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Line-feature-based calibration method of structured light plane parameters for robot hand-eye system

OPTICAL ENGINEERING 2013年第3期52卷

作者： Qi, Yuhan Jing, Fengshui Tan, Min Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

For monocular-structured light vision measurement, it is essential to calibrate the structured light plane parameters in addition to the camera intrinsic parameters. A line-feature-based calibration method of structured light plane parameters for a robot hand-eye system is proposed. Structured light stripes are selected as calibrating primitive elements, and the robot moves from one calibrating position to another with constraint in order that two misaligned stripe lines are generated. The images of stripe lines could then be captured by the camera fixed at the robot's end link. During calibration, the equations of two stripe lines in the camera coordinate system are calculated, and then the structured light plane could be determined. As the robot's motion may affect the effectiveness of calibration, so the robot's motion constraints are analyzed. A calibration experiment and two vision measurement experiments are implemented, and the results reveal that the calibration accuracy can meet the precision requirement of robot thick plate welding. Finally, analysis and discussion are provided to illustrate that the method has a high efficiency fit for industrial in-situ calibration. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/***.52.3.037202]

关键词： structured light plane calibration robot hand-eye system monocular structured light vision line-feature equation of stripe line robot's motion constraints

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Neuro-optimal control for a class of unknown nonlinear dynamic systems using SN-DHP technique

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NEUROCOMPUTING 2013年 121卷 218-225页

作者： Wang, Ding Liu, Derong Chinese Acad Sci State Key Lab Management & Control Complex Syst Inst Automat Beijing 100190 Peoples R China

In this paper, the adaptive dynamic programming (ADP) approach is utilized to design a neural-network-based optimal controller for a class of unknown discrete-time nonlinear systems with quadratic cost function. To begin with, a neural network identifier is constructed to learn the unknown dynamic system with stability proof. Then, the iterative ADP algorithm is developed to handle the nonlinear optimal control problem with convergence analysis. Moreover, the single network dual heuristic dynamic programming (SN-DHP) technique, which eliminates the use of action network, is introduced to implement the iterative ADP algorithm. Finally, two simulation examples are included to illustrate the effectiveness of the present approach. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Adaptive critic designs Adaptive dynamic programming Approximate dynamic programming Neural networks Optimal control Reinforcement learning

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Dual iterative adaptive dynamic programming for a class of discrete-time nonlinear systems with time-delays

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NEURAL COMPUTING & APPLICATIONS 2013年第7-8期23卷 1851-1863页

作者： Wei, Qinglai Wang, Ding Zhang, Dehua Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

In this paper, a new dual iterative adaptive dynamic programming (ADP) algorithm is developed to solve optimal control problems for a class of nonlinear systems with time-delays in state and control variables. The idea is to use the dynamic programming theory to solve the expressions of the optimal performance index function and control. Then, the dual iterative ADP algorithm is introduced to obtain the optimal solutions iteratively, where in each iteration, the performance index function and the system states are both updated. Convergence analysis is presented to prove the performance index function to reach the optimum by the proposed method. Neural networks are used to approximate the performance index function and compute the optimal control policy, respectively, for facilitating the implementation of the dual iterative ADP algorithm. Simulation examples are given to demonstrate the validity of the proposed optimal control scheme.

关键词： Adaptive dynamic programming Approximate dynamic programming Adaptive critic designs Optimal control Time-delay Nonlinear systems

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Adaptive optimal control for a class of continuous-time affine nonlinear systems with unknown internal dynamics

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NEURAL COMPUTING & APPLICATIONS 2013年第7-8期23卷 1843-1850页

作者： Liu, Derong Yang, Xiong Li, Hongliang Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

This paper develops an online algorithm based on policy iteration for optimal control with infinite horizon cost for continuous-time nonlinear systems. In the present method, a discounted value function is employed, which is considered to be a more general case for optimal control problems. Meanwhile, without knowledge of the internal system dynamics, the algorithm can converge uniformly online to the optimal control, which is the solution of the modified Hamilton-Jacobi-Bellman equation. By means of two neural networks, the algorithm is able to find suitable approximations of both the optimal control and the optimal cost. The uniform convergence to the optimal control is shown, guaranteeing the stability of the nonlinear system. A simulation example is provided to illustrate the effectiveness and applicability of the present approach.

