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Unknown system dynamics estimator-based impedance control for lower limb exoskeleton with enhanced performance

Control Theory and Technology 2024年第1期22卷 56-68页

作者： Wenhao zhang Peng Song Mingying Wu Qiang Li xinmin Mo Pingxin Ji Northwest Institute of Mechanical and Electrical Engineering Xianyang712099ShaanxiChina Xi’an Exo-Smart Dynamics Technology Ltd. Xi’an712046ShaanxiChina Department of Mechanical and Engineering Beijing Institute of TechnologyBeijing100081China

In this article, an unknown system dynamics estimator-based impedance control method is proposed for the lower limb exoskeleton to stimulate the tracking flexibility with the terminal target position when suffering parametric inaccuracies and unexpected disturbances. To reinforce the robust performance, via constructing the filtering operation-based dynamic relation, i.e., invariant manifold, the unknown system dynamics estimators are employed to maintain the accurate perturbation identification in both the hip and knee subsystem. Besides, a funnel control technique is designed to govern the convergence process within a minor overshoot and a higher steady-state precision. Meanwhile, an interactive complaint result can be obtained with the aid of the impedance control, where the prescribed terminal trajectory can be adjusted into the interaction variable-based target position by the force–position mapping, revealing the dynamic influence between the impedance coefficient (stiffness and damping) and the adjusted position magnitude. A sufficient stability analysis verifies the ultimately uniformly bounded results of all the error signals, and even the angle errors can be regulated within the predefined funnel boundary in the whole convergence. Finally, some simulations are provided to demonstrate the validity and superiority including the enhanced interaction flexibility and robustness.

关键词： Trajectory tracking Invariant manifold Funnel control Impedance control Lower limb exoskeleton

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Gradient-based algorithms for multi-objective bi-level optimization

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Science China Mathematics 2024年第6期67卷 1419-1438页

作者： xinmin Yang Wei Yao Haian Yin Shangzhi Zeng Jin zhang National Center for Applied Mathematics in Chongqing Chongqing401331China School of Mathematical Sciences Chongqing Normal UniversityChongqing401331China Department of Mathematics Southern University of Science and TechnologyShenzhen518055China National Center for Applied Mathematics Shenzhen Shenzhen518000China Department of Mathematics and Statistics University of VictoriaVictoriaBCV8W 2Y2Canada

Multi-objective bi-level optimization(MOBLO)addresses nested multi-objective optimization problems common in a range of applications.However,its multi-objective and hierarchical bi-level nature makes it notably complex.Gradient-based MOBLO algorithms have recently grown in popularity,as they effectively solve crucial machine learning problems like meta-learning,neural architecture search,and reinforcement learning.Unfortunately,these algorithms depend on solving a sequence of approximation subproblems with high accuracy,resulting in adverse time and memory complexity that lowers their numerical efficiency.To address this issue,we propose a gradient-based algorithm for MOBLO,called gMOBA,which has fewer hyperparameters to tune,making it both simple and efficient.Additionally,we demonstrate the theoretical validity by accomplishing the desirable Pareto stationarity.Numerical experiments confirm the practical efficiency of the proposed method and verify the theoretical results.To accelerate the convergence of gMOBA,we introduce a beneficial L2O(learning to optimize)neural network(called L2O-gMOBA)implemented as the initialization phase of our gMOBA algorithm.Comparative results of numerical experiments are presented to illustrate the performance of L2O-gMOBA.

关键词： multi-objective bi-level optimization convergence analysis Pareto stationary learning to optimize

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Multicolor Ramsey Number of Stars Versus a Path

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Journal of Mathematical Research with Applications 2024年第4期 465-469页

作者： Xuejun zhang xinmin HOU School of Data Science University of Science and Technology of China School of Mathematical Sciences University of Science and Technology of China CAS Key Laboratory of Wu Wen-Tsun Mathematics University of Science and Technology of China Hefei National Laboratory University of Science and Technology of China

For given simple graphs H1,H2,...,Hc,the multicolor Ramsey number R（H1,H2,...,Hc） is defined as the smallest positive integer n such that for an arbitrary edge-decomposition{Gi}ci=1of the complete graph K_n,at least one Gihas a subgraph isomorphic to Hi.Let m,n1,n2,...,nc be positive integers andΣ=Σci=1（ni-1）.Some bounds and exact values of R(K1,n1,...,K1,nc,Pm) have been obtained in literature.Wang （Graphs Combin.,2020） conjectured that ifΣ?≡0 （mod m-1） andΣ+1≥（m-3）2,then R(K1,n1,...,K1,nc,Pm)=Σ+m-1.In this note,we give a new lower bound and some exact values of R(K1,n1,...,K1,nc,Pm) provided m≤Σ,Σ≡k （mod m-1）,and 2≤k≤m-2.These results partially confirm Wang’s conjecture.

