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IEEE/CAA Journal of Automatica Sinica 2022年第6期9卷 1073-1082页

作者： Hefu Ye Yongduan Song Chongqing Key Laboratory of Autonomous Systems Institute of Artificial IntelligenceSchool of AutomationChongqing UniversityChongqing 400044China IEEE

It is nontrivial to achieve global zero-error regulation for uncertain nonlinear *** underlying problem becomes even more challenging if mismatched uncertainties and unknown time-varying control gain are involved,yet certain performance specifications are also *** this work,we present an adaptive control method,which,without the persistent excitation(PE)condition,is able to ensure global zero-error regulation with guaranteed output performance for parametric strict-feedback systems involving fast time-varying parameters in the feedback path and input *** development of our control scheme benefits from generalized-dependent and-dependent functions,a novel coordinate transformation and“congelation of variables”*** theoretical analysis and numerical simulation verify the effectiveness and benefits of the proposed method.

关键词： Adaptive control global property guaranteed performance uncertain nonlinear systems

Graph-geometric message passing via a graph convolution transformer for FKP regression

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Science China(Information Sciences) 2024年第12期67卷 176-190页

作者： Huizhi ZHU Wenxia XU Jian HUANG Baocheng YU Hubei Key Laboratory of Intelligent Robot Wuhan Institute of Technology school of artificial Intelligence and automation Huazhong University of Science and Technology

In this paper, the forward kinematics problem(FKP) of the Gough-Stewart platform(GSP) with six degrees of freedom(6 DoFs) is estimated via deep learning. We propose a graph convolution transformer model by systematically analyzing some challenges encountered with using deep learning regression on largescale data. We attempt to leverage the graph-geometric message as input and singular value decomposition(SVD) orthogonalization for SO(3) manifold learning. This study is the first in which a robot with a sophisticated closed-loop mechanism is described by a graph structure and a specific deep learning model is proposed to solve the FKP of the GSP. Qualitative and quantitative experiments on our dataset demonstrate that our model is feasible and superior to other methods. Our method can guarantee error percentages of translation and rotation less than 1 mm and 1° of 81.9% and 96.7%, respectively.

关键词： deep learning graph-structured learning graph convolution transformer forward kinematics problem Gough-Stewart platform

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Distributed accelerated optimization algorithms:Insights from an ODE

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Science China(Technological Sciences) 2020年第9期63卷 1647-1655页

作者： CHEN RuiJuan YANG Tao CHAI Tian You school of artificial Intelligence and automation Hluazhong University of Science and TechnologyWuhan 430074China State Key Laboratory of Synthetical automation for Process Industries Northeastern UniversityShenyang 110819China

In this paper, we consider the distributed optimization problem, where the goal is to minimize the global objective function formed by a sum of agents' local smooth and strongly convex objective functions, over undirected connected graphs. Several distributed accelerated algorithms have been proposed for solving such a problem in the existing literature. In this paper, we provide insights for understanding these existing distributed algorithms from an ordinary differential equation(ODE) point of view. More specifically, we first derive an equivalent second-order ODE, which is the exact limit of these existing algorithms by taking the small step-size. Moreover, focusing on the quadratic objective functions, we show that the solution of the resulting ODE exponentially converges to the unique global optimal solution. The theoretical results are validated and illustrated by numerical simulations.

关键词： distributed accelerated optimization algorithms exponential convergence ordinary differential equation

Multi-step state-based opacity for unambiguous weighted machines

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Science China(Information Sciences) 2024年第11期67卷 211-221页

作者： Zhipeng ZHANG Chengyi XIA Guoyuan QI Jun FU school of artificial Intelligence Tiangong University school of Control Science and Engineering Tiangong University State Key Laboratory of Synthetical automation for Process Industries Northeastern University

Opacity is a central concept in the issue of privacy security and has been studied extensively in fields such as finite automata, probabilistic automata, and stochastic automata. Here, we investigate the problem of validating multi-step opaque properties through unambiguous weighted machines from the perspective of cyber-physical systems. First, the notion of multi-step state-based opacity for unambiguous weighted machines is presented and defined. It includes two variants of delays with a finite K and infinite steps. Subsequently, the weighted state estimate with K(infinite)-step delay is established by abstracting the possible state set that the system could have through these weighted observations. Meanwhile, to keep the observable weighted sequence consistent between the bidirectional observers, the unobserved weights of the reverse weighted machine are assumed to be reserved. Subsequently, the existence conditions are developed, and the corresponding algorithms, termed the weighted bidirectional observer, are generalized to verify these properties. Finally, several numerical examples are illustrated to demonstrate the effectiveness of the proposed method. Taken together, the current approach will be conducive to a deep understanding of the security and privacy of cyber-physical systems.