关键词： Adaptive dynamic programming Reinforcement learning Policy iteration Adaptive optimal control Neural network Online control Nonlinear system

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Index Modulated OFDM with Interleaved Grouping for V2X Communications 17

Index Modulated OFDM with Interleaved Grouping for V2X Commu...

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IEEE 17th International Conference on Intelligent Transportation systems (ITSC)

作者： Cheng, Xiang Wen, Miaowen Yang, Liuqing Li, Yuke Peking Univ Sch Elect Engn & Comp Sci Beijing 100871 Peoples R China Southeast Univ Natl Mobile Commun Res Lab Nanjing Jiangsu Peoples R China S China Univ Technol Sch Elect & Informat Engn Guangzhou 510641 Guangdong Peoples R China Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

ISBN: (纸本)9781479960781

The rapid penetration of intelligent transportation systems (ITS) into the conventional transportation infrastructure urgently calls for high spectral efficiency high reliability communication technology for vehicle-to-vehicle and vehicle-to-infrastructure (V2X) applications. Since orthogonal frequency division multiplexing (OFDM) is widely considered as a promising candidate for such applications, in this paper we propose a novel variation of OFDM for improved spectral efficiency as well as enhanced reliability in V2X channels with correlated frequency-selective fading and inevitable Doppler effects. Our proposed scheme is built upon a recently emerging technique termed as index modulated (IM-) OFDM. However, different from the existing localized subcarrier grouping, we propose interleaved subcarrier grouping. We then carry out analytical and simulated comparisons to demonstrate the merits of this new scheme in terms of both the bit error rate (BER) performance and the maximum achievable rate (MAR) of the overall system, in V2X channels.

关键词： Frequency selective fading

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Vision-based initial weld point positioning using the geometric relationship between two seams

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2013年第9-12期66卷 1535-1543页

作者： Fang, Zaojun Xu, De Tan, Min Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

This paper presents a novel vision-based initial weld point positioning method for the welding systems of container manufacture. The new method is based on the geometric relationship between the two seams at the two different stages of the whole welding task such as the initialization stage and the welding stage. The torch is aligned with the initial weld point manually at the first stage, and the image feature and the parameters of the seam line are computed. At the second stage, the target image feature of the seam line is firstly computed using the geometric relationship, then the alignment of the torch is automated based on the difference between the target and the current image features. The geometric relationship between the two seams is analyzed, and then the realization of the new method including the image processing, the computation of the parameters of the seam line, and the control system design is given in detail. Finally, experiments are well conducted to prove the effectiveness of the proposed initial weld point positioning method.

关键词： Vision Vision control Welding robot Initial weld point positioning Geometric relationship

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Neural-network-based online optimal control for uncertain non-linear continuous-time systems with control constraints

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IET control THEORY AND APPLICATIONS 2013年第17期7卷 2037-2047页

作者： Yang, Xiong Liu, Derong Huang, Yuzhu Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

In this study, an online adaptive optimal control scheme is developed for solving the infinite-horizon optimal control problem of uncertain non-linear continuous-time systems with the control policy having saturation constraints. A novel identifier-critic architecture is presented to approximate the Hamilton-Jacobi-Bellman equation using two neural networks (NNs): an identifier NN is used to estimate the uncertain system dynamics and a critic NN is utilised to derive the optimal control instead of typical action-critic dual networks employed in reinforcement learning. Based on the developed architecture, the identifier NN and the critic NN are tuned simultaneously. Meanwhile, unlike initial stabilising control indispensable in policy iteration, there is no special requirement imposed on the initial control. Moreover, by using Lyapunov's direct method, the weights of the identifier NN and the critic NN are guaranteed to be uniformly ultimately bounded, while keeping the closed-loop system stable. Finally, an example is provided to demonstrate the effectiveness of the present approach.

