Automatic registration for inspection of complex shapes

With the increase in computing power, new ways of inspecting manufactured parts can be realized. The availability of computing power allows computational alignment between measurements and computer aided design (CAD) models using registration algorithms. The present paper proposes a new inspection approach that removes a constraint of traditional inspection processes related to part alignment. Traditional techniques require a fixture to align the part so the inspection machine can establish a common coordinate system between the measurement and the CAD model. Removing the need of a fixture aids automating the inspection process. The proposed approach employs an automated registration methodology based on two main stages. First, a part measurement in an arbitrary coordinate system is transformed to approximately fit the shape of the CAD model. Then, this approximation is iteratively refined until its convergence. To demonstrate the feasibility of the proposed method, results are demonstrated on measurements obtained from three rapid prototyped parts with complex geometry.     

Automatic registration for inspection of complex shapes

With the increase in computing power, new ways of inspecting manufactured parts can be realized. The availability of computing power allows computational alignment between measurements and computer aided design (CAD) models using registration algorithms. The present paper proposes a new inspection approach that removes a constraint of traditional inspection processes related to part alignment. Traditional techniques require a fixture to align the part so the inspection machine can establish a common coordinate system between the measurement and the CAD model. Removing the need of a fixture aids automating the inspection process. The proposed approach employs an automated registration methodology based on two main stages. First, a part measurement in an arbitrary coordinate system is transformed to approximately fit the shape of the CAD model. Then, this approximation is iteratively refined until its convergence. To demonstrate the feasibility of the proposed method, results are demonstrated on measurements obtained from three rapid prototyped parts with complex geometry.     

Response surface optimization for a nonlinearly constrained irregular experimental design space

Finding optimum conditions for process factors in an engineering optimization problem with response surface functions requires structured data collection using experimental design. When the experimental design space is constrained owing to external factors, its design space may form an asymmetrical and irregular shape and thus standard experimental design methods become ineffective. Computer-generated optimal designs, such as D-optimal designs, provide alternatives. While several iterative exchange algorithms for D-optimal designs are available for a linearly constrained irregular design space, it has not been clearly understood how D-optimal design points need to be generated when the design space is nonlinearly constrained and how response surface models are optimized. This article proposes an algorithm for generating the D-optimal design points that satisfy both feasibility and optimality conditions by using piecewise linear functions on the design space. The D-optimality-based response surface design models are proposed and optimization procedures are then analysed.     

提高圆度误差分离精度的措施

以圆度误差分离技术为例,着重分析了影响分离精度的因素,提出了改善分离精度的数据有效性检验、集合平均、无附加相移数字滤波等措施。同时应用实例说明所述措施的必要性及实用性。     

测量与信息技术

测量是获取信息的重要手段。科学研究、生产、高科技发展都离不开测量。测量技术发展的重要特点是它与信息技术的融合,这是提高测量精度、在线和动态测量、复杂参数和复杂环境下测量、智能测量的需要。这一融合贯彻始终,它包括信号调制与解调、采样与重构、信号融合、数据压缩、滤波、信号变换、时间序列分析、谱分析、数据拟合与建模、模式识别、神经网络、仿真与虚拟、误差分离、误差补偿、冗余技术、决策与智能技术等,它们互相支持。章通过三坐标测量机误差补偿、圆度和轴系误差测量,以及大型工程的柔性坐标测量系统,介绍其在提高测量精度、优化、自标定、丢失信息自恢复、系统重组等方面的作用及其关键技术。     

Influence of index table accuracy on roundness calibration in the multi-step method using monte carlo simulation

The precise and accurate roundness measurement is required year by year. The multi-step method is commonly used in the high-accuracy measurement for the roundness. The multi-step method is the self-calibration of the roundness capable of performing highly-advanced precise measurement. It depends on the reason that is able to separate measurement wave from the spindle rotation component and the form component of hemispherical master. But the mathematical models of the roundness measurement using that method are very complicated, describing numerous parameters and processes. So, recently, the Monte Carlo technique has attracted increasing attention as a very useful method for uncertainty estimation. This paper describes influences of the indexing angle accuracy and the noises generated by the roundness measuring machine, on the roundness measurements, both of which were analyzed by the Monte Carlo simulation. Furthermore, an example of hemispherical master is compared with the actual measurement data between when a reference guide plate is used utilizing the magnetic rotary encoder.     