关键词： logical dynamical systems weighted state machine state estimation opacity cyber physical systems

Comprehensive benchmark datasets for Amharic scene text detection and recognition

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Science China(Information Sciences) 2022年第6期65卷 77-78页

作者： Wondimu DIKUBAB Dingkang LIANG Minghui LIAO Xiang BAI school of Electronic Information and Communication Huazhong University of Science and Technology school of artificial Intelligence and automation Huazhong University of Science and Technology

Ethiopic/Amharic script is one of the oldest African writing systems, which serves at least 23 languages(e.g., Amharic,Tigrinya) in East Africa for more than 120 million *** Amharic writing system, Abugida, has 282 syllables,15 punctuation marks, and 20 numerals. The Amharic syllabic matrix is derived from 34 base graphemes/consonants by adding up to 12 appropriate diacritics or vocalic markers to the characters. Unlike Latin alphabets,

关键词： Amharic script Scene text Text detection Text recognition Amharic text

Equilibrium Strategy of the Pursuit-Evasion Game in Three-Dimensional Space

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IEEE/CAA Journal of Automatica Sinica 2024年第2期11卷 446-458页

作者： Nuo Chen Linjing Li Wenji Mao school of artificial Intelligence University of Chinese Academy of SciencesBeijing 100049 Institute of automation Chinese Academy of SciencesBeijing 100190China

The pursuit-evasion game models the strategic interaction among players, attracting attention in many realistic scenarios, such as missile guidance, unmanned aerial vehicles, and target defense. Existing studies mainly concentrate on the cooperative pursuit of multiple players in two-dimensional pursuit-evasion games. However, these approaches can hardly be applied to practical situations where players usually move in three-dimensional space with a three-degree-of-freedom control. In this paper,we make the first attempt to investigate the equilibrium strategy of the realistic pursuit-evasion game, in which the pursuer follows a three-degree-of-freedom control, and the evader moves freely. First, we describe the pursuer's three-degree-of-freedom control and the evader's relative coordinate. We then rigorously derive the equilibrium strategy by solving the retrogressive path equation according to the Hamilton-Jacobi-Bellman-Isaacs(HJBI) method, which divides the pursuit-evasion process into the navigation and acceleration phases. Besides, we analyze the maximum allowable speed for the pursuer to capture the evader successfully and provide the strategy with which the evader can escape when the pursuer's speed exceeds the threshold. We further conduct comparison tests with various unilateral deviations to verify that the proposed strategy forms a Nash equilibrium.

关键词： Differential game equilibrium strategy pursuit-evasion game threedegree-of-freedom control

Repeatable adaptive keypoint detection via self-supervised learning

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Science China(Information Sciences) 2022年第11期65卷 123-147页

作者： Pei YAN Yihua TAN Yuan TAI National Key Laboratory of Science & Technology on Multi-spectral Information Processing School of Artificial Intelligence and Automation Huazhong University of Science and Technology

Keypoint-based matching is a fundamental technology for different computer vision tasks, in which keypoint detection is a crucial step and directly affects the entire performance. Based on deep learning approaches, the learning-based keypoint detectors have been significantly developed. To further improve the accuracy of high-level matching tasks, the extracted keypoints should provide more accurate point-to-point correspondences and maintain a uniform spatial distribution. Based on this idea, a self-supervised learning method of keypoint detection named repeatable adaptive point is proposed. This method consists of a selfsupervised objective and an optimization algorithm. The objective maximizes the repeatability measure with the sparsity constraint of keypoints. This sparsity constraint is formulated by combining the non-maximum suppression operation and the penalty function of keypoint number, which generally makes keypoints have a uniform spatial distribution. A novel approximate alternate optimization algorithm is proposed to maximize the above objective, whose convergence is proved in theory. The proposed detector is “adaptive” because the combinations of it and some existing descriptors can adapt to high-level matching tasks with a fast convergence speed. Specifically, the combinations of it and SuperPoint/HardNet descriptors achieve stateof-the-art accuracy on three high-level tasks based on image matching, namely homography estimation,camera pose estimation, and three-dimensional reconstruction. Furthermore, the proposed method converges faster on new scenes compared with the state-of-the-art method that jointly optimizes the detector and the descriptor.