关键词： adaptive control approximation theory closed loop systems continuous time systems Lyapunov methods neurocontrollers nonlinear control systems optimal control robust control uncertain systems neural network-based online adaptive optimal control uncertain nonlinear continuous-time systems control constraints infinite-horizon optimal control problem control policy saturation constraints identifier-critic architecture Hamilton-Jacobi-Bellman equation approximation uncertain system dynamics critic NN action-critic dual networks reinforcement learning identifier NN policy iteration LyapunovaEuros direct method closed loop system stability

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Numerical adaptive learning control scheme for discrete-time non-linear systems

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IET control THEORY AND APPLICATIONS 2013年第11期7卷 1472-1486页

作者： Wei, Qinglai Liu, Derong Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China

In this study, a novel numerical adaptive learning control scheme based on adaptive dynamic programming (ADP) algorithm is developed to solve numerical optimal control problems for infinite horizon discrete-time non-linear systems. Using the numerical controller, the domain of definition is constrained to a discrete set that makes the approximation errors always exist between the numerical controls and the accurate ones. Convergence analysis of the numerical iterative ADP algorithm is developed to show that the numerical iterative controls can make the iterative performance index functions converge to the greatest lower bound of all performance indices within a finite error bound under some mild assumptions. The stability properties of the system under the numerical iterative controls are proved, which allow the present iterative ADP algorithm to be implemented both on-line and off-line. Finally, two simulation examples are given to illustrate the performance of the present method.

关键词： Domain of Definition Numerical infinite horizon Self tuning Numerical controls Iterative discrete set System stability Converge learning control Approximation error discrete-time performance indicators

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Scene text detection using graph model built upon maximally stable extremal regions

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PATTERN RECOGNITION LETTERS 2013年第2期34卷 107-116页

作者： Shi, Cunzhao Wang, Chunheng Xiao, Baihua Zhang, Yang Gao, Song Chinese Acad Sci State Key Lab Management & Control Complex Syst Inst Automat Beijing 100190 Peoples R China

Scene text detection could be formulated as a bi-label (text and non-text regions) segmentation problem. However, due to the high degree of intraclass variation of scene characters as well as the limited number of training samples, single information source or classifier is not enough to segment text from non-text background. Thus, in this paper, we propose a novel scene text detection approach using graph model built upon Maximally Stable Extremal Regions (MSERs) to incorporate various information sources into one framework. Concretely, after detecting MSERs in the original image, an irregular graph whose nodes are MSERs, is constructed to label MSERs as text regions or non-text ones. Carefully designed features contribute to the unary potential to assess the individual penalties for labeling a MSER node as text or non-text, and color and geometric features are used to define the pairwise potential to punish the likely discontinuities. By minimizing the cost function via graph cut algorithm, different information carried by the cost function could be optimally balanced to get the final MSERs labeling result. The proposed method is naturally context-relevant and scale-insensitive. Experimental results on the ICDAR 2011 competition dataset show that the proposed approach outperforms state-of-the-art methods both in recall and precision. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Scene text detection MSER Graph model Cost function Graph cut

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Design of an off-axis XR photovoltaic concentrator with SMS method

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OPTIK 2013年第22期124卷 5323-5327页

作者： Zhang, M. Dong, H. Geng, Z. J. Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing Peoples R China

We present a novel off-axis XR concentrator design that enables a high efficiency energy collection while avoiding the shadowing problem encountered in the designs of symmetry XR type concentrator. Combining with a 1 cm(2) multi-junction solar cell, the off-axis XR concentrator is able to achieve high optical efficiency of the photovoltaic system. The concentrator design is performed based on the non-imaging optic principle, with one reflective mirror (X) and one refractive lens (R). Both surfaces of the reflective and refractive element are of freeform shapes and fitted as freeform expression in the design analysis. The concentrator has concentration ratio greater than 500x and acceptance angle greater than 2 degrees. A square homogenizing irradiance distribution on the cell is achieved with the help of a suitable rob. The tolerance of the system is analyzed. The results show that the high concentration ratio and greater acceptance angle relax all optical and mechanical tolerances reduce the production and operation cost. (C) 2013 Elsevier GmbH. All rights reserved.

关键词： Solar collectors and concentrators Non-imaging optics Photovoltaic

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