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Tool-path continuity determination based on machine learning method

INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2022年第1-2期119卷 403-420页

作者： Zhou, Bo Tian, Tongtong Zhao, Jibin Liu, Dianhai Chinese Acad Sci Shenyang Inst Automat Shenyang 110016 Peoples R China Chinese Acad Sci Inst Robot & Intelligent Mfg Shenyang 110169 Peoples R China

Computer-aided manufacturing (CAM) software outputs machining data by encoding a tool-path into a series of G-codes which are composed of various lengths of line segments. The discontinuities of these line segments may cause inefficiency for computer numerical control (CNC) system. To achieve high-speed continuous motions, corner smoothing algorithms based on look-ahead methods are widely used. However, it is difficult to meet smoothing trajectories in real-time requirements. Based on machine learning method, in this paper, a support vector machine (SVM) system is presented for directly outputting classification results of the various geometric continuities at the transition corners. The feature values used for generating continuity classification model are extracted from sampling paths of the previous publication work: the machining parameters, length, fairness criteria, the root mean square (RMS) contour errors, and dominant stage type of movement of each sampling path are calculated. The acceleration/deceleration (ACC/DEC) feedrate planning scheme is used to determine the feedrate at the transition corners. Simulations and experiments show that the proposed algorithm can realize accurately and efficiently continuity classification in real-time requirements under the conditions of machining accuracy.

关键词： smoothing algorithm Machine learning Support vector machine Continuity Parametric curve

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A method for removing etalon oscillations from THz time-domain spectra

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OPTICS COMMUNICATIONS 2007年第2期280卷 291-295页

作者： Naftaly, M. Miles, R. E. Univ Leeds Sch Elect & Elect Engn Leeds LS2 9JT W Yorkshire England

We present a simple algorithm for removing or reducing spurious oscillations in the THz spectra which result from secondary reflection peaks in samples or optical elements. The algorithm utilizes the fact that a THz time-domain trace containing secondary peaks can be represented as a convolution of the primary peak and two or more delta functions. The algorithm is applicable for samples which are sufficiently thick that the reflection peak does not overlap with the primary peak, and that do not have strong absorption or dispersion. (C) 2007 Elsevier B.V. All rights reserved.

关键词： THz time-domain spectroscopy spurious oscillations secondary reflections smoothing algorithm

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PROPERTIES OF A CLASS OF NONLINEAR TRANSFORMATIONS OVER EUCLIDEAN JORDAN ALGEBRAS WITH APPLICATIONS TO COMPLEMENTARITY PROBLEMS

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NUMERICAL FUNCTIONAL ANALYSIS AND OPTIMIZATION 2009年第7-8期30卷 799-821页

作者： Lu, Nan Huang, Zheng-Hai Han, Jiye Tianjin Univ Sch Sci Dept Math Tianjin 300072 Peoples R China Chinese Acad Sci Inst Appl Math Acad Math & Syst Sci Beijing Peoples R China

For any function phi from R-r to R-r, Tao and Gowda [Math. Oper. Res., 30 (2005), pp. 985-1004] introduced a corresponding nonlinear transformation R-phi over a Euclidean Jordan algebra (which is called a relaxation transformation) and established some useful relations between phi and R-phi. In this paper, we further investigate some interconnections between properties of phi and properties of R-phi, including the properties of continuity, (local) Lipschitz continuity, directional differentiability, (continuous) differentiability, semismoothness, monotonicity, the P-0-property, and the uniform P-property. As an application, we investigate the symmetric cone complementarity problem with a relaxation transformation. A property of the solution set of this class of problems is given. We also investigate a smoothing algorithm for solving this class of problems and show that the algorithm is globally convergent under an assumption that the solution set of the problem concerned is nonempty.

关键词： Euclidean Jordan algebra Relaxation transformation smoothing algorithm Symmetric cone complementarity problem

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Hidden hybrid Markov/semi-Markov chains

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COMPUTATIONAL STATISTICS & DATA ANALYSIS 2005年第3期49卷 663-688页

作者： Guédon, Y Univ Montpellier 2 INRA CNRS UMRCIRAD F-34398 Montpellier France

Models that combine Markovian states with implicit geometric state occupancy distributions and semi-Markovian states with explicit state occupancy distributions, are investigated. This type of model retains the flexibility of hidden semi-Markov chains for the modeling of short or medium size homogeneous zones along sequences but also enables the modeling of long zones with Markovian states. The forward-backward algorithm, which in particular enables to implement efficiently the E-step of the EM algorithm, and the Viterbi algorithm for the restoration of the most likely state sequence are derived. It is also shown that macro-states, i.e. series-parallel networks of states with common observation distribution, are not a valid alternative to semi-Markovian states but may be useful at a more macroscopic level to combine Markovian states with semi-Markovian states. This statistical modeling approach is illustrated by the analysis of branching and flowering patterns in plants. (c) 2004 Elsevier B.V. All rights reserved.

