piezoelectric actuators present a promising option if actuation of small-sized robot joints is considered. They develop forces of several newtons at velocities in the cm/s range while their dimensions and weight remain small as compared to electric motors. This work presents an approach for modelling a class of contemporary, non-resonant translatory piezoelectric actuators. The proposed modelling approach results in three motor models of increasing complexity independently of the low-level piezoelectric properties of the driving elements. The basic model establishes a static relation between motor velocity and drive frequency for a free-moving motor. The second model is a non-linear extension of the first model which introduces external load forces. The final model introduces time-dependent aspects by employing system identification techniques. The final model is used to develop a force compensation mechanism which restores linearity in the motor operation even in the loaded case. Based on the linearised model, standard control design techniques are applicable to design an explicit force controller. Limits on the performance of the controller are derived. The actual performance of the controller is evaluated both in simulations and experiments by pulling on tendons of different elasticity.