Distortion-oriented welding path optimization based on elastic net method and genetic algorithm

The optimization of welding path is one of the most combinatorial problems in robotic welding. This paper is focused on the optimization for both productivity and quality in robotic welding. The productivity related scheduling problem is similar to the well-known traveling salesman problem (TSP). An optimization strategy for TSP based on the “elastic net method” (ENM) and artificial neural network is suggested in this paper. So for the most welding points which have less influence on the final distortion, they can be arranged in a better way that the welding robot can reach all the points and the total distance is the minimum. For the rest of the welding points, distortion and residual stress are the two main factors concerned. A thermo-mechanical model is developed to predict residual stress and distortion, and a welding sequence with minimum distortion has been found using a genetic algorithm (GA). These two solutions are integrated into the whole optimal welding path according to “nearest neighborhood criterion”. Finally, the optimization strategy is successfully carried out on a real product.     

Analysis of Hidden Representations by Greedy Clustering

The hidden layer of backpropagation neural networks (NNs) holds the key to the networks' success in solving pattern classification problems. The units in the hidden layer encapsulate the network's internal representations of the outside world described by the input data. this paper, the hidden representations of trained networks are investigated by means simple greedy clustering algorithm. This clustering algorithm is applied to networks have been trained to solve well-known problems: the monks problems, the 5-bit problem and the contiguity problem. The results from applying the algorithm to problems with known concepts provide us with a better understanding of NN learning. These also explain why NNs achieve higher predictive accuracy than that of decision-tree methods. The results of this study can be readily applied to rule extraction from Production rules are extracted for the parity and the monks problems, as well as benchmark data set: Pima Indian diabetes diagnosis. The extracted rules from the Indian diabetes data set compare favorably with rules extracted from ARTMAP NNs terms of predictive accuracy and simplicity.     

General variable neighborhood search algorithm to minimize makespan of the distributed no-wait flow shop scheduling problem

This paper addresses minimizing makespan of the distributed no-wait flow shop scheduling problem where there are several identical factories that work in parallel. There are jobs with series of operations that should be allocated to one of these factories and all operations of jobs should be performed in the allocated factories. After starting the first operation of the job, all other operations of the job should be processed without any interruption or delay. The goal is finding allocation and sequence of jobs on each factory such that the completion time of the last job processed in the system is minimized. For the addressed problem, several heuristics available in the literature developed to solve the classical no-wait flowshop scheduling problem have been extended to the addressed problem. Due to NP-hard nature of the addressed problem, a metaheuristic algorithm called General Variable Neighbourhood Search (GVNS) has been proposed which similar to Variable Neighbourhood Search (VNS) algorithm has shaking procedure and local search algorithm but the severity of the shaking procedure depending on the progress of incumbent solution changes. Also, time-saving strategies that allow focusing on promising movements in the search algorithm, as well as the shaking producer of the proposed GVNS algorithm, are incorporated. The performance of the heuristic algorithms and GVNS thorough comprehensive benchmark problems are presented.     

An Interleaved Artificial Bee Colony algorithm for dynamic optimisation problems

Dynamic optimisation problems (DOPs) have attracted a lot of research attention in recent years due to their practical applications and complexity. DOPs are more challenging than static optimisation problems because the problem information or data is either revealed or changed during the course of an ongoing optimisation process. This requires an optimisation algorithm that should be able to monitor the movement of the optimal point and the changes in the landscape solutions. In this paper, we proposed an Interleaved Artificial Bee Colony (I-ABC) algorithm for DOPs. Artificial Bee Colony (ABC) is a nature inspired algorithm which has been successfully used in various optimisation problems. The proposed I-ABC algorithm has two populations, called ABC1 and ABC2, which worked in an interleaved manner. While ABC1 focused on exploring the search space though using a probabilistic solution acceptance mechanism, ABC2 worked inside ABC1 and focused on the search around the current best solutions by using a greedy mechanism. The proposed algorithm was tested on the Moving Peak Benchmark. The experimental results indicated that the proposed algorithm achieved better results than the compared methods for 8 out of 11 scenarios.     