Efficiently solving linear bilevel programming problems using off-the-shelf optimization software

Many optimization models in engineering are formulated as bilevel problems. Bilevel optimization problems are mathematical programs where a subset of variables is constrained to be an optimal solution of another mathematical program. Due to the lack of optimization software that can directly handle and solve bilevel problems, most existing solution methods reformulate the bilevel problem as a mathematical program with complementarity conditions (MPCC) by replacing the lower-level problem with its necessary and sufficient optimality conditions. MPCCs are single-level non-convex optimization problems that do not satisfy the standard constraint qualifications and therefore, nonlinear solvers may fail to provide even local optimal solutions. In this paper we propose a method that first solves iteratively a set of regularized MPCCs using an off-the-shelf nonlinear solver to find a local optimal solution. Local optimal information is then used to reduce the computational burden of solving the Fortuny-Amat reformulation of the MPCC to global optimality using off-the-shelf mixed-integer solvers. This method is tested using a wide range of randomly generated examples. The results show that our method outperforms existing general-purpose methods in terms of computational burden and global optimality.     

Linear models for 1-group two-dimensional guillotine cutting problems

In this study we present integer linear and non-linear models to generate 1-group constrained and unconstrained two-dimensional guillotine cutting patterns, including exact and non-exact cases. These patterns appear in different cutting processes as, for example, in the furniture industry. The models are useful for research and development of more effective solution methods, exploring particular structures, model decomposition, model relaxations, etc. They are also helpful for the performance evaluation of heuristic methods, since they allow (at least for problems of moderate size) an estimation of the optimality gap of heuristic solutions. To demonstrate the effectiveness of the proposed models, we compare them with models of the literature by solving a number of examples randomly generated and an actual example derived from a furniture company. Such results were produced using a well-known commercial software (the modelling language GAMS and the solver CPLEX) and they show that the computational efforts required to solve the models can be very different.     

基于虚拟仪器的圆度仪的研究

在总结国内外圆度检测技术的发展及研究现状的基础上,提出了基于虚拟仪器采用CCD摄像方式来获取机械零件圆度检测信息的方法。对采集到的零件图片进行图像处理,得到零件的圆度特征信息,从而精确快速的检测出零件圆度误差和相关几何尺寸和形位公差,通过与标准件或设计要求的比较,判断出被测零件的圆度是否合格。实验表明本虚拟圆度仪,非接触测量,速度快,准确度高。     

基于量子遗传算法的圆度误差测量研究

提出采用量子遗传算法,以提高圆度测量精度。首先用最小二乘法拟合获得建模数据中圆度图像的圆心坐标和半径;再通过圆度计算剔除不符合要求的圆度;然后用量子遗传算法进行多进制编码,量子旋转门非固定步长调整更新;最后给出圆度误差测量流程。实验仿真显示该算法获得了精确的测量数值,与三坐标测量机测量结果误差相差小于0.005 8 mm,半径相对误差小于0.19%,测量最大误差均在0.01%以内,同时最大误差波动比较平稳,测量不确定度比其它方法值较低。     

Wigner–Ville distribution based diffraction phase microscopy for non-destructive testing

ABSTRACT

The paper proposes an approach for non-invasive measurement of displacement derivatives and defect identification using an optical interferometric technique based on diffraction phase microscopy. Our approach relies on the application of Wigner–Ville distribution method in diffraction phase microscopy for directly extracting the phase derivative information, which is subsequently utilized for non-destructive deformation metrology. In addition, the proposed method offers good computational efficiency and robustness against noise for fast defect inspection. The performance of the proposed method is validated by experimental results.     

Towards automatic adaptive geometrically non-linear shell analysis. Part I: Implementation of an h-adaptive mesh refinement procedure

Effective methods leading to automated adaptive numerical solutions to geometrically non-linear shell-type problems are studied in this work. In particular, procedures for improving the accuracy, the reliability and the computational efficiency of the finite element solutions are of primary interest here. This is addressed using h-adaptive mesh refinement based on a posteriori error estimation, self-adaptive methods in global incremental/iterative processes, as well as smart algorithms and heuristic approaches based on methods of knowledge engineering. Seemless integration of h-adaptive finite element methods with adaptive step-length control makes it possible to maintain a prescribed accuracy while maintaining the solution efficiency without user intervention throughout the process of a non-linear analysis. Several examples illustrate the merit and potential of the approach studied herein and confirm the feasibility of developing an automatic adaptive environment for geometrically non-linear analysis of shell structures.     

Constrained multi-objective optimization using constrained non-dominated sorting combined with an improved hybrid multi-objective evolutionary algorithm

Constrained multi-objective optimization problems (cMOPs) are complex because the optimizer should balance not only between exploration and exploitation, but also between feasibility and optimality. This article suggests a parameter-free constraint handling approach called constrained non-dominated sorting (CNS). In CNS, each solution in a population is assigned a constrained non-dominated rank based on its constraint violation degree and Pareto rank. An improved hybrid multi-objective optimization algorithm called cMOEA/H for solving cMOPs is proposed. Additionally, a dynamic resource allocation mechanism is adopted by cMOEA/H to spare more computational efforts for those relatively hard sub-problems. cMOEA/H is first compared with the baseline algorithm using an existing constraint handling mechanism, verifying the advantages of the proposed constraint handling mechanism. Then cMOEA/H is compared with some classic constrained multi-objective optimizers, experimental results indicating that cMOEA/H could be a competitive alternative for solving cMOPs. Finally, the characteristics of cMOEA/H are studied.     

