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Riemannian Online Optimistic Algorithms with Dynamic Regret

IEEE Transactions on Automatic Control 2025年

作者： Wang, Xi Yuan, Deming Hong, Yiguang Hu, Zihao Wang, Lei Shi, Guodong University of New South Wales School of Electrical Engineering & Telecommunications SydneyNSW2052 Australia Nanjing University of Science and Technology School of Automation Nanjing210094 China Tongji University Shanghai Research Institute for Intelligent Autonomous Systems Shanghai201210 China Hong Kong University of Science and Technology Department of Mathematics Hong Kong Zhejiang University College of Control Science and Engineering Zhejiang 310058 China The University of Sydney Australian Center for Robotics School of Aerospace Mechanical and Mechatronic Engineering NSW2006 Australia

In this paper, we consider Riemannian online convex optimization with dynamic regret, which involves minimizing the cumulative loss difference between a learner's decisions and a sequence of adaptive decisions across dynamic environments over time on Riemannian manifolds. First, we propose Riemannian Online Optimistic Gradient Descent (R-OOGD), which extends the classical optimistic algorithms to Riemannian manifolds, requiring one gradient inquiry per round. We then propose Riemannian Adaptive Online Optimistic Gradient Descent (R-AOOGD) by incorporating the meta-expert framework into R-OOGD. We analyze the dynamic regret of R-OOGD and R-AOOGD in terms of the regularity of the sequence of cost functions and comparators. The dynamic regret bound matches the results in Euclidean space and with a scale adjustment of O(1+κ D2/√1-KD2) related to the sectional curvature lower bound κ, sectional curvature upper bound and feasible set diameter. Finally, we provide numerical experiments to illustrate the performance of the proposed algorithms. © 1963-2012 IEEE.

关键词： Optimization algorithms

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One-Step Laser-Induced Dissolvable PVA Mask for 3D Soft Carbon Electrode Array

One-Step Laser-Induced Dissolvable PVA Mask for 3D Soft Carb...

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IEEE International Conference on Micro Electro mechanical systems

作者： Xuanqi Wang Kai Xue Ruiyu Bai Ye Huang Zimo Zhang Xiaoli You Minghao Wang Honglong Chang Bowen Ji Unmanned System Research Institute Northwestern Polytechnical University China National Key Laboratory of Unmanned Aerial Vehicle Technology Integrated Research and Development Platform of Unmanned Aerial Vehicle Technology Northwestern Polytechnical University China Ministry of Education Key Laboratory of Micro and Nano Systems for Aerospace School of Mechanical Engineering Northwestern Polytechnical University China Sanhang Institute for Brain Science and Technology Northwestern Polytechnical University China Institute of Medical Research Northwestern Polytechnical University China MOE Engineering Research Center of Smart Microsensors and Microsystems College of Electronics and Information Hangzhou Dianzi University China

ISBN: (数字)9798331508890

ISBN: (纸本)9798331508906

This paper introduces a 3D soft carbon electrode array, fabricated through a one-step laser-induced process integrating a water-dissolvable polyvinyl alcohol (PVA) mask. This approach achieves precise conical microstructures and robust conductive channels using hybrid MWCNT@PDMS conductive paste. The soft carbon electrode sites with a 3D conical microstructure are designed to enhance proximity to neural tissue, thereby enhancing electrocorticogram (ECoG) signal quality and enabling effective neural stimulation. The electrode array demonstrates remarkable stretchability (25% over 1,000 cycles without failure) and stability (equivalent to 66 days in vivo). Compared to conventional materials, our electrodes exhibit superior electrochemical properties, including lower impedance (9.7 kΩ at 1 kHz) and higher signal-to-noise ratio (SNR, 61.7 dB). Thus, this one-step process is a cost-effective, scalable solution for recording and modulating central or peripheral neural tissues.

关键词： Electrodes Micromechanical devices Three-dimensional displays Array signal processing Laser stability Recording Microstructure Carbon Laser beam cutting Signal to noise ratio

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Electrochemical activated ZnMn2O4 with Al doping for boosting high-capacity and long-term stable Zn ion storage

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Journal of Energy Storage 2025年 122卷