异形件排样的综合优化算法

本文采用计算机图形学处理技术以及模拟退火算法相结合的方式,按照图形预处理、自动排样、人工交互编辑3个步骤,有效地解决了不规则零件的排样问题,提出了基于三步处理的综合排料优化算法。系统提供的多种算法可方便切换,便于根据不同工艺选择和对结果进行比较。     

Cooperative data fusion of transmission and surface scan for improving limited-angle computed tomography reconstruction

Limited-angle computed tomography allows faster inspection during production, but the reconstruction from limited-angle transmission data is an underdetermined problem which cannot be solved without any prior knowledge of the sample. In this paper, surface data from an optical scan is selected as prior information due to its high accuracy and availability. To incorporate this information, we have developed a new cooperative data fusion model in the compressed sensing framework. The model has been applied to numerical and experimental data and solved with a tailored algorithm. We demonstrate the benefit of the data fusion model and prove the robustness of the algorithm. The results from this study indicate that the data fusion process combines features resolved by both modalities and gives a significant increase in image quality. These improvements enable metrological measurements that are impossible with data acquired with any single modality.     

Shape based reconstruction of experimental data in 3D electrical capacitance tomography

Electrical capacitance tomography (ECT) is a non-invasive and non-destructive imaging technique that uses electrical capacitance measurement at the periphery of an object. The image reconstruction problem in ECT is an ill-posed inverse problem. This paper presents a level set based shape reconstruction method applied to 3D ECT using experimental data. The finite element models have been implemented based on a 32 electrode ECT system to formulate the forward problem. Development of the level set technique enables detection of smaller inclusions and improves the accuracy of boundary shapes of inclusions. The paper uses a shape based method rather than traditional image based methods. The shape-based approach offers several advantages compared with more traditional voxel-based approaches. The incorporation of an intrinsic regularization in the form of a-priori assumptions, regarding the general anatomical structures present in the medium, reduces the dimensionality of the inverse problem and thereby stabilizes the reconstruction. The level set strategy (which is an implicit representation of the shapes) can handle the topological during this reconstruction process. Additionally in this paper a new two-stage level set method has been developed, which shows significant improvement compared with the traditional level set reconstruction algorithm.     

Depth-sensing instrumented indentation with dual sharp indenters: stability analysis and corresponding regularization schemes

In this paper, the stability of the reverse dual indenter algorithms proposed by Chollacoop et al. [Acta Mater. 51 (2003) 3713] to determine the plastic properties of materials has been explored further by using the mathematical theory of inverse problems. To identify the representative stress σ_εr, an explicit form of the condition number has been derived which can be used directly to examine ill-conditioned or ill-posed cases in the inverse problem. Corresponding regularization schemes have been proposed to produce stable results. To determine the plastic properties of materials according to the identified representative stress, the sensitivity matrix properties have been varied to achieve more accurate results. Two methods have been suggested, i.e., introduction of prior knowledge of the model space using the well-known Tikhonov regularization scheme, and systematic investigation of the influence of the tip apex angles on the accuracy of the identified plastic properties. Guidelines for selecting the tip apex angles have also been presented.     

散热器铝型材挤压的数值模拟

采用基于A-L-E算法的HyperXtrude软件,建立有限元分析模型,对散热器铝合金型材挤压过程进行了稳态流动仿真,获得了型材的位移分布和速度分布图,模拟结果与生产实际吻合较好;针对试模出现的问题,对出口速度分布和应力分布进行分析,提出在下模增加阻流台和修改工作带方案,有效地解决了初始模具设计中速度分布不均的问题;最后针对装配后型材平面度达不到要求这一缺陷,对模具工作带进行调整优化,用优化后的模其生产的型材可以装配使用.     