基于多源融合理论的机床圆度误差测量不确定度评定

圆度误差是评价机床加工精度的重要指标.为实现机床圆度误差测量不确定度的评定,对基于球杆仪测量的机床圆度误差的贡献因素及不确定度评定方法进行研究.首先,采用最小二乘法(least sqaure method,LSM)对圆度误差进行评定.然后,基于黑箱理论提出了多源融合误差测量不确定度评定方法.接着,根据球杆仪测量机床圆度...     

Accuracy of centering during measurement by roundness gauges

The effect of centering accuracy on the error for measurement of roundness deviation is considered. A method is proposed for processing the results of measurements based on harmonic analysis, compensating for a given error. Results are given for comparative analysis by the well-known and suggested methods in measuring deviation from roundness on the basis of Monte-Carlo statistical modelling. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 20–22, November, 2006.     

Allocating metrology capacity to multiple heterogeneous machines

The measurement of lots to check process quality is crucial but also a non-added value operation in manufacturing systems. This paper is motivated by semiconductor manufacturing, where metrology tools are expensive, thus limiting metrology capacity which must be optimally used. In a context where multiple heterogeneous machines are sharing a common metrology workshop, the problem of minimising risk while considering metrology capacity arises. An integer linear programming (ILP) model is presented, which corresponds to a multiple-choice knapsack problem. Simple rounding heuristics are proposed, whose results on randomly generated instances are compared with the optimal solutions obtained using a standard solver on the ILP. Additionally, numerical experiments on industrial data are presented and discussed.     

Features in the control of the cross-sectional profile of pistons on out-of-round gauges with model rotation of the spindle

The influence of the centering and adjustment accuracy of the axes of an roundness gauge on the error in the measurement of deviations from roundness is considered. A technique for processing measurement results based on harmonic analysis that makes it possible to compensate for this error as well as errors that have arisen in measurement of a profile with substantial deviations from roundness is proposed. Results of a comparative analysis of the procedural error of the proposed and well-known methods that takes into account the harmonic composition of the measured profiles are presented.     

Computational efficiency of non-linear programming methods on a class of structural problems

Results are presented of an investigation as to the computational efficiency of several non-linear programming algorithms on the constrained structural weight optimization of plane trusses and plane stress plates. The optimization algorithms considered are the methods of sequential linear programming, of feasible directions based on Zoutendijk's procedure P1, and of sequential unconstrained minimizations using the methods of Powell, Stewart, Fletcher–Powell, and Newton. Results are presented on computational efficiency as a function of number of design parameters and as a function of the function evaluation effort to derivative evaluation effort ratio.     

Automatic virtual metrology for wheel machining automation

Total inspection after wheel machining becomes essential for safety consideration and continuous improvement. However, conducting wheel-by-wheel actual metrology is very expensive and time-consuming. A novel idea is to use virtual metrology (VM) that predicts wheel quality based on process data collected from machine tool with a slight supplement of actual metrology data. The technology of automatic virtual metrology (AVM) has been proposed by the authors and successfully deployed in hi-tech industries, such as semiconductor, display and solar cell. The purpose of this study was to propose an approach to apply the AVM system factory-wide to wheel machining automation (WMA) for achieving total inspection of all the precision items of WMA under mass production environment.     

A three-dimensional particle roundness evaluation method

Particle roundness is one of the major shape parameters influencing the micro-and macroscopic mechanical properties of granular materials. Most of the existing particle roundness methods are based on 2D algorithms utilizing particle projections. However, the morphology of a particle projection will be influenced by the subjectively chosen projection angle. Based on the acknowledged Wadell’s definitions of particle corner and particle roundness, an innovative method is proposed to evaluate the 3D roundness of realistic particles in a quantitative and objective manner. This method first reconstructs the particle with a triangular mesh. Then, corner portions are identified by finding the surface vertexes with both a high local curvature and large relative connected area. After corner identification, a sphere-filling method is employed to fill the corner portions with spheres. Finally, the 3D Wadell roundness is computed by comparing the average radius of the filling spheres with the radius of the maximum inscribed sphere. Validation of the proposed 3D roundness evaluation algorithm is conducted by comparing the results of the proposed method with the results from theoretical and other existing approaches. The comparison indicates that the proposed method can be used to accurately and objectively evaluate the roundness of realistic particles.