关键词： keypoint detection convolutional neural network image matching self-supervised learning repeatable

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Nested Saturated Control of Uncertain Complex Cascade Systems Using Mixed Saturation Levels

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IEEE/CAA Journal of Automatica Sinica 2024年第5期11卷 1163-1174页

作者： Meng Li Zhigang Zeng Wuhan National Laboratory for Optoelectronics Wuhan 430074 school of artificial Intelligence and automation Huazhong University of Science and TechnologyWuhan 430074China school of artificial Intelligence and automation Huazhong University of Science and TechnologyWuhan 430074 Key Laboratory of Image Processing and Intelligent Control of Education Ministry of China Wuhan 430074China

This study addresses the problem of global asymptotic stability for uncertain complex cascade systems composed of multiple integrator systems and non-strict feedforward nonlinear systems. To tackle the complexity inherent in such structures, a novel nested saturated control design is proposed that incorporates both constant saturation levels and state-dependent saturation levels. Specifically, a modified differentiable saturation function is proposed to facilitate the saturation reduction analysis of the uncertain complex cascade systems under the presence of mixed saturation levels. In addition, the design of modified differentiable saturation function will help to construct a hierarchical global convergence strategy to improve the robustness of control design scheme. Through calculation of relevant inequalities, time derivative of boundary surface and simple Lyapunov function,saturation reduction analysis and convergence analysis are carried out, and then a set of explicit parameter conditions are provided to ensure global asymptotic stability in the closed-loop systems. Finally, a simplified system of the mechanical model is presented to validate the effectiveness of the proposed method.

关键词： method saturation differentiable

Modeling and adaptive control for a spatial flexible spacecraft with unknown actuator failures

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Science China(Information Sciences) 2021年第5期64卷 177-192页

作者： Zhijie LIU Zhiji HAN Zhijia ZHAO Wei HE Key Laboratory of Knowledge automation for Industrial Processes of Ministry of Education School of Automation and Electrical Engineering Institute of Artificial IntelligenceUniversity of Science and Technology Beijing school of Mechanical and Electrical Engineering Guangzhou University Shunde Graduate school of University of Science and Technology Beijing

In this paper, we address simultaneous control of a flexible spacecraft’s attitude and vibrations in a three-dimensional space under input disturbances and unknown actuator failures. Using Hamilton’s principle, the system dynamics is modeled as an infinite dimensional system captured using partial differential equations. Moreover, a novel adaptive fault tolerant control strategy is developed to suppress the vibrations of the flexible panel in the course of the attitude stabilization. To determine whether the system energies,angular velocities and transverse deflections, remain bounded and asymptotically decay to zero in the case wherein the number of actuator failures is infinite, a Lyapunov-based stability analysis is conducted. Finally,extensive numerical simulations are performed to demonstrate the performance of the proposed adaptive control strategy.

关键词： adaptive control actuator failures infinite-dimensional systems flexible spacecraft fault tolerant control

Optimal Resource Allocation and Feasible Hexagonal Topology for Cyber-Physical Systems

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Journal of Systems Science & Complexity 2023年第4期36卷 1583-1608页

作者： LIU Yifa CHENG Long State Key Laboratory of Multimodal artificial Intelligence Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China school of artificial Intelligence University of Chinese Academy of SciencesBeijing 100049China

Networked cyber-physical systems are facing serious security threats from malicious *** is noted that the networked cyber-physical system should take defense measures into account at the beginning of its *** the conservative defensive perspective,this paper proposes a robust optimal defense resource allocation strategy to reduce the maximum possible losses of the networked cyber-physical system caused by potential ***,based on the robust optimal allocation strategy,it can be proved that the topology of the networked cyber-physical system has a great influence on the loss *** order to further improve security,the effects of adding redundant connections are ***,by taking geographical knowledge into account,a hexagonal construction scheme is proposed for providing a geographically-feasible and economically-viable solution for building networked cyber-physical systems,where the loss function has a cubic decay.

关键词： Cyber-physical system hexagonal city planning optimization resource allocation