作者： Xu, Shusheng Xiong, Haichao Wang, Zhaozhao Ma, Hui Sun, Xuecheng Wang, Peiqingfeng Zhu, Jiaqing Shi, Xue-Rong School of Materials Science and Engineering Shanghai University of Engineering Science Shanghai201620 China School of Mechanical and Automotive Engineering Shanghai University of Engineering Science Shanghai201620 China Microelectronic Research & Development Center School of Mechatronics Engineering and Automation Shanghai University Shanghai200444 China Shanghai Key Laboratory of Automotive Intelligent Network Interaction Chip and System The School of Microelectronics Shanghai University Shanghai200444 China State Key Laboratory of Coal Conversion Institute of Coal Chemistry Chinese Academy of Sciences P.O. Box 165 Shanxi Taiyuan030001 China

Although spinel ZnMn2O4 (ZMO) is of great promise as a cathode material for Zn ion storage, the limited capacity and poor stability significantly hinders its practical applications. In this work, with Mn-BTC as the precursor, Al-doped ZnMn2O4 (AZMO) micro-spheres with an incorporated carbon skeleton were prepared by a two-step process involving low-temperature calcination and electrochemical activation. AZMO micro-spheres with hollow structures effectively shortens ion diffusion pathways and provides abundant active sites for Zn2+ storage during the electrochemical reactions. Meanwhile, Al doping leads to strong Al[sbnd]O bonds in ZMO framework, which not only prevents the structure transformation and Mn dissolution, but also optimizes the ion states and the band gap of the AZMO cathode. As a result, the synthesized AZMO cathode exhibits a larger reversible specific capacity of 526 mAh g−1 (0.1 A g−1) and better cycling stability (81.76 % capacity retention after 2000 cycles at 2 A g−1) than the original ZMO. Furthermore, coin-type and soft-packed Zn ion batteries (ZIBs) based on the AZMO cathode were also assembled with excellent electrochemical properties, demonstrating the great potential for energy storage and flexible electronic applications. © 2025 Elsevier Ltd

关键词： Boron carbide

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Design,Fabrication,and Analysis of Flapping and Folding Wing Mechanism for a Robotic Bird

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Journal of Bionic engineering 2020年第2期17卷 229-240页

作者： Seung Wan Ryu Jong Gu Lee Hyoun Jin Kim Department of Mechanical&Aerospace Engineering and Automation Systems Research Institute Seoul National UniversitySeoul 08826Republic of Korea

Emulating periodic main wing movement of a bird for generating lift and thrust remains a significant challenge in developing a robotic *** sequences of main wing motion are comprised of flapping,folding,bending,and *** this paper,we concentrate on the flapping and folding motion,and design two wing mechanisms based on a 4-bar linkage structure:one is only for Flapping Motion(FM)and the other is for simultaneous Flapping and Folding Motion(FFM)during a wing *** derive relationships between length and angle of links to analyze kinematic characteristics of the mechanisms and conduct an optimization to select the length parameters of links that allow maximization of the flapping *** run a simulation to confirm the performance of the optimized parameters by examining physical properties,and fabricate two wing mechanisms *** particular,the folding motion is achieved without using an additional *** measurements to investigate a lift profile of each mechanism and their quantitative comparison of the performance of both types confirm the benefits of the folding motion in the perspectives of wing frequency and *** expect that our kinematic formulation,design procedures,and comparative measurement results can help develop a wing mechanism to create a truly biomimetic robotic bird.

关键词： biomimetic robotic bird flapping and folding wing mechanism wing kinematics force measurement

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Study on the High-Speed Penetration and Shear Failure Mechanism of Beach Sand

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Materials 2025年第9期18卷 1922-1922页

作者： Zhu, Jianzhong Li, Jiangquan Kong, Yun Dong, Mingming Li, Yuqiong Zou, Meng Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology Tianjin300384 China Key Laboratory for Bionics Engineering of Education Ministry Jilin University Changchun130022 China School of Mechanical Engineering Beijing Institute of Technology Beijing100081 China Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences Beijing100190 China State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing100190 China Guangdong Aerospace Research Academy Nansha Guangzhou511458 China

In this paper, the contact parameters of beach sand are calibrated based on the discrete element method and the optimal design method, and the obtained parameters by calibration are used as input for the angle of repose simulation. The relative error between angle of repose simulation results and experimental results is 3.27%. Based on the penetration and shear tests, simulation models were constructed to study the pressure shear failure mechanism of beach sand under high-speed conditions. The high-speed penetration simulation shows that with the increase of the penetration rate, the influence area of the sinkage plate gradually increases, and the stress of sand particles also increases. When the penetration rate increased from 0.5 m/s to 8 m/s, the pressure on the plate increased 12.7 times, indicating that the bearing capacity of the sand increased significantly with the increase of the penetration rate. The high-speed shear simulation shows that in the stable shear stage, the average shear torque initially increases slightly with the increase of speed, and then decreases significantly when the speed exceeds 4 m/s. This is because as the shear rate increases, the disturbance of the soil by the shear plate increases, the velocity of soil particles increases, resulting in a decrease in the number of soil particles in contact with the shear plate, thereby reducing the shear torque. © 2025 by the authors.