关键词： forward-backward algorithm hidden Markov chain hidden semi-Markov chain macro-state plant structure analysis smoothing algorithm viterbi algorithm

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Two aggregate-function-based algorithms for analysis of 3D frictional contact by linear complementarity problem formulation

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2005年第50-52期194卷 5139-5158页

作者： Zhang, HW He, SY Li, XS Dalian Univ Technol Dept Engn Mech State Key Lab Struct Anal & Ind Equipment Dalian 116024 Peoples R China Dalian Univ Foreign Languages Ctr Comp Dalian 116002 Peoples R China

Three dimensional frictional contact is formulated as linear complementarity problem (LCP) by using the parametric variational principle and quadratic programming method. Two aggregate-function-based algorithms, called respectively as self-adjusting interior point algorithm and aggregate function smoothing algorithm, are proposed for the solution of the LCP derived from the contact problems. A nonlinear finite element code is developed for numerical analysis of 3D multi-body contact problems. Four numerical examples are computed to demonstrate the applicability and computational efficiency of the methods proposed. (c) 2005 Elsevier B.V. All rights reserved.

关键词： 3D frictional contact problem linear complernentarity problems aggregate function interior point algorithm smoothing algorithm

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An Improved Unsupervised Approach to Word Segmentation

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China Communications 2015年第7期12卷 82-95页

作者： WANG Hanshi HAN Xuhong LIU Lizhen SONG Wei YUAN Mudan Information and Engineering College Capital Normal University Beijing Bayi High School

ESA is an unsupervised approach to word segmentation previously proposed by Wang, which is an iterative process consisting of three phases: Evaluation, Selection and Adjustment. In this article, we propose Ex ESA, the extension of ESA. In Ex ESA, the original approach is extended to a 2-pass process and the ratio of different word lengths is introduced as the third type of information combined with cohesion and separation. A maximum strategy is adopted to determine the best segmentation of a character sequence in the phrase of Selection. Besides, in Adjustment, Ex ESA re-evaluates separation information and individual information to overcome the overestimation frequencies. Additionally, a smoothing algorithm is applied to alleviate sparseness. The experiment results show that Ex ESA can further improve the performance and is time-saving by properly utilizing more information from un-annotated corpora. Moreover, the parameters of Ex ESA can be predicted by a set of empirical formulae or combined with the minimum description length principle.

关键词： word segmentation character sequence smoothing algorithm maximum strategy

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An Intelligent Deep Learning-Based Direction-of-Arrival Estimation Scheme Using Spherical Antenna Array With Unknown Mutual Coupling

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IEEE ACCESS 2020年 8卷 179259-179271页

作者： Famoriji, Oluwole John Ogundepo, Oludare Y. Qi, Xiaokang Zhejiang Univ Inst Marine Elect & Intelligent Syst Ocean Coll Zhoushan 316021 Peoples R China Fed Univ Petr Resources Dept Elect & Elect Engn Effurun 562101 Warri Nigeria Zhejiang Univ Lab Appl Res Elect ARE Hangzhou 310027 Peoples R China

Spherical antenna array (SAA) has become highly attractive where hemispherical scan coverage is required as it can provide uniform directivity in all the scan directions. Various direction-of-arrival (DoA) estimation methods suffer from different problems, such as low accuracies in mismatched conditions, high computational complexity and poor estimation in a harsh environment. Another critical concern is mutual coupling (MC) characteristics between the array elements. These problems affect the quality of the navigation signal in harsh environments. This paper presents a robust DoA estimation and mutual coupling compensation technique based on convolutional neural network (CNN) for Spherical Array. Spherical harmonic decomposition (SHD) is used to facilitate feature extraction in two sets, which contains different features about the elevation and azimuth of the source for DoA estimation. The features serve as input to the learning technique for separate estimation of elevation and azimuth, which consequently reduce computational complexity as against the joint estimation of DoA. Learning methods for DoA estimation with few frames and dense search grids within the spherical array configuration are presented. To solve the MC error, the DoA estimation scheme is also used to obtain accurate spectrum peak in the multipath scenario with unknown MC and sharper spectrum peak via the unique structure of the MC matrix and spatial smoothing algorithms. In all, experimental results, which is the ground truth to test any procedure, show the effectiveness, validity, and potential practical application of the proposed technique.