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Reinforcement learning-based cost-sensitive classifier for imbalanced fault classification

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Science China(Information Sciences) 2023年第11期66卷 113-126页

作者： xinmin zhang Saite FAN Zhihuan SONG State Key Laboratory of Industrial Control Technology College of Control Science and Engineering Zhejiang University

Fault classification plays a crucial role in the industrial process monitoring domain. In the datasets collected from real-life industrial processes, the data distribution is usually imbalanced. The datasets contain a large amount of normal data(majority) and only a small amount of faulty data(minority); this phenomenon is also known as the imbalanced fault classification problem. To solve the imbalanced fault classification problem, a novel reinforcement learning(RL)-based cost-sensitive classifier(RLCC) based on policy gradient is proposed in this paper. In RLCC, a novel cost-sensitive learning strategy based on policy gradient and the actor-critic of RL is developed. The novel cost-sensitive learning strategy can adaptively learn the cost matrix and dynamically yield the sample weights. In addition, RLCC uses a newly designed reward to train the sample weight learner and classifier using an alternating iterative approach. The alternating iterative approach makes RLCC highly flexible and effective in solving the imbalanced fault classification problem.The effectiveness and practicability of the proposed RLCC method are verified through its application in a real-world dataset and an industrial process benchmark.

关键词： imbalanced fault classification fault diagnosis industrial process monitoring deep reinforcement learning cost-sensitive learning policy gradient sample weights

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Saturation Estimation with Complex Electrical Conductivity for Hydrate-Bearing Clayey Sediments:An Experimental Study

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Journal of Ocean University of China 2024年第1期23卷 173-189页

作者： XING Lanchang zhang Shuli zhang Huanhuan WU Chenyutong WANG Bin LAO Liyun WEI Wei HAN Weifeng WEI Zhoutuo GE xinmin DENG Shaogui College of Control Science and Engineering China University of Petroleum(East China)Qingdao 266580China School of Water Energy and EnvironmentCranfield UniversityCranfield MK430ALUnited Kingdom Department of Alternative Energy PetroChina Research Institute of Petroleum Exploration&DevelopmentLangfang 065007China School of Geosciences China University of Petroleum(East China)Qingdao 266580China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266071China

Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S_(h))models for reservoir evaluation and monitoring.The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz.The effects of clay and Sh on the complex conductivity were analyzed.A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer(EDL),respectively.The quadrature conductivity increases with the clay content up to 10%because of the increased surface site density of counterions in EDL.Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90.Three sets of models for Sh evaluation were developed.The model based on the Simandoux equation outperforms Archie’s formula,with a root-mean-square error(E_(RMS))of 1.8%and 3.9%,respectively,highlighting the clay effects on the in-phase conductivity.The fre-quency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance(E_(RMS)=11.6%and 13.2%,re-spectively)due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements.The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra.One pair of inverted Cole-Cole parameters,i.e.,characteristic time and chargeability,is employed to predict S_(h) with an E_(RMS) of 5.05%and 9.05%,respectively.

关键词： gas hydrate complex electrical conductivity hydrate-bearing clayey sediment hydrate saturation Simandoux equation frequency dispersion Cole-Cole formula

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Identification of important factors influencing nonlinear counting systems

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Frontiers of Information Technology & Electronic Engineering 2022年第1期23卷 123-133页

作者： xinmin zhang Jingbo WANG Chihang WEI Zhihuan SONG State Key Laboratory of Industrial Control Technology College of Control Science and EngineeringZhejiang UniversityHangzhou310027China

Identifying factors that exert more influence on system output from data is one of the most challenging tasks in science and engineering.In this work,a sensitivity analysis of the generalized Gaussian process regression(SA-GGPR)model is proposed to identify important factors of the nonlinear counting system.In SA-GGPR,the GGPR model with Poisson likelihood is adopted to describe the nonlinear counting system.The GGPR model with Poisson likelihood inherits the merits of nonparametric kernel learning and Poisson distribution,and can handle complex nonlinear counting systems.Nevertheless,understanding the relationships between model inputs and output in the GGPR model with Poisson likelihood is not readily accessible due to its nonparametric and kernel structure.SA-GGPR addresses this issue by providing a quantitative assessment of how different inputs affect the system output.The application results on a simulated nonlinear counting system and a real steel casting-rolling process have demonstrated that the proposed SA-GGPR method outperforms several state-of-the-art methods in identification accuracy.

关键词： Important factors Nonlinear counting system Generalized Gaussian process regression Sensitivity analysis Steel casting-rolling process

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Data-driven soft sensors in blast furnace ironmaking:a survey

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Frontiers of Information Technology & Electronic Engineering 2023年第3期24卷 327-354页

作者： Yueyang LUO xinmin zhang Manabu KANO Long DENG Chunjie YANG Zhihuan SONG State Key Laboratory of Industrial Control Technology College of Control Science and EngineeringZhejiang UniversityHangzhou 310027China Department of Systems Science Kyoto UniversityKyoto 606-8501Japan Research Institute Baoshan Iron&Steel Co.Ltd.Shanghai 201900China