关键词： Fracture mechanics

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Mission planning for repeated multi-spacecraft non-contact debris removal

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Chinese Journal of Aeronautics 2025年

作者： Hang XU Lujiang LIU Yanning GUO Youmin GONG Bin SONG Guangfu MA Department of Control Science and Engineering Harbin Institute of Technology Harbin 150001 China Shanghai Institute of Aerospace System Engineering Shanghai 201109 China Zhengzhou Research Institute Harbin Institute of Technology Zhengzhou 450000 China School of Mechanical Engineering and Automation Harbin Institute of Technology Shenzhen 518055 China

Non-contact debris removal methods are fuel-efficient in a single operation compared to contact-based strategies as spacecraft don’t need to match debris velocity. To comprehensively analyze this scheme, maneuvering schemes for maximum debris removal with minimum fuel consumption, including task assignment, sequence planning, and trajectory planning, must be formulated. The coupling between variables’ dimensions and optimization results in task assignment poses challenges, as debris removal is repetitive and uncertain, leading to a vast search space. This paper proposes a novel Greedy Randomized Adaptive Search Procedure with Large Neighborhood and Crossover Mechanisms (GRASP-LNCM) to address this problem. The hybrid dynamic iteration mechanism improves computational efficiency and enhances the optimality of results. The model innovatively considers unsuccessful single removal by using a quantitative method to assess removal percentage. In addition, to improve the efficiency of sequence and trajectory planning, a Suboptimal Search Algorithm (SSA) based on the Lambert property and accelerated Multi-Revolution Lambert Problem (MRLP) solving strategy is established. Finally, a real Iridium-33 debris removal mission is studied. The simulation demonstrates that the proposed algorithm achieves state-of-the-art performance in several typical scenarios. Compared to the contact-based scheme, the new one is simpler, saving more fuel under certain conditions.

关键词： Space debris Planning Non-contact method Optimization Greedy randomized adaptive search procedure

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Mode-coupled infinite topological edge state in bulk-lattice-merged mechanical Su–Schrieffer–Heeger chain

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Extreme Mechanics Letters 2025年 77卷

作者： Jang, Yeongtae Kim, Seokwoo Kim, Minkyung Kim, Guenil Kim, Eunho Rho, Junsuk Department of Mechanical Engineering Pohang University of Science and Technology (POSTECH) Pohang 37673 South Korea School of Mechanical Engineering Gwangju Institute of Science and Technology (GIST) Gwangju 61005 South Korea Division of Mechanical System Engineering Jeonbuk National University Jeonju 54896 South Korea Department of JBNU-KIST Industry-Academia Convergence Research Jeonju 54896 South Korea of Mechanical-Aerospace-Electric Convergence Engineering Jeonbuk National University Jeonju 54896 South Korea Department of Chemical Engineering Pohang University of Science and Technology (POSTECH) Pohang 37673 South Korea Department of Electrical Engineering Pohang University of Science and Technology (POSTECH) Pohang 37673 South Korea POSCO-POSTECH-RIST Convergence Research Center for Flat Optics and Metaphotonics Pohang 37673 South Korea

Band topology has emerged as a powerful tool for designing mechanical engineering systems, from phononic crystals to metamaterials. Various design principles — whether bulk-based or lattice-based — have been proposed and successfully implemented according to unit cell structures. Here, we present a bulk-lattice merged Su–Schrieffer–Heeger (SSH) chain constructed from single-column woodpile metamaterials. This system consists of a lattice array of cylindrical particles, where each particle's bulk dynamics exhibits local resonance-mode coupling with wave propagation. We demonstrate that topological edge states emerge in direct correspondence with these local resonance modes, manifesting as mode-coupled topological states. Experimentally, we observe the initial emergence of these mode-coupled topological edge states, with their frequencies accurately predicted by nonlinear characteristic equations rooted in continuum dynamics and topological symmetry. Additionally, the system's weak nonlinearity enables simultaneous frequency shifts, allowing multivariate tunability in its topological states. © 2025 Elsevier Ltd

关键词： Bulk-lattice-merged SSH chain Mode-coupled topological edge state Nonlinear effect Topological metamaterials Wave localization