滚柱式超越离合器故障的脉冲诊断方法

滚柱式超越离合器的故障诊断是国内外工程界的难题。介绍利用脉冲诊断方法诊断离合器故障的新方法,并应用基于高斯函数的小波快速算法分离出了故障信号,进一步分析了冲击频率。实验结果表明方法行之有效。     

Design and Kinematics of a Parallel Manipulator for Manufacturing

This paper presents a new model of parallel manipulator for manufacturing, whose mechanism comes from the general Stewart platform which has the advantages of high rigidity and high load capacity. A scheme of the link mechanism is also proposed to make the link structure very simple. The mechanism parameters are optimized by workspace analysis of the parallel mechanism. With the view of kinematics equivalence between parallel mechanism and serial mechanism, by way of hypothesis serial mechanism and branch hypothesis serial mechanism, an efficient kinematics algorithm has been developed. The problem, derived motion produced by the link structure, has also been solved conveniently.     

An efficient MLP-learning algorithm using parallel tangent gradient and improved adaptive learning rates

Poor convergence is a common problem of gradient-based multi-layer perceptron (MLP)-learning algorithms. It is claimed that using a deflecting direction like momentum and adaptive learning rates (ALRs) can improve the convergence performance. For a more reliable and faster MLP learning, we introduce the parallel tangent gradient with adaptive learning rates (PTGALR) algorithm that uses parallel tangent deflecting direction instead of the momentum. Moreover, we use two independent variable learning rates, one for the gradient descent and the other for accelerating direction through the parallel tangent. Also, we propose an improved ALR computation algorithm that calculates the learning rates with a dispensable error oscillation. This adaptation algorithm has two outputs: one is the applied learning rate and the other is used for a better learning rate estimation in the next iteration. Moreover, the proposed ALR computation algorithm models the error function as a one-dimensional quadratic function of the learning rate when it is needed. The implementation results of PTGALR for some well-known binary and real MLP problems show higher and faster convergence with lower oscillations than the similar adaptive learning algorithms.     

应用于组态软件的自调节模糊控制算法设计与实现

现阶段大多数组态软件中自带控制模块的控制算法过于简单，导致控制性能不高，为了解决这个问题，在传统模糊理论基础上提出了一种改进的自调节模糊控制算法，该算法能够根据误差变化实时调节修正因子，并采用VB6.0编程语言将提出的自调节模糊控制算法进行了实现，生成了一个相应的ActivX控件，最后将该ActivX控件加载到LabVIEW组态软件中，为其增加了更加先进的控制算法。实验结果显示：提出改进的自调节模糊控制算法具有良好的控制性能，相应的ActivX控件在LabVIEW组态软件中表现出较好的实时性和可靠性。     

The binary phase diagram evaluation program

The availability of compiled and evaluated information on phase diagrams fulfills many needs in scientific, technological and commercial applications. The well-known compilations published during the late 1950's and 1960's have been in constant use, but a formal compilation and evaluation program which would update and extend these compilations has been lacking, with the result of an ever-increasing gap between published and evaluated data. The Binary Phase Diagram Evaluation Program is intended to rectify this situation during the next several years.     

基于视觉图像传感的精密脉冲TIG焊焊缝跟踪

针对某复杂曲面薄壁不锈钢工件精密脉冲TIG焊中的焊缝跟踪问题 ,本文研究了一种基于视觉传感的高精度、高实时性焊缝跟踪技术。根据脉冲TIG焊的工艺特点 ,该技术通过选择特定波长的滤光片及合理的曝光时刻 ,采用工业CCD摄像机获取可直接分辨出焊缝、熔池和钨极的清晰、放大的焊接区图像。采用VC语言设计的图像处理算法 ,可以快速准确地识别出焊缝中心线 ,提取钨极偏离焊缝中心线的方向和距离 ,驱动步进电机调节焊炬位置 ,实现高精度、高实时性的焊缝跟踪。试验结果表明 ,该技术的单幅图像处理周期小于 12 0ms,能实现焊炬运动方向与焊缝偏差角小于 3 0°的焊缝跟踪 ,满足了复杂曲面的薄壁不锈钢工件的精密焊接要求。     