The blast furnace is a highly energy-intensive,highly polluting,and extremely complex reactor in the ironmaking process.Soft sensors are a key technology for predicting molten iron quality indices reﬂecting blast furnace energy consumption and operation stability,and play an important role in saving energy,reducing emissions,improving product quality,and producing economic benefits.With the advancement of the Internet of Things,big data,and artificial intelligence,data-driven soft sensors in blast furnace ironmaking processes have attracted increasing attention from researchers,but there has been no systematic review of the data-driven soft sensors in the blast furnace ironmaking process.This review covers the state-of-the-art studies of data-driven soft sensors technologies in the blast furnace ironmaking process.Specifically,wefirst conduct a comprehensive overview of various data-driven soft sensor modeling methods(multiscale methods,adaptive methods,deep learning,etc.)used in blast furnace ironmaking.Second,the important applications of data-driven soft sensors in blast furnace ironmaking(silicon content,molten iron temperature,gas utilization rate,etc.)are classified.Finally,the potential challenges and future development trends of data-driven soft sensors in blast furnace ironmaking applications are discussed,including digital twin,multi-source data fusion,and carbon peaking and carbon neutrality.

关键词： Soft sensors Data-driven modeling Machine learning Deep learning Blast furnace Ironmaking

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Intelligent identification of oceanic eddies in remote sensing data via Dual-Pyramid UNet

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Atmospheric and Oceanic Science Letters 2023年第4期16卷 29-36页

作者： Nan Zhao Baoxiang Huang xinmin zhang Linyao Ge Ge Chen School of Computer Science and Technology Qingdao UniversityQingdaoChina Laboratory for Regional Oceanography and Numerical Modeling Laoshan LaboratoryQingdaoChina School of Marine Technology Institute for Advanced Ocean StudyOcean University of ChinaQingdaoChina

海洋涡旋是大洋中重要的组成部分,对海洋能量和物质的输送至关重要.海洋涡旋的检测和表征无论是对于海洋气象学,海洋声学还是海洋生物学等领域都具有重要的研究价值.本文基于UNet架构,并结合金字塔分割注意力(PSA)模块和空洞空间卷积池... 详细信息

海洋涡旋是大洋中重要的组成部分,对海洋能量和物质的输送至关重要.海洋涡旋的检测和表征无论是对于海洋气象学,海洋声学还是海洋生物学等领域都具有重要的研究价值.本文基于UNet架构,并结合金字塔分割注意力(PSA)模块和空洞空间卷积池化金字塔(ASPP)构造了Dual-Pyramid UNet模型,以平面异常和海表面温度数据中进行海洋涡旋的识别.实验在北大西洋和南大西洋两个涡旋活跃区域进行并选用多个评价指标对识别结果进行评价以证明模型的优异性能.

关键词：海洋涡旋识别深度学习金字塔分割注意空洞空间卷积池化金字塔 U型网络架构

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First attempt of barrier functions for Caputo's fractional-order nonlinear dynamical systems

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Science China(Information Sciences) 2023年第7期66卷 313-314页

作者： Zheren ZHU Pengfei HUANG xinmin zhang Yi CHAI Zhihuan SONG College of Control Science and Engineering Zhejiang University State Key Laboratory of Industrial Control Technology School of Automation Chongqing University Key Laboratory of Complex System Safety and Control(Chongqing University) Ministry of Education

Dear editor, In the past two decades, scholars have begun to use system dynamical models and state motions to study the safety of a system to realize the analysis, diagnosis, and control of system safety. This safety ...

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Occurrence of internally ovipositing non-agaonid wasps and pollination mode of the associated agaonid wasps

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Plant Diversity 2017年第3期39卷 130-134页

作者： xinmin zhang Darong Yang Key Laboratory of Forest Disaster Warning and Control in Yunnan Province College of ForestrySouthwest Forest University Xishuangbanna Tropical Botanical Garden Chinese Academy of Sciences

Figs(Ficus, Moraceae) and their pollinating fig wasps(Hymenoptera, Agaonidae, Chalcidoidea) are a striking example of obligate mutualism and coevolution. Agaonid females enter the figs to lay their eggs,but also actively or passively transport pollen into the figs at the same time. We examined eight related fig tree species pollinated by host specific Eupristina agaonids to determine the relationships between pollination mode, host pollen, ovule ratios and the ability of the figs to recruit additional non-agaonid pollinators. Uniquely amongst the eight Eupristina species, the pollinator of Ficus curtipes has nonfunctional pollen pockets and no coxal combs, showing that it pollinates passively. Reflecting this, the anther-to-ovule ratio of F. curtipes is unusually high.In addition to the agaonids, figs support many species of 'non-pollinating fig wasps'(NPFW) that are typically ovule gallers or parasitoids. These mainly oviposit from outside the figs but there are a few species of NPFW that are like agaonids and enter the figs to oviposit. Two of the eight Eupristina pollinated fig trees support host specific internally-ovipositing fig wasps belonging to the chalcidoid genera Diaziella(Sycoecinae) and Lipothymus(Otitesellinae). Reflecting the trees' pollination modes, these fig wasps act as supplementary pollinators of F. curtipes, but not of Ficus glaberrima, where agaonid pollination is active.

关键词： Agaonidae Ficus Parasites Pollination Coevolution Mutualism

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