关键词： Direction-of-arrival estimation Estimation Mutual coupling Antenna arrays Feature extraction Harmonic analysis Azimuth Spherical arrays DoA estimation mutual coupling learning method spherical harmonic decomposition CNN smoothing algorithm

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A continuous RRT*-based path planning method for non-holonomic mobile robots using B-spline curves

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JOURNAL OF AMBIENT INTELLIGENCE AND HUMANIZED COMPUTING 2022年第7期14卷 8693-8702页

作者： Eshtehardian, S. A. Khodaygan, S. Sharif Univ Technol Dept Mech Engn Tehran Iran

Rapidly exploring random trees (RRT) are sampling-based approaches being widely applied for path planning of mobile robots. Since the output of these algorithms usually is a stream of discrete lines involving discontinuity at the linking points, kinematic constraints restrict the robot's movements. Consequently, robots may not pass discrete points in the path correctly. Hence, the using CAGD (Computer-Aided Geometry Design) curves can run simultaneously alongside those algorithms or may run after that to make a smooth path and that's the way in which non-holonomic constraints can be considered perfect and robots can be droved autonomously across them about the collision detection method which executed by the main sampling-based algorithm like RRT*. In this paper, an approach based on the combination of RRT* and B-spline is proposed for smoothing the path which is generated by RRT*-based algorithms, which are one of the most famous groups of algorithms in artificial intelligence. Some new functions are added to the outcome of the RRT* algorithm. To avoid collision in the generated path, some corrections are also provided. Finally, for illustrating the efficiency of the proposed method, the algorithm is implemented in the simulation environment of Webots(R) and for verification, the obtained results are compared and discussed.

关键词： Path planning RRT algorithm smoothing algorithm Non-holonomic mobile robots B-spline curves

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Walking Step Length Estimation Using Waist-Mounted Inertial Sensors With Known Total Walking Distance

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IEEE ACCESS 2021年 9卷 85476-85487页

作者： Thanh Tuan Pham Suh, Young Soo Univ Ulsan Dept Elect Elect & Comp Engn Ulsan 44610 South Korea

This paper presents a new constrained optimization-based smoothing algorithm for walking step length estimation using waist-mounted inertial sensors, where the total walking distance is known. The walking trajectory is estimated by double integrating acceleration. Due to sensor noises, the walking step length estimation accuracy degrades as the walking distance becomes longer. To tackle this problem, we introduce a known distance straight-line walking trajectory constraint and a constant speed constraint to the smoothing algorithm. These constraints reduce the walking step estimation accuracy degradation even for long walking distance. Two experiments are conducted to evaluate the pedestrian trajectory and walking step length estimation accuracy. The accuracy of a 20 m walking trajectory estimation has been investigated in the first experiment. This experiment compares the estimated position and velocity with Lidar-based references. The second experiment is to demonstrate the usefulness of the proposed walking step length estimation method. The result shows that the average of mean relative errors is 0.6801% for three different walking speed levels. The proposed method can be applied to generate training data for walking step length estimation without requiring spatial infrastructure.

关键词： smoothing algorithm constrained optimization inertial sensors walking step length estimation trajectory estimation

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THE ORTHOGONAL V-SYSTEM DETRENDED FLUCTUATION ANALYSIS

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FLUCTUATION AND NOISE LETTERS 2011年第2期10卷 189-206页

作者： Lin, Aijing Shang, Pengjian Ma, Hui Beijing Jiaotong Univ Dept Math Sch Sci Beijing 100044 Peoples R China Tsinghua Univ Res Inst Informat Technol Beijing 100084 Peoples R China

The Detrended Fluctuation Analysis (DFA) and its extensions (MF-DFA) have been proposed as robust techniques to determine possible long-range correlations in self-affine signals. However, many studies have reported the susceptibility of DFA to trends which give rise to spurious crossovers and prevent reliable estimations of the scaling exponents. Lately, several modifications of the DFA method have been reported with many different techniques for eliminating the monotonous and periodic trends. In this study, a smoothing algorithm based on the Orthogonal V-system (OVS) is proposed to minimize the effect of power-law trends, periodic trends, assembled trends and piecewise function trends. The effectiveness of the new method is demonstrated on monofractal data and multifractal data corrupted with different trends.

关键词： Orthogonal V-system (OVS) Detrended Fluctuation Analysis (DFA) crossover trend smoothing algorithm

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