Nature-inspired computing approach for solving non-linear singular Emden–Fowler problem arising in electromagnetic theory

In this research, the well-known non-linear Lane–Emden–Fowler (LEF) equations are approximated by developing a nature-inspired stochastic computational intelligence algorithm. A trial solution of the model is formulated as an artificial feed-forward neural network model containing unknown adjustable parameters. From the LEF equation and its initial conditions, an energy function is constructed that is used in the algorithm for the optimisation of the networks in an unsupervised way. The proposed scheme is tested successfully by applying it on various test cases of initial value problems of LEF equations. The reliability and effectiveness of the scheme are validated through comprehensive statistical analysis. The obtained numerical results are in a good agreement with their corresponding exact solutions, which confirms the enhancement made by the proposed approach.     

A fuzzy irregular cellular automata-based method for the vertex colouring problem

ABSTRACT

Vertex colouring is among the most important problems in graph theory which has been widely applied across different real-world problems. In vertex colouring problem (VCP), the goal is to assign a distinct colour to each vertex of the graph in such a way that no two adjacent vertices have the same colour. This paper presents a fuzzy irregular cellular automaton (FICA) for finding a near-optimal solution for the VCP. FICA is an extension fuzzy cellular automaton (FCA) in which the cells of the automaton can be arranged in an irregular structure. The aim of the proposed method is to reap the benefits of both FCA and irregular cellular automata while minimising their drawbacks. To evaluate the proposed method, various computer simulations have been conducted on a variety of graphs. The results suggest that the proposed method is able to achieve better results in terms of the minimum number of required colours and the execution time of the algorithm, compared to other peer algorithms.     

Application of inverse techniques to determine heat- transfer coefficients in heat- treating operations

An existing sequential function specification algorithm for the solution of the inverse heat conduction problem (IHCP) has been applied to determine the response of both the surface heat flux and the surface temperature of flat stainless steel samples subjected to water quenching under controlled laboratory conditions that ensured one-dimensional heat flow. From this information, combined convective and radiative heat-transfer coefficients have been obtained as a function of steel surface temperature. The computer code was subsequently modified to solve the IHCP for air-cooled cylindrical carbon steel samples. In the algorithm, the problem is linearized by assuming the thermophysical properties of the steel to be fixed at values from the previous time step while estimating the current surface heat flux, which results in a more efficient code without a severe loss of accuracy. When compared with iterative (“brute force”) methods commonly used in the past, techniques like sequential function specification offer a more robust strategy for solving the IHCP. By including information on future measurements, while solving for the unknown surface heat flux at a particular time, the sequential function specification algorithm effectively prevents over-responses to measured temperatures, and large variations in calculated heat-transfer coefficients, observed when sequential matching is applied, can be reduced. Sensitivity coefficients, a measure of the response of temperature to changes in the unknown surface heat flux which are calculated with this algorithm, can be used to design experiments involving the IHCP effectively.     

基于蚁群算法的无人机协助分发数据算法

基于无人机(unmanned aerial vehicle,UAV)协作通信已成为满足下一代蜂窝用户需求的有效技术,但是UAV的有限能量供给限制UAV的应用.因此提出基于蚁群算法的UAV协助分发数据(ant colony algorithm-based unmanned aerial vehicle assist da...     

Improving harmony search algorithms by using tonal variation: the case of Sudoku and MKP

In this paper we propose an improved Harmony Search (HS) version inspired in the tonal variation of jazz musical improvisation. To evaluate our approach we considered two well-known problems, a Constraint Satisfaction Problem: Sudoku, and a Constraint Satisfaction Optimisation Problem: the Multidimensional Knapsack Problem (MKP). For each problem, we considered an existing baseline HS algorithm to implement our technique: the HS for Sudoku puzzles and, the Adaptive Binary HS for the MKP. The experiments showed that including tonal variation allows HS algorithms to find better quality solutions in both problems.