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Path Classification and Estimation Model Based Prognosis of Pneumatic Cylinder Lifetime

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Chinese Journal of mechanical engineering 2012年第2期25卷 392-397页

作者： CHEN Juan SONG Chunwen QI Xiaoye WU Wei School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Aerospace System Engineering Institute Shanghai 201108China China Academy of Civil Aviation Science and Technology Beijing 100028China

Prognosis is a key technology to improve reliability,safety and maintainability of products,a lot of researchers have been devoted to this *** to improve the predict accuracy of remaining life of products has been *** predict the lifetime specification of pneumatic cylinders with high reliability and long lifetime and small specimen,this paper put forward the prognosis algorithm based on the path classification and estimation（PACE） *** model is based entirely on failure data instead of failure *** cylinders normally characterize with failure mechanism wear and *** the minimum working pressure increases with the number of working cycles,the minimum working pressure is chosen as degradation *** model is fundamentally composed of two operations：path classification and remaining useful life（RUL） *** classification is to classify a current degradation path as belonging to one or more of previously collected exemplary degradation *** estimation is to use the resulting memberships to estimate the remaining useful *** order for verification and validation of PACE prognostic method,six pneumatic cylinders are *** test data is analyzed by PACE *** is found that the PACE based prognosis method has higher prediction accuracy and smaller variance and PACE model is significantly outperform population based prognostics especially for small specimen *** model based method solved the problem of prediction accuracy for small specimen pneumatic cylinders＇ prognosis.

关键词： lifetime prognosis remaining useful life（RUL） path classification and estimation model Weibull distribution pneumatic cylinder

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Intelligent sequential multi-impulse collision avoidance method for non-cooperative spacecraft based on an improved search tree algorithm

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Chinese Journal of Aeronautics 2025年第04期 382-397页

作者： Xuyang CAO Xin NING Zheng WANG Suyi LIU Fei CHENG Wenlong LI Xiaobin LIAN School of Astronautics Northwestern Polytechnical University National Key Laboratory of Aerospace Flight Dynamics Northwestern Polytechnical University Unmanned System Research Institute Northwestern Polytechnical University National Key Laboratory of Unmanned Aerial Vehicle Technology Northwestern Polytechnical University Integrated Research and Development Platform of Unmanned Aerial Vehicle Technology Northwestern Polytechnical University Northwest Institute of Mechanical and Electrical Engineering Shanghai Institute of Satellite Engineering Shanghai Academy of Spaceflight Technology

The problem of collision avoidance for non-cooperative targets has received significant attention from researchers in recent years. Non-cooperative targets exhibit uncertain states and unpredictable behaviors, making collision avoidance significantly more challenging than that for space debris. Much existing research focuses on the continuous thrust model, whereas the impulsive maneuver model is more appropriate for long-duration and long-distance avoidance ***, it is important to minimize the impact on the original mission while avoiding noncooperative targets. On the other hand, the existing avoidance algorithms are computationally complex and time-consuming especially with the limited computing capability of the on-board computer, posing challenges for practical engineering applications. To conquer these difficulties, this paper makes the following key contributions:(A) a turn-based(sequential decision-making)limited-area impulsive collision avoidance model considering the time delay of precision orbit determination is established for the first time;(B) a novel Selection Probability Learning Adaptive Search-depth Search Tree(SPL-ASST) algorithm is proposed for non-cooperative target avoidance,which improves the decision-making efficiency by introducing an adaptive-search-depth mechanism and a neural network into the traditional Monte Carlo Tree Search(MCTS). Numerical simulations confirm the effectiveness and efficiency of the proposed method.

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Real-time Bezier interpolation satisfying chord error constraint for CNC tool path

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Science China(Technological Sciences) 2016年第2期59卷 203-213页

作者： FAN Wei LEE ChenHan CHEN JiHong XIAO Yao National NC System Engineering Research Center Huazhong University of Science and Technology Institute of Mechanical Manufacturing Technology China Academy of Engineering Physics Aerospace Engineering Department Zhejiang University

G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuous tangenc t and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings i：1 these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining：（1） chord error should be rigidly constrained; （2） G01 points should be interpolated; （3） cur,,ature should be continuous （G2）; （4） machining should be applicable to spatial cases; （5） real-time performance of computaEion is *** on these various requirements, this study proposes an interpolation scheme using CUDlC t^ezler curves anu mciuucb illl adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-elror-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable ：o 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpola- tion in surface quality and machining efficiency.

关键词： real-time CNC machining stretch energy jerk energy loop-free chord error

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